Removing cranks with stripped thread

[jordyr]

Hi all, I've been trying without success to remove my cranks, to then also remove and possibly replace the BB. The thread is pretty much completely stripped on each side so crank pullers are a no-go, and I've tried using a gear puller to yank them out, also without success (and now I'm left with a bent chain ring)... the cranks will be thrown out so I've actually resorted to a hack saw around the circumference of the crank where it hugs the BB - I'm open to any tips at this stage, particularly if there are no specialist tools or angle grinders involved, so thanks in advance to anyone who can help!

[find_bruce]

I presume this is either a square taper of octalink type crank. I have done exactly what you want to do, but my method is was what you are hoping to avoid - I turned the frame upside down & used an angle grinder to cut through the bottom bracket shaft. Sorry I couldn't be more help

[P!N20]

Is the bike ride-able? When I stripped the thread on an old Shimano 600 crank I just went for a ride and it came loose within minutes.

[twowheels]

Wedge between bb cups & cranks. Apply heat first with creme brulee torch.

[Tim]

I've read of successful removal and no damage with drill chuck wedges.

[uart]

I've read of successful removal and no damage with drill chuck wedges.

Yes wedges could work. Grease them so that they slide easily and Insert them so that they go in opposite directions. Then with hammers tap them both inward, at the same time, so that they slide over each other. This will expand the crank off.

I actually made a (very crude) pair of wedges like that in about half an hour using just a hacksaw, bench grinder and file. That was to get a tapered drill chuck off, but it's a very similar arrangement to the tapered spindle on an old set of cranks.

BTW. It's weird how many old bikes I come across with the threads totally destroyed on either one side or the other. People cross threading in the removal tool seems to be the problem.

[Tim]

BTW. It's weird how many old bikes I come across with the threads totally destroyed on either one side or the other. People cross threading in the removal tool seems to be the problem.

I've stripped the thread twice.
First time the crank puller tool wasn't done up tight (with a spanner) and pulled straight out of the crank with the crank threads following.
Second time I didn't remove the crank retaining bolt, inserted the puller, and pulled the thread out again.
I'm a slow learner.

[find_bruce]

BTW. It's weird how many old bikes I come across with the threads totally destroyed on either one side or the other. People cross threading in the removal tool seems to be the problem.

Alloy cranks v steel tool - as you say cross thread & its goodbye to alloy threads

[Duck!]

If the crank bolts have been viciously overtightened the sides of the hole can be squashed in over the tips of the spindle, sometimes enough to stop the driver of the tool fitting through the hole properly, instead catching on the crank, turning the tool into a very effective thread stripper. A worn tool can also cause the same problem; sometimes the tip of the driver can flare out from long-tem use and not fit into the hole properly.

the cranks will be thrown out so I've actually resorted to a hack saw around the circumference of the crank where it hugs the BB - I'm open to any tips at this stage....

A better option if destruction is not an issue is to cut across the butt of the crank, in line with the spindle. You may need a very fine cutting tool like a Dremel or similar to get in to the inner edge of the crank without damaging the frame. Wedge open the slot and the crank should then release from the spindle quite easily.

[OnTrackZeD]

Is the bike ride-able? When I stripped the thread on an old Shimano 600 crank I just went for a ride and it came loose within minutes.

+1
Yep I've done it too.

You'll need to loosen the bolts first btw.

[Ivanerrol]

Penetrene is your friend. We use it in the auto side all the time.
Soak the crank ends with Penetrene over night.

If the ends haven't burred over as Duck mentioned the cranks will be much easier to remove.
I used a pickle fork and Penetrene. Pickle fork is a ball joint removal tool. - You need to be careful though.

(Penetrene is also very good for gunked up shifters)

[jordyr]

Spot on, I had no idea they were flared over the spindle, and put all my weight behind the crank pullers. Put a lot of effort into unknowingly stripping that thread actually...

Thanks for all the help, I'll give the wedges a go under some heat and if all else fails, probably cut straight through both the crank end and spindle on one side with the grinder... will let you know how it goes!

[bychosis]

When this happened to me I just cut through the soft alloy crank with a hacksaw until I could use a hammer and smash it off the BB axle. Took a couple of strategic cuts. The hacksaw was barely tickling the hardened axle.

[WyvernRH]

Spot on, I had no idea they were flared over the spindle, and put all my weight behind the crank pullers. Put a lot of effort into unknowingly stripping that thread actually...

Thanks for all the help, I'll give the wedges a go under some heat and if all else fails, probably cut straight through both the crank end and spindle on one side with the grinder... will let you know how it goes!

Like Bychosis says, you don't have to cut the axle. If you are not confident with your skill using a small angle grinder or dremel just use a open ended hacksaw to cut down thru the alloy until you are almost through to the axle and give it a tap and twist with a chisel or old screwdriver in the slot. The hacksaw won't hurt the hardened axle even if you do touch it. A bit of heat carefully applied would help once you have cut the slot. I've had to do this a couple of times with clunkers someone has brought in for me to work on.

Richard

[bychosis]

Found this old pic of the home made crank extractor that I attempted to remove a stick crank with. It just stripped the bolt. You can see on the right what I ended up doing with the hacksaw.

The second time with stuck cranks I got as far as almost stripping the thread on the cranks then I went straight for the grinder and chopped them off.

[jordyr]

Sorry all for the late update - in the end I used a bit of a combination between the hacksaw and grinder, most of the work was with the hacksaw and as previously mentioned, a few strategic cuts. The main reason I used the grinder was to cut the arms on the chainring side crank, which kept getting in the way of the saw (and my hand). You could also cut them with the hacksaw but it's difficult to hild everything still when you've just removed the opposite crank.