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hexalobe (Industrial) (OP)
30 Mar 12 12:34
Hello,
I'm trying to calculate the amount of pressure required for rotary broaching. I've found a few charts online, and we can see what the machine is telling us the pressure is, but I'm looking for a formula for calculating thrust lbs. in different materials, using a 1/4" hex for example. The pilot hole is already drilled, so the calculation is just for cutting the corners out of the hex hole.
Thanks!
BillPSU (Industrial)
30 Mar 12 18:01
The minimum broach force for a round hole is calculated

Force = 3.1416 x hole dia before broaching x number of teeth engaged x rise per tooth / 2 x constant

Constant is based on material in psi

Aluminum                    200,000 - 300,000
Brass                       200,000 - 300,000
Bronze                      350,000
Cast Iron                   200,000 - 350,000
High Temp alloy steel       Up to 600,000
Lead                        60,000
Mild Steel                  450,000
Steel Casting               400,000

This calculation does not take into account other factors such as cutting fluid, chip breakers, hook/face angle, sharpness.
hexalobe (Industrial) (OP)
1 Apr 12 20:21
Looks great, thanks for your help!

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