I need to make a tapered mandrel. Material choice?

Thanks folks. Good food for thought

Unfortunately, I don't have any welding capability at this time, hence my thoughts at the process I posted. The reason the shaft needs to be repaired, at least in part, is due to a prior owner using shims or a sleeve in a standard bore pulley. They did a terrible job with it and tried to compensate with a pointed set screw...

That didn't work.

The cutter head and shaft are one piece, so my best guess was to turn it down enough to get a good match with the pulley and work from there. Due to the rotational speeds of this thing (4K+) I wanted to avoid taking off any excess material and hopefully preserve the strength of the shaft.

woochucker said:
...
Can you shoot a pic ? if it's what I think, just remove the blades, mount it between centers and just friction hold it, to smooth it.
Click to expand...
I can, though I think you have the right idea. It started life as a single bar, turned, milled, and drilled.
 
You need t make a mandrel to make a pulley ? How big is the pulley ? Mandrel doesn't have to be tapered to do your job. If you chuck up a larger piece of stock steal or aluminum , turn the bore size just so it's a little tight to push on , drill and tap the stock to say 3/8- 16 or 24 . Then with a thick washer bolt the pulley material to your now mandrel , if need be the shaft can be cut short so the bolt holds tighter even. With out taking it out of the chuck it will stay on center no mater any run out it will be on center.
 
You just need to skim the shaft between centers to get nearly a full cleanup, with a generous radius where it meets unworn area. Then take a piece of steel stock large enough to machine down to match a new pulley, bore it to fit very close to whatever size you ended up with on the existing shaft and perhaps even shrink it on. Just part it off at that point. Heat the sleeve, freeze the shaft. Once you have it on and it's stable, back between centers and finish turn the OD. If it makes you more comfortable, drill a dimple thru the sleeve into the shaft for the set screw. HOWEVER.....


My 1947 Delta has a keyed shaft, if I'm not mistaken, so there is a complication that requires a slot to be cut in the sleeve. Only has to be as long as the key, if there is one though. Hopefully, the shaft isn't so damaged that you end up machining it down enough to lose the keyway.
 
I would cut the shaft off, drill and bore a hole about 1" into the cutter head, bevel the edge with a good weld bevel. Then make a oversize stub shaft that would be a slip fit in the hole, even a slight interference fit, weld it in place. Last machine the new stub shaft to size.
 
I might (if I were you) take the head to a weld shop and have them build the shaft up with weld probably Tig weld with mild steel, bring it home and chuck the good end carefully for concentricity with the bad end held in a steady rest, then recut the center to make sure that the weld did not warp the shaft, then support it with the center and recut the shaft to the original size, and key it, then make or buy a new pulley, or possibly sleeve the old one if there is enough thickness to allow a sleeve that has enough wall thickness for a keyway.
Recutting the center is done with either a tool that can be adjusted to the correct angle (30 deg off the center line) or a center reamer (looks like a center drill with no straight portion, just a sharp point) a center drill will pretty much just follow the old pilot drill, but one can be held in a boring bar holder with the lips horizontal and be used like a boring tool, set out to enlarge the existing hole, then be set on center and be used to ream the center back to concentricity.
 
Lathe a tapered hole in your pulley for an H bushing and your problems will go away...
 
Fix weld up the shaft and turn to size needed. Then I would use a woodruff cutter and use the size needed for pulley . Moon keys are better then straight type in my opinion . At least for this type of machine .
 
Here s a mandrel I made. I couldn t get something dialed in and also wanted to add to the shop so I came up with the idea of a press fit of friction drive and also to be able to place it with the spacers where I want it. Taper of 9985" to 1.0015". Moved the tailstock over before finish size to come to this taper. Used it a few times now. I had the stainless off a propshaft given to me so cost me my time. There s a bushing I used for a press fit and the larger boss as well a press fit. Didn t have the stock diameter so had to use plate for that one. So if you make one it s going to be a project so I d go the easy route and turn it down and bush the shaft. Easy peasy! Or have fun with a mandrel project.

image.jpeg

image.jpeg

image.jpeg
 
Last edited:
You must log in or register to reply here.
Back
Top