11 ms·

Hand Scraping a Truly Flat Plane (1908) [pdf]

163 points by rkagerer 7y ago

rkagerer 7y ago
Same content, but this link might be a little quicker: https://archive.org/details/engineeringremin00port/page/233/mode/1up https://archive.org/details/engineeringremin00port/page/233/... If you're interested in the topic, here's some more discussion: https://www.practicalmachinist.com/vb/general/possible-make-grind-polish-flat-surfaces-manually-295976/#post2441051 https://www.practicalmachinist.com/vb/general/possible-make-... Skilled hand scrapers... can generate plane surfaces accurate to 40 millionts per foot. The same method applied to lapping of glass can generate flats to 1/2 millionth per foot... The average guy working in an open shop careful of cleanliness and uncontrolled heat input to the work will find 0.0005 per foot readily achievable and 0.0002" per foot with a little more care and effort.
- HeyLaughingBoy 7y ago
  Without even opening that second link I can guess that Forrest Addy chimes in at some point :-) [edit] haha. That was even his quote :-)
wcunning 7y ago
I got into machine rebuilding after buying a reasonable 1950's machine shop worth of equipment a few years ago when I started in the auto industry after my master's degree. I happened onto a Craigslist ad of a machine rebuilder going out of business near the office and I picked up basically the whole kit -- cast iron surface plates, power and hand scrapers, bluing medium, etc etc. It took another 6 months before I ran into a guy who was willing to teach me to use all that equipment, up near Flint. He spent a whole career doing fitting and repair for a CNC dealer traveling all over the state and a piece of the rest of the midwest. He was just about the nicest guy I've ever done business with, and he supplies equipment and advice to a huge percentage of the Youtube machinist crowd, plus he saved me the couple grand it would have cost to go take one of Rich King's classes. All in all, this is a great skill that will persist for a long time, longer than you might think, even if modern machines use replaceable linear rails rather than scraped ways. If you feel like taking it up, watch one of the many Youtube videos from Stefan Gotteswinter or Keith Rucker. Look into the equipment, but think about building your own carbide sharpener, scraper and handle.
- Blackthorn 7y ago
  What's the name of his YouTube channel (assuming that's what you meant by supplies advice)?
  - kalak451 7y ago
    I assume he is talking about Richard King. I don't think he has his own channel. but as mentioned Stefan Gotteswinter and Keith Rucker both have videos of the scraping skills they learned from him. (Rucker has actually hosted several of King's classes in his workshop) edit: I clearly misread the end of OP's post. Definitely not talking about Richard King.
    - Balgair 7y ago
      Chiming in to say ThisOldTony is alright. https://www.youtube.com/user/featony https://www.youtube.com/user/featony Stefan Gotteswinter: https://www.youtube.com/user/syyl https://www.youtube.com/user/syyl Keith Rucker: https://www.youtube.com/user/ksruckerowwm https://www.youtube.com/user/ksruckerowwm Richard King: https://www.youtube.com/results?search_query=Richard+King https://www.youtube.com/results?search_query=Richard+King
    - wcunning 7y ago
      He did years of scraping before he met Rich, but he did take a Rich King class to learn power scraping. Made it easier to justify skipping the expensive class for me.
  - wcunning 7y ago
    He doesn't have one, but Solid Rock Machine did a tour of his shop a while ago. He mostly supplies advice and equipment through the grapevine and Practical Machinist.
joncrane 7y ago
This is fascinating. I don't know all the terminology perfectly, but I get the gist. I love how transparent and ingenious they are. (BTW did anyone else think of the Rick and Morty episode where Rick builds a "perfectly flat" platform for Morty to experience?)
- doomjunky 7y ago
  I'm familiar the the bubble, Morty. I also dabble in precicion, and if you think you can even approach it with your sad, naked, caveman eyeball and a bubble of f* air, you're the reason this species is a failure, and it makes mis angry! Experience True Level!
0xff00ffee 7y ago
I read this on a whim and now I'm amazed: I never considered algorithms as part of mechanical engineering. Very clever. And in a pedantic reading of Richard Dawkins, this is the kind of "meme" he was talking about.
- Animats 7y ago
  I never considered algorithms as part of mechanical engineering. Oh, yes. Metal work is all about calculating. The classic book is "Machinery's Handbook", published for 105 years. Machinist's toolboxes often have a built-in space for it.
  - defterGoose 7y ago
    The "bible" though, is "Foundations of Mechanical Accuracy" by Moore. Machinery's Handbook is more of a practical reference used in the shop (like when you want to know what a certain spline or thread profile should look like), whereas Foundations is more theoretical.
    - 0xff00ffee 7y ago
      Is there a good book for sheet metal bending? There are lots of things I'd like to make, but when I think through it, the bends always run into each other (at least in my head). Which is why I haven't bought a break yet. Would love to learn the basics about tools, marking, cutting. (My cuts always drift, and deform the metal, would like to learn how to NOT do that.)
nohuhu 7y ago
Thanks for submission, a really interesting read! I'm into restoring old woodworking machinery, and hand scraping is one of the methods for truing lathe ways that I've read about. Could possibly be required for the Walker-Turner lathe I'm working on. :)
- mauvehaus 7y ago
  Also a woodworker here. I have to ask: how bad are the ways on this lathe and how could they get worn? Moving the banjo and tailstock on a wood lathe shouldn't wear the ways the way the routine use of a metal lathe wears the ways.
  - analog31 7y ago
    The worst thing is neglect, rust, and accidental damage. In low volume use, e.g. proto shop or home shop, the ways should be virtually eternal. Keep them covered, clean and oiled.
  - nohuhu 7y ago
