Thread: TIG Welding bandsaw blades

Pete F asked how I weld up my blades, so I've put this together. First, the usual disclaimer – I'm not an expert but this is the way that I've found works best for me. I'm also not a qualified welder, so some of my technique may be a bit ropey, but (again) it works for me.
My bandsaw is a 4x6" from Ozmestore which I think is a good buy. I bought it on a recommendation from a friend with a jobbing shop business who did not have one, but one of the other cheap import types. However, he recommended getting a bandsaw with a swivelling head rather than one where the vice was angled, and this was the smallest I could find. It does have two minor detractions – firstly it is fixed speed – good for steel. I have cut plastics Al, brass, bronze, CI and others with it so that's not a big problem. The other minor issue is that the blade is small (1470mm) and is tensioned with spring pressure (no adjustment). In real terms that means that the blade must be 1470mm, +/- 1 to 2mm.
I started welding bandsaw blades as after getting my bandsaw I got the local saw works to make up some blades for me. Apart from costing a bomb, I had to take them back 3 times because they got the length wrong and at the end of it their joint was so bad that the blade broke after 2 outings. One alternative was a resistance blade welder but they were not cheap. Thinking about this and doing an internet search, I discovered someone who claimed that blades could be TIG welded. As I'd just bought a TIG, this sounded like a good learning experience if nothing else.
The first step was a jig to hold the blade (photo 1).This one is some Al from the scrap box. The step is slightly less than a blade thickness and dimensioned so that the teeth are in free space. The gap between the blocks is around 30mm. Hold down is with some wing nuts and mudguard washers, with studs secured with loctite into the blocks. If I were doing this again I'd consider stainless. These are ZP and I sometimes wonder whether with the heat it's a good idea. Another (probably better) alternative would be some toggle clamps. Also with the jig is a block of copper. This is a backing for the blade so that it does not meld through (learning experience no. 1).
I have a container with pieces of old blade chopped into pieces around 20 to 25mm long. I use these as run-on/ run-off tabs. I found that otherwise I would blast a notch in the edge of the blade so that I had a stress raiser. Even then with the gap there can be trouble. My TIG has a thumb control for current and I set the machine up so that it has a maximum of 38 to 40A. The blade material is 0.65mm thick. I find that I can reweld broken blades without an issue so typically I'll have several blades hanging on a hook in the shed ready to go, a couple of new ones and a couple of repaired ones. I scrap them usually due to tooth wear.
The steps are –
1. (If making from new) cut the stock off square – good joint fit up is essential. I use a square as a guide to ensure the tinsnips cut straight. (photo 2)
2. Clean the ends of the blade (remove oil and other crap)
3. Position in the jig with the copper block underneath and the run on/ run off tabs on either edge of the join. I hold the end of the run on tab in position with the filler wire until I have an arc going (photo 3)
4. Weld. The bead needs to follow the join and be flat-ish rather than a lump that is proud of the surface. Fill any notches at the edges and try not to weld over too many teeth. (photo 4 - a little lumpy at the ends but that's better than a notch)
5. Leave the blade where it is and slide out the copper block. Using a blow torch (mine is MAPP) heat from underneath the weld to anneal. I try to get a bright red around 10mm either side of the weld. Allow to cool in still air. (photo 5 - it's not really purple - the camera IR sensors were overloading I think)
6. Remove from the jig (and do a few more – it's quicker to do a batch of blades)
7. Using an angle grinder, cut the run on/ run off tabs off. If you try bending them off with pliers you can crack the weld or surrounding metal
8. Using a grinder (bench or angle) dress the weld back until it's flush. The back where the copper block was will only need a slight touch up. Don't over dress as that then becomes a weak spot (but then if you don't dress enough the blade will jam). You could make up a gauge but I haven't found it necessary. Dress the weld on the tooth side of the blade so it is flush with the tips of the teeth (no sudden jerks when entering/ leaving the cut). Dress the opposite side too but this can be a little proud as it will flatten slightly with use.
I then park the finished blades on a hook ready for a change in tooth pitch, a break or replacement due to wear. Before I started using the copper block and the tabs I found that I was getting breaks at the weld – usually due to notching the blade. Now breaks are usually 'off weld'. The chances are that you will know a blade is getting ready to break because you'll hear a regular noise when it enters the cut. You can either change it when convenient or let it go until it breaks – which is suddenly no big deal because you have spares and a way to fix or replace the broken one.
While it is best to have only one weld in a blade, I have blades that have 2 or 3 welds in them. It is not an issue because TIG welding blades does not shorten them and they only break at weakest place. If you have a blade that has lost some teeth in one spot or jammed and so has kinked, cutting a piece out and replacing is possible too.
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