4th axis as a lathe...

[WilliamD]

I'm in the process of building my CNC router, and will post some pictures when I have some decent progress. I have a wood lathe that I'm going to use as my 4th axis. i basically took off the head and will hook a stepper to it instead of a AC motor. I know that this will suffice for the tolerances I'm looking for on wood. But I'm also setting up a 4th axis on an Industrial hobbies mill. Will it hold the same tolerances a regular lathe will hold? I know it's pretty abstract. If it's just a matter of inconvenience, I can deal with that. But if the 4th axis with mill setup won't hold tolerances like a lathe, then I'll have to get a lathe also. I'm also working on a design with my wood router, to have the lathe head and tailstock incorporated in the bed. It should be interesting. That way I don't have to continuously set it up, plus I can turn something up to 10" in diameter. Any observations or info would be greatly appreciated!

[Bruggles]

theoretically you could have a lathe type tool holder that attatched somehow to the z axis and it would be a lathe. With a spinning tool and part, it will be hard to do some lathe operations, like threading, mainly beceasue of tool availibility. I'm sure you could make an attatchement that would attatch to the head somehow and hold lathe tools.

[JBV]

What about attaching a lathe tool in a vise on the mill table, and the workpiece in a endmill holder to do some turning? I need to turn some 10 mm parts and only have a mill...

[mwp]

JBV, I have heard of people doing this before... I'm actually considering doing this to make some handles with my cnc mill... nice curves with little effort compared to making them on my manual lathe. Heck, now that I think about it, I could mount several tools around the table and use the mill to do multiple operations with different tools--and then use the toolchanger to load multiple parts in the spindle. A cnc lathe of sorts.. The only drawback is that I do not have enough endmill holders in any particular size to make a decent run of anything.

Bruggles, why not just buy a 60deg angle end mill for threading? Trying to do internal threading could be quite a problem though (on a vertical mill anyway).I guess it would be best just to do that in a different setup (vertical thread milling using helical interpolation in V mill mode). Regarding the single point attachment for the quill on the IH mill, I would be a little careful on a R8 spindle mill as they are not all that robust. This would also require quite a 4th axis to drive the setup. I think that it would be expensive to end up with the speed and torque required for lathe use while having the little to no backlash desired for a normal 4th axis.



Mitchell

[Mcgyver]

its innovative, really like the idea re 4th axis for wood. you could do alls kinds cnc ornamental turning. might want to gear the axis for smoother helixs etc, then again 200 steps (or whatever) may be enough.

don't like it for metal. The bearings in a wood lathe are not going to be of the same quality for starters, and trying to cut a round shape with an endmill is brutal. its slow, uses up expensive cutters (vs blank bits in the lathe) and leaves a crappy finish. You will also always have tailstock alignment issues without V ways.

The mill can be pressed into service as a lathe by mounting the work directly or on an arbor in the spindle and holding a tool in the vice. thread milling is fast, but not with tapered endmill. Having done a lot of threading and milling, I would not want to mill threads with a tapered endmill, expensive and slow.

i think your wood idea is great ....feel free to prove me wrong , but for metal you will be happier with a lathe

[WilliamD]

Thanks for the replies so far! I should have clarified some things though. As far as the router cnc, the lathe on their with a stepper will not be spinning fast. I'm going to have a flat or 60 degree cutter in the router, moving along the x axis. The stepper on the lathe will simply turn it slowly, with the router doing the cutting. I'm not too worried about this setup, as the stock will not be turning fast at all, so no real vibration from an off balance part. They already have setups like this for wood, and wood parts don't need to hold those .001" tolerances, definetly not for my work. But for the IH mill, and the metal, I was wondering if the operation could be the same. I'm going to get a nice 8" rotary table from enco, and hook a servo up to it. It sounds like end mills and mill cutters are not designed for lathe work, or it's at least an expensive way to do it. I'll probably just end up getting a lathe and CNC retrofiting it.