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Rotary Broaching Tool Holder
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08-09-2013, 07:03 PM
The holders do have the 1º off axis center of rotation, and that's why it's important to do the engineering right and always use the same length of broaching tool. The tip of the broach itself must rotate about center. If the tip of the tool isn't there, you get oversize shape and poor tool life. Under really bad conditions, you get destroyed tools and workpieces.
08-09-2013, 07:59 PM
Indeed Pix, the position of the broach tip's critical, the run of the mill tailstock or turret mounted holders dont have any adjustment and so have to use bits of one.specific length for their geometry to work. It occurred to me that a QCTPmounted broach holder would allow easy adjustments to put the bit in the righ place.
I can appreciate that a lot of lathes wouldn't have enough force from the carriage feed though, particularly with larger broaches. If anyone knows of a table of broaching force for different sizes and materials, a link would be useful!
Rules are for the obedience of fools, and the guidance of wise men...
(Douglas Bader) 
This is a good place to see about rotary broaching http://www.slatertools.com/rotary-broaches#.UgYHOti0zq4
And another http://www.genswiss.com/products.htm (From PixMan's post)  DaveH
08-14-2013, 08:29 AM
I'm looking at something like this, to fit in the tool post.
This is a 3D sketch from Ken Irwin's design and drawings. DaveH 
08-14-2013, 12:16 PM
Not to sound really dumb but what is the advantage over push / pull broach?
I've done a little broaching of bead roller dies and pullmax collets
oldgoaly, proud to be a member of MetalworkingFun Forum since Jun 2013.
08-14-2013, 01:08 PM
08-14-2013, 01:16 PM
Thats it exactly, hard to broach a blind hole.
Free advice is worth exactly what you payed for it.
Greg
08-14-2013, 01:33 PM
but could the tool be pushed??? well it is??? it's the spinning that has me stumped! is so it can be used in a lathe style machine? easier to chuck up and release? A friend Bill Carriel made a a couple a broaches to do a 4-Cyl chevy door latches before they were reproduced. They have a square thru hole and a round recess for screw head. just 2-3 inch long with 4 teeth.
oldgoaly, proud to be a member of MetalworkingFun Forum since Jun 2013.
(08-14-2013, 01:33 PM)oldgoaly Wrote: but could the tool be pushed???Yes if you are superman  Because the tool bit is going around (with the work piece) and wobbling it takes tiny cuts at a time. The cutting edge is moving around so that hex tool bit is not cutting on all 6 edges at once but just a small part of it. Clear as mud DaveH
08-14-2013, 04:49 PM
(08-14-2013, 03:31 PM)DaveH Wrote: Yes if you are superman The rotary broaching tools use but a fraction of the force needed for traditional stationary push or pull broaching. In my days working in screw machine shops as a setup guy, programmer and operator (later process engineer and supervisor), I used the Genevieve Swiss broaching tools to make Torx and hex sockets in the heads of Ti6Al-4V titanium alloy bone screws. With those, I had to go back into the hole with a solid carbide drill, boring bar or (in some cases) end mill to clean out the big chip left at the bottom of the hole. Those sockets couldn't be done in a cold header machine as a socket head cap screw or set (grub) screw is done. That method leaves no burrs at the bottom. |
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could be it is easier to do shallow blind holes.