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From: Steve Hoas
Categories: Saw cracks
Date: 02 Nov 2001
Remote Name: 220.127.116.11
Hi there. I use a Lincoln sp255 welder for our band saw cracks. This is a computorized welder that can have numerous presets for various thickness of saws programed into it. We have used this welder for 4 years now finding it to be the best after trying numerous others. We use a chrome- moly wire,.035 with a 95%argon 5%CO2 gas mix. The wire feed speed and welding voltage cam be ajusted at the stinger if required. One very important thing we do is to preheat the saw to approximatly 900 degrees. I generally just bring it up to a straw color before I weld the crack. I built a copper plate with a slot for the teeth to sit in. It also has a heater on it and two clamps to hold the saw down while welding. This gives an even weld bead on the back side if the saw. After the preheat and the weld I let the saw sit until it is below critical temperatur and then anneal it using the "shadow" method which if done right will be a barely visible red if the lights are turned out. The saw is then let to cool below critical temp again on the copper pad before moving it off to cool at air temp before dressing the weld.Be very carefull not to over heat the weld when dressing it. If it gets too hot (turns blue) you will get cracks again. I use a 4inch angle grinder with 64grit sanding disks to do this. I also have an air powered die grinder for doing the gullets.I also weld on teeth with this unit as it gives much better finish than if the fitter welds the teeth on with a torch at the grinder. If my repaired cracks are not too (under 2") long I hardly have to do any work on them as far as benching is concerned, that is how well this system works.