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jacampb2
01-17-2009, 04:54 PM
MY tig machine is a 28 year old dial arc 250 with a HF box add on. Lowest current in DC is 35amps. Is there any way to further limit it? I am doing some sheet metal work on an old truck, using ERCuSi wire and even 35 amps is way to hot. I would think 15 amps or so would be golden. So, any ideas on cutting it back further? Maybe run it in AC and put one big power diode in line with the torch, if I am thinking right, it gives me a kind of half assed pulsed DC, being only half rectified AC...

Give me some ideas. I can weld it at 35 amps, but anything more than a half inch of bead at a time really starts to warp the panel. As it is, I am going to have to cut out what I did and start over...

Thanks,
Jason

piniongear
01-17-2009, 05:11 PM
I would suggest you start looking for small 135amp Mig welder that would run .023 wire, Such a machine will allow you to weld 22ga up to 1/8 inch easily.
The price is not bad for a brand new machine and a used Mig would be even better.
I do not believe there is any way to 'reduce' the output of your Tig machine. Even if there were, the cost would be better put toward the purchase of a machine that will do what you want to do IMHO......pg

jacampb2
01-17-2009, 06:31 PM
Thanks, I gave away a MM135 ages ago, I wish I hadn't, as they are nice for stuff like this, but not much else. I own a MM251R, and have .023 drive rollers. I don't care for how poorly .023 feeds, regardless of the welder. I did a lot of this work with .030, and did okay, but it took forever stitching everything up and if the fit isn't perfect, the mi blows right through.

CuSi wire for the mig may be an option, but my local supplier didn't have anything but tig wire on hand, thus the choice to go tig.

Later,
Jason

piniongear
01-17-2009, 08:18 PM
Thanks, I gave away a MM135 ages ago, I wish I hadn't, as they are nice for stuff like this, but not much else. I own a MM251R, and have .023 drive rollers. I don't care for how poorly .023 feeds, regardless of the welder. I did a lot of this work with .030, and did okay, but it took forever stitching everything up and if the fit isn't perfect, the mi blows right through.

CuSi wire for the mig may be an option, but my local supplier didn't have anything but tig wire on hand, thus the choice to go tig.

Later,
Jason
I too owned a MM135 and found it too small for any serious work other than light sheet metal. So I bought a Millermatic 251 and sold the 135. No regrets there.
I do automotive sheet metal welding easily using ER70-6 wire in a .023 size with the MM251.
Then I switch to .045 ER70-6 for the heavier metal welding.
So, if you have a 251 machine, that's perfect for what you need to do, just change to the smaller wire and 75/25 gas mix..........pg

agrip
01-17-2009, 08:30 PM
The lowest cost, right now, way to limit the welding energy is to put a limiting resistor in the welding circuit.

The most "miky mous" approach is to use two pieces of galvanized water pipe with several parallel pieces of wire of the same length between them. You need to drill and tap some screw holes in the pipe wall.

With the welder set on lowest current, force the welding current to also pass through this variable resistor you have rigged and let it soak up the surplus.

The wires between pipes will get hot about 3 - 400 watts worth. You have to provide for that, but a few experiments will give you the control and results you want. I would start with about 6 iron wires 4 feet long.

Run the ground wire normally from the work but terminate on one of the pipes nailed to a 2x4 hung about 6 ft off the floor.

6 wires going straight down to the other pipe hanging from those wires.

Use a #6 copper wire from the lower pipe to the welder ground stud.

If the wires get too hot, add another wire.
If you have too much weld energy, lengthen the wires. or eliminate a wire.

Hth Ag

jacampb2
01-18-2009, 11:14 AM
I was wondering if that approach would work. I thought possibly a resistance current limiter may damage the welder, as it is always trying to maintain constant current, but on thinking about it again, it *should* work. My thoughts were a 5 gallon water/salt resistor... What do you think?

shawnspeed
01-18-2009, 02:12 PM
You could use ac and the Hi freq. and vary your arc length ...silicon bronze likes Ac ...Also I am assuming you do not have a foot pedal or finger tip control???Also how far apart are you tacking the work???I would suggest tacking every 2" then come back and tack between the 2" tackcs and come back and tack between those tacks until the panel is tacked every 1/2" ,allowing the panel time to cool , also hammer/dolly the joint along the way to make sure everything stays strait. When you start filling in between the tacks do a 1/2" then skip 5-6 do a 1/2" Skip 5-6 Ect til you get to the end of the panel, hammer/dolly , cool reapeat until done...I had my first job out of school with Ron Fornier and he had me brasze the fins on a '63 Studeibaker hawk this way...very little distortion, but it took 3 days,but saved time metal finishing and doing the final leadwork(bondo was a bad word in the shop at that time)...Good luck , Shawn

agrip
01-18-2009, 02:38 PM
Salt-Water resistors have been used a very long time for low ohm high dissipation applications. Rugged and once adjusted do not change much.
Just don't kick the bucket, with your mask on.
2 ohms X 15 amps = 30 volts

You have to adjust the electrode area, and I myself would not use a chloride or chlorate salt particularly in a weld shop. Humor intended, there is more than one way to kick the bucket.
Hydrogen is a small problem if your ventilation isn't appropriate.

