[bogiestl]

I'm FINALLY making the bulk of the parts for the darn thing... (took a job driving a truck for a while)

And I'm basically just going to set it up to make stuff I've been making, only a little fancier.

The bulk of what I do is steel, with some aluminum. I'm going to need capability to put serial numbers and the like on round pieces, but also have the capability to do heavier cuts, preferably either with a good solid motor, or if they aren't moving, some sort of braking system.

What would you guys suggest? The Harmonic Drive setups look very interesting. I'm a little leery of a rotary table adaptation, altho I may consider using one for a fifth axis, but I'm really not sure it could hold the degree of tolerance for doing the numbering and lettering.

Also sort of considering a hybrid made of a minilathe headstock. Pros would be that it would already have a chuck mounted, but I'd be worried about the belt system not being solid enough for heavier cuts.

So... Three options - Chinese Harmonic Drive (uh... I'm on a budget...), 6" rotary table, or Harbor Freight lathe headstock. Which would you choose?

[hoss2006]

For steel I'd avoid the lathe headstock version unless you go with a very high torque stepper, the harmonic drive would be best if the chinese drive is really a harmonic drive.
Hoss

[bogiestl]

For steel I'd avoid the lathe headstock version unless you go with a very high torque stepper, the harmonic drive would be best if the chinese drive is really a harmonic drive.
Hoss

Yeah, I'm a little leery of the little "engraving" 4th axis dealies...

I figure I can buy a HF minilathe for about $425 or so (coupon...), and then rig a belt drive. I am thinking that if I set it up for lathe operation too, that could be a plus - just mount a small toolholder on the Mill's Z... That would primarily be used for facing stuff, so no big deal. The ways and compound will go to a buddy's frankenmachine. But that _is_ far in the future.

Primary drive for the 4th axis operation would be a fairly high torque stepper, with a nice wide belt. Does anyone what the practical limitation on reduction via belt drive and pulleys would be? I can go for shallower cuts - what I really want to be able to do is engrave 8 pt. type tho... If a heavier cut takes several shallow cuts, and thus takes longer to do, fine...

[mduckett]

If you just want the head stock for a mini-lathe, Little Machine Shop should have the complete assembly for sale, around $150 or so. --md

[bogiestl]

If you just want the head stock for a mini-lathe, Little Machine Shop should have the complete assembly for sale, around $150 or so. --md

I'm also thinking that I'd like to spin it as a lathe (for doing some repetitive simple operation stuff, like facing part blanks) - Which will likely mean two motors, and a way to swap belts between them. Was looking at the Hossproject where he did what appears to be something similar (altho I haven't had much time to dig into it). I'm also musing on seeing if I can sandwich in a piece of steel to serve as a brake rotor, and mount a motorcycle caliper to act on it. Or possibly even just set up a manual index on the back for when things need more rigidity.

Right now, for some of the stuff I have been doing, I have been using a Chinese copy of a Hardinge horizontal/vertical 5c indexer. It works fine, but it would be nice to have the capability to walk off and let things run. And there is no way that it can be used for stuff like engraving lettering, or non-indexed designs.

[mduckett]

Here are a couple more links fwiw (not affiliated in any way, just passing on what I've seen).

Mini Machining Center - final design 4th axis - scratch built servo powered - YouTube
4th Axis Mega-Duty introduction including design, build and install details - YouTube

--md