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01-14-2011, 09:42 AM #1
Making a keyway in a pulley bore with a punch press?
I have a punch press (Benchmaster 3 tons) and other tooling. I don´t have a broaching set.
Can I machine a keyway along pulley bore by using this tiny press as a slotting device?
01-14-2011, 10:01 AM #2
Most machinists would consider other options.
A lathe and the proper tool can eventually create a keyway.
Chuck the pulley, install the cutting tool on the carriage, and take many small cuts, hand cranking the carriage to force the tool into the metal.
01-14-2011, 10:03 AM #3
Make SOLID! tooling to hold the part. And then no more than .002" per pass until you gain confidence.
There may be too much slop in the punch head though.
Clamp the part for each punch.
Use a 5-6' wooden pole to press the release. SAFETY! Wear safety everything! Stand away!
It should NOT be done in a RUSH! Take time to think it through.
I think it's doable.
01-14-2011, 12:04 PM #4
First find a piece of tubing or pipe with the right I.D., then drill pulley hub to match O.D. of tubing, then cut slot for keyway on insert in vice with hacksaw or whatever, then insert it into pulley and tack weld in place. A strong glue or a set screw might work if no welder. THIS ALL DEPENDS ON HOW MUCH FORCE WILL BE ON PULLEY. Keep in mind how the pulley attaches to shaft, might have to make insert the same length as hub or a litter shorter for weld. Also keep in mind that you might have to grind weld to insert holding clip to shaft, so don't get too sloppy on weld. I have no broach either and did this to my tractor pulley 2 years ago and it is still working. I thing this would be better than forcing tools, and less pain.
01-14-2011, 12:15 PM #5
What's the pulley made of and how big is the ID?
I've read that back in the day this was a routine job for the "vise hand" to do w/ a chisel and a file and a little bit of time. I tried it by hand a bit ago in iron pulley and was actually way quicker than I expected.
01-14-2011, 01:17 PM #6
Back in the early 50s we had a 14" shaft that the 1 1/4" key that had come loose and widened the keyway. The fan that it powered was bricked into a 360' chimney so removing it to machine a new keyway was not an option. The fitter and I (apprentice) spent over two days cutting a new keyway with chisels, files, riffles and scrapers cutting a new one and fitting a new key. The keyway in the 16' pulley was ok. I know it's OT but the posts reminded me of my sore knuckles until I learned to hit the chisel not my hand. Peter
01-14-2011, 01:33 PM #7
One problem may be the length of the keyway. Mechanical punch presses have maximum force at he bottom of the stroke and much less force above that point.
If the keyway was an inch in length the force at the start of the cut will be much, much less than 3 tons. The force might be so little it'd be impossible to get the cutter started.
In my area bearing and power transmission equipment sellers offer pulley broaching for a nominal charge. That's what I would do if I didn't have the correct equipment.
01-14-2011, 04:53 PM #8
"What's the pulley made of and how big is the ID?"
Pulley is cast iron and ID is 1.125". Keyway should be about 1.250" in length.
01-14-2011, 05:08 PM #9
Not too big but room for access. I say old-school, get a chisel and be done with it. You'll have your keyway before you get done setting up to try anything else, I suspect.
01-14-2011, 07:01 PM #10
If you have access to a lathe ,machine a plug to fit the bore.Then drill a hole just undersize of your layout lines.Pull the plug and finish with a file.
If you have a mill ,you could cut a key in the plug and use a high speed tool to broach out the key , chamfer all but the cutting edge.
01-15-2011, 06:26 AM #11
Punch press with incorrect application is a disaster waiting to happen, not a bad idea but I vote for the saw blade, file and chisel method. A whole lot safer and much more controllable. At least if you screw it up it won't happen so dang fast, LOL. You can DO IT!
01-15-2011, 06:58 AM #12