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Brazing a bandsaw blade

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Forum topic by runswithscissors posted 03-31-2013 05:19 AM 1013 views 0 times favorited 13 replies Add to Favorites Watch
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runswithscissors

951 posts in 680 days


03-31-2013 05:19 AM

Ironically, I had just been reading a post a few days ago about repairing a broken bandsaw blade. I have a 14” Grizzly, which I converted to cut metal by putting in a jackshaft and a couple of step pulleys. It’s a real workhorse. I have my local saw shop make me up 1/4” variable pitch bimetal blades. These are able to handle everything from 18 gauge to 1/4” steel (occasionally thicker). So I was cutting a piece of steel for my Unisaw riving knife project when suddenly something went bang, and all came to a stop.

Hmmm, I thought, could be a broken blade. And it was. Since it is the weekend, and the saw shop is closed until Monday, I thought I’d see about fixing it myself. I ground facing bevels (about 1/4” long) on the 2 ends, smeared flux on them, and clamped them, overlapping the ends like a scarf joint. I clamped the blade with the type of welding clamp used for butt joints (don’t know the name of that one). Heated with a propane torch for a few seconds, and the silver solder (I still had a fragment left from previous projects) just flowed right into the joint. And then I ground both sides flat, and we’ll see how it holds up. I suspect I won’t get a lot more life out of it (they typically last me a couple of years or so), and I’ll have to order a new one Monday.

What’s interesting is that I did not do the usual recommended thing of hammering a piece of solder flat and fixing it in between the overlapping ends. I just got the joint hot, and the solder flowed right into the joint.

]I guess my point is (beside a bit of bragging) is that if I can do it, you can do it. It was easier than I thought.


13 replies so far

View Loren's profile

Loren

7556 posts in 2303 days


#1 posted 03-31-2013 05:27 AM

I just repaired one today. I had tried to cut too sharp curve and
my brazed blade broke. Re-brazing was easy. Almost too easy.

The braze is likely to be the weak point but still pretty strong
and repairable.

-- http://lawoodworking.com

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runswithscissors

951 posts in 680 days


#2 posted 03-31-2013 05:29 AM

The break in mine was not at the weld, but a few inches from the weld.

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Loren

7556 posts in 2303 days


#3 posted 03-31-2013 06:32 AM

... could be metal fatigue. Wheel diameter is relevant,
as is tempering.

Keep at it. I am.

-- http://lawoodworking.com

View Airspeed's profile

Airspeed

425 posts in 557 days


#4 posted 03-31-2013 03:09 PM

I use my MIG to weld my broken blades all the time, I grind the ends down a little, clamp the blade to a piece of scrap with a slight gap between the ends then carefully fill the gap with weld. I then grind it flat. I haven’t had a weld break yet and I’m no expert welder!

-- http://smg.photobucket.com/albums/v655/aaronhero/

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MrRon

2834 posts in 1899 days


#5 posted 03-31-2013 03:28 PM

It sounds like you “soldered” the blade, not “braised” it. If the silver solder ran easily into the joint, it was a soft silver solder which will not hold up A brazing alloy contains at least 50% silver while silver solder is around <10% silver.

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RussellAP

2950 posts in 942 days


#6 posted 03-31-2013 03:30 PM

Blades are only 10 – 15$ Order a couple spare.

-- A positive attitude will take you much further than positive thinking ever will.

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1yeldud1

290 posts in 1697 days


#7 posted 03-31-2013 03:42 PM

MrRon – I use Harris 45 or 54(?) silver solder 1/32 diameter or the shim stock style to build and repair the majority of my blades. The initial cost of silver solder is expensive but it only takes a small amount and seems to work well on my 1/4 and 3/8 blades for wood. I have NOT tried these blades on metal as I work in a local tool shop and I “sneak” my metal sawing in when I get off work. I have tried to use a band saw blade welder and to tig weld but by far the easiest way I have found to repair / build blades for me is with a propane torch and silver solder

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runswithscissors

951 posts in 680 days


#8 posted 03-31-2013 08:14 PM

Mr. Ron: I got this silver solder originally for brazing stainless, and it works well for that if the metal is not too massive (which can make sufficient heating difficult). It is Harris “Safety Silv” 56, (cadmium free), 1/16” diameter. That’s 56% silver. I think it flows well in blade brazing because the small metal cross section heats up to red hot very quickly. I also use MAPP gas, which burns hotter than straight propane. The “silver brazing alloy” is very expensive, but a little goes a long way. My tapered overlap of the blade ends (like a scarf joint) was about 1/4” long.

Airspeed: I haven’t tried MIG, and if I do so, it will be with trepidation. That’s because I’m not skilled at welding very thin steels. They tend to burn up on me, so that I get a hole rather than a weld.

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1yeldud1

290 posts in 1697 days


#9 posted 03-31-2013 09:11 PM

I tried to tig using 6 to 10 amps – I had no filler rod to add that was below .035 in diameter. If I had had filler rod that was say .010 to .012 I might have had some success. I spent more time grinding off the excess weld that the time it took me to silver solder the other blades. I have NO experience with mig welding so I am completely new to that subject. The blade welder on the band saw at work is really set up for heavier blades that I am using at home. True it does have settings for the smaller blades but it makes a HUGE deposit of metal when it is done requiring me to do a lot of grinding when finished.

Runswithsissors – I am using the same brand of wire except it has 45% silver – this is what my employer buys ( I can purchase it thru them at a discount) your alloy IS a better alloy for this application – possibly next time Ill give it a try – thanks !

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Airspeed

425 posts in 557 days


#10 posted 04-01-2013 01:37 PM

Sounds like soldering is a much easier process! I’ll have to try that next time I break a blade. I have silver solder, heck, I may even snap an old blade to see how it works! Thanks for posting your method.

-- http://smg.photobucket.com/albums/v655/aaronhero/

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MrRon

2834 posts in 1899 days


#11 posted 04-01-2013 09:51 PM

If the blade breaks at the joint, it’s because the joint was contaminated with body oil, or wrong flux and brazing material or too much or too little heat. If it breaks beyond the joint, it’s because it hasn’t been annealed after brazing. The joint is brittle and the area has to be annealed by passing the torch over the joint a few times, somewhere around 600°f and allowd to cool slowly.

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Surfside

3154 posts in 829 days


#12 posted 04-03-2013 04:14 PM

Good to hear that. Re welded band saw blades easily break. It’s welded part is its weakest point.

-- "someone has to be wounded for others to be saved, someone has to sacrifice for others to feel happiness, someone has to die so others could live"

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Grandpa

3133 posts in 1331 days


#13 posted 04-03-2013 08:20 PM

Lots of info here. I immediately thought of a metallurgist that worked in the same dept with me. He defined a weld as a series of continous flaws joing 2 pieces of sound metal. Always remember that.

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