Group Project: Rotary Broach-- Building complete, all shipped out!

So to be clear, this is the list;

1- ErichKeane-cutting bits (better be one damn extensive set!) ; ) #3 on diagram and misc bearings/screws
2- GunsOfNavarone Backing/angle plate Part #1 on diagram
3- ttabbal spindle housing
4- T Bredehoft) sindle

InkedThe breakdown_LI.jpg
 
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GunsOfNavarone said:
So to be clear, this is the list;

1- ErichKeane-cutting bits (better be one damn extensive set!) ; ) #3 on diagram and misc bearings/screws
2- GunsOfNavarone Backing/angle plate Part #1 on diagram
3- ttabbal spindle housing
4- T Bredehoft) sindle

View attachment 369013
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Yep, pretty much :) I'm going to make 2-3 sizes of bits to start, and otherwise make them compatible with the commercial/professional 1/2" diameter bits (which are 1.75" long).

McMaster has a bunch of them available at roughly $100/each, but at least they are available.

I noticed while designing this that a bunch of the designs use non-standard bits that you basically need to grind yourself, so having commercially available alternatives was important to me.

One such concern is that if you grind yourself (and don't have a cyndrilical grinder!) You are stuck to the 1/2" major size (so .433 hex or so). You'll note that the TomMakesHere has that problem (and is a non-standard size, so you're stuck with those.).
 
Hmmmm...interesting and concerning. I don't do HSS, say on my mill, as I do not have sharpening skills, I go carbide inserts. So, I won't be sharpening bits, I'll be buying new ones. $100 a pop??! I guess I should do some searches for .500" broaching bits....there has got to be a reasonable source somewhere!
 
GunsOfNavarone said:
Hmmmm...interesting and concerning. I don't do HSS, say on my mill, as I do not have sharpening skills, I go carbide inserts. So, I won't be sharpening bits, I'll be buying new ones. $100 a pop??! I guess I should do some searches for .500" broaching bits....there has got to be a reasonable source somewhere!
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Yeah, bits for these are expensive! Fortunately minor dressing of them ends up being just a stone across the flats.

My idea was to custom make 2-3 for each of us (square or hex!) That should cover us. Sadly, there doesnt seem to be any Chinese manufacturers of these.

If you have the ability to harden O1 you could make them out of that, or potentially use carbide to cut the hss. I'm using my surface grinder with a diamond wheel I think.
 
I gotta say...their adjustment free holder sounds pretty awesome. I really am a bit lost as to why a small amount of movement of the spindle (radially-so the broach can center itself), isn't possible for us (?)
 
GunsOfNavarone said:
I gotta say...their adjustment free holder sounds pretty awesome. I really am a bit lost as to why a small amount of movement of the spindle (radially-so the broach can center itself), isn't possible for us (?)
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Do they have a good image of one that I can perhaps see to copy? I just was on my phone and saw they have bits at 1/2 of McMaster prices.
 
ErichKeane said:
This place : has them ft $50 each! https://www.polygonsolutions.com/ro...ches/hexagon-rotary-broaches-half-inch-shank/

They even have through-hole versions, which have the ability to go into a tighter hole, since the air can escape backwards!
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Their broaches are ok I’ve purchased a few at the tune of $70-$80 each.

Their m2 broach literally deformed like mild steel I thought it was wild I’ve never seen hss do that???? Must have been some cheap Chinese stuff. They told me the higher grade stuff was better but I never got to use it.
 
Broaches.. I can't imagine using as large as 1/4, I don't work with screws that large (3/8) although I probably could. Most of my projects use screws smaller than 1/4-20. down to and including 4-40. I have tapped holes 2-56, but certainly never will make a screw that small.

Send me a finished print and some steel, I'm ready. Oh, what are we making this out of? I'd suggest either annealed of half hard 4140 or such. If this has been discussed, I missed it, sorry.
 
T Bredehoft said:
Broaches.. I can't imagine using as large as 1/4, I don't work with screws that large (3/8) although I probably could. Most of my projects use screws smaller than 1/4-20. down to and including 4-40. I have tapped holes 2-56, but certainly never will make a screw that small.

Send me a finished print and some steel, I'm ready. Oh, what are we making this out of? I'd suggest either annealed of half hard 4140 or such. If this has been discussed, I missed it, sorry.
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Any sort of steel works, nothing on the tool other than the bit has a critical hardness. 1018/12L14 works, as does 4140.
 
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