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How to silver solder band saw blades

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Blog entry by hydro posted 244 days ago 1949 reads 11 times favorited 14 comments Add to Favorites Watch

This will assist in repairing a broken blade or in making your own blades from coil stock or auction site blade stock. First, you will need some blades. I like to buy coil stock if I can get it for a good price, or I buy blades in bulk that are a little longer than I need. I will cut these down to length.

To solder the blades, you will need silver solder and flux. I use silver solder that I got at the hardware store, and a boron modified flux that I found at McMaster Carr. The boron modified flux gets a better bite on ferrous materials like blades.

You will need to know the finished length of blade that works on your saw. To get the measurement either check the owners manual or take a used blade and cut it to measure. I add 1/8” to the total length to allow for the solder joint. Cut the blade to length using a snips.

To make a strong solder joint you will need to grind the ends of the blade at an angle to create a “scarf joint”. Ideally this should have a ratio of 6:1 joint face to blade thickness. It’s not really critical so I usually shoot for about 1/8” solder surface in the joint.

To ensure alignment of the finished blade, I use a jig that I welded up put of a piece of angle iron and a couple of steel strips. The center is cut out to provide room to solder the joint.

Slightly bend one of the blade ends to make the pieces spring together and ensure a tight solder joint. Clamp the prepared blade into the fixture and apply flux to the ends. Pinch the ends together and feel to be sure that there is no “bump”. If so, adjust until the transition is smooth. Cut a piece of silver solder the length of the joint and place it between the blade ends.

Heat the joint to dull red with a propane torch and watch for the solder to flow out. Hold the heat for a bit to make sure everything is hot enough. The solder will sweat the joint and flow where there is flux.

Let the blade cool in the fixture and grind the face of the blade smooth. Remove from the fixture and grind the other side smooth. Feel to be sure there is no lump at the joint. Last, grind the back of the blade and smooth the edges with a file.

The finished joint should show as a narrow band of solder. The blade is now done and ready to use!

-- Minnesota Woodworkers Guild, Past President, Lifetime member.



14 comments so far

View smitdog's profile

smitdog

79 posts in 707 days


#1 posted 244 days ago

Great post hydro, you make what seemed incredibly hard before actually look doable! Might have to try it out some time. Thanks for posting this.

View HillbillyShooter's profile

HillbillyShooter

4362 posts in 894 days


#2 posted 244 days ago

Thanks! I’ve often considered doing this but have never seen anything as straight forward as your explanation.

-- John C. -- "Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth." George Washington

View stefang's profile

stefang

12592 posts in 1936 days


#3 posted 244 days ago

Nice blog and very helpful. Thank you!

-- Mike, an American living in Norway.

View TopamaxSurvivor's profile

TopamaxSurvivor

14609 posts in 2278 days


#4 posted 243 days ago

great blog, thanks

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View NormG's profile

NormG

3999 posts in 1606 days


#5 posted 241 days ago

Thank you

-- Norman

View Blackie_'s profile

Blackie_

3292 posts in 1114 days


#6 posted 240 days ago

Hi Hydro

Thanks for the link, I do have a question that I’ve managed to pick up from others in another thread that I posted which is called annealing, this is new to me but after looking it up it means to temper the weld, is this another step that needs to be done and if so what is the process?

Thanks

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at http://www.facebook.com/randy.blackstock.custom.wood.designs

View Grandpa's profile

Grandpa

3048 posts in 1277 days


#7 posted 240 days ago

What I remember from my metals class in college about annealing is it is a process to soften the material and not to temper it. There were 3 processes. Harden, temper and anneal. To harden you heat the metal cherry red and cool quickly usually by dipping it in a liquid. I saw a guy, making a cold chisel, let his chisel roll off a table after it was hardened and it shattered. to anneal we heated to cherry red and allowed the metal to cool slowly usually by laying it up and letting it cool slowly. In this state you could work the metal with hand tools. you could easily file it and shape it. When it was tempered it was “toughened”. This stage made a tool usable. it was durable. To do it in the shop we had pretty crude methods but we tried. We hardened the metal then we reheated it to a straw purple and quenched it in water. It was crude like I said but it made some tools usable. If we had used temple sticks we would have probably made better chisels but they were not mentioned at the time. I have since learned about these. They are available at welding shops. Get the temperature range you want and need. It changes when that temperature is reached.

