Hi I am having my pantah crank ( well it's a 650 allazzura crank but let us not quibble) reground in the next week. Looking at the original pantah workshop manual it says -quote "After crank pin grinding the crankshaft should be heated (550 degree C sulphonitriding followed by crankpin polishing". The polishing bit makes sense but is this sulphonitriding something regular engineering crankshaft people do? What have others done with regrinding earlier Ducati plane cranks? Best regards Keith MM Ps auto type has given me 'regrouped'not 'reground' sorry cannot edit it. Moderator help?
Surely any workshop which regrinds crankshafts professionally should be able to offer heat treatments to suit. If not, find one that can.
I agree, one would hope so. It's just got to HT Howard who seem to be competent (anecdotally collected information) I am speaking to them tomorrow. Will keep you posted. Surprised no one on the forum has not had a crank reground ( or regrouped as my iPad wants to say!)
I've had plenty of nitrided car cranks reground over the years and never needed any of them renitrided. If it's just one size down that you're grinding to then the case hardening should be sufficient. If in doubt speak to the machine shop, they may also have a tool for testing hardness.
Hi thanks for your real world information itiejim. The engineering shop man said they rarely need to do it but is trying to get a quote from the heat treater he usually uses. I got a finger in the air figure for the heat treatment and had a massive shock. (He said the heat treaters do work by weight!) It just so happened a good second hand 650/750 pantah crank came up on the German eBay site with two con rods AND with new shells as £165. Cutting a long story short I have bought it. Now I have your feedback I may ask the engineering workshop to just grind down to the new undersize shells. This way I think I have two potentially good cranks. Or two that will die in a short time. You have to laugh!!!! This was supposed to be a budget rebuild.
You're obviously trying to do it properly, so the budget bit always takes second place! If your crank grinds up well, just one size down, I'm sure it'll be fine. Good luck.
Steve, sounds like you've got the specific knowledge to answer this one. My rebuilding experience is all with car engines, albeit some fairly high performance V8s. As with most things it comes down to who you know and trust with your machining. I've used my machinist for over 20 years and trust him to tell me what he can and can't do!
