Crankshaft crack detection

[ronan]

I have a motorcycle crankshaft sitting here years. It was hard-chromed on the main bearing journals at some stage before i got it. At one step in the crank on one of the mainshafts, there is what looks like a crack, but i cannot tell if it is the chrome or not. Is the penetrant dye system any use for testing it ? I have only ever used it on things like water tanks.

 

[Wedg1e]

In theory yes, but the dye will stay in a crack in the chrome as well as it will in the base metal.
It might show up on x-ray if it's deeper than just the chrome, but I appreciate not many people have an x-ray system in their workshop
A good ultrasonics technician could probably determine if there's an echo from a crack under the chrome.

 

[doubleboost]

The first test on a car crank was to hold it on one finger "hanging" then tap it with a hammer it should ring like a bell .,
If it sounds dead it will be cracked
Only ever used dye penetrant to confirm a known crack

 

[ronan]

The first test on a car crank was to hold it on one finger "hanging" then tap it with a hammer it should ring like a bell .,
If it sounds dead it will be cracked
Only ever used dye penetrant to confirm a known crack

Yes i done that and it does ring ok, i think its just a ragged edge from the hard-chroming, but i want to be sure before i put it in an engine and waste money if it does break or shear off. All the engine reconditioning places here are gone.

 

[Pete.]

I should think that magnaflux would show a deep crack but not so much a flaw in the chrome coating.

 

[minimutly]

I had an xpag crank that rang as good as all the other specimens I was given. The dye penetrant crack test showed a crack exactly where they all fail. So don't trust the ring test, unless it really is a bad ring - a good ring is no guarantee.

 

[Munkul]

Can you grind or file the chrome coating down, or is it in too delicate a spot? If you can take off the surface defect and then dye-pen, it should show an indication if it's a proper crack.

 

[Stueeee]

If a crank is OK with a penetrant dye test I get it Magnafluxed. Over the years I've had two cranks that which subsequently failed Magnaflux after passing good with Ardrox. I do the dye test first because I'm paying £70 to get a four cylinder crank done.

 

[ronan]

Can you grind or file the chrome coating down, or is it in too delicate a spot? If you can take off the surface defect and then dye-pen, it should show an indication if it's a proper crack.

I might be able to get under it with a carbide tipped tool in the lathe, then crack test. All the old little engine reconditioning workshops here are gone, no one i can leave it into to get it tested, and puppy dog has made sending anything to the UK a pain in the fundament.