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We return this month to our series on the essential criteria for brazing, to complete our current series on some fundamental issues about brazing filler metals (BFMs). As was discussed in my previous article on Essential Criteria for Brazing, if you are using BFM powder in your operations, it’s essential to not only control the mesh size of the BFM powder you are using (covered last time), but also to know and specify the ratio of BFM powder to the gel-binder in the brazing paste.   The gel-binder is cellulose-type gel-like substance added to the powder to form a creamy blend of powder and gel that can be extruded from a cartridge through a dispensing tip.  So, whether you are using BFM powder directly, or are using a pre-formed shim/ring of BFM, or BFM in paste form, you must always ask yourself this simple question: “how many times can I fill the braze joint with the BFM that I am using?” Hmmm….   The obvious answer is “one time” only! No matter how good you are, you cannot cram any more BFM into the joint after that joint has been filled by the molten filler metal ONE time! by Dan Kay

We look now at the fifth of the seven important criteria for good-brazing that are listed in Table 1, namely, the use of fixtures in the brazing process. Fixtures hold the parts being brazed, whether it is a metal vice holding parts for torch brazing, or a large furnace-grate on which parts are set for furnace-brazing, just to name two types of fixtures. The important thing to always remember about fixtures is that they usually represent a large mass of metal (the material most often used in fixturing) that absorbs a lot of heat and can thus significantly increase the brazing time needed to complete a braze.

Fixturing. People often do not have a proper understanding of the roll of fixtures in brazing. It can, in fact, have a significant effect on the performance and profitability of any brazing process, be it an operation performed by torch, induction, or furnace. I recently had someone tell me that when they had implemented the fixture-recommendations they learned from my brazing seminar that they had attended, the profitability of that brazing operation went up over 75%. Yes, fixturing is a very important topic that needs to be evaluated thoroughly and properly implemented to optimize your brazing operations.

This quiz was not as easy as many of you may have thought. I chose a number of questions that I knew would “challenge” many of you to more clearly think about some of the principles of brazing, and how it works, especially as it might compare to welding. Over my 45-years of teaching brazing and working with it extensively – hands-on — in the field, I’ve seen a lot of “misconceptions” out there about brazing and how it should be correctly applied. I hope this quiz has challenged some of your own thinking on the topic, and opened your eyes and thinking to some new things about brazing you did not know before. Let us each continue to work hard to apply brazing correctly in our (and our customer’s) work, so that brazing will be more correctly applied and understood.

IMPORTANT NOTE: The Brazing Quiz published in our April column is STILL open for readers to try. Because only a few people actually sent in their replies, we encourage more of you to do so. We’ll then publish the answers in the June column (next month).

We return this month to our series on the essential criteria for brazing, and will look more closely at another aspect of brazing filler metals (BFMs). If you are using BFM powder in your operations, then it will be very important for you to understand and to control the mesh size of the BFM powder you are using, since powder mesh size can affect brazing performance.

A common way to create BFM powder is by melting the raw ingredients for the BFM in a large melting pot using induction heating, and then pouring the resulting liquid metal through a specialized atomization nozzle in which a very high-pressure gas will literally blast the molten metal stream into billions of tiny particles (inside an atomization chamber). The tiny particles will fall by gravity to the bottom of the chamber, solidifying along the way into solid powder particles.

For this month’s column we would like to challenge our readers to have some fun with a brazing quiz. If you would like to try our Brazing Quiz, please e-mail your responses to This email address is being protected from spambots. You need JavaScript enabled to view it., listing the numbers 1 through 20 and your correct “letter” response next to each number. The correct answers (with explanation) will be printed in next month’s (May) article.

We look now at the fourth of the seven important criteria that should be followed in order to insure good brazing, namely, the proper choice of a brazing filler metal (BFM) to use for your application.  You’ll find that you have a number of possible options from which to choose, but always bear in mind that the end-use application should always be the deciding factor when trying to decide on which BFM will be best for your current needs.

There are many different brazing filler metal (BFM) families, and so, for easier identification, an orderly arrangement, such as that shown in the American Welding Society’s A5.8 Specification for BFMs in Fig. 1 helps to categorize these many alloys into groups that are more meaningful.