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Cutting Hardened Steel Answered

So here's my situation... I've lost the key to my U-lock - I'm fairly certain it fell out of my pocket while I was sitting - somewhere :/... Any recommendations on how to cut it? After chewing up 1 hacksaw blade to it's dull tomb, I'm fairly certain it's made from hardened steel. Bugger. From past expirience, bolt cutters don't play nice with hardened steel :p Recommendations? oh, and it's a decent lock - picking isn't an option :/


Angle grinder with a cutting/zip disc. Just make sure you're aware of how dangerous they can be.

With any of these methods....remember to wear eye protection !


10 years ago

We always used to use the dremel reinforced cut-off wheels with great success. Just make sure to use it on the hollow cylindrical cross-bar, NOT the U-bend!

You have 2 options of ease, 1. Get a propane torch and ruin the hardening by heating it up to red hot and then use a hacksaw. 2. Do what they say and use a grinding wheel attached to an angle grinder. Do not use thermite because it will destroy what you're trying to save, it is used for casting iron and will melt right through most stuff in its path. Also if you happen to get some good bolt cutters but can't get enough leverage, you can add long pipes onto the handles and old onto the longer pieces as you cut, it will be magnitudes easier the longer the pipes just don't break the jaws of the cutters :) Good luck.

it is used for casting iron and will melt right through most stuff in its path.

No kidding!

Pat. Pending

I would use an angle grinder for a quick fix or THERMITE if I was going for maximum effect ;-)


Pat. Pending

Thermite doesn't sound like a bad idea... just don't burn the place down :P

. Go to your local welding supply shop and get a grinding disc (the thin kind, like welders use for grinding welds) (or more, depending on the locks and the discs). You may be able to rent the drive ("side arm grinder" IIRC) at the same place. Or try a local tool rental store. Lots of noise and sparks, so use proper safety equipment. . Use a cutting torch. Due to fire hazard, probably not the best idea, but it will work. . A good set of bolt cutters _will_ work. Depends on the jaw material and how much leverage you can get.

What about drilling out the keyhole?

if you own or can borrow a circular saw or grinder, you can use a carborundum blade ($7) to cut the lock. it takes less than a minute to do the actual cut. wear safety glasses, watch out for the sparks on your paint job, don't push on the tool too hard, hold the lock down so it doesn't move while you are cutting, watch out for the blade binding, don't cut your bike frame by accident. blah, blah, blah. get help if you aren't confident.

I agree, good bolt cutters (i.e.: 4000 LB JUMBO Bolt Cutter - Chrome Molybdenum) should do the job.

Bolt cutters should have little problem with hardened steel. Also, you might consider a welding torch to soften the steel.