SS stick electrode choice -- and identifying SS type in square tubing

Doug,

You'd think so, wouldn't you? :)

All I could get out of their tech guys was that it's SS, no grade. Thinking of it a bit late: I could try to get with their Engineering Dept. tomorrow when I next work.

Sheesh, my two remaining brain cells must have lost each other for a while there. :)

John, I can't answer your question directly, but shouldn't the manufacture of the chair be able to give you the specs on the frame? Doug

I would double check to make sure it is stainless for sure. not some pot metal with a chrome finish on it.

also I guess you are asking what rod to use to stick weld it ? I think stick welding would be the last welding process I would use on a wheel chair, stainless or not.

Welding seems to be very akin to my avocation of blacksmithing: You can learn _what_ to do in a few hours, but learning _how to do it excellently_ might take a couple of lifetimes.

Most often I use either MIG or O/A. Can't get the company to buy a TIG, which I'd be more than willing to learn. I _always_ test welds and often make some, sometimes many, practice welds on scrap to test to destruction before I even start on a wheelchair modification.

Since I'm not (yet) an officially trained welder, (I'm working on it) I'm pretty careful about making sure things are joined well.

I'd never forgive myself if my ego or incompetence caused another crip to be hurt. (I'm a 3/4 time wheelchair user myself from MS and a spinal cord injury.)

What I don't know (That's a lot!) I research or ask for information and advice. If something convinces me I really can't or shouldn't do a particular job, I'm more than happy to recommend the job be sent out.

For example: Your point is well taken and we've decided to send the seat frame out to a professional shop.

Interestingly enough, we've had many warranty callbacks and returns of commercially made products and never one on anything I built or modified. I'm rather proud of that.

Just Monday we had an elevating legrest assembly from a very large national manufacturer break during fitting a client. Two pieces of 3/4 square steel tubing, welded at right angles, separated. The welds were beautifully smooth and neat. Only thing is: They only penetrated on one side of the join. Oops.

I call those Lawyers' Welds. :)

As soon as you say medical or stainless you should be talking about TIG. Your story about the footrest is a prime example of why you should NOT be talking about MIG! (Nice bead, no pentration is a common issue in thin material MIG)

cheers.

John Husvar wrote:

Thanks for your comment.

You're sure correct on that! Fortunately, there was no injury, just inconvenience.

I'm always watching to be _certain_ my welds penetrate both sides. I can always clean off too much weld to make pretty-pretty. It's too late to discover too little deposition, poor penetration, or half-joined welds when they break and somebody gets hurt.

As my welding course proceeds, I've noticed a marked improvement in both the appearance of and my confidence in my welds. Never had anything break, but the work gets faster and better looking the first time -- and the wastage or rework gets less -- as time and practice go on. Pre-training, I usually just overbuilt all to heck and gone. Still do, but to a lesser degree.:)

I'm frequently talking up TIG at the shop, but no luck so far. I don't know if they just don't want to spend the money or feel it wouldn't be used enough to justify it.

We also tend to shy away from welding aluminum because it's usually so badly fatigued it's brittle. One of our outside welders says it's not worth it.

We're not manufacturers, but there are some modifications needed at times -- and lots of repairs for people who can't afford new equipment because they fall through the cracks by one rule or another.

I'm also not sure of the company's liability exposure. It doesn't seem to bother the higher-ups. I can't imagine their not-for-profit status protects against liability, though.

this last part is hilarious ... lawyers weld ....:-) , only one side penetrated.

Well, for the next chapter in this brain-bending, tale (AKA As the Stomach Turns)

Called the wheelchair manufacturer's Engineering Dept, told them what we wanted to do, and asked about the kind of stainless they used for the frame.

Response: What stainless? It's all 1018 mild steel tubing, same as you can buy at the hardware store, just powder coated.

I reply: Hmmmmmm. Your tech support folks told me it was stainless, so I called to ask what variety.

Response: Nope, plain mild. You can do pretty much what you want to it and it should weld fine. Guess the powder coat protects the chair OK, does it?

Guess it does at that.

Back to square one: Do we want to do this in-house or not? Only the Boss knows for sure.

This thing is going to take many, many cuts and rewelds, At least 24 cuts and 12 rewelds. I'm just questioning whether there are too many places to make an expensive mistake. They jig them at the factory. We don't have that luxury. The outside welding shop will have equipment to keep things straight and square.

The maker offered to make a new seat, complete, for $1800. Might be a good deal at that price. :)

Especially considering that darn ol'liability.

Put a magnet on the tube. If it sticks, its carbon steel. If not, about the only tube used for wheel chairs will be 304L in either standard or ornamental grades.

For any of the modification or repair of thin wall tubing, you STILL need to go to TIG!!! We build race car frames with 1" x .065 wall tube and MIG weld that........... BUT......... the joints are fitted with less than .030 gap, the metal is new and clean, and my weldor spends an hour or two adjusting and testing the MIG before he starts on the frame. Then he does ALL the welds in one sitting with a couple of other guys rotating the frame so all welds are done down hand. If you don't want or can't do that, use TIG.

