Bandsaw blade repair (brazing)

Got a new way of doing something? Or maybe an old method that needs some clarification.

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charangohabsburg
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Bandsaw blade repair (brazing)

Post by charangohabsburg » Wed Nov 23, 2011 2:12 pm

Over there in that thread I mistakenly wrote "soldering" instead of brazing... OK, as Alastair pointed out it is silver brazing that gets used best for putting together a broken bandsaw blade. The lower the temperature the better because it takes longer to "burn" the blade, i.e. make it too brittle. Unfortunately the lower the melt point temperature of the brazing is, the more it costs. But un the other side you will need ridiculously small quantities, so it does not really matter.

Of course you can also weld a blade. Once on another forum someone even told me that if a broken blade was not welded it would not hold together. I can tell you the opposite because I have done it over and over, and every time when the the blade did break again it did at another spot. I reckon he never had repaired a blade, neither brazing nor welding. Just another nerd.

The blade will break again earlier if it was poorly aligned and, even without bumping, will move back and forth when running. So it is essential to get it really well aligned. My first jig for aligning was way too short and yielded poor (but for resawing still usable) results, but those repairs usually did not last long, but it took a long time for aligning in a halfway decent manner when it came to the next repair. :lol:

First, the broken ends have to get squared and bevelled for the scarf joint. To get the same bevel on both ends I clamp them together and grind the bevel on the grinding wheel (using leather gloves, it's kind of a scary action, don't let the grinding wheel catch the blade...)

Image

Then align the blade on the jig, lay some tiny pieces of brazing material on top of the joining line and apply some heat. I use a cheap CampingGaz-like aerosol blowlamp - cheaper than these here. You really don't need a lot of power to get this ridiculous amount of steel to cherry red.

Then it will look a bit like this:

Image

File away the excess material, and it will look a bit like this but hopefully better aligned (it's a photo from my beginnings) :

Image

My first aligning jig was about 4cm between the indexing/aligning pins at each side, and it was a royal pain to get that blade right, it cost me every time about 20 minutes! Then I decided to spend some money on a 80 cm long rectangular cross section steel tube. The indexing/aligning pins for each blade end are now 35cm apart, and it takes less than 3 minutes to shove the blade in, tighten slightly the 8 wing nuts, lay out some brazing material on the blade and bring it uf to the right temperature. This is how the new aligning jig looks like:

Image

That's an intact blade I put in here as I shot the photo right now and had no broken blades around. :lol:

Here you can see the the aligning pins:

Image

I hope this will save you some money and a lot of time. Going through the whole procedure is almost faster than firing up the computer to order some more blades, and after less than 10 minutes you go ahead with whatever you were cutting into pieces. :D
Markus

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It's only the others who suffer.

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woodrat
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Re: Bandsaw blade repair (brazing)

Post by woodrat » Wed Nov 23, 2011 5:43 pm

Hey Markus, Thanks for the tute...I have just ordered some blades and I quoted the wrong length...not much fun having nobody to blame except self... :?
I will look at this option to be able to remedy the situation...

Thanks again

John
"It's never too late to be what you might have been " - George Eliot

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auscab
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Re: Bandsaw blade repair (brazing)

Post by auscab » Wed Nov 23, 2011 8:36 pm

Thanks Markus,
just for the clarity of the tute , are you using flux as well?

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charangohabsburg
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Re: Bandsaw blade repair (brazing)

Post by charangohabsburg » Thu Nov 24, 2011 12:29 am

Rob, yes I use flux. I forgot to mention it.

John, if I were you I would not start with altering new blades. I don't know how many "a few blades" are for you. As you are a great resawyer it may be enough for getting through the whole learning curve before starting with the last blade though :) . You can't loose anything with a broken blade but you can loose almost everything doing the same with a new blade. If I were you I just would get them exchanged and stick with the additional shipping costs while not familiar with the process after having brazed some old blades.
Markus

To be stupid is like to be dead. Oneself will not be aware of it.
It's only the others who suffer.

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kiwigeo
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Re: Bandsaw blade repair (brazing)

Post by kiwigeo » Tue Dec 20, 2011 4:39 pm

woodrat wrote:Hey Markus, Thanks for the tute...I have just ordered some blades and I quoted the wrong length...not much fun having nobody to blame except self... :?
I will look at this option to be able to remedy the situation...

Thanks again

John
I ordered some 17" blades for my 14" saw. I now have a perfect excuse to throw at the boss should she question why Im buying a new 17" bandsaw.
Martin

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