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20th Jul 2018, 02:53 PM #1
Ways to remove stubborn set screw in motor pulley?
Following the stunning success of asking here how to get out a stubborn shaft key on my d-bit grinder restoration, I'm back with another pull-aparts question.
I've got an electric motor pulley here, mounted on the motor shaft, with an M8 cup-point set-screw that will not budge. It's on my brick-saw restoration, and although the pulley has lived under a belt cover and doesn't look too bad, I think it must be a rust problem?
There are two set-screws, one onto the shaft key, which although quite tough, still came out ok just with WD40 and an ordinary hex key wrench (on inspection, the threads are clean); and this li'l bugger that is set directly onto the shaft, which won't move at all.
I filled it with WD40 for a week, then tried an 18V impact driver. I had it hammering away until the battery went flat. No result.
Actually that was on the second impact bit, since the first one snapped off.
So what next?
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20th Jul 2018, 03:03 PM #2Most Valued Member
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Sit the flange of the pulley on something solid and put a neatly fitting punch in the hex key hole and give it a thump, with a bit of luck that will bury the point in a bit further into the shaft and loosen the screw enough to undo it ? Maybe ?
cheers, shed
ps. I use one of those hand held impact drivers the you crack with a hammer, speaking of which, does anyone know where to get new bits for them?
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20th Jul 2018, 03:35 PM #3Banned
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Ebay used to list them.
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20th Jul 2018, 03:49 PM #4Golden Member
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Gunnaduit,
Maybe the set screw has been loctited, I have run into this before. I used a very fine flame on a portagas hose and heated the screw up then it came out OK.
Bob
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20th Jul 2018, 04:14 PM #5Most Valued Member
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I would think loctite, it is strange that there wasnt any on the other setscrew though. I have drilled a small hole through the bottom of grub screws to release their hold on the walls before (once) it was a pita but worked
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20th Jul 2018, 04:15 PM #6
Yeah, the punch-and-hammer technique hasn't made any discernible difference. It's either I resuscitate the blowtorch kit (needs new gas bottle, was going to get onto that ...), or I just drill it out, get the pulley off (if that hasn't been loctited) and tap out the remains of the drilled-out set screw.
Come to think of it acetone is a solvent for loctite isn't it? Uh, no wait, that's a question been put on Practical Machinist, the problem is the acetone can take days to work down into the thread -- suggestion was apply soldering iron to the screw -- that's quicker for me than getting onto that blowtorch kit ... I'm off to dig out the big soldering iron ...
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20th Jul 2018, 04:17 PM #7Most Valued Member
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What size grub screw are you attempting to remove?
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20th Jul 2018, 04:50 PM #8
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20th Jul 2018, 05:51 PM #9Most Valued Member
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This is what I would try https://www.ebay.com.au/itm/Teng-15-...itleDesc=0%7C0
Try your local repco or supercheap or even kmart, even if it doesn't get your screw loose it will be invaluable in
the future, no workshop should be without one....
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20th Jul 2018, 05:58 PM #10Most Valued Member
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You may have to drill it out if it's that tight.
Surprised it hasn't stripped the hex.
Have you tried tightening it then reversing.
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20th Jul 2018, 07:14 PM #11
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20th Jul 2018, 07:46 PM #12
Hasn't stripped the hex socket on the set-screw, but I snapped the first allen key I tried, then twisted the remaining stump of it up into a corkscrew when I tried chucking it in the 18V drill (lots of torque on those things). Tried tightening then reversing but it didn't help.
Heat didn't do anything (though I don't have a pinpoint burner that really shoots into the screw hole, and the one I have wouldn't heat much - the pulley dissipates the heat too well). Anyway I doubt this set-screw has been loctited, if the other one on the pulley evidently had not been.
Yes it's starting to look like drilling it out is the only way, if there's no other suggestions.
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20th Jul 2018, 08:27 PM #13Most Valued Member
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If the pulley is made from Aluminium, warm it up so that it's too hot to handle, particularly around the hub area. It should expand enough to crack the screw loose. If you're needing to drill it out, use a cobalt drill bit, as by the sound of it, you haven't rounded the socket, it's a good quality grub screw, which will be HARD.
KrynTo grow old is mandatory, growing up is optional.
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20th Jul 2018, 08:57 PM #14
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20th Jul 2018, 11:02 PM #15
Hi Guys,
I've had similar issues with seized grub screws ! A blast with an oxy acetylene torch has worked for me a number of times. The small calor butane blow lamps don't get hot enough fast enough to expand the bulk of the pulley and crack the thread joint. Also sometimes you can get the grub screw to move by tapping the hub with a hammer whilst hot.
The other thing to watch out for is the dimple where the grub screw dug into the shaft it will have distorted and/or raised a burr that will make a puller required to get it off. DAMHIKT I've broken a cast iron pulley in half trying to get it off the shaft, and they are not cheap.Best Regards:
Baron J.
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