Turning 9" pulley on 10" lathe

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t20sl

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Need to turn od of a 9" pulley. Will have a v groove for a 7mm round belt. What tricks on getting that large of od on a SB 10" lathe. Or another way using a mill. I have a face plate but don't see a way of holding a HSS bit in lathe tool holder. Blank aluminum is at 9" od
 
Probably you would need to grind a trick HSS bit that cuts at a 90 deg angle, or fab up some type of offset toolholder
Set the cross slide and compound as far back as you can- spin the compound around if it helps
Don't try to cut the whole v-groove at one time- alternate cutting between left and right sides of the groove to minimize chatter
Make sure the workpiece is fastened securely to the faceplate and use a slow-ish spindle speed
 
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Use a plain old compass to trace out the estimated outside maximum diameter. Use the mill to bore a center hole. Use the mill again to drill out four small(ish) holes in the center, about as far out as your four jaw chuck will be happy holding it. Etch a sketch the part as close to the line as you can, without violating the compass circle you made. Move it to the lathe, anchored to the four jaw chuck by those holes to cut the belt profile. Move the compound and the tool post to use whatever tool you've got to true up the OD to the scribed circle. Figure out how best to align the compound to get a profile tool into the groove area. Grind a high speed steel profile tool to make the belt groove profile at whatever angle it needs to be to match up with whatever presentation angle you just determined would be best. Then if and only if you, the project's destined operator, or anybody else who's opinion bothers you requires this, draw in whatever spoke/weight reduction features you'd like to have, correlated to the four existing holes, and put it back in the mill to take care of that aspect.
 
Turn your compound to face you, and extend it completely. Set the tool post over to the chuck side till it is almost hanging off, and set at an angle. Use a left hand cutting tool. I was able to cut a 12" piece on a 12" Atlas-Craftsman that way. Rigidity did not come into the conversation. It was only aluminum, but I still had to take light cuts.
 
Great suggestions! I don't know the configuration of the cross slide/tool post on a SB10.

I have cheated on my 12" lathe, that actually could turn just over 12.5" before touching the ways. I turned the compound facing the operator (at an angle for clearance) and cranked it all the way out. I mounted my 4-way tool post (gotta love the versatility of those things) at the opposite angle, and used the biggest boring bar that would fit. I turned a 12" disk with features in the diameter and the face this way.

You have to cut slow, and use neutral cutting angles, because both positive and negative rake cause tool deflection (with this setup everything is like a spring).
 
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t20sl said:
Need to turn od of a 9" pulley. Will have a v groove for a 7mm round belt. What tricks on getting that large of od on a SB 10" lathe. Or another way using a mill. I have a face plate but don't see a way of holding a HSS bit in lathe tool holder. Blank aluminum is at 9" od
Click to expand...

Sooner or later that pulley will need a hole in its center. Might as well start there--{incomplete center hole:: pilot drill and center drill}--then do the rest on centers.
 
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