Annealing bandsaw welds

[chewietwo]

I was taught by the old Tool Makers when i got in the trades many moons ago. When welding a saw blade to anneal the blade after weld buy bumping the anneal button till it just starts to turn blue. Then use a file on the weld. There is not a lot that has to be removed and a file doesn't heat up the area like a power grinder does. After you file the weld do a second annealing. i have the best luck with this method.

 

[just Dave]

I have worked with many high end band saws with band welder built in. I have not seen much success by me or anyone else in the shop. I worked for a place that had a stand alone band welder, large, maybe two cubic feet. I can’t remember the maker, but it worked well, near factory weld results. I built a fixture twenty some years ago to TIG weld them, I used 309 filler rod. They work ok but not great.
The diameter of your wheels has much to do with blade life.
I don’t know a lot about saw mills, but 40 hours of run time does not sound like a good life span for cutting wood .
If available I would buy bi- metal blades and see if that helps. They are not generally resharpenable, but last until you make a mistake that ruins it or a few hundred hours of cutting.

 

[HWooldridge]

Bringing it back to cherry red may induce grain growth and create unintended brittleness. Another suggestion would be to make sure the ends of the butt welds don't have a notch or stress riser after grinding. Better to polish out those areas than let a crack start and propagate from a tiny split.

 

[richard newman]

I use the Ideal welder built into my 20" Powermatic #87 bandsaw and have had good results with carbon steel, bi-metallic and carbide tipped blades. Only up to 1/2", which I think is the maximum my welder is rated for, .025 to .035 thick. I use the settings recommended on the welder, heat treat dull red right after welding, grind, heat treat again to blue or purple. I found it difficult to get a good grind with the stone on the welder, use a dremel now with the blade on a curved block of wood, followed by a file. I tension my blades to 25,000 psi using a Starrett gauge, similar to the Doall pictured in post 13. I'm mostly sawing wood on a Powermatic #20, and my blades get very dull, almost never break.

I was pretty amazed at first that my shop welded blades performed so well. I did have to tweak the welder to get perfect alignment at the welds, but otherwise it's stock. What really surprised me was being able to weld the carbide blades, as I'd read that was not possible on a simple welder. I couldn't understand why tho, the blade stock shouldn't be anything particularly exotic, or different from bi-metallics, same concept. Maybe the fact that a carbide blade lasts so long makes the weld more critical, I haven't used mine long enuf to get data on that.

 

[tnmgcarbide]

i'd suggest you take the welder apart, critically clean every part, polish everything nice and shiny and lightly lubricate
every moving part . it may sound like overkill, but years ago i owned a stryco machine that had similar results.... the welds
didn't hold up . they looked good, but were not fusing sufficiently and would fail. the machine appeared clean enough,
but after disassembly and polishing EVERY nut,bolt,contact point and jaw ....the machine welded flawlessly . i could
wrap a 5/8 band around a 2" pipe and the weld would not crack. the extra current was all that it needed .

anyone who does any arc welding can relate to the difference an OK ground and a REALLY good ground has on
weld quality.
good luck

 

[hvnlymachining]

Not knowing anything about your particular blade brand, not all blade metals are alike.

You may have a high carbon low alloy material, which will be easy to cause carbon build up at the "Heat Affected Zone" (HAZ to welders ) this leaves a very brittle spot on both sides of a weld. And potentially both sides of the annealed area. If that's the case you need to temper or anneal very slowly with a torch rather than a welder/annealer. That allows the temperature difference across the blade length to be more gradual and prevent a carbon "wall" in the blade.

 

[surplusjohn]

One variable that may or may not be relevant. Make sure the copper plates in the clamps are flat and clean. It looks like you are getting lots of current so this may not be an issue, however I have found several balky blade welders that gave troublesome performance that had dirty and rough plates. Take them out and flatten on a belt grinder and the problems went away. Low voltage needs alot of clean surface contact

 

[tnmgcarbide]

i don't know your bladestock, but i'm pretty sure all bandsaw coil stock is/was inherently intended to be welded into a circle . should not be an issue . again, check your machine...... cut a foot of material and send it to a brother
member of this site and see if they can cut/weld weld the thing properly . why not?

 

[jackalope]

I’ve never used my DoAll blade welder for my blades. I’ve only silver soldered using high grade silver solder. Bevel both ends for a smooth overlapping fit and hold in a fixture. Simply use mapp gas until flux starts to cook and then add solder. I’ve never had a blade break at a joint EXCEPT when I used old dried flux. Short of that this method has worked flawlessly.

