Broaching

This is my first time broaching.

I am broaching a keyway slot in a pulley bushing. The hole is 1 3/8 and the slot is 5/16". The reason for needing to broach is that I had to bore this pulley from 1.25" to 1 3/8", to accommodate a larger motor shaft.

I am finding it difficult to do with a 3 ton press. It does work, but I feel at the edge of this press's capability. I am concerned that, perhaps, I am doing something wrong, or the broach is dull. So, my question is, what would be a normal force required for broaching iron bushings with a 5/16 broach. The bushing is about 2 inch deep.

I am using tapmagic cutting fluid.

i
Reply to
Ignoramus17181
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Nothing you've described sounds wrong. You might have a dull broach. I've never worried about force aside from breaking broach or failing to get the job done, using a 12-ton press because that's what I have handy.

Reply to
Don Foreman

OK, that's a useful data point.

I am done with this particular broaching task. It turns out that using a different lubricant ("heavy threading oil with sulphur and chlorine") helps somewhat.

The pulley is nicely sitting on the new motor's shaft with the proper key between them.

The reason for all this is that I got a 7.5 HP single phase motor, which will replace the current three phase motor on my compressor. As I mentioned before, I had a three phase motor on this compressor before.

i

Reply to
Ignoramus17181

Iggy, I do it all the time with a 3 ton arbor press and experience no problem. You do have to use the shims and make multiple passes though. However, 2" is quite long. I hope your quide bushing is the same length. It also helps to oil the guide. I also have Tapmagic, but never had the need to use it for broaching. Steve

Reply to
Steve Lusardi

Check here

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a 5/16C broach at a 2.5" loc will need 3960 pounds to push it through.

At 2" LOC you're most likely at 3000 or so......

Thank You, Randy

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Reply to
Randy

Thanks. It would seem, then, that the broach is a little dull.

DuMont sent me a document on broach sharpening and I will try to sharpen this broach.

In any case, as I said, I broached the bushing from that Browning pulley, and it sits securely on the motor's shaft.

i
Reply to
Ignoramus28618

I also use an arbor press. A dull broach lets you know it. I'm thinking since a broach is a tapered cutter, the loads scale linearly as length increases.

The first broach I broke I did it on a hydraulic press. I tried to do the job in one shot. Best to ease up and let the broach recenter or relieve deflection if there is any.

That is the nice thing about an arbor press, easy to let up, fast to shove though for reasonable sizes.

Wes

Reply to
Wes

there is any.

Yes, the nice thing about an arbor press is the "feel" of the handle, which tells me a lot about what is going on.

i
Reply to
Ignoramus28618

Same for those manual feed handles on lathes and mills.

Reply to
Wes

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