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View Full Version : Making sense out of broaches



CCWKen
04-19-2006, 01:02 AM
I re-found some broach bushings in my stash and thought about getting some broaches for them. Got out all the catalogs and what the hay? Type A 1/8 is 1/8 wide. Type B 1/8 is 3/16 wide. What up wit dat? Is the width spec the depth?

I see that the Type is a specific width for A, B, C, D. But why would you cut a 1/8 keyway 3/16 wide? I'm not catching that. :eek:

greywynd
04-19-2006, 01:10 AM
Scratching the grey matter a little here, but isn't the type 'b' style the ones that have a wider body on the broach than the teeth? (Somewhat of a step on each side.) Still cuts a 1/8" keyway, but uses a 3/16" slot in the bushing.

If I'm thinking right, it allows more overlap on bushings/broaches, so that a bushing for a certain bore size can be used for different keyway widths.

Mark

CCWKen
04-19-2006, 01:27 AM
Ah, thanks Mark. That makes sense. I can go to sleep now. :D

Leigh
04-19-2006, 01:36 AM
The larger series (B,C,D) provide more support for the broach, and thus more rigidity. The back (spine) of the broach is both wider and deeper than for the A series. Also the larger series bushings are longer for a given diameter than the A series. The 1/8" A bushing is only 1" long, but the 1/8" B bushing is 1 1/2" long.

Take a look at the product listings in the McMaster-Carr catalog (at http://www.mcmaster.com and search for broaches) for a table that shows all the combinations and dimensions.

John Stevenson
04-19-2006, 04:44 AM
Ken,
Have a read of this web site.
It has a lot of information on it regarding broaches, sizes , use pressures used etc.

http://www.dumont.com/


.

CCWKen
04-19-2006, 07:40 PM
Thanks for the links. That cleared it up fast.

http://www.dumont.com/dm-6.jpg

greywynd
04-20-2006, 01:35 AM
If you really want to 'have fun' get into the details of how to make and sharpen a broach.....hope you like geometry and trigonometry!! While I was still on my apprenticeship, we had a customer want a square broach made for SS.....I think it was for a 3/4 or 1" square hole, but in about 4" thick material....I think after we did some research on what was involved (remember there would be cutting edges on all 4 sides too) and figuring out how many broaches (was going to be way too long to broach in one pass) the cost was just too prohibitive, he ended up wire edm'ing the parts instead.

Mark