So Lets Talk About Mandrels

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gi_984

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Getting ready to machine some pulleys. I do not have any mandrels. I'd rather have solid ones as opposed to the expanding variety. I can only find new production Chinese stuff. Besides old US made ones on E-bay, anybody know of a place to get good quality mandrels for lathe work?
 
Can always make one. Standard taper for these is .0005" per inch.

A taper attachment, compound, or even a turning .002" oversize and filing can make a temporary one in short order. It won't last forever because it won't be hardened but for a few pulleys it should do.
 
mc master. rutland tool now called msc
 
Andre, thanks for the reply. Yes, I considered making one but quickly discarded the idea. If it was for just one job I'd say why not. But I'd rather invest in some good ones to always have readily available. Besides the pulleys, I've got several scale model engine projects planned.
Does anyone have any particular brand mandrels that they like? I found some made by Pratt & Whitney that look nice.
 
Andre said:
Can always make one. Standard taper for these is .0005" per inch.

A taper attachment, compound, or even a turning .002" oversize and filing can make a temporary one in short order. It won't last forever because it won't be hardened but for a few pulleys it should do.
Click to expand...
You can also set the tailstock over to make the taper. Making a mandrel requires some care, it is easy to cut just a little too deep, and then all you have is a tapered loose fitting shaft. I like Andre's file idea for finishing the job...
 
Mandrels are OK I guess, I have many, but I do not use them. I have not turned between centers in many decades and don’t plan on it any day soon. That process can have too many uncertainties in your final accuracy. I make a turned shaft in the chuck that fits the project pulley snugly. That guarantees me dead true. I sometimes thread a hole at the end of the turned shaft and hold the pulley on with a cap screw. As you machine the pulley, the pulley turns the cap screw assuring a tight hold/fit. I would rather hold it on with the set screw. Because tightening the set screw can upset alignment. This is negated in this type of operation…Dave.
 
I think chip has the answer. Turn up some piece of scrap to fit the pulley (do not take it out of the chuck) , about 0.001" oversize. Heat the pulley and let it shrink on. You could also make it loose and Loctite it in place (heat to release). Heat shrinking works great. Go about 0.0005 to 0.0007" per inch of bore. If you cut gently, that will hold well and dead on for accuracy.
 
Hmm, that is an interesting technique. I'm sure I can get good results with either way (mandrel vs chipps&more's suggestion ). As always it will come down to deciding on how much time or money I want to spend.
 
IMHO there is nothing more eye disturbing than to see a pulley wobble when spinning. And to achieve a shop made pulley that does not wobble can be tedious and maybe not successful on your first try either. The hole should be unscaved when the process is done. I’m not sure about mounting with an interference fit. It would be awkward/difficult to get the pulley off without harm the hole/bore. And even more challenging if you just wanted to remove the pulley for inspection and then remount it for more maching…Dave
 
When I need to make something with the bore concentric with the OD or other features on the work, I just turn a quick stub arbor with a threaded hole to secure the work with a cap screw. Normally only takes a few minutes, and you can take the work off or turn it around without losing center.
 
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