removing a key

[BrokenBiker]

any ideas on how to remove a stubborn key from a keyway in a shaft without damaging it, as I don't have facility to make a new one unless I take it into work, and there is very rarely a free mill and this job is an ASAP one

I have tried localised heat and quench, heating the shaft, good old brute force and soaking in penetration oil but still have no luck.

it is a semi circle shaped key, 5mm thick, about 5-6mm deep (from flat to tip of rad) doesn't appear to be that hard (I have dented and gouged it trying to beat it out with a chipping hammer)

it is located in a crankshaft of a lawnmower engine. a Tecumseh vantage 35 to be exact.

need to get the key out so I can get the bottom of the engine off to replace the piston rings and valves. the other keys pretty much fell out with a gentle tap, but this one isn't playing.

 

[julianthegypsy]

There's a company on evilbay selling woodruff keys in all sizes and very cheap, I got one for an ancient milling machine I was fixing a while back. Knock the old one out with a thin chisel/flat tipped punch, being careful not to damage the shaft/keyway.

 

[Flapdisk]

Maybe try some of that spray freezer stuff plumbers use to freeze pipes, to shrink it mate?

 

[Lawnmowerboy]

I can sort you out a chunk of keysteel (EN6A) if needs be. Set to work with a vernier and a good file.

 

[BrokenBiker]

I can get hold of key steel in work, but time is of the esscence with this one, was hoping to just pop it out but its not working.

think I might just have to smash it out and make a new one though. no sign of it coming out without damage at the moment

 

[Rig Pig]

Drill + tap the key and turn / file a point on a bolt & use as a Jack to force the key out

 

[Lawnmowerboy]

Weld something to it if possible

 

[BrokenBiker]

cheers rig, will give that a try. now, where is my M3 tap? lol

 

[biffa]

Make a slide hammer and tack/weld to key? If you have the facilitys

 

[BrokenBiker]

have a slide hammer, but no welder that will go that low...

anyway, its out! gave it one last go with a wood chisel before trying to drill and tap, and it moved a bit, hit it again and again and it slowly prised out. still serviceable as well just need to file a burr off.

I have also realised why it is only mild steel too. noticed the pulley that sits on the shaft was very light. then noticed it is aluminium. not in the best of conditions so will be making another of them out of some melted down bits and bobs that I have waiting. cast into a billet then turn to shape

gotta love some of the crap that gets sent for repairs, especially as im an electrician, not a mechanic lol

 

[rtbcomp]

With a semicircular key tapping one end should cause the opposite end to rise.

Use a brass drift to avoid burring the key.

 

[BrokenBiker]

tried that and it just deformed the copper (don't have any brass spare)

I have a few wood chisels that I have softened for various reasons, so used one of them and it worked. gonna get a diamond burr in there to clean the keyway up a bit to avoid this in the future if it ever comes back to me...

probably will. the engine is known to burn oil, and the guy running it doesn't top it up, runs it dry and it seizes. third time it has happened. only the first time I have had it for repair though

 

[the snooper]

the Tecumseh engines ive had dealings with have thrown the con rods and seem a disposable engine I wouldn't buy anything that had one on it. don't worry about the key way if he carries on running it dry you will be able to inspect part of the con rod from the out side soon

 

[jordan1]

I always though keys were usually made from mild steel, sacrificial like

 

[gordon stephenson]

I would have no hesitation making a key of that size from mild steel.

 

[MattF]

With a semicircular key tapping one end should cause the opposite end to rise.

Should being the operative word. Some keys just refuse to shift without severe persuasion. I have one here which is jammed in solid. I think some plonk has fitted a slightly over width key and hammered it into place.