Stuck sprocket - need advice

[sanddrag]

Okay, I've had lots of really stuck sprockets, hubs, gears, whatever in my time but nothing like this one. I'm trying to take apart this old lawnmower I have (to make a gokart) and one of the sprockets is so stuck on its shaft that it might as well be welded on. This would be a good thing in the future because it will be a drive sprocket/axle but right now it is bad because further down the axle there is a sprocket welded on, and between the two sprockets is a wheel that I need gone. So, I must remove the stuck sprocket to get the wheel off (and install a spacer in its place).

The stuck sprocket has two set screws at 90 degrees from each other which I removed completely. I've tried beating the shaft out of the sprocket. I've tried beating the sprocket back down the shaft (so then I could grind the shaft a little smaller). I've tried twisting it by holding it and the shaft with two Robogrip pliers (and I'm a strong guy too). I've tried WD40. And none of these methods even caused it to budge.

The only thing I haven't tried is heating. Should I give it a shot? I'm afraid the shaft might heat up too and that I could run into the problem of the shaft steel have a greater coeficient of linear expansion than the sprocket steel and that would make the problem even worse.

I don't have access to an arbor (or any other kind) of press right now. Only my muscles, and hammer, robogrips, dremel, sawzall, etc.

I don't really care about saving the sprocket (because I have an identical one) but I do need to save the shaft. So would it be possible to cut the sprocket off with something like a sawzall?

[John Gutmann]

have you tryed a gear puller?

also how hard did you hit the sprocket? maybe it needs the persuasion of a 20lb sludge

and you may wanna try cutting down the middle of the sprocket(like your trying the see the cross section) and stooping Cloe to the shaft, then take a wedge or crowbar and wedge it in and split it, but cut it on both sides first so one can break and the other can hinge.

[Elgin Clock]

Have you tried a monkey wrench? I had a hell of a time getting the bolts off my bumper on my truck, and I used that and it worked.. It messed up the bolts, which I didn't care about..but it worked.

Plus, for lubricants.. there are better things than WD-40.

I can't think of the name of the one I used sucessfully many times already, but I'll try and get the name when I see it next.

[sanddrag]

Originally Posted by Elgin Clock

Have you tried a monkey wrench? I had a hell of a time getting the bolts off my bumper on my truck, and I used that and it worked.. It messed up the bolts, which I didn't care about..but it worked.

Plus, for lubricants.. there are better things than WD-40.

I can't think of the name of the one I used sucessfully many times already, but I'll try and get the name when I see it next.

By monkey wrench you mean like a pipe wrench right? I that would work better than Robogrips; I'll try it. For the penetrating oil, do you mean PB Blaster or Liquid Wrench? I've heard PB is good but have never tried it. I honestly don't know if there's a huge difference between LW, PB, and WD40.

[NoodleKnight]

Originally Posted by sanddrag

By monkey wrench you mean like a pipe wrench right? I that would work better than Robogrips; I'll try it. For the penetrating oil, do you mean PB Blaster or Liquid Wrench? I've heard PB is good but have never tried it. I honestly don't know if there's a huge difference between LW, PB, and WD40.

I was just about to say, try using some Liquid Wrench... then see if you can use some type of hydraulic press.

[Greg Perkins]

i had this problem too a while back, heres what i did... i got some PB "nut buster" and douced the heck out of the keyway/shaft and i let i sit for about 3 hours. then i came back and having the shaft vertically pointing up (mount the motor temporarily so the output shaft is vertical)
, i got a peice or square (or round) stock thats bigger than the shaft but smaller rthan the OD and got a peice of wood and gave it a couple of good whacks w. my 30lb sledge
the sprocket came off the key, and then i was able to remove the key and slide the sprocket of...be wary though you may shatter the sprocket or even bend it.

you could use an oxy-acetelene torch and heat the hell out of it and then beat it off try and get a few pics too...

[Cory]

You could probably very carefully cut a wedge out of the sprocket.

You'd run the risk of possibly damaging the shaft if you don't stop exactly in the right spot.

I'd definitely stick to the penetrating oil and big ol wrench/sledge idea before resorting to hacking it apart, though.

