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tricks for breaking loose pulley set screws?

ironhoarder

Cast Iron
Joined
Oct 9, 2005
Location
Waterford, VA USA
So, I got this old enco mill. Bad motor. Good cone pulley.

My plan is to pull off the cone pulley and scare up nearly any suitable C face 3 phase 1hp motor, fabricate a mounting system based on the old mounting plate and mount the pulley.

Problem- I tried to remove the pulley's set screws. No luck! I figured that it would be a metric allen screw. Well, there are 2 different sizes. I found a metric allen wrench that seemed to fit one of them pretty well. I cleaned it out, put in kroil, held the wrench with pliers, held my mouth just right--and still, it smeared rather than break free. Dang I hate that feeling. You just know immediately when a hex wrench it not biting in properly.

The other screw seemed to be an imperial size- at least none of my metric set would fit at all. Same thing- I got one to fit pretty good- not perfect. I tried as carefully as I could, but it smeared.

I guess they put "roc-tite" on these things in Taiwan :)

So- what next? easy outs? I have a surface grinder, so I had the thought of carefully custom grinding some hex keys just for this purpose.

I may take it up to a motor shop and have them look over the motor, oh and by the way, can you take off that pulley?
 
Weld a washer that just fits inside the o.d. of the screwhead.
The weld a nut to the washer.
Have a candle handy, and while hot from welding, apply wax to the heatedsteel(around the base of the washer).
Get the appropriate wrench, and after minimal cooling time, carefully..back out the bolts usng a back and forth motion as you would with a lathe chuck when it gets tight.
;)

Assuming you moved motor and pulley far enough away from mill not to splatter bbs all over your mill!!!
 
Weld a washer that just fits inside the o.d. of the screwhead.
The weld a nut to the washer.
Have a candle handy, and while hot from welding, apply wax to the heatedsteel(around the base of the washer).
Get the appropriate wrench, and after minimal cooling time, carefully..back out the bolts usng a back and forth motion as you would with a lathe chuck when it gets tight.
;)

Assuming you moved motor and pulley far enough away from mill not to splatter bbs all over your mill!!!

That would be really hard in this case. The set screws are about 1/4-20 or maybe 5/16 (or metric equiv). But the real bummer is that the head of the screws are recessed about 1/2" down into the aluminum pulley. So, no real way to get in there to weld, without totally buggering the aluminum pulley. The hole is just too small and the set screw too deep.

I have tried heating up the pulley with a propane torch an applying pb blaster and kroil while hot.
 
bummer.....didn't think about buggering the aluminum did I???
Those stinkin set screws are hard on hss too....y'might just bore them out with a carbide endmill that's no good for side cutting...unless of course you have a lefty carbide drill just lyin' around.
(edit...John beat me to that one didn't he)

I second the ..."oh by the way "..motion in your op
Best of luck.
 
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Can u drill it out with a carbide bit?
John

I'd love to have a suitable carbide drill bit for this purpose. I have a set of "Bad Dog" bits that have carbide tips. I tried to drill out a setscrew in an aluminum handle recently with one- it simply tore off the carbide from the shank.

Can you suggest what type of carbide drill might work?
 
endmill....I use 'em for that all the time
alot less likeley to grab....

(r.e candle)
no it works like kroil...but instead of burning up,, it follows the heat, and really penetrates well. Also then lubricates as you are backing out the siezed bolt......I didn't believe it either, but it works great
 
Since the motor you have is already toast, you might get a bit more aggressive with the heat and Kroil? Then, grind a slightly tapered key from the next size up and hammer it in. I've sometimes had luck using a socket-mounded hex driver and using an impact hammer. I've also had the hex driver twist like a pretzel or break when faced with a bit of steel/aluminum corrosion.

If that fails, a LH drill bit, a milling cutter, and Omega drill etc. are options. If you attempt to drill this freehand, without some sort of bushing, the drill or mill is likely to wander off into the aluminum. It's worth the effort to make sure it won't wander.

When you're done, retap the pulley for the next larger setscrew or put in a Helicoil.
 
Since it's an aluminum pulley and a steel set screw and you don't care about the motor, try the alum method. If you do a google search on dissolving taps in aluminum you'll probably find alot of differnent, if maybe a bit slow, ideas. Here's one on using Nitric Acid http://yarchive.net/metal/tap_remove.html
And Alum http://www.metal-club.org/Remove.html
Or build you own EDM: "The EDM How-To Book"
by Ben Fleming.
Fleming Publications..ISBN 0-9767596-0-8

Good Luck,
I haven't had to try any of these yet. Must not be trying hard enough!
 
There is another alternative here.

Since the motor is shot, sacrifice it to the machine tool gods.

Cut off the motor shaft, mount in a lathe and carefully bore out the motor shaft to a thin shell which may come out on its own or you can carefully slit it with a file when it gets thin.

I believe then you can back out the setscrews. There is a tool called "Sock Out" or "Sock It Out"...I forget which name, I think you can buy them from McMASter amongst other sources. It is a tapered hexagon that's hammered into the bugged head somewhat like an EZ-out.

Also you can then use standard RH drill bits which should attempt to screw the setscrew into the newly cleaned out bore.
 
If there's a reasonable residue of the hex head left in the setscrews, try this: get a straight piece of slightly larger hex key, and grind it to fit tightly into the head with a very slight taper. Nice sharp corners if possible. You want it to bite in. Hammer it in hard, and then turn it with vise grips or, better yet, an appropriate sized socket. If you have a set of allen key sockets with removable inserts, you can make a sacrificial tip for one of those. The worst it will do is tear up the head a little more, and if you're lucky, it might be just enough to crack it loose.
 
There is another alternative here.

Since the motor is shot, sacrifice it to the machine tool gods.

Cut off the motor shaft, mount in a lathe and carefully bore out the motor shaft to a thin shell which may come out on its own or you can carefully slit it with a file when it gets thin.

Yeah, I thought of that too. I think I'll let the motor shop have a go first to see if it really is shot. I was told that the motor was bad- but maybe it is not a lost cause.

But thanks for the confirmation of the idea.
 
Omegadrills, which I generally get from Travers Tool, are made for drilling out broken taps, for which they work spectacularly. On something as soft as a socket head set screw, they should fly right through.
 
I often use xtruckers trick using the torx wrench, it works very well. Before you do that make sure it has been soaking in a penetrant a while then take a punch that fits the hole and hold it firmly against the top of the set screw and give it a couple of good licks with a light hammer. This will set the point on the screw a little deeper in the shaft and relax the pressure on the threads in the pulley. Be careful about getting too aggressive with driving in the wrench, if you expand or split the screw as you have probably figured out, that will make things difficult.
 
The best method I have found for stripped hexes on set screws is grind a square on an old tap. Grind the square with a shallow taper so the tip just barely fits into the hex. Take care to keep the corners sharp so they bite. Tap your new removal tool into the set screw while turning.

The fellow who told me how to make this tool claimed he had never found a set screw he couldn't remove unless the socket was cracked. If the socket is cracked, its probably end mill time.

The "sock it out" tapered hex tools Matt mentioned are good for SHCS, but I wouldn't use them on set screws.
 








 
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