HEX broach too big for our manual press

[Andy Baker]

Another thought:

While all of this advice is well and good, here is a simple solution. Consider making the size of your starting hole larger. If you start with a bigger starting hole, then the broach will fit down into the hole further and you may not need to buy a new arbor press or create a new setup suggested by the brilliant people in this thread.

For instance, if you are creating a 1/2" Hex hole, start out with a 0.520" hole instead of a 0.500" hole. For most applications, I contend that you don't need the middle of the hex flat to transmit the torque, only the outer 1/3 of the hex flat. (If you want to test this, put a hex wrench on a piece of aluminum hex stock. Hold the stock in a vice and torque the wrench until the aluminum is stripped. You will see that the middle of the hex flat is unused. This is actually the same thing I did when designing the churro many years back.)

Here is a pic to show what I mean:



Hope this helps!

Andy B.

[Cory]

My only concern with this would be that it might be harder to keep the broach aligned with the bore since you no longer are relying on the fit between the .500 dia shank on the broach and the hole in the part to ensure initial alignment.

Otherwise this is a perfectly good way to broach something. You'll see that any parts that have been rotary broached will end up with a rounded center and only have flats on the corners, like Andy drew above, since the broach requires some additional clearance over nominal.

At some point the best solution is just to drop $500 on a new arbor press that is actually large enough so that you can do this easily and more repeatably, if you're going to be broaching a lot of parts.