Thoughts on building a lathe

**Ro@drunner** · Nov 14, 2018, 09:53 PM

I've been wanting to build a lathe for a long time now and am starting to get some ideas going about which direction I intend on going about it. I like the idea of a small lathe but understand some of the pitfalls associated with going small, so I'm going to try and resist going too small.

After looking around quite a bit and checking out many home builds here and on youtube I've kind of settled on the idea of doing a concrete style build. I think it will offer the most solid machine that I can create with the limited resources that I have at my disposal.

The most difficult choices I'm faced with at the moment are concerning the ways and head/tailstock bearing arrangements. The first thing that come to mind is the ease of building of the arrangements involved. Then there is the aspects of rigidity and precision I'm hoping to achieve with the finished machine.

As far as ways go, I've been tossing around the idea of going with an angle iron filled with concrete sort of arrangement. There is also the idea of going with round stock as well but I'm more drawn to the angle iron arrangement. Also note that the idea of concrete is something that I use relatively loosely. I'm considering an epoxy aggregate arrangement as well for some of the pieces.

Next up on my mind is bearing arrangement for the headstock. I'm considering two possibilities at the moment which include tapered roller bearings and then poured babbit bearings. I'm looking to keep run out at a minimum. I'm thinking the poured bearings may be the ticket to keeping things the tightest.

I'd like to hear thoughts and comments from others on the matter of building up a lathe.

**mwmkravchenko** · Nov 15, 2018, 06:19 PM

Babbit can give you pretty tight tolerances at the limit of RPM.

A concrete lathe is doable. So is an epoxy granite type of a base. But the end cost is not going to be small in terms of getting a fully functioning machine.

Are you wanting to do this for a learning experience or to make a fully functioning machine for hobby use?

**Ro@drunner** · Nov 15, 2018, 09:23 PM

My thoughts on building a lathe revolve around the challenge of building one. It would be nice if the end product was capable of basic turning and drilling functions. The intended use is hobby and of course making more tool type projects. To call it full functioning would probably be a bit of a stretch though, but I'm not sure of how far i can push myself in building one up.

Though I will admit at this point I'm more in a thinking and planning on a possible lathe project rather than building one just yet. If it seems feasible for me i may just give it a try.

I had thought of babbit bearings for the headstock based on some recent experiments I made concerning the topic. I was surprised how well they turned out with relatively little effort on my part.

**threesixesinarow** · Nov 16, 2018, 06:46 AM

I picked up an old Bear brake lathe minus all its attachments years ago because it seemed to be a good start for a headstock, plus it had a neat little knee. It has a flat bottom with mounting flanges and holes for four bolts to hold it in place.

There seemed to be a lot of them last time I searched for lathes on Craigslist.

**Frank S** · Nov 16, 2018, 08:26 AM

Constructing machines using concrete as the medium for the bulk of the machine's body has been around for many years I probably should say a few centuries. Lathes are no exception During WWI huge long lathes were cast of concrete as a means to quickly constructing a large machine to machine the long shafts used in boats to drive the propellers and many other things RR rails were commonly used as the ways.
Here is a link to a small comparatively speaking lathe made of concrete
https://hackaday.com/2016/04/20/cast...t-of-concrete/
And here is the open source PDF plans for one
https://www.engineeringforchange.org...e-ver-1-10.pdf
He even has a utube channel with a 5 part series filming the construction this will bring up part 1

**mwmkravchenko** · Nov 16, 2018, 09:17 AM

I watched that series of videos. And I have been decently active on that concrete lathe forum that used to be on the Yahoo forums. That concrete mix in this video begged for more sand in the mix. The as sold concrete mixes are crushed aggregate only the sand acts as a bit of a filler in between the aggregate. I usually mix in about 50% sand and make up for the potential loss in strength by adding in a heaping shovel full of Portland cement. This casting is a first attempt. Not exactly stellar. A good cement mix will have the consistency of a good thick oatmeal. Not runny. And the cross sections can be a fair bit smaller and still posses a great deal of compressive strength.

There is a great channel on Youtube called Tinic LLC. This guy really shows how to make the least amount of concrete the strongest. Including post tensioning methods that make a great deal of sense in constructing a lathe bed and headstock of the greatest possible strength without making a one ton concrete casting.

Do yourself a favour if you want to go through with this and make the bed long enough to bolt a head stock onto the lathe bed. Being able to align it will be of great benefit later. Unless you are capable of doing line boring, then you can pretty much start off with constructing the headstock and slowly have the lathe make the lathe as per the Gingery methods. Parts of what he wrote in his lathe series has application in other lathe constructions as well.

**Ro@drunner** · Nov 16, 2018, 07:48 PM

Now were getting on to some good discussions. I have some good experience in making and doing concrete work. I agree on the point of having too much aggregate in this application would be less helpful. The biggest factor in the strength and quality of concrete mostly lies in using too much water in the mix. Generally speaking though using less water makes the mix stiff and hard to work. Which leads to the necessity of using vibration to move the mix and get the air out and get the mix of sand and aggregate properly placed. The concrete lathe pictured would have come out world's better had the builder tapped the sides of the forms with a mallet for a while during and after for a bit.

There are a variety of other things that easily be added into the mix as well. Plasticizer would have helped for the flowability of the concrete while keeping water content minimal. Also some fiber would be very helpful here as well, metal reinforcement similar to chopped fiber is also available.

My thoughts on using concrete in a build mostly revolve around mass and vibration reduction of the finished lathe rather than a primary structural element. Another big sticking point for me is the adjustment of headstock, tailstock and ways to get everything square and straight. Then being able to keep it all in alignment over time. I think I'm starting to see some possible solutions to the challenges in building a useable machine.

**mwmkravchenko** · Nov 19, 2018, 06:32 PM

If I was going down this track I would be thinking a lot about setting up a rebar cage and a couple of flats in mild steel bar that would be embedded into the concrete and leave you with a surface that could be drilled and tapped, as well as ground to finish dimensions. There are a few way to make a lathe bedways. What is in the plans for the concrete lathe is the result of cheapest and easiest ideas, not really the most durable or accurate. The possible solid backing and resistance to vibration that a heavy mass like concrete can offer will be quickly negated if any part of the lathe is flimsy and allows easy movement. Standard lathe construction of having a very solid bed with equally solid travel ways is the key. The bedways do not need to be "V" ways. Rectangular ways are perfectly workable. Just the beginnings of food for thought.