Thread: Broaching set ups

I've cut key ways for gears with my shaper up to now but now have a smaller key way to cut (1/8" key with a bore less than 1/2" diameter). I have access to a broach set but confess I've never used them before, so I don't really know what force is required. I don't have a press either. What I was thinking was that I could mount an angle plate on one end of the mill table and push the broach with a hydraulic cylinder (alright - car jack) mounted on another angle plate at an appropriate distance away.
It sounds a bodge worth trying to me, but what do others who have used broaches before think? Is there a better way (besides buying a press that I have no room for)? I probably only need a 6 to 8" stroke , so I doubt there is a need for a proper long stroke cylinder unless I need more force.

Michael

The set up your describing sounds like it would work although it would be slow. I have done broaching on my hydraulic press which is essentially just a bottle Jack.

Hi Michael, as a former maintainence worker in the mining industry, it was not uncommon to see people just using a hammer to knock the broach through, and I don't recall any of the hammers being soft either.
Having said that, I think that if you had adequate support for the gear that you are cutting the keyway in, you could probably use a copper or brass hammer to carefully tap the broach through. To protect yourself from shrapnel you could surround the broach with some poly pipe, just leaving the top inch or so of the broach exposed, just keep trimming the poly pipe as the broach descends. You could use the thin wall pipe used for drip lines, and even cut it into 50mm lengths, and by stacking them on top of each other to surround the broach, you would be able to remove them one at a time to access the top of the broach to allow you to hit it. A bit rough I agree, but if you only have one unit to do, the preparation time is short, and cost low.
Just wear your safety glasses, and preferably goggles or visor as well. Cheers,
Rob.

Not sure if I would go the hammer method unless it was the only thing you could do.

Your method may be a little cumbersum but it should work okay.

If you use a 1 tonne jack that will have more than enough force to push your broach.

Is it a single pass broach,or the type you need to use a shim with.

Have you got the bushing or do you need to make it.

You will need to have at least 6" of travel.

You may need to make a small pin the push the broach through the final bit.

If you do want to try knocking it through with a hammer just give a bit of tool steel a couple of good whacks on its end,if there is no change to it then the hammer method might be best.

If you were braoching over the maximum length that your broach will cut you would require around 800 lbs of pressure to pass it through.

If it was me I would cutting the keyway using the lathe, a bit slow but very accurate results can be achieved.
I have done this for a 3/16" keyway and it worked perfectly. A good method for just a 1 off.

The broaches I have are the type that are shimmed with bushes.
I had wondered about a hammer but thought that it could be a good way to break an expensive broach so I think that pushing with a jack is preferable. That does sound like some of the miners I have worked with though.
I did think about doing this on the lathe but as the tailstock only has 4" of travel, it was going to be slow going. I may try it anyway just for comparison. I only have one keyway to cut from new but might drill a few holes in some scrap just to try a few things out first.

Michael

What were you going to do with the tailstock?

Hey Michael,

How about a setup where the broach is located vertically under the mill spindle and driven through the gear by raising the table. You could use a piece of heavy walled pipe under the gear for support and for clearance for the broach when it passes through the gear.

I have a one ton Reeves arbor press made here in the tool capital. I was going to suggest the use of a pedestal drill to drive the broach but thinking about the leverage acheivable with one of the capstan arms on our 3M drills, I dont think you would have enough puff.

BT in Melbourne.

Have you blokes got any idea of the amount of force you need to get the broach through.

If you dont mind a bit of risk or possable repair by all means try the mill or drill press idea.

Another thought if you have a towbar or bull bar on your car you could weld a piece of 12 to 20mm plate to it,then get a piece of pipe as long as the broach plus 50mm,weld this to another piece of plate similar to whats attached to your car,support this base piece against the corner of your house or shed,get someone or something to support the broach and drive the car at it at around 5 to 10 kph.

Hello Peter,

I have some idea. My one ton press runs out of puff (or I do) at about a 3/16" broach in steel. Obviously that depends on the thickness of the material being broached. My largest broach is 1/4". I have a 20 ton hydraulic press but I haven't yet tried that out for broaching. If Michael drilled away some of the metal before broaching the task would be easier.

When I was cutting a keyway in a steel pulley a while back ( pre 20 ton press) I finished the process in my 8 inch bench vice. It was easier than fooling around with packers and spacers with the Reeve. My Record vice opens up to about 12 inches.

Bob.

His 1st method in my opinion showed the most merit depending on the strength of his angle plates,as a guess this might only be a keyway for a change gear,if thats the case you could file it after all its only a 1 off and .125" wide by about.073" deep.

The tailstock in the lathe idea was that as it is a small keyway the tailstock crew may have enough grunt to push it through.
As I said, I might try as a comparison - although I suspect that it won't work simple because the force needed will be too great.

Michael

Micheal it seems that you now have a very good excuse to build yourself a workshop press

Welcome to use my press Michael, if that's any help. It's only a cheap Jimy but claims 12 T so should be enough.

Thanks for the offers guys. I was thinking the same thing as I was logging on...

Michael