[RotarySMP]

Hi Jon,

I have some info on my minilathe conversions here:
http://www.wrathall.com/Interests/interests_index.htm

I replaced the leadscrews on mine with metric acme. Use 187 OzIn steppers on both axis with 2:1 reduction. The Z could do with a either a little more oomph (like say 300 Ozin steppers) or better yet, taking the time to file the undersurface of the bed so that the saddle doesn't have tight spots to bind on.

[JFettig]

Thats pretty cool, nice work. I plan on setting up my X axis like that to to run multiple tool posts, today at work I had 3 tools going on cutting hosebarbs, was some pretty cool stuff!

I hope to get like 2 tools on mine at a time, or Ill make a rotary tool changer for it.

Jon

[RotarySMP]

Thanks for the kind words Jon.

How are you intending to address backlash? I am not too happy with the preloaded brass nuts on X, as they need pretty regular adjustment. I wish you could fit a ball screw in the cross slide.

[JFettig]

I really dont know what I will do about backlash, I think Ill worry about it when I get to that stage


Jon

[RotarySMP]

Ballscrews are the way to go, but on a lathe, it is X which really needs to be backlash free. Z is less critical as you can do all finishing cuts in one direction for most work.

If you can fit a small ball screw in your saddle, you really should. Even a cheap rolled ball screw from McMaster-carr will be better than a preloaded AMCE setup. I realise that cheap rolled ballscrew is not that accurate at0.004"/foot, but then again you only have about 150mm travel so a bad screw will still keep you within 0.002" if you get unlucky.

I have looked at the 3/8" ball screw from McMaster where the nut has a 3/4" diameter, and it might fit. The slot in the saddle is about 20x20mm, but I think the leadscrew centerline is below the center.

I can highly recommend machining out the saddle to increase cross slide travel. If I had not done this, I would not have been able to use the Phase two Wedge type AXA tool post.

[mineralman]

I'm following the cnc thread with interest, as I'm planning to cnc my 8x14 (Kong, you reading?) But I've yet to see a written-in-stone definition of which are the X, Y and Z axes on a lathe. What are the leadscrew, the cross slide and compound designations?
I suppose you never use the compound during CNC.

Larry

[kong]

Ideally, the compund should be removed, which could allow for a more strurdy fixing of the tool post to the cross slide. Since I don't have a mill, I have no way to make a big ol' block of steel to the correct shape for this, so the compound has stayed.
As for the designations, the carriage itself is called the Z axis and the cross slide is the X axis. I guess these are related somehow to a plan view of a part drawn in CAD

[mineralman]

Kong,
Your pictures don't show all, but your 8x14 lathe looks like our Lathemaster CQ6120x320. Is it?

Larry

[kong]

Similar I think, it can be seen over here which is where I bought it from. Very nice lathe, shame to CNC it really, but needs must.

[mineralman]

Nope, not the same. Still, a VERY nice looking lathe. You Brits sure have a lot more choices in machinery than we have in the states. Unfortunately, your prices are waaay high.

[JFettig]

Im taking a look at this again, Im looking for leadscrews but not finding much for decent prices. I am looking for a 3/8" diameter leadcrew for the cross slide, the leadnuts seem to be the expencive part. Ill see if we have the stuff to turn them at work if I remember.

Im actually designing a replacement saddle and cross slide that will give me tons of travel.

I have 3 leadscrews from my mill(2 from my mill and another identical one) one has left hand thread, would work perfectly but too short, I have another Y axis screw and nut, but only one nut, it fits on the existing screw that is on the lathe, but then I would be lacking another if I used that screw.

I have looked around mcmaster quite a bit, if I was to get 5/8" ballscrew, it would cost me about $40 for the entire z axis screw and nut, I woudl have to figure out a way to cover it though.

I looked for leadscrew and nuts, the nuts I have found cost close to as much as 5/8" ballnuts. I was hoping that the 3/8" ballnuts were as cheap as the 5/8" nuts, I would use one of those for the cross slide.

Edit Now that I look at it, it appears that there is plenty of room in my desing for a 5/8" ballscrew and ballnut, I dont know if I want to mess with preloading them though, It would possibly remove a lot of travel and cost a great deal more.

Let me know if you know of any sources.
Jon

[kong]

http://www.pro.com.sg/CNC.htm
Any good? :stickpoke