80/20 benchtop lathe build

[LeeWay]

Well I had such good luck building a mill using good parts with 80/20, that I have decided to go the same route for a small production lathe.
I did convert a 7-12, but with less than stellar results. It is the backlash, general flexing, lack of motor power that directed me to just build new, rather than try to upgrade the 7-12.
It is a much better manual lathe than it is on cnc with stock parts.

Anyway, I have many of the parts already. Some parts are exactly the same as on my mill. The 3060 80/20 base, the THK rails, I will be using the spindle head from the 7/12, much the same way I used the X2 spindle head on the mill.
I will be using a treadmill motor on this but not quite as strong as the one on the mill.

I will be using SDPI timing belts and gears and the existing 270 oz motors and Gecko 201's with a 48 VDC PS.


This will be the first time I fully design something using CAD drawings.
This will be my 4th machine build or my 5th if you count the conversion, but I haven't completely finished the plasma yet, so 4th is about right.
Here is what I have so far.

I will be using 5/8" ball screws and nuts like I used on my router from Mcmaster Carr. I will preload these though.


Several areas I am not sure about yet. Gang tooling is one. I have a cast iron T-slot table from an X Y table that I want to use for mount tooling. I don't need a lot of different tooling on here to start with.
I want to cover the head and part of the motor and include the controls in it. This will also get a sliding lexan cover that has to slide closed before I could start it manually. I do want it eventually under Mach control for the spindle.

While it turned out not needed on my mill, I do intend to fill these extrusions with concrete or hydraulic cement and lead shot.
That should give it a little more mass.

Let me know your thoughts and suggestions.
Thanks.

[sergizmo]

Looks good Lee.

Gang tooling is the way to go. Simple and fast.

Do you plan to do any threading on this lathe? If yes, how will you do so?

[LeeWay]

Thanks Serge.
This is a semi production machine and will mainly just turn 9/16" brass rod. I would like to do some threading eventually. I did some on the mini lathe using gears, but although they worked, they were not pro quality.

I think even with the mini lathe spindle, this build will be pretty rigid for a small bench top. I have proven to myself the concept works with my mill.

It ain't gonna have to weigh as much as a house to get good results in small brass rod. It will have to be faster though. Just a little.
I should be able to get near 6000 RPM with this motor I have. It goes in reverse as well, so I will use a board from cnc4pc for that. I also have an indexer thingy i bought for it, so threading should be fairly easy, should I choose to do it.

I will still have this little lathe converted back to manual if all else fails. I have another spindle head that I may use. Just buy the spindle and new bearings from LMS.

I have woked on the drawing a little more, but don't have time to get them ready to post.
I will do that in the AM.

[digits]

It's looking good so far Lee!

I really am looking forward to seeing how you get on, as I quite fancy an ally-extrusion based lathe myself

Good luck!

[Todd Price]

Whoa dude slow down..... I'm still trying to keep up with your mill build.....lol Keep up the good work.

Todd

[sergizmo]

It should be plenty strong enough. Especially if you use rails as big as the ones on your mill. Those were beefy for a small machine. Like you say, turning 9/16 brass rod will be cake.

What travels are you going for?

Are there any concerns about sustained 6,000 RPM with the stock spindle bearings?

No need for "If all else fails". You did the mill, a lathe should be no problem. Just 2 axis instead of three. Stationary spindle and motor and fewer parts overall.

I look forward to the build.

Serge

[digits]

What sort of chuck are you planning Lee, and do you know that it's good for 6,000 rpm? I can't imagine there's any good place to have to have a surgeon remove a chuck jaw from

[LeeWay]

Thanks, Guys.
Digits, you are correct. I only wanted this a little faster. Right now it runs @ 2900 RPM. I have seen guys speed these up some, but don't recall how fast they went with them.
The motor I have does 4500 on it's own, so I need to belt it down to about 4000 max I think.
I will try to work out the toothing to 3800. That should be plenty fast for this and should still hold up well.
I will also be using a 1/4" polycarbonate shield for the most part.
As it is now, I have no shield and when the parts get cut off @ 2900, about 10% fly up and I need a baseball glove to catch them.

Really the cut off does not need to turn near that fast, but this is not controlled by Mach yet. The little motor on the 7/12 just doesn't have the torque I would like.

Gearing this treadmill motor back down to around 3800 should solve any torque issues as well.

Here is another drawing showing the motor cover.
This will be made from .125 aluminum. The end caps will be stationary and the formed cover would get screwed to some flanges on the caps.


I want to design and build an outboard rod holder for this. Very similar to the steady rest that came with this little lathe, but with adjustable roller bearings.
I have to cut the stock into 18" lengths now to eliminate floppig, but with a rest that far back, I should be able to load 36" rod.

[Jason3]

Now I want to do a lathe too!

...must finish something first...

Is it just for threading in the future that you want to control the spindle with Mach3, or for convenience / cool factor?

Jason

[LeeWay]

I didn't have much luck with controlling the motor on my mill yet, but still haven't given up. I do want it on the lathe for threading, but also to regulate the speed.
I normally run with the lathe full speed peck drilling brass and then turning and parting it.
I would need the ability to set the speed for other materials and types of turning. Especially so if it is a larger part and you have deep turnings. It starts really slow toward the outside and increases in speed as you move to the center. This effectively tries to keep the same surface speed.

I have the little C3 from CNC4PC.

I am not sure how or even if I could use this to control rotation just yet. I'll cross that bridge when I get there.

I have most of the parts I need for this and should start some assembly pretty soon. Like a couple weeks or sooner.

[digits]

I'm sure I'm not the only one looking forward to seeing lots of lovely new pics of your progress

[Jason3]

Interesting... I didn't see any note of the motor you're planning to use - did I miss it?

I had considered using a servo to drive the spindle - is that wise/unwise? My thought was to get something around 1 hp & have Mach3 control it the same as the axis servos. This would perhaps also allow live tooling. Is 1 Hp enough for threading (nothing to coarse pitch, but maybe up to 1.5" dia.)?

It seems straight forward to me, but I don't see a lot of others doing it, which makes me worry there's something I'm missing! Is there a reason not to go this way?

Regards,

Jason

Ps - Pictures!