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

Mheaton92 said:
I think I will try to organize one. I am trying to help with the clamps, but I agree 100%. I didn't want to do the clamps, they didnt seem like a lot of fun because of the simple design. That being said, I will still get in on it. This broach looks awesome, I will one day buy a surface grinder and when I do this build will be first on my list!
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Fortunately I designed this around commercially available bits, so you can get them from McMaster and a few other places! They are costly ($50-$100 each!) , but at least obtainable.
 
ErichKeane said:
Fortunately I designed this around commercially available bits, so you can get them from McMaster and a few other places! They are costly ($50-$100 each!) , but at least obtainable.
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ok cool, I am sure everyone on this forum is just like me and has 100 projects going at once. So it will go on the list. I was in the middle of building a model engine and decided to make a solid tool post. So once the tool post is done I will go back to the engine then onto this now!
 
Hey, so recent hard won lesson... you -must- have a chamfer to get the broach started. If you bore.a shoulder in that is a close fit on the broach, it will not start. It will push a ring of material in :-(

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Got the outer dimension of all the cutters ground. 11 successes out if 12!

I still have no idea how I'm going to cut the cup in the end. A few of them are incredibly tiny, so I have no idea how to get that to happen with a grinding wheel...
 

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For the little ones, maybe something like a dremmel with a grinding stone?
 
ttabbal said:
For the little ones, maybe something like a dremmel with a grinding stone?
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I ordered a Dremel knock off that I'm going to try to clamp to my tool post or something... Best idea I have. You can't use anything other than a thin disk, otherwise they just end up being flat!
 
GunsOfNavarone said:
I could grind my own cups if that helps. I have a flexible shaft grinder...think it's like 10hp! ; )
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I'm going to try on the two that are for me first, if they don't work, I might just send everyone's to you :) I ordered a cheap dremel clone that I am going to try to use on the lathe with some grinding wheels, so we'll see!
 
I found a couple of affordable broaches on ebay for anyone who is interested:
7/32" : https://ebay.us/WhtO3P Looks like this guy has a bunch of them!
5/32" https://ebay.us/fzG17a Same guy, same deal!

These are somewhat common allen wrench sizes, so I suspect some of you might find them useful, partiuclarly since they are only $35 each, significantly cheaper than these usually go for.
 
Is the cup needed? I saw an article where they didn't put the cup and it cut the same.
 
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