Wanted: rotary broach

[GT-6 Racer]

Looking for a small rotary broach ( Slater, Somma, Polygon) to do 5mm internal hex for high school robotics parts. I can grind the broach just need a holder. Can’t spend a fortune, no time to make one now. Thanks

 

[Weldingrod1]

Sorry, all mine are English ..

Sent from my SM-G715A using Tapatalk

 

[MrWhoopee]

I've broached a 3\16 hex by cutting off an Allen wrench, grinding the end to sharpen the corners, mounting it in the tailstock and forcing it into a slightly over-size hole. There's very little stock removal in a small hex.

 

[ErichKeane]

I made one with a build group here last year. If I can find it, you're welcome to borrow it depending on how long you need it.

 

[RJSakowski]

Tormach sells a rotary broach, I don't know how competitive their prices are though.

 

[ErichKeane]

Tormach sells a rotary broach, I don't know how competitive their prices are though.

looks to be $500 for the holder, which is pretty consistent with all the others IIRC.

 

[JRaut]

The version by Hemingway Kits is sssssssuuuuuupppppper easy and quick to make.

Compact Rotary Broach - hemingwaykits.com

Unique projects for the small workshop owner. Please browse our Toolroom and Engine Bay for our latest project kits.

www.hemingwaykits.com

I made one last year or so and it works a treat.

Ordering directly from them would take a while for delivery. But surely you could find plans for similar one somewhere on the web.

If you've got some raw stock and a couple small bearings on hand, you could whip it out in a day or two.

 

[ErichKeane]

Here's the build thread I put together for the one I designed: https://www.hobby-machinist.com/thr...oach-building-complete-all-shipped-out.93241/

I link there to someone else's design in the 1st post, then the one I created (to be easy/quick to make!) around page 12 I think: https://www.hobby-machinist.com/thr...ilding-complete-all-shipped-out.93241/page-12

You MIGHT need to scroll through the rest of the pages to see if I update the sheets at all though.

 

[Huub Buis]

Place a peace of square stock in you tool at an angle of 6°. Use a shim at the corner of the toolpost.
Drill a hole 30 mm deep and if you can, ream it to the required diameter.
Remove the shim and place a ball in the hole. You now have a full functional rotary broach.

Place a bar in the broach and find the spot having the lowest runout. This shows the stickout of your broach bits.

I have made my first rotary broach this way and it works superb. The disadvantage is that you have to position it every time. I have made a second one for the tail stock using contact angle bearings . It needs no setup but is doesn't do a better job than the first one.
Both rotary broaches are in use for several years now.

 

[GT-6 Racer]

I made one with a build group here last year. If I can find it, you're welcome to borrow it depending on how long you need it.

Thanks for the generous offer, but I’ll need to buy or make one. I’ve been putting it off…