carbon woodruff keys and welding a crankshaft

i have heard rumors that there are carbon woodruff keys (like the carbon rod you put in drilled holes while welding) i only come up with carbon steel woodruff keys on a google search. if there is such a thing where would i find them?

looking at alternatives for repairing the balancer key slot in a mercedes 5 cyl diesel crankshaft. had the crank handed to me and i know nothing of this engine but the new balancer has two marks on it so they must be there for a reason and i would prefer to put it back indexed correctly.

my other option would be to weld up the wallered out key slot and cut another. welded a lot of stuff but not a crankshaft. it's forged - i would thing there wouldn't be a problem doing that but maybe someone else can enlighten me.

or make a step key. the original was 5mm but snout's damaged enough that i don't think cutting a 1/4" slot for a straight key will be enough

i also have to spray weld the snout

it's a $2k crankshaft i'm told and the unfortunate shop owner's employee left the balancer loose so he's eating it. not that that is my worry but i sympathize with the situation. both the shop owner and i prefer to put this back correctly so down the road someone else doesn't get into a nightmare.

Make your own, turn graphite to the dia and clamp into the slot, weld each side
Fairly common repair, I even did it on one shaft with Belzona epoxy, lasted a few shifts til a replacement was available (and that had a pocket and insert milled and fitted with a new key way in
Mark

Use copper...Phil

Phil in Montana said:

Use copper...Phil

Click to expand...

can you explain?

oh, make a copper key?

Yes make copper key, when you weld hold the arc away but let the molten metal flow over to the copper, when the shaft cools the copper will shrink a little and should fall out.....Phil

Hi all,
long time lurker here but first post and reply to something I have done. I did a similar repair on a John Deere with crank still in place with TIG and a mini die grinder. Built up the worn side and dressed with 3mm carbide burr afterwards. I was a bit skinnier then but it saved a lot of stripping and reassembly. The guys mechanic took out the rad, cowling and fan for access. Not a lot of heat involved but wrapped a damp rag around to save the oil seal.
Apologies if I have left something out of profile or other mistake.

I have had unobtanium forged crankshafts welded, straightened and ground. If I could avoid welding on a crankshaft, forged or otherwise, I would.

I would firstly find it hard to believe than a Mercedes crank can't be found for considerably less than $2000.

If possible, I would try a non-weld repair such as epoxy or larger step key. Or go 90 or 180 and cut new keyway in crank and balancer.

A close friend of mine owns an auto repair biz. I have helped him on stuff like this and it's almost always a compromise. My friend has learned it's usually best to just turn it in to his insurance company and do the repair 100% right. He had a situation change his perspective on it when a "minimize cost" type repair for his own simple mistake failed and the customer was a lawyer. The customer was a scumbag, but filed a lawsuit and settled out of court for $10k. It was something like an exhaust bolt broke off and he tapped a new hole crooked.

Thats a good point...for whats called a "edumacated bodge",I used to get a mini contract signed by the customer explaining the repair ,likelyhood of failure,and possible damage if it failed ,and an agreement by the customer to indemnify me .....Having done that I also get a signed and witnessed statement that "the repair was not to be used in a licensed,insured,roadgoing motor vehicle"..As someone has said ,there are a legion of scumbags who get cutprice,bodge repairs ,then hit you up thru the small claims/trade practices/consumer protection for all new parts....Dont be a bunny for a con artist.

Be aware that if you weld on one side of the crank nose, the weld will shrink and the nose will not run true due to the weld pulling. We "rekeyway" lots of crank noses and never weld them for that reason if the original nose diameter needs to be maintained. I've seen the end of a crank nose running out almost .010" due to a welded keyway.

the ac delco rep dropped this off for a shop he works with. i previously pointed them to a local crankshaft co and i was told they don't do mercedes cranks. anyway i got the vehicle info this morning and found a reman crank, in stock in orlando, $275.00. took less than 10 minutes and the crank comes from where i first told them.

sigh