[chafik]

Just sharing what I have been doing lately, I have a Cummins mini lathe, and a Grizzly Sieg X3 mini mill. I plan to convert both of the to CNC, and decided to start with the mini mill.

First their was a lot of web surfing to see what other folks did, so this is mostly of compilation of idea, with the X axis conversion being a straight copy of the one rom wrathall.com.

The X axis will take a 3/8-10 acme lead screw, with a bronze nut. The
stepper motor is a 166 oz-in holding torque and the timing pulley ratio is
1:1.5, which would translate to about 380 lbs of thrust. I elongated the
saddle cutout where the nut travels for a slightly longer travel range.
The middle set screw that was previously used to adjust the backlash, was replaced by a ball oil hole, with a hole going straight through the bronze nut.
I also got rid of the compound slide and replaced it with a lock of aluminum.

The Y axis uses a 5/8"-0.2 ballscrew, with the same pulley ration and stepper, for about 444 lbs of thrust. I got rid of the original apron.

I have enough room to use the largest (425oz) Nema 23 steppers available, but hopefully I won't need to. I had those 166 oz-in just laying
around, begging to be used.

I will be using Gecko 302 drives, I already have 2 of them.

The Z Axis is done, and things move smoothly by hand. I thought I was done with the X axis, until I found out the acme screw got messed up, and is not perfectly straight, and the lathe is now out of commission until I get some more funds to spend on it and have someone do it (I have another length of acme stock that is straight.).

Well I guess, I will be focusing on the electronics part (I am an EE) for now, until I get the acme screw done.

[chafik]

More pics:

[Guldberg]

Looks great

[tauntdesigns]

Looking good....

Keep it up (the good work),
Jack

[chafik]

It has been very slow, but there is some progress. I added the limit/home switches for both X and Z, they are all wired to a single CAT5 cable (cut off one end of an RJ45 ethernet cable.)I also installed the slotted optical switch with its disc on the spindle, to do threading, and read the spindle's speed.

[chafik]

Work in progress on the electronics, some pics:

[chich2]

Great thread mate!
You have done some neat work. I will be following your thread closely incase I ever convert my lathe to CNC.
Keep up the work and keep posting the pictures.

Chich.

[acondit]

It looks like you're using the CandCNC MiniIO BOB. I have a couple of them and am well pleased.

Alan

[chafik]

Thanks for the feedback Gentlemen.

Acondit: Glad to hear that you are happy with the CandCNC boards, I have not fired up my board yet.

I am getting there, I will post more pics as (slow) progress is made, and hopefully the last post will be a video of the lathe in action.

Chafik

[whoafat]

I noticed here and in other forums that replacing the leadscrew along the lenngth of the bed can be done successfully. However, questions about replacing the crossslide's leadscew with ballscrews seem to go unansewred or end with an statement that a suitable ballnut is hard to find. I am sure that there is information out there, in this or other forums but I may be looking in the wrong places or use the wrong search criteria. If this question has been answered previously, can anyone direct me to the source, or oherwise, provide some guidance? Please note that I have not named the axes because the first topic above was confusing to me as to whicch was the y-axis,
my apologies,
Wilfred

[tauntdesigns]

On the smaller lathes there is a clearance problem under the cross slide (x-axis). The ballscrew nut for a 5/8" ballscrew is 1.00" (square or round) plus the room that the ball return tube takes up.

There are smaller ballscrews..... but the cost for those are out of most peoples' budget... some of the smaller ballscrews still use a 1" nut (OD).

Some of the work-arounds for this is:
Mounting the screw on the side of the cross slide (hard to keep chips off of, lose a little travel in the z-axis, tailstock can't get as close to the workpiece )

Mount the nut to the front of the cross slide (too many design challenges)

Use a rotating nut design (loss of travel on x-axis)

The one I used:
I mounted the ballnut to the back of the cross slide (ballscrew sticks out the back far enough you have to build a new chip shield for the back of the machine)

Jack
P.S. Not sure any of that makes sence

[whoafat]

Jack,
You have been very helpful. This is a clear and concise explanation of the challenges posed by that mini lathe and the work arounds that have been used. Maybe some of our members will post pictures of their successful workaround. That could be useful for those of us who do not want to reinvent the wheel. Thanks for taking the time,
Wilfred

[tauntdesigns]

You're welcome Wilfred,

I have some pictures of the build I'm working on now.... I still have a few things I need to to do to it before I can call it finished.

I've been lazy lately...... that needs to stop

Here's a link to the build:
http://www.cnczone.com/forums/showthread.php?t=54376

Cheers,
Jack