A common concern in the brazing field is the cleanliness of parts that are to be brazed. Some people think that cleanliness can be achieved by merely heating the parts in a furnace or via a torch-flame, and those high-heat conditions will effectively “burn off” any surface contaminants and render the parts sufficiently brazeable. NOT TRUE!
Parts that are going to be brazed need to be thoroughly cleaned prior to assembly for brazing, which usually involves degreasing of parts and thorough drying. It may also involve a pickling bath to remove any oxides from the surfaces to be brazed. Then, once the parts have been cleaned, they need to be handled and assembled with clean hands in order to maintain that surface cleanliness.
So one important question to answer is: “Can I get my hands clean enough to adequately handle surfaces that will be brazed?” Well, let’s look at what is found on your skin, even after you’ve thoroughly washed them.
First, we are made mostly of water, and the pores of our skin constantly produce moisture (perspiration or sweat) — it’s part of our body’s temperature control mechanism since evaporating moisture tends to keep our skin cooler. Additionally, perspiration contains a lot of body-salts (sodium, potassium, and calcium, etc.), and these need to be constantly replenished via food or via supplements that we take each day.
Our skin also secretes an oily/waxy substance (sebum) which helps to lubricate and waterproof our skin and hair. Some people seem to exude more than others. Our bodies also release skin-acids (known as sapienic acid), which comes from our body’s fatty acids.
We are also an electrical being, with all the neurons and extensive nerve-connections throughout our bodies. So, even if I thoroughly wash my hands, dry them, and then quickly head back out into the work area in the shop, the skin on my hands will already have emitted water and salts onto the skin surface (since that is constantly happening), and if I touch any metallic surface I will leave fingerprints (water, salt, electricity, etc.) — ever notice how your fingerprint can seem to be “etched” onto a super clean metal surface when handled by bare hands?
Add to this array of ingredients already on your hands any additional materials you handle, such as food, deodorants, perfumes, and cosmetics, or dirt on work benches, etc.. All of these are potential contaminants that can hurt brazing (See Fig. 2 on the right)
How can you prevent this? Wear clean gloves! The choice of gloves you use is highly subjective and can range from thin, lint-free cotton gloves all the way to the heavier welding gloves worn to prevent hands from getting burned. Rubber (latex or neoprene) gloves are very popular in many shops.
NOTE: Be sure any gloves of latex or neoprene do NOT have any powder in them since powder can readily contaminate brazing surfaces!
A Very Bad Example of Shop Practice:
I was visiting a brazing shop a few years back and noticed that the people assembling parts for brazing were wearing gloves, but the tips of the gloves were cut off so that they could handle the small parts with their bare fingertips. When I inquired as to why they were doing this, the supervisor explained to me that the workers said that the gloves were a bit too bulky to use for this assembly work, so the supervisor allowed them to cut the tips off to help them assemble the parts more easily.
Obviously, the supervisor didn’t really grasp the purpose of wearing the gloves, and neither did the workers. They were merely obeying instructions that workers must wear gloves for that assembly operation.
Be sure that everyone assembling parts for brazing is not only wearing appropriate gloves for that work but that they also fully understand the purpose of wearing those gloves — namely, to keep their hands (and all the surface contaminants on them) off of the parts being assembled for brazing!
What kind of gloves are you using? Please feel free to share some of your experiences on this subject via return e-mail.
Dan Kay – Tel: (860) 651-5595 – Dan Kay operates his own brazing consulting/training company, and has been involved full-time in brazing for 40-years. Dan regularly consults in areas of vacuum and atmosphere brazing, as well as in torch (flame) and induction brazing. His brazing seminars, held a number of times each year help people learn how to apply the fundamentals of brazing to improve their productivity and lower their costs. Dan can be reached via e-mail at [email protected], and his website can be visited at: http://www.kaybrazing.com/
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