Non-Standard Broaching

Is it possible to do non-standard broaching for example a 1/8" keyway in a 3/8" shaft? If so, could someone tell me which mcmaster p/n broach and bushing would go together for this. Thanks. I’m guessing I would need 3153A16 and 3151A109 but I could be wrong.

First, I’m assuming you want to put a keyway into a 3/8" hole for a shaft. Yes, this is very possible. Second, I would suggest getting a keyway broach set as opposed to individual broaches. Yes, it is more expensive, but over the years, it has certainly paid itself off for both teams I work with. If you want to go with the individual part numbers, then those are correct. Just make sure you select the 3/8" diameter for the latter part number.


I guess the first question I would ask is… why do you want to do this?

If you have a non-standard keyway in a shaft and you want to use a standard piece of keystock, so you’re thinking of using a non-standard key in the shaft, may I suggest looking into stepped keys? Essentially on different sides of the stock they are different widths.

This may make your job a bit easier and a lot cheaper, if this is indeed why you want a bigger keyway.


We have standardized on 1/8" keys for 3/8 and 1/2 shafts. For smaller gears (12-14T) we cut only the first pass of the broach in the gear and cut the shaft keyway deeper. --For the 1/8" broach a shim is included, it takes two passes to cut full depth.— We also cut the depth in the shaft at .063", this is a little shallow per Machinery’s but works for this size shaft.

Sanddrag, those are the correct McMaster #'s.