The constant current thing is reactance in the transformer, not bothered in the least by adding resistance. The two "added" together become impedance.



Hth Ag

jacampb2
01-18-2009, 09:11 PM
You could use ac and the Hi freq. and vary your arc length ...silicon bronze likes Ac ...Also I am assuming you do not have a foot pedal or finger tip control???Also how far apart are you tacking the work?

I wasn't aware that silicon bronze was a AC filler, I was under the impression it was DC. I do have a foot control, but the welder simply does not go any lower than 35Adc. I am fairly certain the low end in AC range is 45a, so I probably not buying myself anything by trying your idea... If you cannot tell, I have not done much sheet metal or body work. I am a fairly good weldor when it comes to heavier steel, but this light gauge metal stuff is a whole new ball of wax. I appreciate the pointers, as for tacks, this particular quarter panel was almost in perfectly with the mig. I had tacked roughly every 1.5"s, then continued around and worked until it was all filled. It took a long damn time, that is why I went and dragged the tig out and bought some CuSi. As a test, I just used it to touch up some of the rougher mig beads, and fill some small holes. I was burning through occasionally with the tig unless I treated it just like the mig, tack, move, tack, move. Toward the end of my touch up, and for the record, it was probably less than 5 inches total of tig welding, there was a huge pop and the panel sucked in. The only thing I can figure, is I had it right on the edge of warping badly with the mig welding, and the tig heat put it over the edge. I *thought* I was out of the woods, as I had the thing fully welded in place. I tried heating and cooling the panel to get it to pop back out with no luck. I am just going to cut it out and start over.



I myself would not use a chloride or chlorate salt particularly in a weld shop.

I am sorry, I don't understand, my chemistry is a bit rusty, but don't all salts have a Cl?

Thanks,
Jason

mark61
01-18-2009, 09:36 PM
I think no matter how low amps you try making long continuos welds in sheet metal is going to warp it. Short 1" to 2" all around then go back and do between the first welds will prevent warping.

mark61

agrip
01-18-2009, 09:50 PM
I have used Silicon Bronze with AC DC and OxyAcey
Makes strong joints without fusing the steel sheets, just doesn't color match very well.
---------------------

Many people think table salt when the word salt is used.

There are carbonate salts, nitrate salts, sulfate salts, phosphate salts, etc.
Depends on the acid available when the salt was created.

Washing Soda is Sodium Carbonate IIRC
Available at some grocery stores, it is commonly used to be the electrolyte in electrolytic de-rusting rigs.

If you use the bucket resistor, I suggest you start with washing soda.
Doesn't take much, start with couple tablespoon per gallon water, add or dilute to "taste".

Hth Ag

jacampb2
01-18-2009, 10:27 PM
Awesome, I have a big ol' box of washing soda for the electrolysis rig... I never realized it was a salt.

It can't hurt to experiment with this. I have already ruined all of the work I had done. If I can get the tig current low enough, I would rather use it than the mig.

Later,
Jason

Bill736
02-05-2009, 10:11 PM
The salt water in a bucket trick reminded me of an electric powered car a group of us built many years ago. We finished the car, but there was a delay in getting the motor speed controller built. Just to experience the car moving under its own power, we rigged up a pair of copper plates in a 5 gallon bucket of salt water, and held them about an inch apart until the car started moving. Crude speed control, but it worked .

mf205i
02-28-2009, 04:30 AM
Years ago I played with this. I had very good results with long leads on the DC side. I used a heavy extension cord, in line, on the ground side.
Although I did not try it, I thought that light bulbs would have worked well and would be easer to tune by adding or removing bulbs.
Keep it simple, Mike

uncrichie
02-28-2009, 04:26 PM
Uh, can't you just run the Dial Arc on 120 instead of 240?

airsmith282
03-01-2009, 06:51 AM
what about using the new HTS-2000 stuff . asimple propane tourch and your ready to rock alot cheaper hten a new mig and the sutff wokrs great you can aslo use sudotec 78 rods and a tourch as well if you dont want to use the HTS-2000 just and idea is all,,

mf205i
03-01-2009, 07:05 AM
Maybe you can, but even if the peripherals all worked, the arc voltage would still be cut in half.
Mike

jauguston
05-01-2009, 08:51 PM
I have a cheap Century AC-DC 240v buzz box I TIG with using DC. I had the same issue not being able to get cool enough for really light work. I asked a friend that is a industrial electrician and he said set up a outlet that fits the welder cord with 120v. It works fine. The cooling fan runs at half speed but he said that would not hurt it. I use a relay with a foot switch on the welder power to start the arc. Ground the tungsten-press the switch and lift the torch to start the arc. Manual gas valve on the torch.

Jim

bobhdus
05-06-2009, 02:02 PM
Sometimes depending on what it is we are welding we will use backing strips made of nonferrous material (brass, bronze, copper etc...) to absorb some of the heat when welding thin sheets of steel or stainless steel. You can also buy solar flux from your local weld supplier that is made for steel and Stainless Steel MIG and Tig welding. It will allow you to really heat things up with minimal distoration or weld puddle fallout. You just mix it with acetone and brush it on. It also leaves a really smooth weld crown on the backside. No need to clean it off on steel either. Welders putty can do the same but you will want to remove it when done. We will also backstep weld as needed.