 

[BOB-OO]

We cut through the weld diagonally looking for any troubles

View attachment 412531
View attachment 412532

For what it's worth also, this is a photo of the last band that came from our supplier, broken from extended use, but not on the weld..!

View attachment 412533

I did snap a photo while heat treating also, with about the colour we have been going to, cherry red then easing it back over a minute or so, but I'm wondering if we should be going more/bright red or less/blue. Or multiple times or torching or what.

View attachment 412534

The band stock is a coil from kasco I think they call it their woodmill series, I don't know any more than that about grade but it is the same as I had the supplier obtain for us, we just got this next one sent directly to us after realising the cost savings and coming across a second hand welder.

This is the story below of all our bands for the past 6 months maybe, long story short a vertical mark is a sharpen and a / is a new band, 3-4 hours work between sharpens usually. Most bands meet their death by metal strike and this isn't recorded but some live long lives. Of all these bands none have ever snapped on the weld.
View attachment 412535

And last pic, the crack that formed on the last band after ~3 hours work. I noticed it start wobbling about 20" from the end of the last cut of the day, we ran it slow and pushed it through anyway hah.. we did try heat treating after cleaning up the weld on this one hence the colour.

View attachment 412536

I've noticed the terms annealing normalising tempering etc all used I don't know what the correct terminology is but, whatever it is that will stop them snapping is what we're after. I suspect we're doing something wrong in this process?

Thanks again for all the responses!

I've welded over 1000 blades using the same methods you are using- that anneal is too hot for a bi-metal blade. Each material is a little different & I've had to send blade stock back more times then I can count bc it was improperly manufactured.
Check also that you are not overheating during grinding. If your grinding in less then 2 minutes your overheating the blade and killing the anneal. when you grind its OK to see a little blue not ok to see red again. I've NEVER used a hand tool grinder- ALWAYS a fixed stone.
A correctly welded will not break at the weld. After you think its right bend it approx. the diameter of the wheel and straighten a few times. Then look at it w a magnifier- any cracks= bad weld.

I've also had to realign and make or shim Jaws to get them dead on, that doesn't look like an issue for you, the welds themselves look good.

 

[JoshNZ]

Apologies again for late response. We are on round 3 of our band since trying the deep blue anneal and no signs of failure so far. It is not our best weld or grind job either. We did reinstate the stone, it is so awfully slow (seems to burnish rather than abrade even after dressing) I took it down to barely proud with an angle grinder then back to the stone and it left an untidy job but, we're still joined. Will get a few more welded up and report over the coming weeks how we go. Thanks again for all the input.

 

[SND]

For many years I've been tempering all my bandsaw blade welds with a propane soldering torch. Best way to control the heat and get the right color and time. I do this with every pre-welded blade I buy no matter which brand.

There was even a time where I would throw the entire blade in the oven at 500F for an hour when it was blade stock that wanted to crack everywhere, it helped blade life a lot.

 

[dian]

proper annealing/tempering is done for up to 2 hours at specified temperature. just saying.

 

[SND]

proper annealing/tempering is done for up to 2 hours at specified temperature. just saying.

Or only a minute or 2 to do the weld on saw blade with a propane torch and pretty much guarantees that's not where it's gonna break, it's a hell of a lot better than the little anneal button on the bandsaw's welder.

 

[JoshNZ]

We've still not had a break since changing to heating to blue colour after welding. Doesn't seem to matter whether we do it before or after dressing the bead now. Am back to using an angle grinder and flap disc too, that doesn't seem to matter either.

Appears going cherry red was the culprit. Thanks again - great one for us to have dialled in.

 

[James H Clark]

For years we had good luck bringing it to a dull cherry after weld, but this was non bi-metal blades. After bi-metal blades became common, we used store bought blades.
jc

 

[Bill D]

Those onboard welders claim not to be used for bimetal blades. I suppose the tempering and heat treat are different for each metal type.
Bill D

 

[richard newman]

Those onboard welders claim not to be used for bimetal blades. I suppose the tempering and heat treat are different for each metal type.
Bill D

Maybe, but I've been welding bi-metallics with mine with excellent results. Carbide also

 

[boslab]

This is just a question, I have a suspicion, somewhat remote that some kind of light peining of the weld might do somthing, probably make it worse but there’s a remote chance it would help, or the cheese has slipped off my cracker, again .
When I say light I mean very btw
Mark