Hi guys, have any of you made perfectly round things on your mills?

I am trying to make some replacement pulleys for one of those X-2 belt drive kits, but I don't have a lathe.

I am sure I've seen a video somewhere of a CNC'ed mini-mill turning stuff with the stock mounted in the spindle and lathe tools on the table, but I can't seem to find it. Has anyone tried it, or got a link?

See the link in post #2 : http://www.cnczone.com/forums/showthread.php?t=30900

See the link in post #2 : http://www.cnczone.com/forums/showthread.php?t=30900

Thanks, that's the one :cheers:

He's only turning some pretty small diameter stuff - I have seen a couple of mini-lathe chucks with MT2 arbors that might fit my X-1, but they seem to be designed for tangs, not drawbars, and I really wouldn't want 1/2kg of metal spinning at 1000+ rpm falling out of my spindle! I suppose I could try drilling and tapping the tang though...

Not much point mounting a chuck. The rigidity issue is the MT2 arbor, so you may as well mount the workpiece directly on a MT2 arbor and take light cuts. You could mill the pulley conventionally, within say 20 thou over size, then finish it mounted in the spindle.

Just some thoughts

Regards
Phil


Thanks, that's the one :cheers:

He's only turning some pretty small diameter stuff - I have seen a couple of mini-lathe chucks with MT2 arbors that might fit my X-1, but they seem to be designed for tangs, not drawbars, and I really wouldn't want 1/2kg of metal spinning at 1000+ rpm falling out of my spindle! I suppose I could try drilling and tapping the tang though...

Not much point mounting a chuck. The rigidity issue is the MT2 arbor, so you may as well mount the workpiece directly on a MT2 arbor and take light cuts. You could mill the pulley conventionally, within say 20 thou over size, then finish it mounted in the spindle.

Just some thoughts

Regards
Phil

Cheers Phil - I will give it a go.

I seem to be in the sticky situation that I have a few parts that would be best done on a lathe, but I don't really have enough of them to really justify the cost or space-requriements of a lathe. I'd also need to CNC it, which would add extra cost and effort.

What I am considering is mounting a lathe head and motor on my mill's table, and putting a lathe tool-post on the side of the mill's head. This would give me X and Y under CNC, and if I used a servo to drive the lathe-chuck, might even be good for screw-cutting :)

People use the mill as a lathe technique on the smaller diameter stuff, not sure how big your pulley has to be or how many settings it needs to have but if you can get it mounted well to the spindle and take like cuts I think it may work out ok. As Philbur mentioned you could get it as close to the final size conventional milling and then try to cut the detailed features for the belt using light cuts. I am just not sure what the max diameter of the work piece should be for doing this, a 6" pulley may be pushing it a little. I am assuming you plan to use aluminum stock?

Bo

I wonder if it's possible to use a live center mounted on the (locked) table, an x-y add-on table for moving the bit.

I had wondered about mill-lathing too.To make a tooling or a mould to make a 20" wheel, it would take a lathe that not even Grizzly would carry, and would have to lifted in place with a crane. Cast wheels would have to have be tweaked, too.

I imagine that the speed would have to be reduced and guards made to have any measure of safety.

[Okay, I admit it, as a project, I wanted to make some wheels.]

Hi guys - thanks for the replies - loads of good ideas there!

I finally took the plunge and bought a bandsaw at the weekend - should have been the first thing I bought after my mill! Anyway, I needed an excuse to cut up some metal, so I decided to CNC my rotary table :)

My plan now is to make some more tooling for my rotary table - I plan to cut a 50 or 75mm diameter perfect disc out of some rectangular stock with the table horizontal, and then I thought I could make a pulley by milling a deep grove in the side of it while mounting the rotary table vertically. I also have a 3-jaw lathe chuck that I picked up cheap a while ago that I plan to mount on the rotary table. It won't be quick, but it should be round!

I also picked up a couple of books on lathes - I still haven't given up on the idea of adding a horizontal spindle to my table, and then mouting a tooling post on the side of the mill head.