Rotary Broach

A

Arcstar*

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Hey guys. I'm thinking about getting one of those rotary broach sets from eBay. They are kind of expensive. I don't want to buy junk but I don't need one to make aerospace parts either.

They have lots of shank styles to choose from but am thinking of getting the 5/8" straight shank so I can share it between my monarch and chucker.

I've never used one. Any suggestions or recommendations.

As always much appreciated for any help I can get!
 
I was intrigued by them also, and I have hot yet figured out exactly how they manage to plunge in and scoop out perfect hexagons socket heads. Before you splash out on eBay, give YouTube a search. I think there is a content on how to make them. When you talk of "sets", you want to think ahead about which of the broaches in the set will see much use. For some, it might be "hardly any", or "maybe never". Compare this to the knowledge that they might be, relatively easy to make. At least check it out to see if we be all wrong about the anticipated difficulties, or even if one would want to get into something like that..

I am trawling memory here, and I don't want to mislead you, but I think it might have been Stefan Gotteswinter, or maybe Joe Pieczinsky, or one of the YT machine content experts. Even if you don't go the route of making one, consider buying just the one or two you need right now.

There are some things where you absolutely need the flexibility and resource potential of a whole set, like for instance, a set of reasonable drill bits up to 12mm in 0.1mm increments, or gauge blocks, (very obviously). I am not sure that holds true for rotary broaches. Right now, just because you got me motivated, I am going to have a peek at YT to see if I can find the how-to on making a rotary broach again.
 
graham-xrf said:
I was intrigued by them also, and I have hot yet figured out exactly how they manage to plunge in and scoop out perfect hexagons socket heads. Before you splash out on eBay, give YouTube a search. I think there is a content on how to make them. When you talk of "sets", you want to think ahead about which of the broaches in the set will see much use. For some, it might be "hardly any", or "maybe never". Compare this to the knowledge that they might be, relatively easy to make. At least check it out to see if we be all wrong about the anticipated difficulties, or even if one would want to get into something like that..

I am trawling memory here, and I don't want to mislead you, but I think it might have been Stefan Gotteswinter, or maybe Joe Pieczinsky, or one of the YT machine content experts. Even if you don't go the route of making one, consider buying just the one or two you need right now.

There are some things where you absolutely need the flexibility and resource potential of a whole set, like for instance, a set of reasonable drill bits up to 12mm in 0.1mm increments, or gauge blocks, (very obviously). I am not sure that holds true for rotary broaches. Right now, just because you got me motivated, I am going to have a peek at YT to see if I can find the how-to on making a rotary broach again.
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Thanks Graham. I'm doing exactly that now, looking through YT. There are lots of videos on the subject. This Old Tony is pretty good. Always good to hear from you're guys prospective though.

Sorry I started you down the rabbit hole but maybe we can explore wonderland together . Keep me posted on your progress and I'll do the same.
 
Yup - I did remember it right. At least two YT folk have made the Hemingway kit, (Brandon and Stefan)
Brandon (Inheritance Machining) did feature his take on it. There are excellent videos, including those by This Old Tony.

The basic idea is to make the shape polygon on the end of the cutter, giving it a "dished concave" end, and with a short taper, to give the points some clearance angle, making it look like a tiny (sort of) dovetail cutter. Then, mounted in a live spinning holder, and offered up at 1°, it chew its way into the pre-drilled socket hole, and turns the hole into a internal polygon.

One version showed the live collet holder mounted onto a tool post, held on by a couple of C-Clamps, and the compound set to 1°.
Anyways, Brandon (Inheritance Machining), Artisan Makes, and Stefan all have good videos on what to do.
 
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