Thread: Joining Bandsaw Blades Help!!!

Go to the Carbatec site, they have a system for sale.

G'day Stinky

Sounds like the join is either dirty or you didn't get the steel hot enough.

First of all everthing must be CLEAN, clean with sand paper and use some metho or white spirits and don't touch with your hands once cleaned. Even just a light touch with your finger can leave enough oily residue from your hands to effect the joint.

You need to get the steel to the point where it's just starting to get a very faint cherry red which will allow the silver solder to sweat itself to the steel. The steel needs to melt the solder not the flame from the torch.

Hi, from the "Getting the most out of your bandsaw" book published in the 1950's by Delta (later Rockwell) - a great early book for bandsaw users.
Picture of homemade jig being a heavy metal hinge with a large hole bored through the hinge leaves next to the hinge pin and a wing nut to hold it shut. Apparently this is used to clamp the two parts of the blade together with the join visible through the holes for soldering.
Quote: "The blade should be ground square at the ends and then beveled for a distance of one tooth so that, when lapped, the joint forms a single tooth.....The joint is painted with a solution of borax crystals dissolved in water "
(my comment: must be the equivalent of flux).
Quote:"...a piece of silver solder is placed between the two laps of the blade and the blade is then clamped tight in the jig"
(my comment: a diagram shows the piece of solder looking like a postage stamp)
Quote:"Heat from a propane torch is then directed at the joint and held until the solder melts and runs. Excess solder is filed off, although a slight bump is almost inevitable with this type of joint".
(my comment: the diagrams have a hefty hinge so they must be using a large propane torch.
I hope this is of some help.
Paul

A system I used for many years, was to file the two ends to form an overlapping splice for a distance of about 6mm. Used a small gas torch to heat the joint till the flux and silver solder melted. As has been mentioned, heat the blade till the solder melts then clamp lightly with a pair of pliers. The joint at this point will be quite brittle. Release the clamp on one side of the joint and reheat the whole joint for about 20mm each side to a dull cherry red and let cool slowly. This system worked for me, but now I buy hardened teeth throw away blades. I intend to go back to the old system as soon as I can get some files for my saw sharpener.
Jim

Thanks for the feedback .... certainly gives me some other things to try.

I don't think that my little torch is going to be able to heat the blade to a cherry red, I might have to look for an alternative. It should be able to do the job as it is the same as the one in the Carbatec kit by the looks of things. More frustration ahead this weekend

Stinky

Invest in an old kero blowlamp off Epay. I got mine around $25. Not only cheaper to run but hot as Satan's fart.

You could probably melt the blade if you so wished.

There's been an old kero job at almost every Sunday Market I've ever attended... I think it's part of the market's Code of Practice.

A quick check that all is in working order (although leather washers usually need replacing) an offer of $5- and...

Hi Sir Stink,

Blade temperature appears to be the trouble in your description.I am brazing 10 or blades a year at school (for 3 saws)

http://www.woodworkforums.ubeaut.com...Bandsaw+blades

is the link.
Have a read up and get a bigger lpg torch.The blade needs to get red hot and better.

If I did not describe it in the text,the flame should not be used to melt the solder.

Critical points are:

1. Scarf the blade to get a longer joint edge -say 30 degrees.
2. Cut with plain tin snips -not aviation snips-serrations will cause cracks and failure.
3. Bevel the scarfed faces -45 degrees- a handfile will do
4. Shiny clean around joint faces- to 6mm back from cut edges.
5. Cut 3 or 4 mm length -not more- and place centrally along joint line on the butt with flux where you want it to flow.
6. Heat under joint until blade goes red and S/Solder starts to fuse through bevelled edges.
7. When cool inspect for fusion on other side.
8. File off excess S/Solder

Give us a PM if you get stuck.

Grahame

I have completed a diagram on the layout of the blade joint gemetry to make things a bit clearer.
I hope !

Grahame

Thanks Grahame,

After my initial attempts I came inside and searched the forums and read your post. It was that post that gave me the idea of a housing joint (for want of a better description) as I found the solder wasn't strong enough.

The following points are something I had trouble following given the flame that I was using:

"There are a few critical factors in play when you attempt to silver solder
1. The flame setting setting is critical and that is basically the lowest heat value that well melt the silver solder.

2. Heat placement and timing -
As I said just hot enough and held just long enough across the under part of the joint. Just long enough to melt and fuse the separate pieces and then you quickly move the heat source away. You are dealing with a few thou thickness of rapidly oxidising steel blade!"

When I was heating the flame had no problem melting the solder but the blade wasn't even warm. I assume now that it is best to heat the blade to a temperature that is just hot enough to melt the solder.

Speaking of flames is this what I should be looking for?
http://www.woodworkforums.ubeaut.com...ad.php?t=48917

Yes Sir Stinkalot I remember the shellite burner.

Not having tried one on a silver solder job I am a loss to advise you.
I suspect the problem with it will be too much heat.

I believe the success of the bond is controlled by heating the parent metal to a temperature that will fuse the silver solder.
The problem is that silver solder has a narrow window of fusion.Only a few degrees too many over the melting temperature and the zinc in the alloy flashes to a gas and that it folks, party over.

The trick is to jig up some how and heat from below while the s/ solder is sitting on top straddling the joint. If you have fluxed both sides,top and bottom,the s/solder will capillary for you.

The blade ends must be held in exactly the right place by your jig.
Unless you already one one I would not rush out and get one.
I think it would be a PITA to regulate the heat,If money is the problem grab a small LP set up.

Grahame