Hex Broaching?

[Brandon Holley]

Obviously you need to ensure that the broach is kept perpendicular to the part's face for the entirety of the broaching process. Hex broaches take some patience to get through, but taking your time will go a long way in helping out.

If you have a lathe- you can simply start the part there and move it to the arbor press to finish to get a nice straight broach. If you do not have open access to a lathe, you can try this:

I've had success making jigs and guides for broaches. Essentially I just machined a part that had a large face to mate against the part I was broaching. I drill and broach the guide to same size I was broaching my new part. I carefully feed the broach through the guide, lined up the hex properly, and put the whole stack together on the press and then began broaching my new part slowly, especially in the first few teeth.


Also make sure you are liberally lubricating the part you are broaching as well as the broach itself.

-Brando

[Gray Adams]

Start it on a lathe if you can. If you can't, just constantly take 5 or so steps back and check how straight it looks from a distance (from multiple view points as well), and adjust as necessary.

Also, don't stack multiple parts and broach them together. It may work sometimes, but we had a bad experience when a machinist in the NASA trailer at CMP tried it. They broached all 4 gears at the same time, they ended up crooked, and we had to have them weld it shut and try again.

[artdutra04]

Similar to Brandon's post, I've had success with a jig that holds the broach colinear with the arbor press ram. Here's a simple mockup of this idea:



The square inset in the top fits over the end of the ram. The small hole on the front face is for a 1/4-20 or similar size set screw to hold the adapter onto the ram (you can also use a thumbscrew or similar fastener to mount/remove it).

The through hole in the bottom is a reamed hole that provides a very tight clearance fit around the shank of the broach. The tighter this clearance fit, the more accurate the broach alignment will be. When properly machined with tight tolerances, this adapter can be used to quickly and accurately hex broach objects in one operation (no need to start on a lathe).