
Hand Scraping a Truly Flat Plane (1908) [pdf] - rkagerer
http://www.galleyrack.com/images/artifice/machine-shop/surface-finishing/hand-scraping/engineeringremin00port-pp233-237-img303-307-production-of-an-original-surface-plate.pdf
======
dekhn
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
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)

~~~
analog31
There's a lovely article from 1886, written by Henry Rowland, who made the
first decent diffraction gratings. He wrote about his process of lapping the
screw threads to take out minor local errors. His screw didn't have to do a
lot of work, but it had to be damn uniform.

[https://en.wikisource.org/wiki/Encyclop%C3%A6dia_Britannica,...](https://en.wikisource.org/wiki/Encyclop%C3%A6dia_Britannica,_Ninth_Edition/Screw)

~~~
Stratoscope
That is a marvelous article, thank you!

This sentence under _Mounting of Screws_ rings true today:

> The principle which should be adopted is that no workmanship is perfect; the
> design must make up for its imperfections.

------
wcunning
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
What's the name of his YouTube channel (assuming that's what you meant by
supplies advice)?

~~~
kalak451
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
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)

------
rkagerer
Same content, but this link might be a little quicker:
[https://archive.org/details/engineeringremin00port/page/233/...](https://archive.org/details/engineeringremin00port/page/233/mode/1up)

If you're interested in the topic, here's some more discussion:
[https://www.practicalmachinist.com/vb/general/possible-
make-...](https://www.practicalmachinist.com/vb/general/possible-make-grind-
polish-flat-surfaces-manually-295976/#post2441051)

 _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
Without even opening that second link I can guess that Forrest Addy chimes in
at some point :-)

[edit] haha. That was even his quote :-)

------
WalterBright
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
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
What is that trick?

~~~
Gibbon1
The trick is mark the end of the line and then draw towards it. With practice
you can draw eyeball straight lines.

~~~
mturmon
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.

------
lsllc
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!

~~~
jedimastert
>
> [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
He really has, his newer stuff is epic! In these dark times, he's kept me
quite entertained!

------
anateus
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
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.

------
leni536
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?

------
ryanobjc
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
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.

------
205guy
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.

------
Prcmaker
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.

------
NikolaeVarius
Not flat but similar idea

[https://www.cmog.org/article/hale-reflecting-telescope-
palom...](https://www.cmog.org/article/hale-reflecting-telescope-palomar)

Imagine hand grinding telescope lenses

[https://www.youtube.com/watch?v=MjUcBWYVF9s](https://www.youtube.com/watch?v=MjUcBWYVF9s)

~~~
Sharlin
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.

~~~
DanBC
I like this video from John Dobson about handmade telescopes, where he builds
a complete telescope including hand grinding the mirrors.
[https://www.youtube.com/watch?v=snz7JJlSZvw](https://www.youtube.com/watch?v=snz7JJlSZvw)

------
tempestn
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.

------
joncrane
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
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!

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

~~~
ivankirigin
Here for this comment.

For those who don't know:
[https://www.youtube.com/watch?v=IMeain2cvBM](https://www.youtube.com/watch?v=IMeain2cvBM)

------
csours
Abom79's hand scraping experience:
[https://www.youtube.com/watch?v=pT5KWvglp_c](https://www.youtube.com/watch?v=pT5KWvglp_c)

------
rfrey
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.

------
nohuhu
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
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.

~~~
nohuhu
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. :)

~~~
mauvehaus
Ah, I hadn't thought of rust. Good call. My experience with the tops of my
table saw and band saw is that as long as they were ground pretty smooth
originally, they don't really pit and I can scrape the superficial rust off
and have a pretty good surface. They were, however, stored inside-ish. I could
see a barn find in bad shape suffering a lot more than that.

I love the look of the old W-T stuff too, but I've somehow become a Delta man
for the stationary tools, probably because of the ubiquity of their old stuff.
None of mine is old enough to have the _really_ nice castings. My Unisaw is
from '78, and it has the sheet metal base rather than the old cast one. My 14"
band saw is (I think) pre-war, but the original buyer didn't spring for the
cast art-deco base :-(

Do you have pictures or a build thread on this project? I'd love to see it.
And kudos to you for doing the paint and cosmetic stuff. There is nothing I
hate more than doing paint.

My Unisaw is covered in _years_ of (somebody else's) overspray. I've stripped
it off the chromed fence rails because it was interfering with it working, but
the cabinet? Screw it. I can live with it. My 14" drill press, however was
flaking off (somebody else's) 3 or more poorly applied coats onto me and
anything I drilled. I stripped and repainted that, but that's how bad it has
to be for me to entertain painting. The paint job is not what anybody would
call flawless, but at least it isn't coming off :-D

~~~
nohuhu
> I could see a barn find in bad shape suffering a lot more than that.

Yeah well, in between being a bottom feeder and looking for fun, machines
usually come to me as project pieces rather than usable tools. :) I'd never
opted to restore any of these rust buckets if I'd depend on them to do
woodworking for a living; that said, the purpose of a hobby is to occupy my
mind and give me a challenge that is rarely encountered in my day job anymore.
So, the rustier, the better. :)

> I've somehow become a Delta man for the stationary tools, probably because
> of the ubiquity of their old stuff.

