Found affordable rotary broach, any feedback

[yul m6]

Have long wanted to get a rotary broach holder, but found them too expensive since LMS discontinued theirs. Found this one from Janco on ebay, and I'm wondering if anybody has experience with it.

http://www.ebay.com/itm/NEW-Wobble-Broach-Rotary-Broach-Tool-Holder-5-8-Shank-for-1-2-Broaches-/190696928324?pt=LH_DefaultDomain_0&hash=item2c666c3444

[dp]

If you don't need a monster size unit they're not difficult to make:

http://mikesworkshop.weebly.com/rotary-broaching.html

Others here have made them using other simple designs (see Search). If you're clever you can make one that uses off-the-shelf broaches.

[Zahnrad Kopf]

Made this for about $40 in bearings and scrapbinium 4140HT...

[krutch]

Used on on a BP when I worked in Peoria years ago. Liked it so much got one for my shop. haven't used it yet.

[Alistair Hosie]

Sehr gut gemacht meine lieber Zahnrad Kopf sehr schon.Meinen Schwester hatte nur tungsten carbide Zahne,Sie seiht aus vie eine crocodile.Alistair

[Tamper84]

Ok I will take this one on. I know what a broach is and what it is for. But what are these used for? Dont bust me too hard on this one. I am following advice from a previous thread on getting active on this board! lol

Thanks,
Chris

[DR]

This broach has no way to center it so you need to provide a way, unless your machine is very accurate.

Have long wanted to get a rotary broach holder, but found them too expensive since LMS discontinued theirs. Found this one from Janco on ebay, and I'm wondering if anybody has experience with it.

http://www.ebay.com/itm/NEW-Wobble-B...item2c666c3444

[Paul Alciatore]

Tamper,

Nothing wrong with asking questions, even basic ones. The basic idea of using a rotary broach is to be able to make a hole that has a different shape instead of round. Thus, broaches (tools for the rotary broach) could be made in different shapes like square, triangular, hexagonal, pentagonal, D shaped, splines, internal gear shapes, etc. The techniques for making them are limited, especially in a small shop.

The principal of operation is perhaps not explained well in some write-ups. Here is one with a drawing that helps to show the principle. Look about 3/4 of the way down the page.

http://en.wikipedia.org/wiki/Broaching_%28metalworking%29

And here is one that shows a rotary broach in action.

http://www.slatertools.com/sales-support-service/videos/rotary-broach-and-tool-holder-demostration?gclid=CKDx4MHHiLECFXPDtgod3QGDHg

I did say they were for making non round holes but you may notice that one of the scenes in the video shows an external knurl being broached with a rotary broach. So, it can work both ways. It is really a very nifty tool.

[TGTool]

Ok I will take this one on. I know what a broach is and what it is for. But what are these used for? Dont bust me too hard on this one. I am following advice from a previous thread on getting active on this board! lol

Thanks,
Chris

There have been some prior threads giving more detail than I can, but basically a rotary broach is used on a lathe or mill to produce a non circular contour. Most common example perhaps is a hexagonal hole like that in the head of a socket head cap screw. Those are made a different way, a forging type operation, but in a small shop and for only one or a few pieces the rotary broach can give you holes in unusual contours, provided it doesn't have to be too deep - maybe 1-1/2 to 2 times nominal diameter. The cutting tool itself, in the case of a hex, is just a hex with a small depression in the center and a clearance angle on the sides. The "rotary" part is arranged so that the tool spins with the work, travels in a straight line with the centerline of the work, but is tipped at a small angle, perhaps just one degree. This relationship means that each edge or point of the cutting tool is pressed successively down through the workpiece reducing the force required compared to simply pushing a hex straight into a round hole. A clever idea and a nice tool.

[Tamper84]

Thank guys! I have some reading to do!!

Thanks,
Chris

[Polygon]

Rotary Broaching Video

Here's another great rotary broaching video:

http://www.youtube.com/watch?v=uTsPXFy7Xx0

[Zahnrad Kopf]

Sehr gut gemacht meine lieber Zahnrad Kopf sehr schon.Meinen Schwester hatte nur tungsten carbide Zahne,Sie seiht aus vie eine crocodile.Alistair

Vielen Dank. Vorsicht. Ich sagen Ihren Schwester was Sie sagen!
"Ich glaube nicht, schneiden Zahne. Ich schneide Zahnraumen."

[Polygon]

This broach has no way to center it so you need to provide a way, unless your machine is very accurate.

The old screw machine style broach holders are adjustable and can be aligned with a little bit of work. If yours has the wings on it with all the set screws then it's adjustable.

However, both the adjustable and adjustment-free holders have a little bit of end-play. If you can put a chamfer on the hole +.005" per side larger than the sharp corner dimension, usually the broach will find its way and follow the hole.

Also, most rotary broach manufacturers recommend pilot holes drilled 3% oversize. This is helpful because it causes smaller chips, reduces the pressure required, and reduces the amount of extra pilot hole depth required.