BROACHES WANTED

Depends on the thickness of the part being broached, and, naturally, the material. I used a compound leverage 3/6 ton Dake to push a 1/4" broach through roughly 2-1/2" of mild steel. It could be done with the leverage set at 3 tons, but was difficult. Sorry, no broaches available, at least from me.

Harold

This would depend on how much metal you were attempting to remove at a push. I watched a tool and die maker quickly knock out a single tooth broach out of a piece of round tool steel and then he just through it in the collet on the Bridgeport and cut the slot a thou or two at a time advancing the work into the broach.

Yes. Here is a link to the Dumont website which includes required pressure for various size broaches:

-Bill Fill Olympia, WA

Apparently not all T&D men are created equally. Most of them are wise enough to know that broaches are sized for the thickness of material that is to be removed so you should exercise some restraint when making a selection. Long objects produce a lot more chip than do short ones, so the relief configuration is often quite different from broach to broach, as is the depth of cut. The way they're made, it's usually pretty hard to get one started in something that allows too large of a cut per tooth. Pretty hard, but apparently not impossible.

Harold

He wasn't making the broach for a customer, he just needed a key slot in one or two parts right away. Had he been making a tool for someone I'm sure he would have made one to work in a production environment.

Long objects produce a lot more chip than do short ones, so the

My point was that the light chip load and single point set up did not require much pressure. As to your point about proper broach design I yield to your experience.

I more or less assumed that. I think my point is that he may have not used good judgment in selecting the broach. Just like a saw blade, if you don't have a specific number of teeth in contact, things can go wrong. Makes me wonder if he wasn't trying to broach something relatively short and it was able to go off location because there were no teeth in contact with the starting hole. A thin piece, thin enough to drop in the relief area, is what I had in mind.

You are correct in your point, for I, too have done that numerous times, using the quill of a Bridgeport as a shaper. It doesn't require much effort to take the cut so long as you feed it lightly, the tool isn't too large, and the tool has the right rake angle.

As to my experience, don't let me fool you. I've made broaches, ground broaches, and used them, but not much. Enough, however, to be familiar with them. It's just plain old common sense where taking cuts is concerned. Not much difference, lathe, mill, broach, they all cut in similar fashion. If you understand cutting geometry, it's not all that difficult.

Harold

For those sizes it's probably not the pressure that will get you, it's the clearance under the ram. Check the broach lengths as standard vs. your ram height just to make sure you can make them work. In a pinch I've seen people to the horrible process of hammering the broach down an inch or so with a dead blow hammer to gain the required clearance. Terrible way to do things as it mushrooms the top of the broach but some days there are emergencies where things need to get done....

Koz

snipped-for-privacy@spoof.com wrote:

I think my point is that he may have not used

If I recall he was cutting a key slot in a pulley or a cam, I think it was about 3/4 deep, 5/8 dia. hole and about a 3/16 slot.

Since this was an expedient way to cut the key slot, why do you suggest that he may not have used good judgment?

Because he *may* have selected a broach that was intended to broach very thick material. I thought I made that clear. It's possible for a broach to pick up too much material when the broach is not suited to the job at hand. Tensile strength of broaches is (or should be) staggering. Tool steels in particular are very tough, often in the 250,000 PSI range, so breaking a complete tooth seems real strange. I suspect there was more to this story than you've told, which might address the cause of the tooth failure. I don't doubt it happened, but feel there's a good reason it did.

Harold

I was wondering where you were going with this, Harold. Roger descrbed what seemed to me to be a perfectly good expedient for cutting a quick and dirty keyway. Did you take his quote, "I watched a tool and die maker quickly knock out a single tooth broach" to mean the guy broke a tooth on the broach? I think he meant that the toolmaker was skilled enough to quickly make (knock out) a usable tool.

Ned Simmons

Am I missing a post in this thread? Roger says a machinist made an expedient broach and used it to cut a keyway. I don't see any mention that it broke.

Gary

Duh! Yep, that's exactly what I did, not realizing he was saying the T&D man MADE a broach, not broke a broach. Doesn't take me long to get lost, does it? My turn to look stupid. (Again?) :-)

Thanks, Ned. Seems once I get my mind set, it takes a lot to get me thinking another direction.

Harold

Chuckle.

Only when viewed through my eyes, Gary.

Harold

I apologize for my poor choice of words.

Don't feel bad about the foot in mouth it happens to us all sooner or later. Luckily it is only temporary.

Chuckle! Not necessary to apologize, Roger. I use the same terminology. I just got a brain cramp and couldn't let go of it. What's important is that we are all on the same page now.

Snicker! Temporary? You apparently don't know me well! :-) I have a select spot in a dark place where I often park my head.

Be well,

Harold