Sprocket set screws rusted/frozen to sprocket

[creia]

I bought an old mower over the weekend just to get the 1976 Briggs 3Hp Model 80232 engine for one of the rebuild/restorations. They ALWAYS have an old (rusted) pulley or sprocket on the crank end, that can be a challenge to remove- some more so than others. That being said I have always been able to eventually remove them, until this engine. The set screws securing the small sprocket have frozen/rusted to their threaded holes in the sprocket, so I cannot remove them. I have been using Gibbs penetrant for 2 days along with an occasional tap-tap in the hope to unfreeze them and using a LOT of force with an allen wrench- to no avail. Here's my question:
Short of cutting the sprocket off, (which I could do with a Dremel with a metal cut off) does anybody have any other tricks/techniques to share. How about applying heat (propane torch)? Do I risk warping the crank?
Thanks for any help,
Michael

[RoyM]

I would try drilling the setscrew out using a left hand bit. I know those things can be a real bear, you just have to be patient.

[creia]

I would try drilling the setscrew out using a left hand bit. I know those things can be a real bear, you just have to be patient.

Hello Roy. Thank you fore your reply and suggestion.Please forgive my ignorance and question as I have never used one before.
1. Is it preferable to try drilling it out with a left hand bit so that the bit (hopefully) bits into the setscrew and turns it out?
2. The size of the drill bit would need to be just slightly larger than the center hole of the setscrew (where the allen wrench inserts), correct?
Michael

[bgsengine]

I bought an old mower over the weekend just to get the 1976 Briggs 3Hp Model 80232 engine for one of the rebuild/restorations. They ALWAYS have an old (rusted) pulley or sprocket on the crank end, that can be a challenge to remove- some more so than others. That being said I have always been able to eventually remove them, until this engine. The set screws securing the small sprocket have frozen/rusted to their threaded holes in the sprocket, so I cannot remove them. I have been using Gibbs penetrant for 2 days along with an occasional tap-tap in the hope to unfreeze them and using a LOT of force with an allen wrench- to no avail. Here's my question:
Short of cutting the sprocket off, (which I could do with a Dremel with a metal cut off) does anybody have any other tricks/techniques to share. How about applying heat (propane torch)? Do I risk warping the crank?
Thanks for any help,
Michael

Lots of tricks I have picked up over the years, I'd start from the least invasive /damaging to the ones that reach the point of cutting it off - Heat enough to turn the sprocket hub orange (JUST orange in a dim light, or in shop, not in sunlight) should not bother the crankshaft Try to localize heat as much as possible to focus only on the area immediately surrounding the set screw. But before I reach that point, I may do one of these:

1) If the allen wrench fits tight and snug with no play into the socket (So that you could pretty much twist the allen wrench itself) then I might instead get a specialized allen driver socket (The kind you use with a ratchet wrench) and a breaker bar (a cheapie one from harbor freight) and apply torque to try and loosen and while that torque is applied, whack the breaker bar squarely over the socket/allen/setscrew - often that shock is enough to pop it loose enough to start working it back and forth to gradually break away the rust in the threads.

2) the quickest shortcut before heat gets involved, if you don't need to keep the sprocket, you need a very high quality drill bit (and hope nobody has put in a grade 8 setscrew or heat hardened it trying to remove it) and size the drill bit to completely drill out the threads that the set screw fits into , then use the threaded hole the set screw is in as a pilot hole to drill out the whole shebang - If the end of the set screw is like most, it'll have a bit of a rounded end that isn't threaded so when you break through the last thread there may be enough meat to it that your drill bit will stop drilling and not drill into the crank. (BUt still be careful, It won't hurt a whole lot to have a dimple drilled in the crank in most cases, but bear in mind you could possibly drill a bit too far., so having a way to gauge your depth of drilling will be helpful) However, if drilling isn't gonna do it (heat hardened set screw from someone else trying to remove it with a torch, for example, or maybe set screw is a long one that sticks out above the sprocket shank? or other possibles) then you may have to resort to cutting the whole sprocket off (I.E. a hand grinder with cutoff wheel? Hacksaw? Dremel?)