    I haven't gotten to measuring wear on the ways yet, don't think I'll need to scrape them but that's a possibility. This is a pet project of mine, a barn find that was in a pretty bad shape when I got it: rusty, crusty, with missing parts and undesirable modifications by previous owners. Specifically the ways are pitted from rust; worse in places that were exposed to the elements. I'll have to try and measure the effect of this pitting on tailstock positioning. I don't think banjo positioning is going to be affected, the ways are not that bad. But then there's always the obsession with perfection, so who knows. :) I have a soft spot for pre-1950 Walker-Turner machinery, their aestetics are off the charts; I'm trying to restore this lathe to its former glory, or even better. Not quite a classic car showroom condition but as close to it as I can get without spending a fortune in time and money. :) The current stage is painting; turned out it's pretty tricky to spray glossy enamel so it would level out smooth! Especially in our cool and humid coastal climate, paint takes a while to dry and even longer to fully cure so the process is quite challenging. Not to mention the countless hours it took to grind out casting imperfections, apply bondo filler, sand it, etc etc. I thought I was getting into woodworking but found that restoring machinery is lots of fun in its own right, and nothing compares to the satisfaction of using a well made and beautifully restored vintage tool. Especially when I'm the one who did the restoration. :)
deleted 7y ago
[deleted]
anateus 7y ago
Folks who enjoyed this may appreciate Simon Winchester's recent book The Perfectionists, where he covers this method amongst other things. Core to the idea of perfection are machine tools, what we in software often refer to as a toolchain. The way the toolchain revolution allowed us to go from intricate one off clockwork to reliable longitude measurement, better locks, and industrialized machinery parallels compilers, operation systems, etc.
- mauvehaus 7y ago
  I thought he went rather quickly from some of the earliest processes (boring, for instance) to stuff that's so abstract as to be removed from anybody's practical experience (disregarding metrologists, of course) and then goes farther into philosophical matters than I found interesting. I would have much more a book that stayed in the realm of machine tools for about half the content, covering the process of bootstrapping precision in the pre-electronic era. An interesting third quarter could discuss the limits of precision in practical mass manufacturing and the ways we work within tolerances that are economical. The engine block and head of an internal combustion engine have a large and irregularly-shaped mating surface that's subjected to repeated heating and cooling cycles. How flat do they have to be for a gasket to seal them effectively? The last quarter of the book could cover developments in the era of CNC, and talked about the interplay between electrical components (e.g. stepper motors) and mechanical components (e.g. lead screws, timing belts, etc) and what we gain and lose in using those type of processes. Boring a hole for example, remains more accurate than CNC'ing it on a mill because good control when one x or y approaches zero becomes difficult both mechanically and mathematically. Anybody interested in this sort of thing might enjoy "How Round is your Circle", by the way.
- Ericson2314 7y ago
  I wish we took as good care of our tools as they did!
NikolaeVarius 7y ago
Not flat but similar idea https://www.cmog.org/article/hale-reflecting-telescope-palomar https://www.cmog.org/article/hale-reflecting-telescope-palom... Imagine hand grinding telescope lenses https://www.youtube.com/watch?v=MjUcBWYVF9s https://www.youtube.com/watch?v=MjUcBWYVF9s
- hinkley 7y ago
  From what I understand, hand-grinding small mirrors is down to process as much as skill. Solid grinding compounds, once they start to wear, end up wearing themselves too. If you keep the pieces moving just so, you can eyeball a rough radius with the grinding material, and it will smooth itself out while smoothing the glass until they mate up. Basically once you have a wheel with a high precision axle, you can make lots of curves or straight lines.
- HeyLaughingBoy 7y ago
  Thanks for the reminder. About 25? years ago I bought the book How to make a Telescope and two six-inch blanks and grinding materials and set off to grind my own mirror. I never finished (it was super boring and really humid in the basement of my rented apartment) and I have no idea where the "blanks" are anymore but now I live in an area well outside of town where I can see the Milky Way with the naked eye if my neighbors turn their lights off so it might not be a bad project to restart. Bonus: I have the room to build a grinding machine so I don't have to do it all by hand.
- CliffStoll 7y ago
  Today, large telescope mirrors are finished using ion figuring: neutral atoms are shot at the surface of the mirror blank, for a precision ablation of a few angstroms. This works especially well for hexagonal mirror segments, because you can control the surface shape right to the edge of the mirror. Mechanical figuring (using ceramic or glass blanks) has troubles near the edge.
- Sharlin 7y ago
  Hand grinding telescope lenses (well, usually mirrors) is a fairly accessible hobby; you need patience more than anything else. It’s amazing how little technology you need to attain sub-micrometer precision.
riskneutral 7y ago
There's a guy who used to give classes on hand scraping and machine rebuilding https://www.youtube.com/watch?v=TH7tZZdUr2w https://www.youtube.com/watch?v=TH7tZZdUr2w
paypalcust83 7y ago
It's interesting to get more precise and accurate machines out of the ones came before. These days, if you want to get milling and grinding down to 1 micron without lapping using only your own expertise and some parts from eBay (air bearings and precision-ground slabs): https://youtu.be/sFrVdoOhu1Q https://youtu.be/sFrVdoOhu1Q The creator (Dan Gelbart) demonstrates nitrogen-tight parts without bearings, and claims zero wear or lubrication needs. #AvEclub
- jbay 7y ago
  It wasn't nearly so easy. Dan hand-scraped in several surfaces on the lathe; for example the headstock, to get the axis parallel to the ways, and so on.
ryanobjc 7y ago
I've been doing woodworking with handtools, and it's amazing what 90 year old tools can do. I bought an old stanley plane in good condition, and was able to start pulling cuttings that are 4/1000" easily. My modern lee valley plane is even easier to set, and I just did a 1/1000" shaving. That means you can surface a piece of wood to 1/1000th of an inch. This is the kind of accuracy you typically associate with modern CNC machining. Wood is an interesting medium - it's always in motion so it's in some ways more challenging than working with steel. You can't just machine and glue wood together if you want to make something that'll last for centuries, like old furniture used to. The art is still alive, and I encourage people to check it out!
- dekhn 7y ago
  I think most people would say, although you might observe such sizes when cutting wood, temperature and humidity will swamp out those precisions within a day or two.
dekhn 7y ago
