Detailed Rotary Broach

Detailed version of my #TMC2020 entry where I build a rotary broach.
A rotary broach lets you cut internal (and external) features such as a hex, spline or a square into an existing hole. This is very useful to make custom tools.

I also have a cinematic version of the build here:
   • Cinematic Rotary Broach #TMC2020 Entry  

All of my links:
https://linktr.ee/Tom.Make.Here
Here you can find plans, tools for sale, behind the scenes and other ways of supporting me

Some easier broach grinding methods here:
   • Easy Rotary Broach Tool Grinding  

Big thank you to Emma and Steven for hosting and judging the competition entries this year
   / emmawatchrepair  
   / rslng52  

The special steels used (4140 and 1214) are from Tyne Valley Metals. Check them out for some offcuts.
https://www.ebay.com.au/str/tynevalle...
  / tynevalleyenterprises  
I plan to do more videos soon where I show where certain steels provide benefit. Stay tuned.

Competition playlist here, go and give the other entries some love!
   • #tmc2020  

Please excuse the noise from the rain in places

0:00 Plan overview
0:34 Making the backplate
1:38 Starting the body
1:55 How to bore to a shoulder
2:51 Cutting grooves in the body
3:21 Drilling the body flange
4:05 Interesting metrology technique
5:20 Adding material back to a bore
6:30 Making the spindle
7:14 Setup to grind hex tools
8:19 Grinding the hex tools
8:48 Assembling the tool
9:19 How a rotary broach works
10:16 Testing the tool
12:15 The money shot