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:

All of my links:
Here you can find plans, tools for sale, behind the scenes and other ways of supporting me

Some easier broach grinding methods here:

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

The special steels used (4140 and 1214) are from Tyne Valley Metals. Check them out for some offcuts.
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!

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

[jackhawley]

i don't get why you need it to spin? why not push it in without the chuck spinning?

[ArmchairDeity]

1:46 - LMAO OMG dude using the rust for machinists blue was a brilliant move... I love it!

[sivakumarastrocure]

Very nice. Your tequenics used is very superb with available tools. This is called by the name of Efficient Machinist. Thank you. 💯🤝

[Nope-gu]

The bearing is correct. Back check it with some gauge blocks and that same mic. Earlier in the project when chucking you need to check for whip.

[miguelcastaneda]

what i use to cup out tip is an old carbide drill i ground with shallow angle and for side clearance on broach i shim up end of spindex with a .015 shim works out to a degree and a half

[stephenfinch]

Yep bought the plan can’t wait to get started

[metalshopwithtroy]

Wow, loved your video. Well presented and will be downloading the plans
Keep up the great work i see you on emmas wednesday live from time to time.
Thank you for sharing

[KathrynLiz]

Nice video... been going to knock up one of these for some time
Referring to your measurement issue with the bearing being over an inch, back in the mid 1960s I found, at an engineer's supply shop closing sale, a 0-2" Mitutoyo Mike... I have never seen another one, but it's very handy just to have one mike for all measurements from 0 to 2" with not anvils to change or anything...

[eugencsl]

Dunno man, liked the cinematic version but also like this one ... can t choose between em. Nice videos, keep them coming 👍🏼 good day

[larrymatsumoto]

Love to have one of those rotary broach tool great video

[CraigsWorkshop]

Brilliant, Tom. Love hearing the explanations and seeing the details.

[CreaseysWorkshop]

That's a great video. Very ingenious measuring techniques!

[TRENDewyZ]

Great video. You do very nice work, both in the content and delivery.

[bigmikeh]

Thank you for sharing. This is different broaching than I’m used to. I’ve seen broaching bars that cut inside splines in GM Front wheel hubs, I’ve broached key ways. But not this way. Think I might try this in my home shop. Great job

[lookcreations]

Enjoyed that. Thanks for the details. Will watch it again when I make something similar down the line. Good luck with the TMC 👍😎👀

[billbaggins]

One of those tools that I comprehend without fully understanding 😁 Nice job Tom and welcome to my subscription list.

[TABE-O]

Nice one. Great vid. Thanks for sharing

[EverettsWorkshop]

Nice! Another tool on the "I want to build it someday" list, thanks for sharing!

[erik....]

I tried building one a few years ago but it broke my tool bit on the first try, and haven't tried it since.. It should work though unless something is very off. I got a tool grinder since then so maybe I should try it again.. Thanks for reminding me.

[homemadetools]

Beautiful work as always. We posted this video on our homemade tools forum :)