One of my favorite parts of Feynman's brilliant talk about the limits of minaturizing mechanical devices, "There's plenty of room at the bottom": """If, for instance, having made a small lathe with a pantograph, we find its lead screw irregular – more irregular than the large-scale one – we could lap the lead screw against breakable nuts that you can reverse in the usual way back and forth until this lead screw is, at its scale, as accurate as our original lead screws, at our scale. We can make flats by rubbing unflat surfaces in triplicates together – in three pairs – and the flats then become flatter than the thing you started with. Thus, it is not impossible to improve precision on a small scale by the correct operations. So, when we build this stuff, it is necessary at each step to improve the accuracy of the equipment by working for awhile down there, making accurate lead screws, Johansen blocks, and all the other materials which we use in accurate machine work at the higher level. We have to stop at each level and manufacture all the stuff to go to the next level – a very long and very difficult program. Perhaps you can figure a better way than that to get down to small scale more rapidly.""" Many ideas contributed to the modern process of 5nm lithography, but having flat surface plates whose precision is determined by the correct application of operations rather than an external standard has turned out to be one of the most profound. Now, of course, you can buy a granite surface place with accuracy exceeding almost anything available 100 years ago, for $30. And there are youtube videos of flat surface aficinados who scrape their own.
- Animats 7y ago
  Making a precision lead screw is an important step. Maudslay invented the modern metal lathe. His original, from around 1800, is in the Science Museum, London, and it has most of the features of a metal lathe of 1900. Or today. A screw cutting lathe requires a good lead screw as its reference. Maudslay invented a "screw origination machine"[1], a clever special-purpose device for making a more accurate screw than the one you have. It only cuts soft metal, so the screw it makes is used in a second lathe to make one in hard steel. This is another of the key steps in bootstrapping to precision. Early precision work was limited to flat things and round things. Take a look at a steam locomotive from around 1900. Every surface that has to be held to a tight tolerance is flat or round. That's because the precision tools of the era were the planer, lathe, and drill. The general purpose milling machine came later. Incidentally, this is the real reason manholes were round. In the great era of city sewer-building, you could make round metal manhole covers easily, by casting and a quick lathe pass. The ring into which they fit could also be easily finished on a lathe. Making an iron rectangular frame and a lid to fit it would have been a much harder and more expensive job. [1] https://gracesguide.co.uk/Henry_Maudslay:_Machine_Tools https://gracesguide.co.uk/Henry_Maudslay:_Machine_Tools
oyebenny 7y ago
This reminds me of that Rick and I'm already seeing where Dr Sanchez shows Morty what absolute level is.
- ivankirigin 7y ago
  Here for this comment. For those who don't know: https://www.youtube.com/watch?v=IMeain2cvBM https://www.youtube.com/watch?v=IMeain2cvBM
lsllc 7y ago
If you're interested in metal working/machining and like "Dad jokes", check out This Old Tony on YouTube: https://www.youtube.com/channel/UC5NO8MgTQKHAWXp6z8Xl7yQ https://www.youtube.com/channel/UC5NO8MgTQKHAWXp6z8Xl7yQ Here's his surface grinder rebuild which includes milling and hand-scraping various surfaces to get them dead flat. https://www.youtube.com/watch?v=RjwKQCiDgBQ https://www.youtube.com/watch?v=RjwKQCiDgBQ He's super talented and the videos are fun!
- gorgoiler 7y ago
  > dad jokes ”Well this isn’t the freshest mill in the world but I figured if I was going to bite off more than I can chew I might as well go the whole nine yards” Hah. You weren’t kidding.
- jedimastert 7y ago
  > https://www.youtube.com/watch?v=RjwKQCiDgBQ https://www.youtube.com/watch?v=RjwKQCiDgBQ Oh my goodness, is that what his older videos looked like? He's grown an incredible amount as a storyteller and video producer. Wow
  - lsllc 7y ago
    He really has, his newer stuff is epic! In these dark times, he's kept me quite entertained!
- jjoonathan 7y ago
  You just clicked on a video about making a mostly-square block of metal even more square. (pause) Just saying. I was hooked from the start!
- Prcmaker 7y ago
  I get great enjoyment out of Tony, but the dry humour of Mr Pete really does it for me. https://www.youtube.com/channel/UCKLIIdKEpjAnn8E76KP7sQg https://www.youtube.com/channel/UCKLIIdKEpjAnn8E76KP7sQg
tempestn 7y ago
This video in Dan Gelbart's 'Building Prototypes' series is a great look at producing highly accurate (flat) surfaces. https://www.youtube.com/watch?v=cwdoUjynpEk https://www.youtube.com/watch?v=cwdoUjynpEk Edit: the scraping technique in this PDF is shown at about 13:00.
cartoonfoxes 7y ago
I've done this myself recently, and it's a worthwhile experience if you have the patience for it. If the short treatise in the OP interests you, I would suggest the book 'Foundations of Mechanical Accuracy', PDF easily available though I won't link here. I can also recommend the bible of hand scraping, 'Machine Tool Reconditioning and Applications of Hand Scraping' otherwise known as the Connelley Book.
csours 7y ago
Abom79's hand scraping experience: https://www.youtube.com/watch?v=pT5KWvglp_c https://www.youtube.com/watch?v=pT5KWvglp_c
rfrey 7y ago
People wanting a full treatise on hand scraping should look into Machine Tool Reconditioning by Connelly, available on the used market and the usual other sources. A close runner up for books is Foundations of Mechanical Accuracy by Moore. If you can get a physical copy of the latter, and can afford it, you should - the photographs are magnificent.
Prcmaker 7y ago
While I was studying engineering I worked in a machine shop. In that time I hand scraped or lapped a good few bearings and surfaces. Fast forward six years, researching optical sensing, and I've had to pull those old tricks out of the bag recently. For some reason, of all the skills and techniques I've learned, manual or academic, making a properly flat surface remains the most satisfying.
GaryNumanVevo 7y ago
Maybe a home machinist can answer this question. If I'm on a desert island, I know how to make a flat plane via ABC grinding. How do I make a right angle? Do I decide on a measure, grind 12 gauge blocks to the same height and make a 3-4-5 triangle?
- defterGoose 7y ago
  Same method essentially. You need three roughly square pieces that are checked for bearing against each other repeatedly, but this time you also have intermediate steps of checking each face for flatness against the master.
- SAI_Peregrinus 7y ago
