Saturday, February 16, 2013

First V.D., Then TB

That's Valentines Day and then Torch Braze. I repaired a saw vise for Surly the other night at the college using the torch brazing process. The Intro class I'm teaching covers Oxy-Fuel Cutting (OFC), Oxy-Acetylene Welding (OAW), Torch Brazing (TB), Shielded Metal Arc Welding  (SMAW), and Gas Metal Arc Welding (GMAW), also known as MIG. There are over two hundred welding processes, all of which have some sort of capitol letter, abbreviated form. There are new methods, like Friction Stir (FSW), and archaic ones like Atomic Hydrogen (AHW). I can usually navigate among the alphabet soup of the most common abbreviations but I don't profess to know them all, or even to have seen many of them. Not much opportunity to see electron beam welding (EBW) in my neck of the woods, for instance, but Torch Brazing? I've got that mastered.

The saw vise is made from cast iron - perfect application for brazing. I'm not sure how old the vise is, I couldn't find any markings on it. That in itself is rather unusual. Anyone with the ability to design and cast something like this made from multiple parts would normally have taken pride in the job and included their name someplace. It's got the typical black enamel finish that covered most of these types of tools. Might be it was sold under several brand names. They would put on a gold decal that stood out nicely on the black paint to identify the seller, rather than the maker.

It was easy enough to repair. Grind a little bevel on both sides of both pieces and grind the "casting skin" back from the edge of the crack a little. Preheat the parts a little and then slowly bring it up to welding/brazing heat - kind of a dull red. Bring the brazing rod into the joint and it should flow into the joint as the temperature of the rod comes up as does the temperature of the cast iron. You never want to overheat the part because you'll burn the brass or the cast iron and the filler metal will never stick to the base metal after that without grinding it off and starting over.

After my paranoia post, kind of good to get back to project postings. I have been staying busy, though. I welded up a clutch arm for a little Ducati last week but forgot to get a picture of it before my buddy picked it up. He modifies the arms, with my help, by making them longer. He then slots the case out for clearance and makes a little bracket for the clutch cable outside of the case rather than internally. This gives much more leverage to the arm making it easier on the hand to squeeze the clutch lever on the handlebar. Seems most all of the older Ducatis required some muscle on the clutch lever. My 750 is like that as well.

Enjoy the weekend.

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