Popular Woodworking 2008-06 № 169, страница 49

was on the road teaching a woodworking course recently when my band saw blade broke. Not carrying a spare meant buying a replacement locally.

It had been 20 years since 1 began silver brazing my own band saw blades, and 1 had forgotten what a broken band saw blade means for woodworkers who don't. First, there is the inconvenience of stopping operations while shopping for the blade. Second is the cost. Third is the disappointment in the poor quality of the weld on the band.

My store-bought blade got me through my immediate need, but it soon broke. All these factors are improved by making your own band saw blades.

What must be the best-kept secret in the band saw market is worth your time to learn. Dependence on pre-dimensioned blades can be a thing of the past. What you need to know and the tools you use and the materials to make your own are all readily available. No special machinery, no elaborate instruction, no obscure source of supply.

You can make up your own band saw blades in 10 minutes using nothing more than a propane torch and a holding jig. Buy the same band blade material you are currently using from the same supplier and you'll save 50 percent to 70 percent. And you'll get back to work doing what you came to do in the first place - working wood in your shop.

Silver Brazing vs. Resistance Welding

There are two methods for splicing band saw blades: resistance welding and silver brazing. In welded blades, the ends to be joined are cut square and electric current supplies the heat to arc weld the butt joint. Silver brazingjoins usinga fill material of silveralloy. The surface area of the joint is increased by scarfing the ends back about³/16". The heat for joining the ends is from a common propane torch.

Silver brazingisnot the same as soft soldering used in copper plumbing fittings. While both processes use solder, flux and torch heat, brazing is done at a higher temperature, and there is more strength in the band when the filler material is silver alloy. It is, in fact, as strong as the metal itself.

Silver alloys such as N50 or Easy-Flo 3 are examples available today that contain cadmium. Used for decades, we now know that the cadmium in them creates a health risk. Cadmium-free alloy such as BRAZE 505 (visit LucasMilhaupt .com for a brazing book you can download) contains 50 percent silver, 20 percent copper, 28 percent zinc and 2 percent nickel.

Just as with soft soldering, a suitable paste flux is needed to ensure joint surfaces that are free from oxidation. Bothsilveralloyand flux are available in convenient quantities from catalog stores. While the conventional propane torch is used for both solderingand brazing, the temperature range for silver brazing is much higher: 1,200"F to 1,600°F.

"You can make up your own band saw blades in 10 minutes using nothing more than a propane torch and a holding jig."

Band Saw Blade Stock in the Coil

If the ingredients for brazing are simple and easily obtained, what about the band saw blade material itself?

Olson Saw Co., a major supplier of band saw blades, will sell blade stock in the coil directly to you. Most common types of blades are available, and at significant savings. You also can find other sources for band saw blades in coil form on the Internet (even at the auction site eBay.com) or through olhersuppliers. Other major blade manufacturers, such as Starrett, Lenox and Sandvik, provide blades in coil form. A large and user-friendly source is MSC Industrial Supply Co. (mscdirect.com), which carries Starrett and Morse brands. (Keyword search on the site for a list and price of different types.)

For example, Olson sells .014" x V4" x 6-tooth blades for fine work in a 100¹ coil for

about 50 cents a foot. Coils of .025" x V4" x 6-tooth blade is about 70 cents a foot. Olson doesn't mention the availability or price of the coils on its web site or in its catalogs; you need to call them.

In researching the article I asked folks in the band saw blade industry about this. Their answer was that their customers had been dissatisfied with the results of their shop-made blades. The solution, I suggest, is belter information.

Steps in Making Up Blades

Here is how you go about saving money and gaining independence by making your own band saw blades.

1. Buy a coil of your favorite band saw blade from a supplier.

2. Obtain a "refill kit" for splicing your blade that contains silver alloy and flux from a catalog store.

3. Make a jig for holding the ends of the blade as shown on page 65, or buy one.

4. Cut your band to length (add V4" for the scarf joint).

5. Scarf both ends of the band on a belt sander to prepare them for joining.

6. Align the blade in thejig, add flux and a premeasured wafer of silveralloy into the scarf joint.

7. Heat the joint cherry red with a propane torch.

8. Anneal the blade with several passes of the torch to remove brittleness on either side of the joint.

9. File the joint smooth.

Let's take these steps one at a time. The sources of supply at the end of this article will help you locate the blades and materials you need. Silveralloy sells for $25 to $40 per ounce, and flux is $6 in a 4-ounce jar. Both quantities are more than you will need, so it makes sense to buy a "refill kit" from a catalog store. What is significant to getting good results is knowing about what is called "ribbon solder." This is .003" thick by ¹A" or V2¹¹ wide. A page of this magazine is .003" thick to give you an idea of how thin this is. Cut it with paper scissors and make confetti-sized squares as a pre-measured unit for use. For a V4" blade a piece that is V4" x ³/i6" is plenty.