  You make a box straight edge. First, you make a surface gauge. A heavy weighted base with a pointer you can vary in height and distance from the base. You scrape/grind the base flat using a surface plate as reference. You take something you think is roughly square (a long rectangular prism is good), scrape/grind one face flat with one of your surface plates. We'll call this face 1. Then scrape/grind the opposite face flat, and using the surface gauge to check height (position the box with face 1 down on a surface plate. Position the gauge next to it, with the point touching face 2 somewhere. Slide the gauge back and forth: if it gets pushed up face 2 is tilted up in that direction with respect to face 1. If a gap forms under the tip, it's tilted down.) and thereby get it parallel with face 1. Then scrape/grind two faces which are adjacent to each the first and opposite each other flat. You now have a shape like \_/ or |_/ or such, though with a top parallel to the bottom. You stick your surface gauge along one side, touching at the base and at some point near the top of that side with the indicating point. You then turn the WIP straight edge box 180 degrees, and see if the other side touches the indicating tip or the base first. The distance from touching both at once tells you how far out of parallel that side is from the first. You then proceed to scrape them both to be a bit more flat and parallel. Then you turn the box onto its top (face 2) and repeat that. Using 180 degree rotations in two dimensions will get you a good square. Another thing that can be used as a check (if you can draw) is to build a compass and a straightedge. Side 1 of your box is a good straightedge! You can then use basic geometric construction to make a right angle, and can compare any finished box to that angle.
WalterBright 7y ago
When I was in high school, it was popular among some of the students to make telescope mirrors. The technique of hand-grinding them to incredible perfection was both simple and astounding.
WalterBright 7y ago
I remember one of the "ancient aliens" TV shows back in the 70s which claimed that the precision with which Inca masons fitted stones together was impossible without alien technology. Then an archaeologist showed how fit two stones together with the same precision in about a half hour, using no tools at all. Just rubbing and banging them together. I asked my mom once how the Egyptians could have possibly made the pyramids straight. She replied pull a long string tight, that's the reference. Figuring I had her this time, I asked how they could have leveled the pyramid foundation. She said dig a trench and fill it with water. The water level forms the reference. Mom: 2 Me: 0
- Gibbon1 7y ago
  I remember an interview with an archeologist that studied the Nazca Lines. She said one year she had a grad student who was a farm boy. He showed her how to draw a long straight line by setting up a stick a 1000 feet away and then just walking towards it while dragging a another stick behind him. It was perfectly straight. It's basically the same as the old draftsman's trick for drawing a straight line.
  - wrycoder 7y ago
    What is that trick?
    - Gibbon1 7y ago
      The trick is mark the end of the line and then draw towards it. With practice you can draw eyeball straight lines.
      - mturmon 7y ago
        It’s quite accurate, somewhat hard to believe until you try it a few times. Good enough for many layout tasks if you’re drawing a reference line to cut to, for example. Also works for cutting straight lines with an exacto knife.
- 7y ago
aazaa 7y ago
Reminds me of this guy, who hand-planes engine cylinder heads using a block of wood, straight edge, sandpaper, and feeler gauges: https://www.youtube.com/watch?v=1ch8KYiqSNg https://www.youtube.com/watch?v=1ch8KYiqSNg
freosam 7y ago
Whitworth's method of scraping (mentioned in this article) is explained in this 1858 paper: https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mechanical_Subjects/A_Paper_on_Plane_Metallic_Surfaces_or_True_Planes https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mecha...
leni536 7y ago
Have three planes with curvatures c1, c2 and c3. Scraping 1 against 2 results in curvatures: c1' = (c1-c2)/2 and c2'=(c2-c1)/2 (proof is left as an exercise to the reader). The calculation is similar for scraping 1 against 3 and 2 against three. The three scraping operations define three linear transformations on the curvature vector c=(c1, c2, c3): A, B and C. The article describes a cyclic permutations of these operations, so the final curvature is (A.B.C)^n*c. The absolute value of the largest eigenvalue of A.B.C determines the efficiency of this procedure, it's 1/sqrt(8). It means that by each cycle the slowest mode decays to its 1/sqrt(8) multiple. By each step it decays by (1/sqrt(8))^(1/3) = 1/sqrt(2) on average. Question: Is there a more efficient procedure?
205guy 7y ago
The YouTube channel oxtoolco has a video showing lapping of surface plates. Not the same as hand scraping, but the principle of using a reference surface is similar, and the master plate looks like the illustrations in this 100-year old document. Plus I think with modern synthetic diamond abrasives, you can directly lap the plates against each other. Lapping starts at 17:40 (they do surface measurements first): https://youtu.be/EWqThb9Z1jk https://youtu.be/EWqThb9Z1jk I am no machinist, but I like the glimpse into the hobby/profession shown on channels like this and others that comments have mentioned. In the video, the channel owner hires a company to service his stone regency plates, so there is an expert who comes and uses specialized tools to measure and then flatten the plates (and certify them too). You can see and experience the expertise that the guy has with these physical systems, yet it’s just one niche job in a huge engineering tool chain. It really made me think a lot about metal machining and fabrication, and how those rely on fundamental measurements and properties such as flatness.
xtiansimon 7y ago
While I find random publications--such as this page from _Audels machinists and tool makers handy book_, page 245 Fig 10 & 11 'Method of shifting belt of a counter shaft drive lathe while running...' [1]--about industrial processes utterly fascinating, this one on the Truly Flat Plane is abstruse. [1]: https://babel.hathitrust.org/cgi/pt?id=wu.89089662951&view=1up&seq=281 https://babel.hathitrust.org/cgi/pt?id=wu.89089662951&view=1...
Corvus 7y ago
I am reminded of a problem faced by geometers in antiquity of building straightedges; how do you draw a straight line when you have no existing straight line to copy from? The book “How Round Is Your Circle?” includes some interesting solutions to this problem. https://www.goodreads.com/en/book/show/2449815 https://www.goodreads.com/en/book/show/2449815

