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# Pressure calculation

## Pressure calculation

(OP)
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!

### RE: Pressure calculation

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
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.

### RE: Pressure calculation

(OP)
Looks great, thanks for your help!

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