Broaching advice

[Al_The_Man]

I need to broach a 3/16" keyway in a 3/8" bore steel pulley.
I was advised by one shop that I may have a problem due to the broach taking up the width of the bushing.
Anyone see a problem to this? I have contemplated using the lathe trick with the spindle locked and moving the carriage/tool in the Z dir, manually with the appropriate tool, But I am not sure wether this is feasable with a steel pulley.
Anyone done it?
Al.

[Mcgyver]

wow, big key little shaft. i looked at minuteman's site,
http://www.dumont.com/prodc.html
and they only list 3/16 in B&C, bush sizes for B start at 1/2.

sitting at my day job so can't measure, but from memory a 3/16 broach is going to be very crowded in a 3/8 hole.

I've done steel in the lathe and mill as you describe but can't swear i've done to that width of cut. obviously use light feed, and maybe do it in two passes with a narrower tool.

other options include making your own custom broach (lots of work there, avoid if possible) or a design change. I favour the later. if the keyway in the shaft is 3/16, could you broach say 1/8 and then make a custom key that fit the 3/16 shaft and 1/8 broached keyway?

[cdlenterprises]

Can you wire EDM it?

[Al_The_Man]

Originally Posted by cdlenterprises Can you wire EDM it?

Yes, That did work for me once before, I managed to reciprocate by fixing the guys machine so it did not cost me anything.
Al.

[Mcgyver]

just checked, the 3/16B at its widest is .428, so its not going to work

[Al_The_Man]

Originally Posted by Mcgyver just checked, the 3/16B at its widest is .428, so its not going to work

Thanks, I guess the EDM approach is the option.
Al.

[Willbird]

EDM guys like BEER :-).

I have some 100:1 speed reducers they tossed at work, planetary gizmon, broken guts, anyway they uses a bushing that had a split in it wide enough to grip the key, the setscrew clamped the bushing on the shaft and also made it tight on the key I think, dunno if you could do that for your ap or not, it is about 1/8" wall bushing to grip and key on a 1/2" shaft.

Verbal descriptions can be hard to understand, basically the keyway is all in the bushing, say take a 3/4 od 1/2 id bushing and cut the keyway clear thru making a split bushing with a keyway in it :-)

The other option would be a stepped key to the standard key size for that dia bore.

Bill

[DSL PWR]

My cousin does the "lock the spindle" trick all the time on his mill. Just don't get greedy with the cut. A couple of thou each stroke.

[sluggo]

You could buys a 3/16 broach set and then make your own bushing. We have a minuteman broach set at work and we have done that a couple times for odd combinations.

[Kiwi]

If doing in the lathe: While moving the carriage, push with the tail-stock at the same time. You will find it broaches much better.