163 points by rkagerer 7y ago

Same content, but this link might be a little quicker: https://archive.org/details/engineeringremin00port/page/233/mode/1up https://archive.org/details/engineeringremin00port/page/233/... If you're interested in the topic, here's some more discussion: https://www.practicalmachinist.com/vb/general/possible-make-grind-polish-flat-surfaces-manually-295976/#post2441051 https://www.practicalmachinist.com/vb/general/possible-make-... Skilled hand scrapers... can generate plane surfaces accurate to 40 millionts per foot. The same method applied to lapping of glass can generate flats to 1/2 millionth per foot... The average guy working in an open shop careful of cleanliness and uncontrolled heat input to the work will find 0.0005 per foot readily achievable and 0.0002" per foot with a little more care and effort.

HeyLaughingBoy 7y ago
Without even opening that second link I can guess that Forrest Addy chimes in at some point :-) [edit] haha. That was even his quote :-)

wcunning 7y ago

I got into machine rebuilding after buying a reasonable 1950's machine shop worth of equipment a few years ago when I started in the auto industry after my master's degree. I happened onto a Craigslist ad of a machine rebuilder going out of business near the office and I picked up basically the whole kit -- cast iron surface plates, power and hand scrapers, bluing medium, etc etc. It took another 6 months before I ran into a guy who was willing to teach me to use all that equipment, up near Flint. He spent a whole career doing fitting and repair for a CNC dealer traveling all over the state and a piece of the rest of the midwest. He was just about the nicest guy I've ever done business with, and he supplies equipment and advice to a huge percentage of the Youtube machinist crowd, plus he saved me the couple grand it would have cost to go take one of Rich King's classes. All in all, this is a great skill that will persist for a long time, longer than you might think, even if modern machines use replaceable linear rails rather than scraped ways. If you feel like taking it up, watch one of the many Youtube videos from Stefan Gotteswinter or Keith Rucker. Look into the equipment, but think about building your own carbide sharpener, scraper and handle.

Blackthorn 7y ago
What's the name of his YouTube channel (assuming that's what you meant by supplies advice)?
- kalak451 7y ago
  I assume he is talking about Richard King. I don't think he has his own channel. but as mentioned Stefan Gotteswinter and Keith Rucker both have videos of the scraping skills they learned from him. (Rucker has actually hosted several of King's classes in his workshop) edit: I clearly misread the end of OP's post. Definitely not talking about Richard King.
  - Balgair 7y ago
    Chiming in to say ThisOldTony is alright. https://www.youtube.com/user/featony https://www.youtube.com/user/featony Stefan Gotteswinter: https://www.youtube.com/user/syyl https://www.youtube.com/user/syyl Keith Rucker: https://www.youtube.com/user/ksruckerowwm https://www.youtube.com/user/ksruckerowwm Richard King: https://www.youtube.com/results?search_query=Richard+King https://www.youtube.com/results?search_query=Richard+King
  - wcunning 7y ago
    He did years of scraping before he met Rich, but he did take a Rich King class to learn power scraping. Made it easier to justify skipping the expensive class for me.
- wcunning 7y ago
  He doesn't have one, but Solid Rock Machine did a tour of his shop a while ago. He mostly supplies advice and equipment through the grapevine and Practical Machinist.

joncrane 7y ago

This is fascinating. I don't know all the terminology perfectly, but I get the gist. I love how transparent and ingenious they are. (BTW did anyone else think of the Rick and Morty episode where Rick builds a "perfectly flat" platform for Morty to experience?)

doomjunky 7y ago
I'm familiar the the bubble, Morty. I also dabble in precicion, and if you think you can even approach it with your sad, naked, caveman eyeball and a bubble of f* air, you're the reason this species is a failure, and it makes mis angry! Experience True Level!

0xff00ffee 7y ago

I read this on a whim and now I'm amazed: I never considered algorithms as part of mechanical engineering. Very clever. And in a pedantic reading of Richard Dawkins, this is the kind of "meme" he was talking about.

Animats 7y ago
I never considered algorithms as part of mechanical engineering. Oh, yes. Metal work is all about calculating. The classic book is "Machinery's Handbook", published for 105 years. Machinist's toolboxes often have a built-in space for it.
- defterGoose 7y ago
  The "bible" though, is "Foundations of Mechanical Accuracy" by Moore. Machinery's Handbook is more of a practical reference used in the shop (like when you want to know what a certain spline or thread profile should look like), whereas Foundations is more theoretical.
  - 0xff00ffee 7y ago
    Is there a good book for sheet metal bending? There are lots of things I'd like to make, but when I think through it, the bends always run into each other (at least in my head). Which is why I haven't bought a break yet. Would love to learn the basics about tools, marking, cutting. (My cuts always drift, and deform the metal, would like to learn how to NOT do that.)

nohuhu 7y ago

Thanks for submission, a really interesting read! I'm into restoring old woodworking machinery, and hand scraping is one of the methods for truing lathe ways that I've read about. Could possibly be required for the Walker-Turner lathe I'm working on. :)

mauvehaus 7y ago
Also a woodworker here. I have to ask: how bad are the ways on this lathe and how could they get worn? Moving the banjo and tailstock on a wood lathe shouldn't wear the ways the way the routine use of a metal lathe wears the ways.
- analog31 7y ago
  The worst thing is neglect, rust, and accidental damage. In low volume use, e.g. proto shop or home shop, the ways should be virtually eternal. Keep them covered, clean and oiled.
- nohuhu 7y ago
  I haven't gotten to measuring wear on the ways yet, don't think I'll need to scrape them but that's a possibility. This is a pet project of mine, a barn find that was in a pretty bad shape when I got it: rusty, crusty, with missing parts and undesirable modifications by previous owners. Specifically the ways are pitted from rust; worse in places that were exposed to the elements. I'll have to try and measure the effect of this pitting on tailstock positioning. I don't think banjo positioning is going to be affected, the ways are not that bad. But then there's always the obsession with perfection, so who knows. :) I have a soft spot for pre-1950 Walker-Turner machinery, their aestetics are off the charts; I'm trying to restore this lathe to its former glory, or even better. Not quite a classic car showroom condition but as close to it as I can get without spending a fortune in time and money. :) The current stage is painting; turned out it's pretty tricky to spray glossy enamel so it would level out smooth! Especially in our cool and humid coastal climate, paint takes a while to dry and even longer to fully cure so the process is quite challenging. Not to mention the countless hours it took to grind out casting imperfections, apply bondo filler, sand it, etc etc. I thought I was getting into woodworking but found that restoring machinery is lots of fun in its own right, and nothing compares to the satisfaction of using a well made and beautifully restored vintage tool. Especially when I'm the one who did the restoration. :)