3) If you still cant get it to pop loose, and don't think drilling might do it, you can heat the hub of the sprocket (It should not affect the shaft if you use due care) but odds are decent that it isn't going to help a whole lot more than the above. I never bothered with Lefthand bits myself, as once you got to drilling, may as well go all the way through - lefthand bit would only tend to want to loosen the setscrew, and if you don't get the drill bit perfectly centered and the screw does come loose, it can potentially jam your drill bit in the hole and break it off.

Worst case, you can torch it off , if you can protect the aluminum crankcase from damage and start the oxyacetylene torch right at a sprocket spur, to get the cut started, and follow through smoothly , you'll usually have cut through the sprocket before you start to burn into the crank - BUT!!!! That does require quite a bit of exprience with using the gas outfit cutting torch - I wouldn't recommend it if you have the least doubt, but it can be done. (Ive done it, no trouble, but again I had years of daily practice working the cutting torch at the scrap yard, so...) (Side note: If you can get the metal to the burn point where it is liquid, you can shut off the acetylene entirely and continue/finish the cut on oxygen alone... until you hit a patch of rust or something that isn't steel and it breaks the chain - If your crankshaft is well rusted, you could take advantage of that to keep it from getting damaged from cutting torch...)

I have also had success with holding a bigger hammer solidly against the sprocket one side (Typically a half sledge) and then strike hard and squarely directly opposite on the other side of sprocket hub - shocks the whole shebang and sometimes lets the rust bond break...

[38racing]

If as said the allen bit fits you might be able to us a hand impact driver. Will need socket adapters to get to allan size. I'd cut allan as short as possible. Thats after lots of heat and mant vlaim 50'50 acetone-transmission fluid is the best penetrant, apparently without heat.

[creia]

I bought an old mower over the weekend just to get the 1976 Briggs 3Hp Model 80232 engine for one of the rebuild/restorations. They ALWAYS have an old (rusted) pulley or sprocket on the crank end, that can be a challenge to remove- some more so than others. That being said I have always been able to eventually remove them, until this engine. The set screws securing the small sprocket have frozen/rusted to their threaded holes in the sprocket, so I cannot remove them. I have been using Gibbs penetrant for 2 days along with an occasional tap-tap in the hope to unfreeze them and using a LOT of force with an allen wrench- to no avail. Here's my question:
Short of cutting the sprocket off, (which I could do with a Dremel with a metal cut off) does anybody have any other tricks/techniques to share. How about applying heat (propane torch)? Do I risk warping the crank?
Thanks for any help,
Michael

Lots of tricks I have picked up over the years, I'd start from the least invasive /damaging to the ones that reach the point of cutting it off - Heat enough to turn the sprocket hub orange (JUST orange in a dim light, or in shop, not in sunlight) should not bother the crankshaft Try to localize heat as much as possible to focus only on the area immediately surrounding the set screw. But before I reach that point, I may do one of these:

1) If the allen wrench fits tight and snug with no play into the socket (So that you could pretty much twist the allen wrench itself) then I might instead get a specialized allen driver socket (The kind you use with a ratchet wrench) and a breaker bar (a cheapie one from harbor freight) and apply torque to try and loosen and while that torque is applied, whack the breaker bar squarely over the socket/allen/setscrew - often that shock is enough to pop it loose enough to start working it back and forth to gradually break away the rust in the threads.

