Broaching

[Steve Smith]

I have a low tech method of broaching a hexagon in my african blackwood driver handles; I tookm a 1/4" allen key and ground it to a ~45 degree bevel and then hone it. I mount it in the drill press and with the power off, slowly broach the hole drilled into the handle and cut away a bit at a time. It's rather tedious, so perhaps someone has a better method? This is a typical project below:

 

[TimR]

I have a low tech method of broaching a hexagon in my african blackwood driver handles; I tookm a 1/4" allen key and ground it to a ~45 degree bevel and then hone it. I mount it in the drill press and with the power off, slowly broach the hole drilled into the handle and cut away a bit at a time. It's rather tedious, so perhaps someone has a better method? This is a typical project below:

View attachment 170009

Sounds like a good low tech approach

 

[TXMoon]

Right... what is "broaching"?

 

[rocky1]

broach
noun
\ ˈbrōch

\
Definition of broach
(Entry 1 of 3)

1 : brooch wore a lovely broach on her lapel
2 : any of various pointed or tapered tools, implements, or parts: such as
a : a spit for roasting meat
b : a tool for tapping casks
c : a cutting tool for removing material from metal or plastic to shape an outside surface or a hole (** or, in this case wood **)

broach

verb (1)
broached; broaching; broaches
Definition of broach (Entry 2 of 3)

transitive verb


1a : to pierce (something, such as a cask) in order to draw the contents also : to open for the first time
b : to open up or break into (a mine, stores, etc.)
2 : to shape or enlarge (a hole) with a broach (see broach entry 1 sense 2c)
3a : to make known for the first time
b : to open up (a subject) for discussion a good time to broach the subject



He's drilling a hole in the handle, then using the altered allen wrench broach to make his hole 6 sided to fit the shank on the screw driver Kevin.

 

[TXMoon]

Oh cool. Thank you.

 

[Graybeard]

So Rocky if the wife asks you for noun #1 and you give her verb #2 you might be in trouble? Amazing how one word can be used in so many different ways.

 

[rocky1]

And, that was only 2 of the 3 definitions offered!

 

[Karl_TN]

Guess I'm a little slow. Got any pics to show what you mean by "broaching"?

 

[kweinert]

Well, this is probably overkill and not very useful to you but I found it interesting.

http://www.slatertools.com/rotary-broach-tooling/internal-rotary-broaches/hex-hexagon-1

 

[Steve Smith]

@kweinert Yes, I had found a youtube video on their products. That type of broach is over $100 and the rotary holder can go into the four figures. I'm too cheap for that. If I was pumping these things out by the score, then it would be worthwhile, but I only have 7 or so to make this go around.

 

[kweinert]

@kweinert Yes, I had found a youtube video on their products. That type of broach is over $100 and the rotary holder can go into the four figures. I'm too cheap for that. If I was pumping these things out by the score, then it would be worthwhile, but I only have 7 or so to make this go around.

Yeah, I figured it was overkill. Also don't know how well that tool would work on wood.

I'll ask a dumb question here - have you thought about using a mortising bit? I think the smallest I've seen is 1/4" so it's probably too big. If it was the right size then just 3 cuts with a 60 degree turn between them would do the job.
Just a random thought.

 

[duncsuss]

Just a random thought.

Your random thought and my random thought must have been drinking in the same bar ...

My idea was to get a nice sharp chisel the width of one of the flats on the hexagon, and put the workpiece in a chuck on the lathe. Set the tool rest height so the chisel will be level when the bevel is down, in place to cut the top flat. Tap-tap-tap, then turn the lathe spindle through 60 degrees. Repeat. I expect it's nowhere near as easy as this in practice!

 

[Nubsnstubs]

Yeah, I figured it was overkill. Also don't know how well that tool would work on wood.

I'll ask a dumb question here - have you thought about using a mortising bit? I think the smallest I've seen is 1/4" so it's probably too big. If it was the right size then just 3 cuts with a 60 degree turn between them would do the job.
Just a random thought.

I'll answer your dumb question. A mortise bit is a square, 90 degrees each side. Turn it any angle 45 degrees, and it will make 8 points.

A hexagon is only six sides, where a octagon has 8 sides. I sure as scat hope I'm right.

When I was a young lad fresh out of the Army, I worked in a bearing manufacturing plant in Santa Ana, California. They had 4 broach machines that had what looked like long reamers that would pull through a bearing shell removing a thousandth or two off each piece. They could put 25 shells on the arbor, hit a switch, and within 2-3 seconds, those 25 shells were final sized. Each machine had an operator as it was that fast.

I've seen broaches for making Allen sockets that look like teeth nibbling away at a drilled hole making the Allen socket. Someone ought to make a video with chomp, chomp each time it takes a bite. There are others that just punch down into the drilled hole leaving the size socket required. ............ Jerry (in Tucson)

 

[kweinert]

I'll answer your dumb question. A mortise bit is a square, 90 degrees each side. Turn it any angle 45 degrees, and it will make 8 points.

A hexagon is only six sides, where a octagon has 8 sides. I sure as scat hope I'm right.

............ Jerry (in Tucson)

True - but why do you have to turn it 45 degrees? If it's the right size then you could do a square hole with cut 1 which creates two opposite sides, turn the piece 60 degrees, line up with the corner, cut #2, then do the same for cut #3.

I'm going to have to create a 2D model to see if that makes sense - but that's what was in my mind :)

 

[Nubsnstubs]

Ken, I think I understand what you're saying. I have a mortise set, and will do an actual cut and see if what you just said works. Unfortunately, using a 5/16" mortise chisel, the smallest I have, will make a larger hole than wanted. I should have this done tomorrow afternoon. ...... Jerry (in Tucson)

 

[TimR]

Been thinking about this. I would go one step beyond what you originally intended by using successively larger Allen keys to remove just a little bit at a time . Thus would be more consistent with what broaches in machining do with tapering . It’ll put less stress on your piece I think.

 

[duncsuss]

True - but why do you have to turn it 45 degrees? If it's the right size then you could do a square hole with cut 1 which creates two opposite sides, turn the piece 60 degrees, line up with the corner, cut #2, then do the same for cut #3.

I'm going to have to create a 2D model to see if that makes sense - but that's what was in my mind :)

Doesn't quite work. Draw a hexagon, then drop vertical lines from top-left corner to bottom-left corner, and top-right corner to bottom-right corner. What you have is a rectangle, not a square (it's taller than it is wide). You would need a mortise chisel this profile for your suggestion (three cuts, each rotated 60 degrees) to work.

 

[kweinert]

Doesn't quite work. Draw a hexagon, then drop vertical lines from top-left corner to bottom-left corner, and top-right corner to bottom-right corner. What you have is a rectangle, not a square (it's taller than it is wide). You would need a mortise chisel this profile for your suggestion (three cuts, each rotated 60 degrees) to work.

So it would take 6 cuts instead of 3 - but in the size we're talking here it's not practical.

Sorry, just thinking out loud. Sometimes that's useful as it gets people thinking outside their box. Sometimes it's just noise.