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OT. Bandsaw blade welding, which way is best?

From what I see here, it looks like I just need to take time to build a good fixture for alignment and try a few methods out to see what I prefer. I have some rolls of blade to go buy now so I can be prepared for the next blade failure. ( 100 mile round trip for blades gets old)

Thank you all for your time and suggestions!

Since Dad passed away I don't have anyone I can bounce ideas and questions off of, and you all have been very kind to take the time to allow that. Again,Thank you!
Braze is a cheap method to try. I'll try to remember a pic of my jig tomorrow. If you don't like it, spend the cash on a welder, but if you try brazing 3 blades, I don't think you will. I started from the other direction and strongly regret the $300 I gave for my Doall welder. Unfortunately, no one to resell it to over here!
 
Our tax dollars at work?

I served in the Army so I feel completely entitled to criticize them.



I once bought a stack of NOS Grob blade welders from the army sales .........compared to a Do All welder ,the damn things were near impossible to use ...........which is why I suspect the army had removed them from the saws.
 
I use Starrett “Bi-Metal blades for my contour band saw.
Order pre- made blades from McMastar-Carr comes the next day if I order by 5:00pm (yrmv)
Don’t see a reason to screw making my own.
Electric blade welders won’t give good weld on Bi-metal blades.
Silver braze is fine, but really don’t want to mess with it. Too busy making chips.
Keep a spare blade on hand, when I put it on the saw I order a replacement so no down time.
Cheers Ross
 
I agree with you half heartedly, AlfaGTA.

I usually just keep blades on hand, but with a growing variety of blade sizes, and nobody gets anything here next day without special shipping at great expense. I expect to be needing to do a lot more blade welding myself, especially when it comes to more expensive blades.

Since with the larger band sizes I can save hundreds, to possibly thousands per year by buying old stock and welding myself , I figure it's worth a bit more effort.
 
Here's my simple scarfing jig. Notice, it's a pretty sharp angle to expose enough face of the blade so the braze has enough surface area to grab. Just need to keep the base piece of bar sliding parallel to the sander (I use a 15" disc sander because it's what I have.)

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I found that feature virtually guaranteed one ruined tooth, which was then always the first to fail, starting a domino effect on the ones following it, which is usually how my blades failed when resistance welded.


The doall manuals have instructions on how to mitigate that issue. I can't upload the whole PDF for the welder I use at work because it is too large but here are some screen shots:

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You could probably find the correct manual for your welder on Vintage Machinery:

 
here's my silver brazing jig

I also found I needed to grind a long scarf, but don't go too long or the thin part of the scarf that doesn't have braze will fatigue and snap. I'd guess 3/16" for a 1/2" wide blade.
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My process:
1) grind scarf
2) coat one side in Harris black flux and clamp in jig
3) cut off a piece of silver braze wire, fold it a few times and push it into the flux
4) coat the other scarf with flux and clamp so that it pushes down on the braze
5) heat with a propane torch from underneath until the flux goes glassy and both sides of the joint glow red. Braze should now melt and flow. Squish it a bit with a screwdriver
6) lightly grind off the flux with a dremel and use a bit of sandpaper to get the band bright
7) gently heat up the joint with a torch until it just starts turning brown

That's pretty much it. I wait until I have a bunch to do and then do a batch until the plastic knobs start falling off the jig. I buy weird size 1/2" bands off Amazon for peanuts and make 2 or 3 out of each one.
IMG_20211102_183602.jpg
 
Ive said before about how well my first big Do All welded blades ........and how every electric welder Ive used since sucked so much ......including new Grob welders .........But the crazy thing is ,Ive never been able to find another one of those Do Alls with the 'good' welder ............its getting on 50 years ago now ,maybe I dreamed it all ........was the swinging 70s,after all.
 
It was 25+ years ago when I last witnessed a scarf joint get brazed, but wouldn't that damage or destroy several teeth? Since a good portion of the material I cut is pre (half) hard 4140 & 4340, tooth failure is critical to avoid because as soon as one tooth goes the rest follow closely after.
Maybe I'm missing something?
 
I've not had any teeth fail at the braze joint so far, cutting a wide range of mystery metal. Had a couple of joints fail during the learning process, but those are easy to clean up and rebraze
 
What you
It was 25+ years ago when I last witnessed a scarf joint get brazed, but wouldn't that damage or destroy several teeth? Since a good portion of the material I cut is pre (half) hard 4140 & 4340, tooth failure is critical to avoid because as soon as one tooth goes the rest follow closely after.
Maybe I'm missing something?
What you're describing is exactly my experience with blades welded on my Doall, and the reason I switched to brazing. I use a small flame from the torch and put it mostly on the back of the blade, the non-toothed side. The braze doesn't need enough heat to melt or temper a tooth in my experience, as long as the heat is applied judiciously.
 
If what you're doing works, why change it? Unless you have to weld blades all the time I wouldn't sweat it.

We have some large Do-All saws in our shop that both have blade welders on their sides. Neat and quick little gadgets. As others have mentioned, it is recommended to anneal the joint in some way after welding.

Justin
 
I used to do a ton of silver soldering on dot matrix print heads. Silver solder came in syringes and was pre loaded with flux. Worked great.

I must have welded thousands of blades over 30 odd years. We used to drill a hole in tool steel plates and then feed the blade through the hole to cut internal shapes which were filed and then sheared using the punch. Poor man's EDM 😀.

Could someone post pics of the scarf joint pre welding. I want to give it a try.

Seperate question, I wonder if you could convert a spot welder using the electrics from the welder and a slide system like on the do-all to hold the blade.
 








 
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