2) the quickest shortcut before heat gets involved, if you don't need to keep the sprocket, you need a very high quality drill bit (and hope nobody has put in a grade 8 setscrew or heat hardened it trying to remove it) and size the drill bit to completely drill out the threads that the set screw fits into , then use the threaded hole the set screw is in as a pilot hole to drill out the whole shebang - If the end of the set screw is like most, it'll have a bit of a rounded end that isn't threaded so when you break through the last thread there may be enough meat to it that your drill bit will stop drilling and not drill into the crank. (BUt still be careful, It won't hurt a whole lot to have a dimple drilled in the crank in most cases, but bear in mind you could possibly drill a bit too far., so having a way to gauge your depth of drilling will be helpful) However, if drilling isn't gonna do it (heat hardened set screw from someone else trying to remove it with a torch, for example, or maybe set screw is a long one that sticks out above the sprocket shank? or other possibles) then you may have to resort to cutting the whole sprocket off (I.E. a hand grinder with cutoff wheel? Hacksaw? Dremel?)

3) If you still cant get it to pop loose, and don't think drilling might do it, you can heat the hub of the sprocket (It should not affect the shaft if you use due care) but odds are decent that it isn't going to help a whole lot more than the above. I never bothered with Lefthand bits myself, as once you got to drilling, may as well go all the way through - lefthand bit would only tend to want to loosen the setscrew, and if you don't get the drill bit perfectly centered and the screw does come loose, it can potentially jam your drill bit in the hole and break it off.

Worst case, you can torch it off , if you can protect the aluminum crankcase from damage and start the oxyacetylene torch right at a sprocket spur, to get the cut started, and follow through smoothly , you'll usually have cut through the sprocket before you start to burn into the crank - BUT!!!! That does require quite a bit of exprience with using the gas outfit cutting torch - I wouldn't recommend it if you have the least doubt, but it can be done. (Ive done it, no trouble, but again I had years of daily practice working the cutting torch at the scrap yard, so...) (Side note: If you can get the metal to the burn point where it is liquid, you can shut off the acetylene entirely and continue/finish the cut on oxygen alone... until you hit a patch of rust or something that isn't steel and it breaks the chain - If your crankshaft is well rusted, you could take advantage of that to keep it from getting damaged from cutting torch...)

I have also had success with holding a bigger hammer solidly against the sprocket one side (Typically a half sledge) and then strike hard and squarely directly opposite on the other side of sprocket hub - shocks the whole shebang and sometimes lets the rust bond break...

Thanks Brian. All duly noted. I will report back after I have tried these methods- stay tuned...
Michael

[KE4AVB]

Just a note here about propane torch. They simply can't overcome the heat sinking of the metal except on very small items. Most times it takes something ACE/OX torch to create enough localize heat.

And the Acetone/Trans fluid mix I have using this year myself and it seems to be working very well but still experimenting with it.

[creia]

Update and epilogue:
Short story= SUCCESS!! I was able to get the sprocket off the crank end.
Longer story= I tried the rachett/allen bit with a breaker bar and ended up rounding off the inside of both of allen set screws as the allen bit kept slipping!.
As I did not need the sprocket for this engine's use, I then grabbed my Dremel tool with a metal cut-off wheel and ever so CAREFULLY sliced through the sprocket lengthwise in line with the set screws, just a hair short of hitting the crank. After that I took a metal cold chisel and split the sprocket off of the crank along both the cuts. All-in-all it took about 1/2 hour to do. Luckily, the sprocket was small (only a 10 tooth) , so the sprocket hub was a small diameter to cut through. The crank end was actually in pretty good shape, but heavily surface rusted. After I got the engine running I held a piece of 600 grit sandpaper to the crank end while the engine is running and it cleaned up real nice with a polished look.
Michael

[bgsengine]

Gratz. Yep, sometimes you just gotta cut em off. I have done them that way before as well (but mine was a 5" cast iron pulley, wouldn't have worked well to use the gas torch...) Cut almost to the shaft 180 degrees apart and then split with a cold chisel...

[38racing]

Been there, done that. I should do follow up on how I saved the wheel assembly using hubs. Unfortunately the tine seals leak too.
https://youtu.be/Y4A1rGzUyHE?si=adw_wEw_lUFxgw3O