I just finished the first night back at the votech where I had my first "formal" weld instruction nearly 20 years ago. The shop hasn't changed much. The kids are still pretty hard on the equipment. Three nearly new Miller 350 Syncrowave ( I think) only one that still worked. Only 2 pieces of 3/32 tungsten, burned on both ends, couldn't tell what type. I suspect it was Thoriated since it didn't ballup much on a/c.
The instructor was showing me how to prep the tip for d/c and did not feel that length wise grinding was necessary, all the books I have collected seem to indicate otherwise. Is this one of those techinical points that really dosen't matter ? I plan on trying both methods to see what happens. What do you full time welders really do ? Most of the welding I do is light gauge aluminum with 1/16" zirc. Does pointing that small of tungsten on d/c make a difference ? (not aerospace type work)
My old Heliwelder (trans/rect) on a/c has a much quiter arc than the Miller's squarewave, is this typical of the newer machines ? ( wave form control was set at "balanced" about 2 I think)
Sorry about the long post, this is all just too much fun ! Jim
So he was telling you not to grind the tungsten at all? I was taught to sharpen the tungsten before balling the end, primarily to remove any contaminents in the tugsten. If you don't sharpen it, all the crap from the last time it was used to weld would be in the ball. Also I think it would be alot more difficult to form a nice ball it it is not sharpened to start with.
Depending on what type of grinder I have available and how much amperage I am using, I have ground my tungsten with the grind marks parallel and perpendicular to the centerline of the tungsten.
If you are talking about not grinding a point at all on 3/32" tungsten and leaving it square. I'd have to try it. I have made quite a few welds that RT'd with a pretty big "glob" of steel on them and they didn't appear sharp but never with one left square.
Good Day
G Austin
As I understood it, he felt that pointing was needed, just not paticular about the direction of the final grind. I also did not get a straight answer about how far to break off a contaminated tip, but I assume they are trying to conserve consumables. He felt it only necessary to regrind the tip, I have been breaking off about 1/4 to 3/8" and blunt pointing the tip before heating and balling the tip. (also using a piece of copper pipe to preheat on, read that somewhere also) Preheating seems to help stablize the arc quicker, I'm still having the most trouble getting a tack weld started without getting to large of a bead. Getting both edges of lap heated together takes some practice.
Is butt welding pop cans really good practice or just something to keep the apprentices humble :) ? There is something neat about pushing those shiny puddles of aluminum around anyway....
Thanks again, Jim
A similar subject on aluminum was posted a few weeks ago.
I sometimes ball the tungsten just slightly on a tapered electrode to maintain a narrow or focused arc for thin aluminum. Like most welders I did not want a big lump where any of the the tacks were. The way the machine is set-up (waveform, balance, frequency, etc.) would determine how much dressing and how much balling was required for a given application.
This will work to a point (no pun intended) depending on the type and size of electrode, the current used, shielding, material thickness, etc. We used the copper block primarily to ball the tip, not to preheat the electrode. Starting twice typically is not considered very productive in many companies.
This is where DC welding of nonferrous materials comes in handy. Preheating is often not used even for thick weldments or weldments with a lot of mass which acts as a heat sink (resulting in troublesome or slow arc starting). I've welded 3/4" aluminum without preheat and passed x-ray no problem. Did not have a choice in the matter anyway, if you could not do it, then you were shown the exit.
Sometimes I needed an electrode somewhere in between a 1/16" and 3/32" and I would dress the tungsten with a very long taper. Then ball the end as noted above. I have tried the longitudinal grinding and it did not make much difference to me, particularly after the first start. For some reason this is important when I was doing PAW. I still have not figured this one out. Possibly due to the arc constriction(?).
I typically never broke off the end unless the contamination was extreme. I agree with just grinding to clean. That's lot's of $ when you get to buy your own.
Maybe you can contract Dave Sisk for composing "Shiny Puddles" from "Tiny Bubbles".
they say the difference between grinding parallel and grinding perpendicular had to do w/ the current flow and the stability of the arc. it sorta makes sense...if the tiny grinder stone marks are magnified you'll see that it's not smooth, but more like long ridges and valleys over the piece you've ground on. the electricity flows on the path of least resistance, and so, if the grind marks are perpendicular to the tungsten, the current path is going to be to the interior portion. if they're parallel, the current will flow all throughout the tungsten.
as for pointing the tungsten or not pointing, that all depends on how big of an area you want to heat up. if you're welding a thick piece then a bigger ball might be desired. for thin pieces, you don't want to heat things up so much, so a point will allow you to form a tiny ball. it's kinda like the heat of a flame...a bigger flame will heat things up faster than a smaller flame, eventhough they're both at the same temperature.
i think the squarewave machines are louder because the transition from + to - is much more abrupt than in the older AC machines where the same transition is more like a sine wave (gradual). it could also be the settings you're using.
stay away from that thoriated tungsten...it's not good for welding aluminum!
The above posts have covered it pretty well. The textbook does say to grind the tip longitudinally and the reasons stated above are valid, However we don't all have the best tooling available and unless your working at lower amps you may not experience difficulty with grinding the way your teacher suggested, experience will dictate that.
Just a note on safety. Do not grind tungsten electrodes that have been fouled by dipping into aluminum on a stone grinding wheel. If you have done this just re-dress your wheel to remove the loaded aluminum. The belt sander is a much better tool for the job and with it you can get your tip prep lines made the way you want.
Experience is probably still the best teacher and often provides the most memorable lessons. I really appreciate all your thoughts and promise to mantain an open mind. (actually my wife says it's completly empty !!)
I'm going to take my own tungsten along to class tues night just in case the supply situation has not improved.
In regards to wheel grinding, does the stone tend to contaminate the tip more than a belt (aluminum specifically) or will frequent stone dressing avoid the problem? (I don't own a belt sander) If I touch the tip with the rod, lots of alum, probably better to break it off than just retip ?
Is there a prefered method to clean really weathered aluminum ?
most of the repair work I would like to try is badly oxidized making good welds even more difficult. From past posts, carbide cutting to shiny metal was favored ? Very cold in NW Ohio tonight, going to have to heat up some aluminum just to keep warm. thanks again, Jim
a belt sander doesn't have as many pores for the aluminum to get stuck in.
if you can actually see a drop of aluminum on the tungsten, yes, break it off and re-grind it. i've tried just re-grinding a fouled tip and that doesn't seem to solve the erratic arc problem. expensive as it is, i'd rather weld w/ a tungsten that has no contaminants. after a while you learn the rhythm and technique of TIG welding, so the number of times you actually have to break off the tungsten reduces.
to clean off heavily oxidized aluminum use a stainless steel wire wheel. you can also use a grinder wheel, but that's not such a good idea on thin stuff like what you plan on welding. don't use a carbon steel wire wheel because that will contaminate the area w/ carbon. and don't use your stainless steel wheel for anything else but aluminum to ensure your welds don't get contaminated.
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