Why do auto darken hoods say no use for gas welding?

My Nexgen lens has a setting for torchcutting which is a #5, but the instructions say it is not for gas welding. I have no idea what drugs they are doing. It works fine for gas welding.

I don't have one of my own but i've used them. As I understand it, most autodarkening hoods will not activate at the relatively low light level put out by oxy flames.

StaticsJason

I was going to ask you about the Nexgens. Someone (was it you?) said there were only two hoods good for low power tig - Nexgen and another. Wondered if the sensitivity was good enough for gas.

StaticsJason

I'm going to take a wild ass guess that the things trigger based on UV radiation plus they need UV to charge. I have a nice lightweight headset for OA and have never tried my MIG hood to see if it triggers. Thus, it's just a guess.

--G--

Statics wrote (clip) As I understand it, most autodarkening hoods will not activate at the relatively low light level put out by oxy flames. ^^^^^^^^^^^^ I have seen an auto-darkening helmet activated by the flint striker spark. I believe it is the sudden burst of light that activates the helmet--not the brightness.

I don't know why a helmet would be OK for oxy cutting, but not for gas welding, unless it's possibly the shower of bright yellow sparks that keeps it turned on. You don't normally get much of that when you are welding.

What did you mean by "goo for low power tig?" I have a Speedglas helmet. I've noticed it will trigger at 50 amps while welding sheet aluminum but that it's near impossible to see the puddle at all (and a fast moving puddle it is!). I haven't played with it much but I would suspect the difficulty is that the darkness needs adjusting, it triggers fine. Maybe the batteries need replacing.... When you say low power what amp level are you talking about?

Wasn't there some sort of special lens made by some small company just for aluminum welding that would allow you to see the puddle better? It cut out the yellow light better or something like that?

John

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I'll vouch for the tinman filters. They made a huge difference for me in gas welding aluminum. I now strongly prefer gas over TIG for welding or brazing aluminum from .060 thick down to .005 or so.

I was refering to low amperage inverter TIG welding. The Nexgen and the Speedglas 9000xi are the 2 best for that.

For gas welding there is no sensitivity problem since you are not triggering the lens at all, just setting it. On a Speedglas hood you just turn it off for a #5. For a Jackson lens you just set it to "Torch".

The Jackson Nexgen is sensitive enough to react to a 5 amp inverter TIG weld. The Speedglas 9000xi is good down to 1 amp.

Inverters create a darker (dimmer) arc than transformers, so if you are using an inverter outside in the sun on thin materiel, most LCD lenses will not react. The Nexgen and 9000xi will.

but you can use Gold-Didymium or Gold-Cobalt goggles as used by the glass industry.

I have a pair of each, and they both work for gas welding aluminum, and give full UV protection.

You can buy them from Oberon Safety and Wale Apparatus

I have the TM Tech 2000 lense for gas welding aluminum. It is not rated for MIG/TIG as I recall :

--G--

The electronics in an autodarkening hood look for a light pulse with an amplitude rise in the microsecond to millisecond range to trigger properly. It's hard to get that when cutting or welding with gas.

Its the sudden flash of the arc starting they're looking for.

Cheers;

C.W. Thomas

My Speedglas will turn on with just the flash from a striker. It will also trigger from florescent (sp?) lighting if you look up at the bulb. Which should give you an idea of how much the bulb is actually turning on and off each cycle.

John

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Why do you say you prefer gas over tig? I've got a bunch of aluminum boxes to make out of .060" material and was going to tig the corners.

Thanks,

John

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Do you think you could plasma weld aluminum with those glasses and the HF 45850 plasma torch?

I owned one for a month, and was impressed, but returned it as I never could arrange a meeting with the welding instructor at NVCC Manassas.

The torch is not listed at HF under a search by keyword "plasma" but a search for item number "45850" produces the correct page. Curious, that.

Yours,

Doug Goncz (at aol dot com) Replikon Research

I do experimental machining the way it ought to be done, with one hand on a text book, the other on the lathe, and one ear on the telephone getting free help from people all around the world.

The lenses you are probably thinking of are called "cobalt blue". Sometimes they are hard to find but they work very well for gas welding aluminum.

TIG would probably work well there and would be a lot faster than gas. I like gas because the welds are more ductile, but that shouldn't matter on box corners. I'd probably TIG box corners with a steel backup block in the corner. I'd start at the open end of the corner and weld toward the 3-sided corner.

They're not nearly dark enough to protect you from a visible arc. The advantage to them is that they cut the yellow sodium flare from gas welding flux while otherwise affording very good visibility. I'd guess they're about a shade 3 or 4.

I do believe you are right sir. The direction of the weld you mention is correct but I hadn't thought of using a steel back up block. I've used aluminum back ups for welding sheet steel so I imagine it would work in reverse.

John

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