Shop Made Rotary Broach with plans

**PJs** · Feb 8, 2019, 12:46 PM

Outstanding write up, drawings and pics, JR! Top Shelf! Tolerance and design, most excellent. I assume you use these on your bigger lathe. Would love a little short video in operation if you are up to it, and curious what grease you use for the ball...molly?

Thanks Much!!
PJ

**jjr2001** · Mar 3, 2019, 03:58 PM

Hi PJs, Thanks for your comments, much appreciated. I am using a moly chassis grease, just standard stuff for old school auto ball joints etc.
I do use it on my "bigger lathe" which is only a "mini lathe" or 7x16 like the one LMS sells. The lathe seems to handle it ok with the new 1hp motor.

I will try to get a video of it on a test piece.

Cheers, JR

**old_toolmaker** · Feb 8, 2019, 07:04 PM

jjr2001,

Nice job, jjr2001!!!
That is a great tool to own and I just have to make one for my own.

**jjr2001** · Feb 8, 2019, 09:24 PM

Thanks Dick, I think you will like the results.
Cheers, JR

**jjr2001** · Feb 10, 2019, 06:26 AM

Thanks TM, I am not sure how the 3 sided square broach would work.
Does it require a second pass after rotating it 90 deg to cut the 4th side?

Cheers, JR

**Toolmaker51** · Feb 10, 2019, 10:37 AM

Originally Posted by jjr2001

Thanks TM, I am not sure how the 3 sided square broach would work.
Does it require a second pass after rotating it 90 deg to cut the 4th side?

Cheers, JR

You've got me...Slater's the go-to for rotary broaching. They spec .0005 or less tolerance capability on tooling. I've not needed to production broach, the few polygons were arduously milled for finishing in a shaper, sinker or wire EDM

Closest I've been is milling sinker graphite electrodes

or setup and run shaper

A mentor from Long Beach, CA, absolute wizard of horizontal turret lathes, had them. I expect the tool was indexed from a rougher to finisher or changed front retainer? These were very large, he probably made them in the 30's or 40's. As an employee, 'his' largest turrets were big bore oil country machines.

**jjr2001** · Feb 10, 2019, 12:08 PM

Thanks for the info TM.
Cheers, JR

**raymcm** · Feb 28, 2020, 05:53 AM

JR,
what's the depth of the hole in the broach holder part ? 0.500 dia. it shows the overall length..

**jjr2001** · Feb 28, 2020, 10:54 AM

Oops, looks like I missed that one! The depth of the hole for the broach socket is .860".
That is to the edge of the drilled hole and not the depth including the drill point which is of course a bit more by about .125" .

Good luck on your build. The tool works pretty good for me.

Cheers, JR

**wtss12** · Apr 15, 2022, 06:50 PM

Very nice and seems simpler to make then some I’ve seen. I purchased the plans for one and did attemp to make it. It wobbles and such but haven’t gotten it to work yet. I think I am going to give this a try. Less complicated to build.
Thank you for the plans
Bill