Myford Super 7 Lathe CNC Conversion anyone?

If you poke around on alibaba, you might find a 10mm ballscrew. Here are some to get you going.
www.alibaba.com/product-detail/TBI-SFK-B...24838.0.0.SdqTMd&s=p

Could you make a standoff so you could move the nut away from the dovetail?

Thanks Rod, been banging my head against the wall trying to get damn alibaba to play ball with 10mm ballscrews, nice find there. Funny how the small stuff is way more expensive than the bugger stuff!

And yes, will have to make a standoff to attach the ballscrew nut to, the inside thread bit will be the tricky bit for a novice lathe user

racedirector wrote: Thanks Rod, been banging my head against the wall trying to get damn alibaba to play ball with 10mm ballscrews, nice find there. Funny how the small stuff is way more expensive than the bugger stuff!

And yes, will have to make a standoff to attach the ballscrew nut to, the inside thread bit will be the tricky bit for a novice lathe user

You'll be amazed once you get it done! I'm all self taught in my home shop over the last few years. With what I've done to build my plasma machine, I think I can build almost anything I choose to now.

What inside thread?

Oops, the inside thread of the nut standoff. The nut would be a R1003T3-RSK which is a round nut with a threaded section (M18-1), the standoff would need a hole in it with a thread to accept the nut. I could simply bore the hole to 17mm and then buy an M18-1 tap and do it by hand I suppose.

You're not wrong about the satisfaction of doing things like this, felt the same way when I built my Mechmate router.

I don't think you will need to tap a hole. If you look at that link again, get the SKF01004 Nut with the flange on it. Its only 14mm x 20mm. (the second of the 2 nuts they show).

You might need to be creative with a 2 part standoff if the mounting holes on the lathe clash with those on the nut. Maybe there is a part that attaches to the lathe using cap screws in counterbored holes. Then a plate for the ball nut to mount to that has a turned boss to locate it in the bore.

Seeing you have a lathe, this is an easy and sturdy way to mount a stepper
image missing http://i210.photobucket.com/albums/bb270/rodweb/Lathe/Rotary%20Taable/DSC_5246_zps413f139b.jpg

Your nut would attach to the plate at the Rotary table end.

The standoffs have a tapped hole at the stepper end and a male thread at the RT end. You can align the stepper by adjusting how deep the threads are engaged... No need to use hex rod, thats what I had.

I'm envisaging you'd end up with something similar to this with the ball screw nut in the plate that attaches to my Rotary table/

racedirector wrote: So I have disassembled the apron and cross slide only to find that the cross slide has stuff all room for a ballscrew.

This is a common problem.
I used to have photos on cnczone of how I got round that with my mini-lathe, but they disappeared when they pulled the plug on Picasa.
However, thinking about it, it might not be that relevant anyway, as the mini-lathe has the nut on the cross-slide, and the Myford has it on the saddle.

I used a very small pulley (barely bigger then the screw) and T2.5 belt to turn the screw, with a needle-roller to take the belt tension. I then moved the thrust bearings towards the user, mounting them in a housing that replaced the handwheel bracket (I kept the handwheel). Moving the thrust bearings out of the way was a big help in making stuff fit.

It is possible that a rotating-nut arrangement might help. As the Myford moves the screw and not the nut, this might make getting the drive in easier. But I suspect that there basically isn't room.

Depending on how much space there is between the lathe and the wall, I think I would be looking to mount the motor round the back, driving the end of an extended screw with a belt drive. T2.5 and T5 belts have effectively zero backlash, and let you wrap the drive round itself for compactness. Even if you don't do this, a belt drive will take up less axial space than couplings.
whether you but the thrust bearings in the front side or back side would be a matter of taste. I think I would use the front side, where the handle is, but I don't have a Myford to look at to decide.

The best nut-diameter to screw-diameter ratio seems to be the RSH1605 nut, which is 1" diamter and takes a 16mm screw. However it has a surprise, there is an external ball return tube not shown in the catalogue.
Here is how I got round that with my mill

I used the same nut on my lathe, but have more space than you.

The only nut that will fit down the existing hole in the saddle is for a 6mm screw, and that probably isn't worth considering.
However, my Mini lathe ran for years with an 8mm ballscrew and it never gave any trouble. So you could consider that.
(When I say "Mini Lathe" it was a 9 x 30 lathe, about the same size machine as a long-bed Myford, but made with half the metal)

How much space do you have between the centre of the saddle hole and the underside of the cross-slide?

The right answer might be a complete new saddle casting, with space for a ballscrew and built-in mounts for the Z-nut. With the Myford bed design this isn't beyond the realms of possibility (It would be rather more of a challenge with an inverted-V bed)