broach designation

blockmanjohn · Mar 21, 2018

Hi, I was wondering what exactly the letter means after the size of the broach, for example 1/8 A? I have only seen A and B but are there more?
Thanks, John

Gordon · Mar 21, 2018

The letter is the width of the body. A=1/8 B=3/16 C=3/8 and so on. It is possible to have two broach widths with different letters. There can be 1/8 A and a 1/8 B for instance.

blockmanjohn · Mar 21, 2018

Thanks for the help Gordon. If I understand you correctly, a 1/8A would be for a keyway that is 1/8 deep, and 1/8 wide? Thanks again, John.

Gordon · Mar 21, 2018

Actually a 1/8 A would cut 1/8 wide x 1/16 deep. A 1/8 B would also cut 1/8 wide x 1/16 deep. Half of the key is in the shaft and half of the key is in the sprocket/gear/flywheel etc. The adapter for the A would have a 1/8 wide groove and the B would have 3/16 wide groove. Each size would cut about 1/2 of the depth then a shim would be placed in the adapter behind the broach and the remainder of the depth would be cut. The adapter would be the diameter of the bore (for example 1") of the piece receiving the keyway with a groove (keyway) 1/8 wide for a A broach or 3/16 wide for a B broach. Now are you confused enough?

blockmanjohn · Mar 21, 2018

So the difference between an A and a B broach is the thickness of the heel that goes into the bushing keyway? The actual teeth would still be 1/8" wide. I'm trying hard to understand this. Thanks for your patience, John.