Silver soldering (actually brazing?) bandsaw blades - what do I need?
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  1. #1
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    Default Silver soldering (actually brazing?) bandsaw blades - what do I need?

    Hi folks,
    My beloved DoAll blade welder just went up in smoke, I believe. Because of my remote location, I don't have a way to get a used transformer over anytime soon (and DoAll doesn't sell them for that 70's(?) machine anyway).

    I'm on my last saw blade and won't have a way to get factory-welded ones sent over for another year, and have a lot of sawing to do between now and then.

    I do, however, have someone flying over in a week, and the lightest thing I can think for them to bring to solve the problem is the stuff to silver solder.

    I have soldered electrical stuff and copper plumbing before, but past that have zero experience with soldering or brazing.

    I read several message board threads about silver soldering blades, but am left with a few questions.

    1) As I understand, soldering silver would have 1-3% solder, but everyone is recommending 45% silver solder for bandsaw blades, which I think means they're actually recommending silver brazing, right?

    2) The only non-welder heat I have available is a handheld butane torch. The biggest blade I'm trying to weld is 1", but most are 3/4" and 5/8" - will I be able to get enough heat out of a handheld butane torch to do that? (I assume so?) I'm not talking about a micro torch, more like a Bernzomatic but using Butane instead of Propane.

    3) Most of the threads about welding blades that I read were by wood guys - does this soldering treatment stand up to sawing steel? Also, can I use it on bimetal blades, which are just about all of what I use?

    4) Other than the torch, I think I need flux and braze alloy. I found these two, are they what I need?
    A) Braze alloy - Safety Silv 45 Harris 4531 Safety Silv 45 Silver Brazing Alloy 1 t.o.: Heating Cooling: Amazon.com: Industrial & Scientific
    B) Flux - Stay Silv Brazing Flux Harris SSWF1 Stay Silv Brazing Flux, 1 lb. Jar, White: Amazon.com: Industrial & Scientific

    The fixturing I can easily take care of - what I need to know is if this will produce a good weld. Some people seem to prefer butt welded, some say a silver soldered joint is more durable. I have had great success with my DoAll welding Lenox Classic, but have had a lot of broken joints from it on the Lenox Neo I run on my Ellis (because they don't make Classic in 5/8").

    Thanks!

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    I actually prefer a properly brazed joint to a welded one. We put up a few dozen blades a year in our shop and have everything from the industrial welders to the jobbers attached to the DOall metal master. I like the brazed joint for its inherent ductility and strength.

    You made a good selection in silver and flux. I standard propane plumbing torch will get you to heat just fine. The benefit to having more heat available is to localize the heat and not draw back too many teeth. Make some heat sinks into your fixture or to clamp on to minimize annealing.

    The trick to a good joint is to have a consistent lap angle between the blades. Looking towards the face of the teeth the angle may be 5-10 degrees depending on thickness. on 3/8" blades for example I like about a 3/4" lap length.

    I hope this helps. Through trial and error you will be successful and maybe even converted.

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    Quote Originally Posted by BSCustoms View Post
    I actually prefer a properly brazed joint to a welded one. We put up a few dozen blades a year in our shop and have everything from the industrial welders to the jobbers attached to the DOall metal master. I like the brazed joint for its inherent ductility and strength.

    You made a good selection in silver and flux. I standard propane plumbing torch will get you to heat just fine. The benefit to having more heat available is to localize the heat and not draw back too many teeth. Make some heat sinks into your fixture or to clamp on to minimize annealing.

    The trick to a good joint is to have a consistent lap angle between the blades. Looking towards the face of the teeth the angle may be 5-10 degrees depending on thickness. on 3/8" blades for example I like about a 3/4" lap length.

    I hope this helps. Through trial and error you will be successful and maybe even converted.
    Any chance any one has a pic of the fixture and the heat sinks ? I was trying to use brazing silver solder and it doesn't work for me , I ended up tig welding them with 304 stainless and it is holding but its not great .

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    What BSCustoms said. I have been brazing my own blades for over 30 years and get very good results. It's all in the grinding your scarf joint. This can be done fine on a wheel if you are careful but a belt sander gives you more control over your angle and length of scarf. If you don't have a MAPP torch you can use the propane torch. I have used MAPP cylinders on a propane torch and you will get a bit more heat although they are not designed to burn MAPP. Don't go crazy with the amount of silver you use. If your scarf is ground correctly it should only take a very small amount of silver to fill the gap (about the size of a BB or less for a half inch blade). What I do is put the blade ends in a fixture to make sure the back of the blade is straight across the braze (very important so your blade will run true). I take a small piece of silver and put it in the joint. Spring tension should hold it there. Heat the joint until it flows and stop. You will probably have to file the joint somewhat when you are done because there always seems to be a slight bump where the scarfed ends stop. Let me know if you need a picture of the fixture and I will post it.

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    Check out Youtube. You will find a detailed narrative of the fixture, materials, and the process. Regards, Clark

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    Titanium fixture.
    I don't silver solder blades,but I have done small quantity production silver soldering of similar products.I was able to buy cheap small scrap blocks of titanium on ebay and small titanium alan screws from McMaster carr. NOTHING STICKS to titanium and the heat and flux has no effect ,even after years of use. Edwin Dirnbeck

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    Quote Originally Posted by JasonPAtkins View Post

    1) As I understand, soldering silver would have 1-3% solder, but everyone is recommending 45% silver solder for bandsaw blades, which I think means they're actually recommending silver brazing, right?
    yes, they are recommending silver brazing. I've always known silver solder to be the 45% + stuff, i.e. Easyflo, Silflo, etc that has a tensile strength up around 45,000 psi or more..vs those silver bearing solders of 3000-4000 (numbers may be off a bit, its an order of magnitude point). I don't know who (or why) someone started to call those low percentage soft solders silver solders, but calling it silver brazing makes it crystal clear. Then a jeweler joins the conversation, who iirc have their own nomenclature around solder and silver, and it gets even more confused.

