Hello J-ROD, you will likely need to determine what type of over-lay rod is needed to make this repair first. I haven't done this sort of thing in many years so I can't help you with any rod suggestions, however there is one of the fellows on the forum here that works for Stoody and by using the search function you might be able to figure out his screen name and be able to contact him for suggestions. If you have a welding supplier in your area that you feel is competent to help you with selecting the proper build-up rod I would try to get with them so that you can get the specifics of how to apply a particular weld build-up electrode. If there is lot of build-up to be done you will first want to apply "soft" weld metal to cushion the final layer of the hard-rod, most folks will use E-7018, E7014, or a similar type of rod. Preheat is definitely a good idea before starting the repair, I believe around 300F to 400F would suffice. If you do plan on doing the welding with the idler still on the machine you will want to be sure to ground directly to the idler itself and not anywhere else on the machine, this will prevent damage to the bearings in the part. It's really best if the repair can be made while the idler is dissassembled so that you can avoid over-heating the bearing races, yet I have seen many done while still on a machine. Hope this has been of some help. Best regards, aevald