Making an internal keyway without a broach?

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Can it be done? I suspect not, but I figured if anyone knew a way, they'd be here. :)

I need to make a spacer to go between two pulleys on a 1" shaft with a 1/4 key.


Ah. I should've known Mr. Pete would have the answer. I think I can make that work.

@mmcmdl - I'm not comfortable with oversizing the bore to accommodate the key as it's on a motor shaft that will be spinning @ 3600 RPM and don't want it wobbling.

I might use a combination of approaches: drill a 3/16ths hole off-center in the keyway posistion and then bore the main hole on center. That would take a lot of the work out of broaching (scraping?) the final keyway.

You know they also sell lock collars that are keyed . Machine it to your spacer length .
Or a locking collar (not keyed) with setscrew.

I like the suggested idea of drilling a hole to clear the key. Your spacer can’t “wobble” if it is sandwiched between the pulleys and it has a correct bore.

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Assuming you have a lathe, Mr Pete covers this in one of his videos.

Cheers,... Jon.

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I agree with Jon, I've done this many times. Take small bites and it turns out great.

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A little sideways input, if I may. I often use a shaper to cut internal keyways. When I'm serious about a pulley et al. In most cases, I use a couple or three hacksaw blades strapped together to make the basic cut. And a three square file to finish dressing it. There are hacksaw blades that will enter a 1/4 inch hole. And files that will work 1/8 inch keyways. Crude, but cheap. And usually faster than setting up the shaper. Usually, the shaper only comes into play when I'm doing something for someone else. The above suggestion is basicly using the lathe carriage as a shaper, albeit a little slower.
If it's just a spacer, why cut an internal keyway? Make a bushing and cut a section out for key clearance. Essentially a "C" shape.
Several perfectly logical suggestions about ways to do it without an internal keyway, but I got fascinated by the methods of doing a keyway without a broach.

Plus, I'm retired and it's going to be a loooooong winter, so what the hey, why not do it the hard way.

Cut a piece of round stock, faced it on my big lathe, center drilled it, scribed a circle at the 1" dimension for the main bore.

Then I set it up with a vise and a V-block in my drill press and drilled a .221 (?, too lazy to go look at my letter drills to get the exact measurement) hole centered over the 1" diameter.

Back to the big lathe, drilled in steps out to my biggest bit which is 3/4 inch.

Then, seeing as I don't have a boring bar for the big lathe yet, went to my little lathe and started boring the hole out to final dimension. Going great too, if only .003 at a pass. Then my Grizzly 8688 quit. A bit of troubleshooting seems to indicate that the motor control board failed.

Researching it here, found a guy that fixes them for a flat rate and he just happens to be right here in Maine. Board will go out in the morning, project on hold until its repaired and returned.
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