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View Full Version : Rotary broaching - the easy way



drmico60
09-19-2011, 01:27 PM
I have developed a tool for rotary broaching that is very simple to make. It also facilitates making the cutters. Further details are here:
http://mikesworkshop.weebly.com/rotary-broaching.html
I hope this will be of interest to other members of this forum.
Mike

MichaelP
09-19-2011, 02:28 PM
Cleaver! Thank you for sharing the design, Mike. Very interesting and easy to make, indeed.

bborr01
09-19-2011, 02:42 PM
Nice job Mike. Thanks for posting the link.

Brian

PaulT
09-19-2011, 06:15 PM
Pretty slick.

Somebody should make up and sell an Aloris quick change version of this design, I'd buy one, I'm too busy trying to make enough money to keep food in everyone's mouth to build one.

Paul T.

Chris S.
09-19-2011, 06:19 PM
That's as slick as .. uh ......... grease! ;) Though, I will humbly admit that I didn't get it at first. :D

Chris S.
09-19-2011, 06:26 PM
Just had a thought....

This broach belongs in the "Shop Made Tools" sticky!

http://bbs.homeshopmachinist.net/showthread.php?t=39202

Chris

jkilroy
09-19-2011, 06:37 PM
Thats great work. And as someone with a pillar style tool post I am going to shamelessly rip off your reverse collet style tool post right away. Did you harden your tool post or at least case harden?

Your Old Dog
09-19-2011, 07:28 PM
Thanks for the post. Very cool setup. I think even I could pull that one off !

firbikrhd1
09-19-2011, 09:10 PM
Just had a thought....

This broach belongs in the "Shop Made Tools" sticky!

http://bbs.homeshopmachinist.net/showthread.php?t=39202

Chris


It most certainly does! Great job!

drmico60
09-20-2011, 02:52 AM
Thats great work. And as someone with a pillar style tool post I am going to shamelessly rip off your reverse collet style tool post right away. Did you harden your tool post or at least case harden?

The post that I made is unhardened mild steel. It has been in use for more than 5 years and is not showing any significant wear.
Mike

fishfrnzy
09-20-2011, 08:40 AM
Mike,

Very nice indeed. A simple design that lookseasy to build. Thank you for posting. For those that havenot checked out the rest of the site, there is a lot of other good stuff there as well that looks easy to make, with pretty clear instructions. Worth the look IMHO.

jkilroy
09-20-2011, 03:14 PM
I do mean this as a compliment but the OP doesn't seem to be a person constrained by conventional thinking. Very nice work on the web site for sure.

loply
09-21-2011, 08:05 AM
Hi Mike/OP,

Sorry but I don't understand - does the cutter rotate relative to the workpiece when in use, or is it just static and being pushed in?

It sort of looks like the cutter is essentially just a punch which is being pushed into the hole? Or have I got that all wrong?

Cheers,
Rich

drmico60
09-21-2011, 08:29 AM
Hi Mike/OP,

Sorry but I don't understand - does the cutter rotate relative to the workpiece when in use, or is it just static and being pushed in?

It sort of looks like the cutter is essentially just a punch which is being pushed into the hole? Or have I got that all wrong?

Cheers,
Rich

Hi Rich,

The cutter rotates at the same speed as the workpiece (it has to or it would break the tool). Because the tool is at a slight angle to the axis of the work it chisels one edge at a time into the workpiece as it rotates. This requires much less force than to try to chisel all 6 edges at the same time.

Rotary broaching is a well established technique for cutting polygonal holes. (Google rotary broaching and you will find much information.) Most rotary broaching tools are complex, tailstock mounted and hence expensive. All I have done is to make a very simple tool that performs the same job.

Mike

Chris S.
09-21-2011, 11:05 AM
Not to be picky.. but your "Hot Wire Cutter" schematic contains an error.
http://mikesworkshop.weebly.com/hot-wire-cutter.html
Neon lamps require a current limiting resistor; unless sold as an integral unit. Perhaps a note to this fact would be apropos.

Chris

drmico60
09-21-2011, 03:32 PM
Not to be picky.. but your "Hot Wire Cutter" schematic contains an error.
http://mikesworkshop.weebly.com/hot-wire-cutter.html
Neon lamps require a current limiting resistor; unless sold as an integral unit. Perhaps a note to this fact would be apropos.

Chris

The neon used was a moulded plastic component with internal neon and resistor rated for 240 V use. I will add a note to the Hot Wire webpage.
Mike

RTPBurnsville
09-21-2011, 04:46 PM
Great idea, thanks for sharing..... Also you have a nice website.

Robert

j king
09-21-2011, 04:57 PM
I like your web site also. Very neat and organized.Nice job.

Paul Alciatore
09-21-2011, 06:12 PM
That is a great design and I have saved it in my future projects folder. Thanks.

As an alternative to your expanding tool post, it would work well on the post I designed.

http://img.photobucket.com/albums/v55/EPAIII/Disassembled.jpg

My round post is front/center in the picture and it has a flat on it to allow for indexing. It has a 1" (25.4mm) diameter so the size is very similar. Your holder could be modified with a saw slot and a clamping screw to mount it while allowing it to be rotated to the necessary angle. I don't know if the hollow formed by the flat on my post would be a problem or not, but if it is, a "D" shaped filler piece could be easily made to fill it in. Just cut a slice from round stock and mill it down on the flat cut side to the correct size. Your height setting screw would work just fine as I used a similar one in my design: it is somewhat hidden in a counter-bore on the top of the tool holders and it rests on the flange on the bottom of the tool post.

The complete description of my QC post was published in the Feb/Mar 2010 issue of Machinist's Workshop if anybody is interested.

drmico60
09-22-2011, 12:57 PM
Paul Alcatore - great toolpost
Jking, RTPBurnsville, JKilroy, Fishfrenzy - many thanks for your kind words regarding my website. Feedback, good or bad, is always useful.
Mike

KEJR
09-22-2011, 09:14 PM
I wonder if it would be much more work to mount the cutter tool into a ball bearing, perhaps with a taper that accepts different tools (or maybe even slip fit). Obviously this design works for this application. Thanks for sharing.

drmico60
09-23-2011, 04:43 AM
I wonder if it would be much more work to mount the cutter tool into a ball bearing, perhaps with a taper that accepts different tools (or maybe even slip fit). Obviously this design works for this application. Thanks for sharing.

Yesterday I made a cutter holder that replaces the original cutter and enables the cutter to be interchanged as you suggest, see:
http://mikesworkshop.weebly.com/rotary-broaching.html
If the tool was to be in continuous use then I agree a ball bearing might be advantageous but for occasional use I think the present design will probably out last me.
Mike

drmico60
09-28-2011, 04:47 PM
I have made a modification to my rotary broach that enables the cutter to be withdrawn under power. I have also added a link to a video of the tool in use, see:
http://mikesworkshop.weebly.com/rotary-broaching.html
Mike

rmuell01
09-28-2011, 10:18 PM
wonderful tool, I have a bit that's looking for a holder, think I'll make one.

OT but if you could have clickable photos that expand larger, that would be great.

Rob