I can definitely relate to that, W-T makes a minority of my resto projects.
Most of them are Delta as well, as I'm looking to build myself a fully
equipped vintage woodworking shop. I'm almost there in fact, as several
projects are nearing the assembly stage: a '64 Unisaw, a '52 HD Shaper (going
in tandem with the Unisaw), a '54 14" bandsaw, a '60 combo sander, a mid-50s
LD shaper, and a '42 6" jointer that I got for free in a total rust-bucket
condition. _That_ one was a challenge in itself, especially the motor.

It's just Walker-Turner machines are so beautiful, they're special. Next up
after the lathe is a 1939 16" bandsaw, the final quest machine that I acquired
last fall. I'll have to fight scope creep real hard on that one...

> My 14" band saw is (I think) pre-war, but the original buyer didn't spring
> for the cast art-deco base :-(

Ye shall seek and ye shall find, if you want to. :) Besides trawling your
local Craigslist (that's where I find my projects), sign up on
[http://www.owwm.org](http://www.owwm.org) and post an ad in BOYD forum. Cast
iron bases do come up for sale somewhat regularly. Beware that even looking at
that website is _very_ dangerous, slippery slope ahoy. ;)

> Do you have pictures or a build thread on this project? I'd love to see it.

I don't usually take pics of the resto projects... I guess I'm just lazy. If
you're into vintage tool porn, check out the OWWM community I linked above,
and its sister site
[http://vintagemachinery.org](http://vintagemachinery.org). Lots of drool
inducing pics there, I really cannot add anything that hasn't been done
already. :)

> The paint job is not what anybody would call flawless, but at least it isn't
> coming off :-D

That's usually enough for many cases... If a machine doesn't have a
sentimental value, why, just refurbing it to acceptable mechanical condition
is par for the course. That's what I did with my current set of machines; no
offense to Grizzly but their utilitarian cabinet saw aestetics do not really
justify the amount of work that goes into stripping and repainting. A vintage
Unisaw, on the other hand... I had to learn how to do cabinet scale
electrolysis derusting, some basic metalworking, spray painting techniques,
not to mention mechanical and electrical challenges. Heaps of fun! :)

Checked out your website... Wow. I have a long, long way ahead to that kind of
woodworking projects. ;)

~~~
mauvehaus
Oh dear, another OWWM'er on HN :-) I lurk, but I mostly try to avoid that
rabbit hole unless I'm trying to solve a specific problem. Turns out, I waste
enough time on the internet already without drooling over the work people do
there restoring old machines to better-than-new condition. Seriously, some of
those folks are nuts (as you well know).

It sounds like you've got a nice shop going. I'm a little jealous. My
stationary tools are actually stashed in a literal barn right now because I no
longer have a basement to put a shop in. I work out of a makerspace, but
that's closed due to present conditions, so I moved my bench into my living
room. I gave in and fetched my band saw, and it's now sitting on my covered
porch. And I have no blades for it at the moment. I'm getting a lot of
exercise milling lumber entirely by hand. Honestly, my arms are going to fall
off (or get huge) if the lockdown continues much longer.

I'm with you on the modern tools, by the way. On the vintage stuff, a lot of
companies really took pride in their industrial design (as you well know). And
even the totally utilitarian stuff has stylistic variation between
manufacturers. The only difference between Grizzly and current Powermatic
tools is the color of the paint. I remain hopeful that Festool having proved
that there's a market for higher-priced tools means that somebody will start
making nice stationary tools again.

That's probably a lot to hope for, though I recently discovered that
Northfield is still chugging along and so is Tannewitz. They're out of my
price range for the time being, but I hope they survive long enough for my
price range to intersect their prices! It's a real pity that Oliver is now yet
another nameplate on the same castings from overseas. The school I went to has
a vintage 166 jointer and a 399 planer that I'm in love with.

> Checked out your website... Wow. I have a long, long way ahead to that kind
> of woodworking projects. ;)

Thanks! I'm a long way from making actual money at this. I'm lucky to be
married to somebody very supportive. We'll see how the economy does. I have a
couple of paid projects that appear to be holding, and we'll see where things
go from there. I guess there's always software to go back to?

------
aazaa
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)

------
GaryNumanVevo
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?

~~~
SAI_Peregrinus
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.

------
riskneutral
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)

------
xtiansimon
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=1...](https://babel.hathitrust.org/cgi/pt?id=wu.89089662951&view=1up&seq=281)

------
Corvus
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)

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cartoonfoxes
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.

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freosam
Whitworth's method of scraping (mentioned in this article) is explained in
this 1858 paper:

[https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mecha...](https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mechanical_Subjects/A_Paper_on_Plane_Metallic_Surfaces_or_True_Planes)

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WalterBright
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.

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paypalcust83
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
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.

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0xff00ffee
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
_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
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
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.)

