Rotary broaching cutters

[Kram]

I'm intending to try this soon but couldnt find much detail about the cutters.

The commonly used cutting angle seems to be 1-1.5 degrees off centre and so 2-3 degrees of clearance is needed on the cutter.

The end of the cutter, Im unsure if it can be flat ground or if it needs to be concave to have adequate sharpness.

I was intending to start with CR-V hex key bits as I have several spares, should have no problem in mild/free machining steel.

 

[Agroshield]

What is the relationship between the A/F size of the cutter and the A/F size of the allen key which is meant to fit into the broached hole?

What I am saying is if you use an 8mm allen key to try to make a hole to accommodate an 8mm allen key, will it work?

See 8.1mm dimension here and measure an actual 8mm allen key:

https://www.aliexpress.com/item/1005008135484360.html (torx broaches also available).

 

[Kram]

I had not seen that they are available to buy, although I dont currently use aliexpress and would prefer not to. I cant see them on amazon or ebay.

Using a hex key I may get an undersize hole then, I'd like to try it anyway and can always make a cutter from scratch if needed.

 

[Slowcoach]

Hemmingway do kits apparently and that old Tony did a vid a few years ago.

 

[dieselsamurai]

Building one of these definitely on my project list , there are a lot of videos on youtube most are 1.5 degrees