Bear in mind I graduated college almost 50 years ago and this is what I remember doing. We also welded our band saw blades in the shop for metal cutting band saws. We have a machine that cut it, we ground it on the same machine and it electrically welded it together. I never felt like we had great success but we did have fair success. I Looked a the process above and think this looks like a good one. The only improvement I would suggest might be the cut on the end of the blade. This is cut at approx. 90 degrees. If it were cut at a 90 or 60 degree angle it might be stronger. There would be more surface to weld together so it should be stronger.

Hydro, thanks for sharing this process with us. This is something more of us should try. I do have a question. Why buy longer blades and shorten them? Did I miss something? If you are buying blades why not get the correct length? Can you not buy the correct length for your saw?

View hydro's profile

hydro

208 posts in 353 days


#8 posted 240 days ago

Grandpa- I buy longer blades on Ebay because I can get a great deal on them. Less expensive even than buying the coil stock. They are usually surplus industrial blades.

BTW, your essay on hardening, tempering and annealing is spot on. Thanks!

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

View Grandpa's profile

Grandpa

3048 posts in 1277 days


#9 posted 238 days ago

OOPS! I meant to say a 45 or 60 degree angle. there would be a longer cut for more holding surface. I was just curious why you would buy a 180 inch blade when you needed a 144 inch blade and have another weld. I suppose you cut them on the first weld??

View hydro's profile

hydro

208 posts in 353 days


#10 posted 238 days ago

Yes, I cut out the original weld to shorten them. Also, the 90 degree solder joint has proven more than strong enough over time. If done right the blade eventually just wears out, gets dull, or fatigues and breaks some where else. Its much easier to fabricate a 90 degree joint as well. On the last set of blades (131”) I was able to get 10 Lenox Woodmaster blades for a little more than $6.00 each.

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

View Grandpa's profile

Grandpa

3048 posts in 1277 days


#11 posted 237 days ago

Hey! don’t mess with perfection. If it works then use it. You are doing great at $6 per blade. Maybe you should go into business….ha

I am sure the 90 deg. cut is easier to solder and easier to match. I just remember the blades we made in school from roll stock. We were a bunch of college age kids and cutting metal most of the time so that probably tells me we got a decent weld. Thanks for sharing your experience in this blog.

View a1Jim's profile

a1Jim

112000 posts in 2179 days


#12 posted 237 days ago

Great blog lots of great info
Here are a couple things on line covering the same subject . your approach works great.

http://www.leevalley.com/us/wood/page.aspx?cat=1,41036,41048&p=41049

http://www.youtube.com/watch?v=PIEX6FVovWI

-- http://artisticwoodstudio.com Custom furniture

View Dallas's profile

Dallas

2857 posts in 1089 days


#13 posted 237 days ago

I see you are using 35% silver. Is there any particular reason or will 45% or 15% do?

The only silver soldering I have ever done is on HVAC systems.

How thick is the solder you use? How much heat? Will a real propane torch work? Like the kind using a 20-100 lb tank? or does it need MApp or the 14 oz. butane torch?

-- Improvise.... Adapt...... Overcome!

View hydro's profile

hydro

208 posts in 353 days


#14 posted 237 days ago

Dallas, The solder is just what the hardware store had. If you want to try another alloy, do some research as to how applicable it would be for joining steel. I use a regular propane torch, no need for anything hotter. You just need to get the blade/solder to a red color to allow the solder to flow.

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

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