Guy,
You've apparently missed Lawrence's excellent point about Aluminum and grinding wheels and exploding and high-velocity flying debris. Perhaps Lawrence can give some more insight into what's happening with the grinding wheels. If I had to guess, and this is only a guess, I'd say the Aluminum, being soft, fills the spaces in the wheel as you grind. Then, also being an excellent conductor of heat, transmits enough energy(heat) into the wheel to weaken or break the chemical bonds of the material used to hold the wheel together, and combined with centrifugation(defined as "being subjected to centrifugal action" which surely applies to a spinning grinding wheel), the wheel disintegrates.
I've had the misfortune of working around people grinding Aluminum. While the wheel didn't explode, I was pelted with liquified Aluminum, which acts much the same way as liquid solder does when it hits the floor. Cool effect on concrete. But it rapidly leads to a bad day when you have to peel it from your neck!
Also, I don't see a problem with using a drill, as long as the Tungsten is ground from the point back. What's the difference? The resultant striations(grooves) are still longitudinally orientated, perfect for GTAW, and the smooth flow of electrons. The belt sander will also give a smoother finish, as it is of a finer grit, more like a diamond wheel will produce.
I might also add that I find it acceptable to do a "rough" finish by grinding the point sideways(90 degrees to the length of the Tungsten) to establish the basic point geometry, but should always be given the final finish longitudinally, again, to correctly orientate the striations.
Dale Simonds
Dale,
Thank you for more fully explaining the technical aspects of my advice about *cleaning* tungsten electrodes. I know myself to be longwinded in my responses at times, but when a topic is not fully detailed we get criticism in the form of posts such as the one above. Generally I ignore critics but this is a safety Issue, your swift and accurate words are a benefit to everybody who reads them.
The quality point that Guy did manage to make is this. One really ought to check out advice and be sure that the topical authority applies to the job at hand.
Now in giving this particular advice I used data gathered from first hand training and experience in the aerospace industry. Beltsanders are employed for cleaning aluminum deposits from tungsten electrodes all through the trades. Boeing, Lockheed, The United States Navy and Airforce all supply belt sanders to craftsmen in order to clean aluminum from tungsten electrodes. This is a black and white Issue and not up for debate. Putting aluminum onto a rotating grinding wheel is wrong and an unsafe practice. If you have been doing so please ask your shop supervisor redress the wheel or replace it.
Two nice links to grinder safety online for those who appreciate sourced material
http://www.tarleton.edu/~policy/safe0401.htm
http://www.ganoksin.com/borisat/nenam/grinding.htm
As for diamond wheels, the aluminum will just clog them up and quickly render them useless. Your boss will not be happy to pay for ruined diamond wheels at $100 bucks a pop. I have written several posts on the blessing a diamond wheel can be, but aluminum-welding operations are not top of the list for this type of equipment.
Furthermore, Tapping a pointed tungsten electrode on a steel surface will only fracture the point and make more likely the possibility for tungsten inclusion/contamination of the work at arc initiation. Tungsten is harder than steel-(any steel) and will be splintered and chipped rather than blunted by the tapping, the resultant fractured pieces, not being cleanly removed, are then ready to fall off into the weld puddle. Just try it once and look at the thing under magnification.... When an Electrode is cleaned and prepped with the desired angle, If you wish, you may remove the sharp point on the wheel or belt in order to achieve the desired tip geometry. Lanthanum electrodes are particularly susceptible to fractures so if you're using them this advice is extra important.
Lawrence Bower
Welding Instructor
United Airlines
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