Detailed Rotary Broach #TMC2020

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: https://youtu.be/A-NizgMX10k 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: https://youtu.be/FQUGZQdFiRc Big thank you to Emma and Steven for hosting and judging the competition entries this year https://www.youtube.com/user/emmawatchrepair https://www.youtube.com/user/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/tynevalleymetals https://www.facebook.com/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! https://www.youtube.com/playlist?list=PLUNkS7pOL3zvriadIoi-6uNYkxx1y71Xj 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