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anateus 7y ago

Folks who enjoyed this may appreciate Simon Winchester's recent book The Perfectionists, where he covers this method amongst other things. Core to the idea of perfection are machine tools, what we in software often refer to as a toolchain. The way the toolchain revolution allowed us to go from intricate one off clockwork to reliable longitude measurement, better locks, and industrialized machinery parallels compilers, operation systems, etc.

mauvehaus 7y ago
I thought he went rather quickly from some of the earliest processes (boring, for instance) to stuff that's so abstract as to be removed from anybody's practical experience (disregarding metrologists, of course) and then goes farther into philosophical matters than I found interesting. I would have much more a book that stayed in the realm of machine tools for about half the content, covering the process of bootstrapping precision in the pre-electronic era. An interesting third quarter could discuss the limits of precision in practical mass manufacturing and the ways we work within tolerances that are economical. The engine block and head of an internal combustion engine have a large and irregularly-shaped mating surface that's subjected to repeated heating and cooling cycles. How flat do they have to be for a gasket to seal them effectively? The last quarter of the book could cover developments in the era of CNC, and talked about the interplay between electrical components (e.g. stepper motors) and mechanical components (e.g. lead screws, timing belts, etc) and what we gain and lose in using those type of processes. Boring a hole for example, remains more accurate than CNC'ing it on a mill because good control when one x or y approaches zero becomes difficult both mechanically and mathematically. Anybody interested in this sort of thing might enjoy "How Round is your Circle", by the way.
Ericson2314 7y ago
I wish we took as good care of our tools as they did!

NikolaeVarius 7y ago

Not flat but similar idea https://www.cmog.org/article/hale-reflecting-telescope-palomar https://www.cmog.org/article/hale-reflecting-telescope-palom... Imagine hand grinding telescope lenses https://www.youtube.com/watch?v=MjUcBWYVF9s https://www.youtube.com/watch?v=MjUcBWYVF9s

hinkley 7y ago
From what I understand, hand-grinding small mirrors is down to process as much as skill. Solid grinding compounds, once they start to wear, end up wearing themselves too. If you keep the pieces moving just so, you can eyeball a rough radius with the grinding material, and it will smooth itself out while smoothing the glass until they mate up. Basically once you have a wheel with a high precision axle, you can make lots of curves or straight lines.
HeyLaughingBoy 7y ago
Thanks for the reminder. About 25? years ago I bought the book How to make a Telescope and two six-inch blanks and grinding materials and set off to grind my own mirror. I never finished (it was super boring and really humid in the basement of my rented apartment) and I have no idea where the "blanks" are anymore but now I live in an area well outside of town where I can see the Milky Way with the naked eye if my neighbors turn their lights off so it might not be a bad project to restart. Bonus: I have the room to build a grinding machine so I don't have to do it all by hand.
CliffStoll 7y ago
Today, large telescope mirrors are finished using ion figuring: neutral atoms are shot at the surface of the mirror blank, for a precision ablation of a few angstroms. This works especially well for hexagonal mirror segments, because you can control the surface shape right to the edge of the mirror. Mechanical figuring (using ceramic or glass blanks) has troubles near the edge.
Sharlin 7y ago
Hand grinding telescope lenses (well, usually mirrors) is a fairly accessible hobby; you need patience more than anything else. It’s amazing how little technology you need to attain sub-micrometer precision.

riskneutral 7y ago

There's a guy who used to give classes on hand scraping and machine rebuilding https://www.youtube.com/watch?v=TH7tZZdUr2w https://www.youtube.com/watch?v=TH7tZZdUr2w

paypalcust83 7y ago

It's interesting to get more precise and accurate machines out of the ones came before. These days, if you want to get milling and grinding down to 1 micron without lapping using only your own expertise and some parts from eBay (air bearings and precision-ground slabs): https://youtu.be/sFrVdoOhu1Q https://youtu.be/sFrVdoOhu1Q The creator (Dan Gelbart) demonstrates nitrogen-tight parts without bearings, and claims zero wear or lubrication needs. #AvEclub

jbay 7y ago
It wasn't nearly so easy. Dan hand-scraped in several surfaces on the lathe; for example the headstock, to get the axis parallel to the ways, and so on.

ryanobjc 7y ago

I've been doing woodworking with handtools, and it's amazing what 90 year old tools can do. I bought an old stanley plane in good condition, and was able to start pulling cuttings that are 4/1000" easily. My modern lee valley plane is even easier to set, and I just did a 1/1000" shaving. That means you can surface a piece of wood to 1/1000th of an inch. This is the kind of accuracy you typically associate with modern CNC machining. Wood is an interesting medium - it's always in motion so it's in some ways more challenging than working with steel. You can't just machine and glue wood together if you want to make something that'll last for centuries, like old furniture used to. The art is still alive, and I encourage people to check it out!

dekhn 7y ago
I think most people would say, although you might observe such sizes when cutting wood, temperature and humidity will swamp out those precisions within a day or two.

