Homemade Lathe

Hi,

We're working on our own lathe design and are looking for feedback on it. Here's the page with pictures of the second design, which we changed it to after some feedback:
Open Source Lathe Design 2

We're using the entire shaft to mount the spindle, and the bolts from each section adjust the level to keep anything from coming loose and to add extra support. The far bolts can be set to the correct height and left there while the near ones can be loosened to adjust the slide distance and then tightened so that the far bolts keep their height set and the cross slide and tail stock keep their alignment with the spindle.

It's somewhat similar to these lathe designs:
Drummond
Scope
Kneller

I will write up a list of what we are going to be doing with the lathe later, so we can see if what we are building will meet our needs. Basically we're looking to bore out steam engine parts.

Pictures:
http://openfarmtech.org/images/3/3e/Lathe_2.0_1.jpg
http://openfarmtech.org/images/6/69/Lathe_2.0_2.jpg
http://openfarmtech.org/images/9/9c/Lathe_2.0_XYZ_3D_1.jpg

The hydraulic motor is powered by the LifeTrac engine (LifeTrac - Open Source Ecology).

Is it going to work? Are we missing anything critical?

Thanks for any feedback,

Jeremy

I have had a few lathes over the years and now have an 8" swing Atlas. But my favorite was a southbend 12".

I looked at your pictures and the links to the other sights and do have some feedback. First is that you need a very strong support for the headstock. Al tough you have the plates there they may not provide good dimensional control. Look at the pictures of the other lathes and you will see a common design of the head stock support being a massive casting. That's for a reason. If you like your design make the plate behind the chuck out of 2" thick stock and then box in the entire head stock support to prevent any chance of bending.

Same for the tailstock. It needs to be supported better. If you were building a wood lathe you would be OK but the forces on a metal lathe are huge, even when taking small cuts. Subtle shifts in the bending moments of the part and lathe would screw up the dimensions of the cut from end to end.

Another comment is on the center shaft that supports the tool post. The weakest point (or highest bending point) would be at the middle of the lathe, yet the ends would not deflect much as they are supported by the end brackets. This too would need to be a very sturdy piece unless you are not concerned about dimensional a accuracy over the length of the part. I'm not sure if your 1 7/8 bar stock would be strong enough. If you have the capability to run a bending calculation fix the ends of the shaft and put a 300# load in the center and see how much deflection you get. It better be .001" or less.

My old south bend had a ways (the part that the carriage/tool holder travels the length of the lathe on) that was an inverted "V" shape. By snugging down the carriage adjustments it was very accurate. The Atlas that I have now has rectangular ways and it will jiggle just a bit with heavy cuts (like 10 thousands on stainless.

If the bolts on the carriage are riding on the ways, you would want some sort of brass/bronze cups under them. Letting hard bolts drag over unhardened steel would wear pretty quick and screw up the accuracy in short order.

my 2 cents and input from 25 years as an engineer and lathe hobbyist.

Are you going to run it off the tractor PTO?

Looking at the bill for parts on the open source design#2....seems that you would be $1000 on your way to buying a real lathe.

stuartshomepc said:

Another comment is on the center shaft that supports the tool post.

Click to expand...

Jeremy, I totally agree with Stuart. I noticed right away the bar holding the tool rest appears very weak.

It's a clever design, with 4 bolts or dowels riding against the base, getting leverage to prevent twisting. However, the round bar or tube would have to be very robust to prevent it from deflecting side ways. If the 4 dowels could run in tracks, the only way it could go would be upward, and that wouldn't be a problem.

Too bad railroad rails aren't more precision. Man, that would make one heck of a solid track for your tool rest.

I would spend the money on a real lathe. Power feeds, threading, multiple speeds and a more ridgid machine are all built in to machines that are 50 years old or more and still have a lot of life.

That is a nice design but I think our technology passed that design many years ago. For what your are going to have in parts and machine work to make that lathe I think you can find a solid used one.

Dan

Yeah, $1000 will get you a nice used lathe, often with some tooling.

I bought this Clausing 4902 for $700 IIRC.

Another good place to look for used lathes is govdeals.com... this is an online auction for government surplus...I have a friend that bought a nice leblond lathe for $850...It also had some tooling included...I'm currently looking for a small mill....

I agree with I would not waste my money on a home made lather you can find used one out there that still has lot of life left in it . too bad you not closer I have a very nice shendon I am trying to sell includes a tracer attachment

also a recc. to buy a lathe. no doubt, building it will be fun. you MAY save a small amout in cash...esp. if you have all the material laying around. The time and expense required to have one even close to the rigidity and function of a manufactured lathe is huge. You do much more on a lathe than just turn parts. the grinding, drilling, milling (if you desire), threading etc place a lot more demands on your design. I have come across quite a few home made lathes. The number that were the same or better than your run-of-the-mill 9 inch southbend are zero. Sure there was one that was nice..but you would have to use custom stuff to drill, change gears to thread (and the complexity of that gear train alone is a bunch of work).