hard surfacing?

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hi guys; i have a cam shaft at work to build up. i am going to tig it,i have sodel tig 245's. i would like to get a little advise for i never used these before.the supplier had nothing.i am thinking 4-500f for pre heat,and may be a little post,should i use a blunt tungsten or sharp,peenning between passes?oh to get the cam out of the vessel it would be a real big job we would have to split the bolck and turn it sideways,possibly cut the side out of the ship. thank all advise is appriciated.                                  Steve
Reply:Originally Posted by steve oickle i have a cam shaft at work to build up. ...i never used these before.the supplier had nothing...  ...to get the cam out of the vessel it would be a real big job... possibly cut the side out of the ship...                                   Steve
Reply:What is the engine?  Is the cam a one-piece forging or is it built-up?  If the cam is built-up, the manufacturers usually have some system for replacing lobes.  Usually, the old lobe is split with a grinder and a new bolt-on lobe installed in its place.  It seems to me like there would be some incompatibility between the hardened roller on the cam follower and a hardfacing rod on the cam lobe.  I don't know of any engine that requires the blocks be seperated in order to do a camshaft replacement.  They usually slide out the front.  Seperating a cylinder block from the bedplate is a big deal, but sliding the cam out the front of the engine and cutting a few holes in the ship isn't too big of a deal.Considering the costs/risks of failure in this case, you should really contact the manufacturer of the engine.  I'm certain they will have some means of repairing the cam.  If the cam cannot be repaired by the manufacturer, maybe someone like In Place Machining could do it?Last edited by 76GMC1500; 09-10-2007 at 02:03 AM.
Reply:job complete.welded fine,no cracks or warpage sanded and polished fine.it is actually a little harder.
Reply:I'd say fatigue resistance would be more important than hardness in a roller cam applicatoin.  What kind of engine is this?  Number of cylinders/horsepower, manufacturer, highspeed/medium speed/slow speed?  Heavy fuel or lighter distillates?  It was the fuel pump lobe, no?
Reply:I'm sorry, but I think hardfacing a roller cam is a terrible idea without taking into consideration the fatigue resistance.  As much money as you save the shipping company, the ships are usually worth enough money to justify a proper camshaft lobe replacement.  Afterall, the consequences can be quite severe.
Reply:you have a good point;but just doing what the customer wants.yes it was a fuel pump lobe.                                     thanks for yor interest
Reply:The cam and shaft are most likely chrome moly steel.  An ER70 electrode or possibly even a chrome moly electrode would have probably been best for making the repair.  I'm sure the lobes are case hardened, but nowhere near the hardness of a hardfacing electrode.