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    Silversmiths and jewelers use silver solders that have a range of melting points so that an object can built up in stages. 'soft'solder has a lower melting point than 'hard'solder.

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    B) Flux - Stay Silv Brazing Flux Harris SSWF1 Stay Silv Brazing Flux, 1 lb. Jar, White: Amazon.com: Industrial & Scientific
    My recommendation is that you get the same brand of flux, but get the black flux, not the white flux. I have found the black is more reliable.

    Best wishes --- Allen

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    I can rewind your transformer. I have an old DoAll bandsaw that may have the same transformer. If so, I can possibly make a replica of the windings and you can use your iron core, saving shipping. Another possibility would be for you to send the charred windings less core and I can copy it. A picture of the transformer would help.

    Bill

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    I bought a blade butt welder soon after getting my first metal bandsaw, so I have never tried brazing a blade. I have been doing silver brazing since around 1956, so I could do a blade if I wanted to. The various silver brazing alloys are available in wire and sheet form. The thin sheet is ideal for placing between the scarfed ends of the blade, with a coat of flux, ready to heat with a small torch. Jewelry makers almost always snip off a tiny piece of sheet gold or silver solder when sizing or repairing rings and brazing other tiny joints. You don't want to waste gold.

    I took a quick look at eBay just now and found a really cool antique German Ideal brand electric bandsaw blade brazing fixture. It looks like a good design, though I don't know if the electric part is working. Check out the alignment design and the large heat sinks on each side of the joint. The German fixture has a couple of screws in that area, which guide a pliers-type clamp to squeeze the joint together once the silver is melted.
    Antique Ideal Hard soldering & brazing butt splice for band saw blades Germany | eBay

    Here is an antique USA Oliver brand electric brazer that is less elegant than the German unit. It seems to have a built-in lever clamp that may squeeze the scarfed joint together after the silver is melted, minimizing an increased thickness in the blade at the joint.
    Antique Oliver Machinery Co. Vulcan Brazer BandSaw Blade Welder Machine Vintage | eBay

    I suspect that bandsaw blades were always brazed when they were first invented. Then someone invented the electric butt welder, which became the normal way of joining blades in industry, whether by the blade makers or by welders attached to a saw. But if brazing used to work, it obviously still does. It requires more time and skill, which is why it is not done by the blade makers themselves. I can think of one potential fault in my reasoning. All bandsaw blades were carbon steel back in the early days. Solid HS and bimetal blades probably came along after electric welders were in use. I recall seeing something years ago about solid HS blades requiring a different sort of electric butt welder, maybe including a more elaborate heat treatment/annealing feature.

    This guy has sold a simple brazing kit on eBay for years. Make or Repair Band Saw Blades with Sure-Splice Kit--Fast Repair Welder Brazer | eBay

    Here is a similar simple device. new milford Make-Repair Band Saw Blades Splicer Kit Welder/ Brazer ic-2 tool | eBay

    Larry
    Last edited by L Vanice; 03-07-2018 at 11:25 AM.

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    Either of those hard solders and fluxes will work. I do not scarf the joint, mostly because I am not good at it. Instead I half lap the joint using a 1 x 42 belt sander. I use hard solder tape which I believe is .004 thick and 1" wide. I cut a piece of the tape the size of the lap. Usually 1/2" wide and 5/8" long. I try to remove the same amount from each end til the blade will be flush with the tape in between. Sometimes I do not get the exact amount ground off but as long as the finished blade is flush or slightly under size then the solder will work.
    I use SRI (Stan Rubinstein INC ) solder and flux. They have a web site.
    I cut a 3/4" x 1" deep botch in a 1/4" x 1-1/2" x 1-1/2" steel angle. The notch is for the torch under the joint. The angle iron has 4 pointed 10/24 screws ,2 on each side of the joint to hold the blade straight. Bolted 4 scraps of steel to the angle at the screw areas ,tapped each one .I ground a dull point on the screws. That is it for the fixture.
    Flux each end, install the tape, make sure the blade is straight.
    I apply heat from a propane torch from under the fixture til the solder flows. The solder will melt fast , maybe under 30 seconds. When the blade is cool you will have to do a bit of grinding to remove any excess solder and make both sides of the blade flat.
    Usually takes 2 or3 minutes at most with an air die grinder .
    I do not anneal the joint after hard soldering. Never had a problem so I eliminate that step. Some people do anneal the joint.
    mike

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    It's pretty quick to scarf the joint if you've got a shop grinder or sander handy. Hold the loose ends of the blade together and parallel with each other, but twist one end of the blade so the teeth are facing the other way. I.e., teeth on one end aligned with the back on the other side. Push the upper end of the blade forward a bit so it overlaps the lower end of the blade by about your desired scarf length. Holding the two ends together, present them at the desired scarf angle (fairly shallow) to the grinder or sander.

    Unless your grinder wheel is extremely small diameter, this grinds complementary scarfs on the two ends, so when you put the ends together for brazing the joint is straight.

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