Home Built Rotary Broach

[jumps4]

7hc
right under his drawing he explains about the 1 and 2 degree sides to the holder. he is holding the cutter 1 degree off center when he adjusts the tool holder position. see the angles in the corners.
steve

 

[Bill Gruby]

The 1 degree offset gives you free rotary motion. The bit holder needs room to move.

"Billy G"

 

[jumps4]

when i get the time I'm going to try to make one that will fit in my qctp boring bar holder just for fun.
I have some o1 1/2" tool steel for cutters.
steve

 

[7HC]

I did read the part about angling the sides one and two degrees, but I didn't understand the significance.

Ok, I re-read it and it's becoming clearer.
You experienced guys can visualize what's going on a little better than I can.........but I'll get there in the end!

M

 

[jumps4]

I'm a complete novic also
I went to cnc because I can draw easier than work the machine I always end up turning the crank the wrong way or something:whistle:
steve

 

[Bill Gruby]

I don't know anything about this brand but at this point it's going cheap.

http://www.ebay.com/itm/Somma-Tools...075?pt=LH_DefaultDomain_0&hash=item3cc9e064eb

"Billy G":thinking:

 

[7HC]

I don't know anything about this brand but at this point it's going cheap.

http://www.ebay.com/itm/Somma-Tools...075?pt=LH_DefaultDomain_0&hash=item3cc9e064eb

"Billy G":thinking:

At the moment it is, even with the huge markup on shipping. :huh:

M

 

[7HC]

I have a broaching question!

For square, hex, oct, star, etc. broaching, you first drill a slightly undersized hole in the workpiece, no problem.

What kind of starting point do you use for a 'D' shaped broach?

It has to be central in the workpiece, and drilling a hole will remove material where the flat of the 'D' needs to be. :thinking:

Thanks,

M

 

[Tony Wells]

I haven't looked, but actually I'd be a little surprised if you could wobble broach a d-hole. Rotary broaches are pretty limited on the amount of material they can remove to bring in the desired profile. A d-hole would have to be drilled just under the flat to centerline dimension, and on most, that would leave quite a bit of material to remove. I have my doubts. I've done and seen a good bit of wobble broaching, and there's a little more to it than meets the eye if you want the tooling to last, and make any time on the parts. Also, the finish of the flats (or whatever shape) isn't all that slick, at least in the materials I've worked with. I've done D-2, 4140/42, 660 Bronze, Aluminum Bronze, and BeCu. It's a slick process, no doubt, but it's hardly prefect.

 

[7HC]

I haven't looked, but actually I'd be a little surprised if you could wobble broach a d-hole. Rotary broaches are pretty limited on the amount of material they can remove to bring in the desired profile. A d-hole would have to be drilled just under the flat to centerline dimension, and on most, that would leave quite a bit of material to remove. I have my doubts. I've done and seen a good bit of wobble broaching, and there's a little more to it than meets the eye if you want the tooling to last, and make any time on the parts. Also, the finish of the flats (or whatever shape) isn't all that slick, at least in the materials I've worked with. I've done D-2, 4140/42, 660 Bronze, Aluminum Bronze, and BeCu. It's a slick process, no doubt, but it's hardly prefect.

I don't know if it's a wobble process, but rotary broaches are available for both D and Double D profiles.
I guess it would be used to engage a shaft with a flat, but I was just wondering how it would be started, as a circular starter hole would remove metal that was required for the profile.



Thanks,

M