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Building the most accurate DIY CNC lathe in the world [video]

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177 points pillars | 9 comments | 03 Sep 25 13:47 UTC | HN request time: 0.673s | source | bottom
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WillAdams ◴[03 Sep 25 16:02 UTC] No.45117323[source]▶
For folks who are not familiar w/ machine shops, the lathe is a fundamental tool in a shop, and is the only tool in a shop which can replicate itself --- there is even a book series which uses this conceit, the "Gingery Books":

https://gingerybookstore.com/

where Vol. 1 has one setting up an aluminum casting foundry in one's backyard, and Vol. 2 has one using it to make a lathe which is then used to either improve itself or make a better lathe, then one uses it to make the balance of the tools in a machine shop.

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jjk166 ◴[03 Sep 25 16:55 UTC] No.45118024[source]▶
A lathe can't actually replicate itself completely. Specifically, a lathe can only make ways smaller than its own cross slide's stroke. It would also be impossible to make a typical lathe bed on a lathe, though you theoretically could design an unconventional lathe bed that is possible to make on a lathe, even if grossly impractical.

The real starting point for machine precision is rubbing 3 granite plates together.

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1. IAmBroom ◴[03 Sep 25 17:01 UTC] No.45118087[source]▶
Lathes can certainly make cylinders, and a tube-based lathe bed is not a stretch.

A lathe can't replicate its own assembly, of course. It can't seat the spindle in the constraint bearings, for instance.

A CNC (without the word lathe) can make most of itself, and possible all. Nope: certainly all, if two of its dimensions fit within its work volume.

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2. jjk166 ◴[03 Sep 25 17:22 UTC] No.45118330[source]▶
But it can't make cylinders as long as its own guide ways.
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3. SAI_Peregrinus ◴[03 Sep 25 17:28 UTC] No.45118387[source]▶
Lathes can make cylinders, but not of unlimited length in one setup so they lose some accuracy making cylinders longer than their carriage travel. And their beds are by necessity longer than their carriage travel, since the carriage rides along the bed and isn't infinitely thin. They also can't make things like motor stator laminations, and you definitely need a motor for a replica of a motorized lathe. So lathes can't replicate themselves exactly.

Milling machines are also just lathes with a different orientation, an extra travel axis, and a motor optimized for higher speeds & lower torques, it's possible (and reasonably common) to use a mill like a lathe or a lathe like a mill in many cases. So "only machine" part is also a stretch.

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4. fapjacks ◴[03 Sep 25 19:11 UTC] No.45119425[source]▶
make me a truly flat surface
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5. HeWhoLurksLate ◴[03 Sep 25 21:18 UTC] No.45120521[source]▶
if the purpose is to bootstrap, you could also use something like a leather belt drive off a central shaft, which would require different power sources but ones that a higher percentage of could be made with a lathe
6. saintfire ◴[03 Sep 25 22:52 UTC] No.45121234[source]▶
It would be hard to make a human into a truly flat surface. I suppose if you have big enough granite blocks...
7. ekaryotic ◴[04 Sep 25 00:03 UTC] No.45121800[source]▶
most lathes have a hole in the chuck to feed the work through. so if the material is ground down by hand to a diameter small enough to fit in the hole then to be turned and then removed and flipped over it's possible.
8. vdqtp3 ◴[04 Sep 25 15:56 UTC] No.45128695[source]▶
> Milling machines are also just lathes

Mills are more limited than lathe - they don't have leadscrews, which are a necessity in the "build yourself" phase. You cannot make arbitrary threads with a milling machine. Thread milling gives some capability in this arena, but that's a CNC process.

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9. WillAdams ◴[04 Sep 25 21:01 UTC] No.45132138{3}[source]▶
One can make arbitrary threads (vertically) on a CNC using a single point cutter (limited by the height of the Z-axis/thickness of the stock which one can fit a tool over/into):

https://community.carbide3d.com/t/thread-milling-in-metal-on...

A manual lathe will often have a gearbox which allows cutting threads on it:

https://www.youtube.com/watch?v=E_KF3n3oo08