dekhn 7y ago

One of my favorite parts of Feynman's brilliant talk about the limits of minaturizing mechanical devices, "There's plenty of room at the bottom": """If, for instance, having made a small lathe with a pantograph, we find its lead screw irregular – more irregular than the large-scale one – we could lap the lead screw against breakable nuts that you can reverse in the usual way back and forth until this lead screw is, at its scale, as accurate as our original lead screws, at our scale. We can make flats by rubbing unflat surfaces in triplicates together – in three pairs – and the flats then become flatter than the thing you started with. Thus, it is not impossible to improve precision on a small scale by the correct operations. So, when we build this stuff, it is necessary at each step to improve the accuracy of the equipment by working for awhile down there, making accurate lead screws, Johansen blocks, and all the other materials which we use in accurate machine work at the higher level. We have to stop at each level and manufacture all the stuff to go to the next level – a very long and very difficult program. Perhaps you can figure a better way than that to get down to small scale more rapidly.""" Many ideas contributed to the modern process of 5nm lithography, but having flat surface plates whose precision is determined by the correct application of operations rather than an external standard has turned out to be one of the most profound. Now, of course, you can buy a granite surface place with accuracy exceeding almost anything available 100 years ago, for $30. And there are youtube videos of flat surface aficinados who scrape their own.

Animats 7y ago
Making a precision lead screw is an important step. Maudslay invented the modern metal lathe. His original, from around 1800, is in the Science Museum, London, and it has most of the features of a metal lathe of 1900. Or today. A screw cutting lathe requires a good lead screw as its reference. Maudslay invented a "screw origination machine"[1], a clever special-purpose device for making a more accurate screw than the one you have. It only cuts soft metal, so the screw it makes is used in a second lathe to make one in hard steel. This is another of the key steps in bootstrapping to precision. Early precision work was limited to flat things and round things. Take a look at a steam locomotive from around 1900. Every surface that has to be held to a tight tolerance is flat or round. That's because the precision tools of the era were the planer, lathe, and drill. The general purpose milling machine came later. Incidentally, this is the real reason manholes were round. In the great era of city sewer-building, you could make round metal manhole covers easily, by casting and a quick lathe pass. The ring into which they fit could also be easily finished on a lathe. Making an iron rectangular frame and a lid to fit it would have been a much harder and more expensive job. [1] https://gracesguide.co.uk/Henry_Maudslay:_Machine_Tools https://gracesguide.co.uk/Henry_Maudslay:_Machine_Tools

oyebenny 7y ago

This reminds me of that Rick and I'm already seeing where Dr Sanchez shows Morty what absolute level is.

ivankirigin 7y ago
Here for this comment. For those who don't know: https://www.youtube.com/watch?v=IMeain2cvBM https://www.youtube.com/watch?v=IMeain2cvBM

lsllc 7y ago

If you're interested in metal working/machining and like "Dad jokes", check out This Old Tony on YouTube: https://www.youtube.com/channel/UC5NO8MgTQKHAWXp6z8Xl7yQ https://www.youtube.com/channel/UC5NO8MgTQKHAWXp6z8Xl7yQ Here's his surface grinder rebuild which includes milling and hand-scraping various surfaces to get them dead flat. https://www.youtube.com/watch?v=RjwKQCiDgBQ https://www.youtube.com/watch?v=RjwKQCiDgBQ He's super talented and the videos are fun!

gorgoiler 7y ago
> dad jokes ”Well this isn’t the freshest mill in the world but I figured if I was going to bite off more than I can chew I might as well go the whole nine yards” Hah. You weren’t kidding.
jedimastert 7y ago
> https://www.youtube.com/watch?v=RjwKQCiDgBQ https://www.youtube.com/watch?v=RjwKQCiDgBQ Oh my goodness, is that what his older videos looked like? He's grown an incredible amount as a storyteller and video producer. Wow
- lsllc 7y ago
  He really has, his newer stuff is epic! In these dark times, he's kept me quite entertained!
jjoonathan 7y ago
You just clicked on a video about making a mostly-square block of metal even more square. (pause) Just saying. I was hooked from the start!
Prcmaker 7y ago
I get great enjoyment out of Tony, but the dry humour of Mr Pete really does it for me. https://www.youtube.com/channel/UCKLIIdKEpjAnn8E76KP7sQg https://www.youtube.com/channel/UCKLIIdKEpjAnn8E76KP7sQg

tempestn 7y ago

This video in Dan Gelbart's 'Building Prototypes' series is a great look at producing highly accurate (flat) surfaces. https://www.youtube.com/watch?v=cwdoUjynpEk https://www.youtube.com/watch?v=cwdoUjynpEk Edit: the scraping technique in this PDF is shown at about 13:00.

cartoonfoxes 7y ago

I've done this myself recently, and it's a worthwhile experience if you have the patience for it. If the short treatise in the OP interests you, I would suggest the book 'Foundations of Mechanical Accuracy', PDF easily available though I won't link here. I can also recommend the bible of hand scraping, 'Machine Tool Reconditioning and Applications of Hand Scraping' otherwise known as the Connelley Book.

csours 7y ago

Abom79's hand scraping experience: https://www.youtube.com/watch?v=pT5KWvglp_c https://www.youtube.com/watch?v=pT5KWvglp_c

rfrey 7y ago

People wanting a full treatise on hand scraping should look into Machine Tool Reconditioning by Connelly, available on the used market and the usual other sources. A close runner up for books is Foundations of Mechanical Accuracy by Moore. If you can get a physical copy of the latter, and can afford it, you should - the photographs are magnificent.

Prcmaker 7y ago

While I was studying engineering I worked in a machine shop. In that time I hand scraped or lapped a good few bearings and surfaces. Fast forward six years, researching optical sensing, and I've had to pull those old tricks out of the bag recently. For some reason, of all the skills and techniques I've learned, manual or academic, making a properly flat surface remains the most satisfying.

