Making up band saw blade problems

[gary hart]

Could you just be buying too thick of a blade for the wheel radius? Sounds like your having an awful time getting it to hold..

It is true I'm using a 3/4 wide blade on a saw designed for a 5/8" blade. That will cause blade fatique and early cracking of the blade but should have no affect on a good silver brazed joint which is just as strong as any other part of the blade.

I was given to understand that the two faces of the scarf should be fairly rough- as in ground with a coarse wheel, not smooth like a surface grinder would give. That gives the solder a textured surface for a better hold.

Doc.

Maybe but haven't read that. Have had no problems when silver soldering a ground high speed lathe bit to steel. Maybe when joining some dissimilar metals that may be an advantage.

mig welded mine - wasnt easy but after several attempts on an old blade I got the right settings and technique...

Have had some success mig welding using a run on and run off strip on each side of the weld but even then it destroys some teeth in the joint area

When annealing, take it till it just turns blue. That should give it a hard spring temper and still be well below the braze temperature.

Agree. Even though it is below the braze temperature the braze joint can be weak at higher temerature and any movement of the weak joint will give a bad joint which might not show up until later.

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Anyway, I solved my problem with joint failures on the 3/4" wide bi-metal blades and getting good joints now. Was just writing to show my problems along the way and maybe give some insight to someone having problem like this. gary

[Toolguy]

Gary-
I've been fighting with this for a while now. Thanks a lot for taking the time to document and post all this. My 3/4 bimetal blades are around $40 each. I have several broken ones lying around waiting for the right fix. Good blades are not cheap. Also, now I can think about buying a roll of blade stock to save some bucks. Thanks again. Best Regards.

[Black_Moons]

How thick are your blades exactly? and how big are your bandsaw wheels?

The reason thick blades 'crack/fail' on too small of a wheel is because of stress, I suspect that same stress is not good for joints either. And clearly, if it breaks at the joint, the joint is not as strong as the rest of the blade.

[gwilson]

I haven't tried to braze those big blades.However,I used to have to silver solder 1/4" carbon steel blades for a school shop. The blades were just clamped with pliers just after the solder melted. Then,filed bright and heated to a spring blue color. I found them more "boy proof" than welded blades.

My Roll In saw has a bunch of those 3/4" bi metal blades waiting for use. My welder will only do 1/2" blades. Not sure what I will do when I run out of those $40.00 blades. Being retired now,it may be some time before I do!! My little 4"X6" saw does most everything I need to do,and it takes 1/2" blades.

[gary hart]

How thick are your blades exactly? and how big are your bandsaw wheels?

The reason thick blades 'crack/fail' on too small of a wheel is because of stress, I suspect that same stress is not good for joints either. And clearly, if it breaks at the joint, the joint is not as strong as the rest of the blade.

Agree any breakage at joint or at the edge of the heated up area is a fault of bad joint or bad annealing. Believe this should be the last place to break as it should have less temper then rest of blade.

This is on a horizontal bandsaw and wheel diameters are 9.75" and the blades are Lennox bi-metal with a thickness of .036". They are called bi-metal but the blade seems to be the same material through out. It requires a carbide drill to drill in the back side of the blade.

The blades are expensive but bought these reasonable on Ebay being an odd ball size and to big for my saw. Made up 6 blades from 4, two of the blades of have two joints.

[Black_Moons]

the blade has less temper yes, but the joint is weaker then the blade... evident by it failing before the blade.
0.036 sounds wayyy too thick for a 9.75" wheel bandsaw. I don't think id go past 0.025. From what iv read, even my 14" wheel wood bandsaw should not be used with over 0.025" blades.

They where too big for your bandsaw because they are not designed to run on such a small bandsaw due to the thickness vs wheel size.

[gary hart]

Agree using the bigger blades on saw is cruel punishment on the blade and on the saw. But, it sure does make nice straight cuts. Would not recommend anyone change there saw to use a wider blade then was intended for.

The blades are too thick for the radius of the wheels and sure will not get the life out of them if used on a bigger saw. Been using this size blade on the saw (Kalamazoo horizontal) for about 3 years now and getting by with fair blade life.

[Your Old Dog]

Here's how I've done it.

I made a jig to hold the blade and then removed a circular area of the jig where the scarf joint is made. I let the blade ends overlap in the jig and position them over the circular cutout of the jig. Then I take a Dremel with a cutoff blade and cut on a compound bias to achieve more holding power. I hammered some of my silver solder lat obtained from the welding store, slipped it between the joint and fluxed it. I then heated it up with a soft flame till the solder melted. The joint damn near fell apart when I released the two bolts holding the blade to the jig.

1. I think I should have annealed the blade before trying it.

2. I think I've had the blades bolted to tightely into the jig and the blade weakend when it cooled down and retracted/shrunk.

3. I'm trying all this on bi-metal blades and don't know if that is part of the problem?

My jig worked extremely well for holding the overlapping blade ends for cutting on the bias with the dremel. That much worked fine.

[gwilson]

I would think that a compound bias would sooner than ever fail. You've got all the stress on the tips of the triangles when the blade starts to bend around the wheels. when the tips fail,so does the rest. Negates the extra soldering area you think is making the joint stronger.

[Your Old Dog]

I would think that a compound bias would sooner than ever fail. You've got all the stress on the tips of the triangles when the blade starts to bend around the wheels. when the tips fail,so does the rest. Negates the extra soldering area you think is making the joint stronger.

Thanks, you might be right about that. I was working on the premise that a longer joint would mean more silver solder hence more holding power?