[John Gutmann]

[quote=Greg Perkins]...and gave it a couple of good whacks w. my 30lb sledge
QUOTE]

whoaaa!!!! i Never knew there were 30lb sludges.

[dlavery]

whoaaa!!!! i Never knew there were 30lb sludges.

30 pound sledge: 30 pound sludge:

-dave

[Evan Austin]

Hey Sanddrag,
If the shaft is flared on the end from hitting it even a little bit, a gear puller may not be enough to pull the sprocket off. Think of it this way, if the shaft gets flared out ten thousandths of an inch, that will be like trying to press together (or in this case, apart) an extremely hard press fit. Check the shaft with calipers to be sure. If it is flared, fix the end with a good file or a bench grinder.
My only suggestion for loosening the sprocket would have been to heat the shaft and sprocket hub area, then spray with penetrating oil while it is still hot. I know it sounds a little dumb to spray light oil on very hot metal but it has always worked for me and never yet caused a fire (emphasis on YET). Good luck with the go kart, that's gonna be fun!

[billbo911]

Originally Posted by dlavery

30 pound sledge: 30 pound sludge:

-dave

Leave it to Dave to resort to pictures (they do paint a thousand words) to point out the subtle differences between "Sledge" and "Sludge". Thanks for the clarification Dave!!!

[sanddrag]

Well, I did enlarge the end of the shaft when I beat on it. That was my mistake and I don't know what I was thinking. I guess I was in a hurry last night because it was getting dark. I've done it the right way many times before, I'm not sure why I didn't this time.

Anyway, I bought the gear puller. They had a smaller one (4" I think) that was only $6.49 so I got it. That might have been a mistake. It fit fine and everything, but right away the bolts in the thing started bending. I think I snapped like 3 of them by the end of this ordeal. You get what you pay for I guess. Additionally, the metal pieces started bending.

When I was first starting out, the point on the tip of the gear puller screw was just forcing itself into the shaft instead of pulling the sprocket off. I'd say the tip went a good 1/8" into the shaft.

Anyway, what it finally took to get this thing off was one regular adjustable wrench on one of the legs of the puller (to keep it from rotating) with a cheater pipe on the wrench. And then a vice on the shaft to help hold it and the sprocket and the legs of the puller to keep them from rotating. And then a huge 15" adjustable crescent wrench (I've seen bigger, but this thing is a monster) on the hex on the puller screw. With all the strength I had put into that 15" adjustable crescent wrench, I finally was able to get this thing off the shaft. I then ground the shaft a little and the new sprocket slides on and off just great.

All in all, I hope I never have to do that again. Also, strangely enough, the puller has a lifetime warranty so I'm going to take it back and get a new one. I think I'll replace the bolts with Grade 8s though.

[Andrew Blair]

Hey, somewhat unrelated but fun: the back of the PB blaster can has a melting styrofoam cup on it. It does what it shows too, in about 8 seconds. Went through about half a can and 6 cups playing with it. I'd imagine it would've done a good job on your sprocket.

[Al Skierkiewicz]

Sanddrag,
Sometimes pushing the sproket further on the shaft, then grinding down the mushroomed end works better than forcing it off.
Dave, sometimes you are downright scary. Although using the two together does bring back memories of Gallagher and a watermellon.

[sanddrag]

I tired pushing (read: beating) it down the shaft but it wouldn't go. Yes, my methods are somewhat scary sometimes. When those bolts broke, they shot out a good 20 feet. And yes I continued to operate the device with bent bolts. Anyway, my scary methods are better then gnawing it off with me teeth though so what can I say.

Another scary project was using one of those thin plastic square Crystal Geyser one gallon water bottles as a 100psi storage tank (oh, and it was beautifully duct taped on). It was for a little air cannon. Anyway, I was waiting for the pressure to build up and thought "just a little more" and then the tank shot off of the piping arrangement and flew about 40-50 feet away. Surprisingly, the tank never ruptured despite how thin the plastic is.

Anyway, back to the sprocket. This sprocket had those two set screws, one of which going into a little bit of a hole drilled in the shaft. I think a previous owner of the mower must have jammed a rock in the blade causing the shaft to spin in the sprocket which made a nasty groove in the shaft (from the set screws) which resulted in the sprocket being incredibly stuck.

I'm glad it's all taken care of now.