GaryNumanVevo 7y ago

Maybe a home machinist can answer this question. If I'm on a desert island, I know how to make a flat plane via ABC grinding. How do I make a right angle? Do I decide on a measure, grind 12 gauge blocks to the same height and make a 3-4-5 triangle?

defterGoose 7y ago
Same method essentially. You need three roughly square pieces that are checked for bearing against each other repeatedly, but this time you also have intermediate steps of checking each face for flatness against the master.
SAI_Peregrinus 7y ago
You make a box straight edge. First, you make a surface gauge. A heavy weighted base with a pointer you can vary in height and distance from the base. You scrape/grind the base flat using a surface plate as reference. You take something you think is roughly square (a long rectangular prism is good), scrape/grind one face flat with one of your surface plates. We'll call this face 1. Then scrape/grind the opposite face flat, and using the surface gauge to check height (position the box with face 1 down on a surface plate. Position the gauge next to it, with the point touching face 2 somewhere. Slide the gauge back and forth: if it gets pushed up face 2 is tilted up in that direction with respect to face 1. If a gap forms under the tip, it's tilted down.) and thereby get it parallel with face 1. Then scrape/grind two faces which are adjacent to each the first and opposite each other flat. You now have a shape like \_/ or |_/ or such, though with a top parallel to the bottom. You stick your surface gauge along one side, touching at the base and at some point near the top of that side with the indicating point. You then turn the WIP straight edge box 180 degrees, and see if the other side touches the indicating tip or the base first. The distance from touching both at once tells you how far out of parallel that side is from the first. You then proceed to scrape them both to be a bit more flat and parallel. Then you turn the box onto its top (face 2) and repeat that. Using 180 degree rotations in two dimensions will get you a good square. Another thing that can be used as a check (if you can draw) is to build a compass and a straightedge. Side 1 of your box is a good straightedge! You can then use basic geometric construction to make a right angle, and can compare any finished box to that angle.

WalterBright 7y ago

When I was in high school, it was popular among some of the students to make telescope mirrors. The technique of hand-grinding them to incredible perfection was both simple and astounding.

WalterBright 7y ago

I remember one of the "ancient aliens" TV shows back in the 70s which claimed that the precision with which Inca masons fitted stones together was impossible without alien technology. Then an archaeologist showed how fit two stones together with the same precision in about a half hour, using no tools at all. Just rubbing and banging them together. I asked my mom once how the Egyptians could have possibly made the pyramids straight. She replied pull a long string tight, that's the reference. Figuring I had her this time, I asked how they could have leveled the pyramid foundation. She said dig a trench and fill it with water. The water level forms the reference. Mom: 2 Me: 0

Gibbon1 7y ago
I remember an interview with an archeologist that studied the Nazca Lines. She said one year she had a grad student who was a farm boy. He showed her how to draw a long straight line by setting up a stick a 1000 feet away and then just walking towards it while dragging a another stick behind him. It was perfectly straight. It's basically the same as the old draftsman's trick for drawing a straight line.
- wrycoder 7y ago
  What is that trick?
  - Gibbon1 7y ago
    The trick is mark the end of the line and then draw towards it. With practice you can draw eyeball straight lines.
    - mturmon 7y ago
      It’s quite accurate, somewhat hard to believe until you try it a few times. Good enough for many layout tasks if you’re drawing a reference line to cut to, for example. Also works for cutting straight lines with an exacto knife.
7y ago

aazaa 7y ago

Reminds me of this guy, who hand-planes engine cylinder heads using a block of wood, straight edge, sandpaper, and feeler gauges: https://www.youtube.com/watch?v=1ch8KYiqSNg https://www.youtube.com/watch?v=1ch8KYiqSNg

freosam 7y ago

Whitworth's method of scraping (mentioned in this article) is explained in this 1858 paper: https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mechanical_Subjects/A_Paper_on_Plane_Metallic_Surfaces_or_True_Planes https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mecha...

leni536 7y ago

Have three planes with curvatures c1, c2 and c3. Scraping 1 against 2 results in curvatures: c1' = (c1-c2)/2 and c2'=(c2-c1)/2 (proof is left as an exercise to the reader). The calculation is similar for scraping 1 against 3 and 2 against three. The three scraping operations define three linear transformations on the curvature vector c=(c1, c2, c3): A, B and C. The article describes a cyclic permutations of these operations, so the final curvature is (A.B.C)^n*c. The absolute value of the largest eigenvalue of A.B.C determines the efficiency of this procedure, it's 1/sqrt(8). It means that by each cycle the slowest mode decays to its 1/sqrt(8) multiple. By each step it decays by (1/sqrt(8))^(1/3) = 1/sqrt(2) on average. Question: Is there a more efficient procedure?

205guy 7y ago

The YouTube channel oxtoolco has a video showing lapping of surface plates. Not the same as hand scraping, but the principle of using a reference surface is similar, and the master plate looks like the illustrations in this 100-year old document. Plus I think with modern synthetic diamond abrasives, you can directly lap the plates against each other. Lapping starts at 17:40 (they do surface measurements first): https://youtu.be/EWqThb9Z1jk https://youtu.be/EWqThb9Z1jk I am no machinist, but I like the glimpse into the hobby/profession shown on channels like this and others that comments have mentioned. In the video, the channel owner hires a company to service his stone regency plates, so there is an expert who comes and uses specialized tools to measure and then flatten the plates (and certify them too). You can see and experience the expertise that the guy has with these physical systems, yet it’s just one niche job in a huge engineering tool chain. It really made me think a lot about metal machining and fabrication, and how those rely on fundamental measurements and properties such as flatness.

xtiansimon 7y ago

While I find random publications--such as this page from _Audels machinists and tool makers handy book_, page 245 Fig 10 & 11 'Method of shifting belt of a counter shaft drive lathe while running...' [1]--about industrial processes utterly fascinating, this one on the Truly Flat Plane is abstruse. [1]: https://babel.hathitrust.org/cgi/pt?id=wu.89089662951&view=1up&seq=281 https://babel.hathitrust.org/cgi/pt?id=wu.89089662951&view=1...

Corvus 7y ago

I am reminded of a problem faced by geometers in antiquity of building straightedges; how do you draw a straight line when you have no existing straight line to copy from? The book “How Round Is Your Circle?” includes some interesting solutions to this problem. https://www.goodreads.com/en/book/show/2449815 https://www.goodreads.com/en/book/show/2449815