Hex Broaching?

[Alan Ing]

Hex broaches are expensive. Following 254's and 968's lead, we have been hex broaching much of our hubs for various things for the past 3 years. One problem that we have always had is that it is sometimes tough to get the broach to cut perpendicular. Our arbor press is a bit on the small side, I think its a 2 ton press. We ususually start the broach on a lathe using the tailstock as a ram, and then finish up on the press. Even then, sometimes the broach runs crooked. This year, we are going to try rotary broaching. The holder itself is very expensive, up to $700 new. But the broaches themselves are about $60 - $80 (half the cost of a push broach). They are usually used on cnc lathes, but can be used on manual ones. I bought a used holder on ebay sometime ago. I think it was about $150. There is a guy who makes and sells his own branded swiss type holder on ebay for $200. Might be the way to go. The nice thing about rotary broaching is that it is much more likely to be perpendicular since it is cut on the lathe. It also can broach blindholes. check out www.slatertools.com and watch the video you can just buy the broaches from them and then buy a holder on ebay to save a ton of money. I would not suggest this for smaller lathes. I consider our 13" and 14" lathes about the smallest I'd want to try this on.

I already broached a 7/16" hex in some aluminum for fun and it was surprisingly a lot easier than I thought it would be. Next week I'll try a 1/2" hex and report back if anyone is interested. The only thing I don't like, is that rotary broaches are a bit oversized. A 1/2" hex broach is actually .505" this is to account for wear, but for $10 more you can have them grind a broach to .500" if you can wait a couple of days. We will just cut our hex shafts a bit larger.