The outside sh> RoyJ wrote:

So why do you even own a MIG if it is such a terrible process?

Shawn

Because when MIG is set up correctly, it will pour down perfectly adaquate fillet welds 2 to 3 times faster than comparable stick welding and 10 to 30 times faster than comparable TIG welds. For robot welds, we figure 30" per minute production rate. (An human can match that but not for long!) MIG can also be used by lower skilled operators for many production applications. The key is proper setup.

The physics of the plasma in the arc is one reason for the problem. In order to maintain a stable arc, the MIG wire must be positive. The elctron flow is from the work to the wire, 2/3rds of the heat is concentrated in the wire, only 1/3 in the work. The result is the wire melts fast, gives you lots of deposit, but the work does not get as hot, sometimes does not fuse well.

MIG is the very first choice for producti>>Put a magnet on the tube. If it sticks, its carbon steel. If not, about

I guess you just caught me on a bad day. Very often on this group someone says 'MIG will give good looking welds that aren't strong' or something similar. This IMO is not a complete statement. I would say "When not used correctly, MIG will give good looking welds that aren't strong. ALL processes could potentially produce inadequate welds in untrained or inexperienced hands. For some reason MIG is generally accused of this more than others. I would guess this is due to the abundance of affordable 110v MIG machines out there that aren't being used correctly. Someone once compared the 110v MIG to a hot glue gun and I nearly started this rant with him. I guess I read that one on a good day. I have many welding machines available to me, including a 110v MIG, and each has its' appropriate time and place to be used. For me, the MIG is the answer roughly 80% of the time because of the type of welding I do, and at least half of my work is repair work. Of all the repair work, MIG is and excellent solution for the majority of it. Because of the type of welding you do, you'll have different numbers.

I tend to use the term MIG to describe both solid wire and flux cored wire processes. Your explanation of the physics only applies to solid wire MIG, not flux core. Again I will point out that these variations of MIG have a proper and improper usage.

If your weldor spends up to 2 hours just setting up the machine and then requires a few guys to continually move the work during the actual welding of the frame, wouldn't you save many man-hours by just using the TIG?

As for the OP, if this job were outsourced, MIG is very likely the process the outside shop would use unless you specify TIG.

Shawn

I would not argue with your comments. Flux core does give a much better penetration since it has electrode positive. But it is mainly used in low end 110 volt machines that get a well deserved bad rap and in some of the very high production envrionments. The middle ground all uses solid wire.

As for the frame welding, we may not do a frame for months on end. The machines need to be tuned, find the proper spool of wire, etc. Then some test time to get in the groove again. I wouldn't just start TIG on a final frame either. As for the flipping, best way to minimize distortion is to do short welds on opposite sides. If you can get all downhand welds, so much the better.

Of course, s>>The physics of the plasma in the arc is one reason for the problem. In

Because with other processes, it's very hard to make a nice looking weld, that's not tied in properly, the deposition is tied to closely with the heat. Mig, as a process lends itself to LOF that the untrained eye can't detect. This isn't true with other processes. All of this predates the "abundance of affordable 110v mig machines".

JTMcC.

Someone once

Not in outside construction. There the middle ground IS flux core.

JTMcC.

Gee, that sounds familiar! Me, too. :)

Thanks, All, for your advice and no little enlightenment. The consensus seems to be TIG is best, but it may not be possible for me.

What about OA? I generally get nice welds with it and it's actually easier for me to see that both sides of a joint fuse. Seems to me that would be second best. It'd have a bigger heat-affected zone, but is that really much of a problem with mild steel?

If I end up having to do this in-house, my question is: How far from best is too far for reliability? I don't want to end up repairing this thing every few months or worse having it break and cause an injury. We'll have to warranty it to some degree, if we make it a custom-built chair. (New chair, but too big a seat for the now intended client -- The original client passed away before it arrived from the factory.)

As usual, the shop guys are in between the boss and the customer and each wants something just different enough from the other to make it interesting.

JH> RoyJ wrote: >> Of course, since I haven't been able to get the powers that be to >> pop for a TIG machine, we go with what we have. :)

JH> Gee, that sounds familiar! Me, too. :)

JH> Thanks, All, for your advice and no little enlightenment. JH> The consensus seems to be TIG is best, but it may not be possible for me.

JH> What about OA? I generally get nice welds with it and it's actually JH> easier for me to see that both sides of a joint fuse. Seems to me that JH> would be second best. It'd have a bigger heat-affected zone, but is JH> that really much of a problem with mild steel?

Properly done, OA is good enough to build the frame of an airplane, so it should be good enough for a wheel chair, if you are confident that your welds will be sound.

Actually, brazing with a suitable alloy (copper-nickel or similar) should be plenty strong with proper fit-up. You will likely want to chop off the frame, grind new fishmouths at the end of the tubing and attach it at the same points as original, anyway.

JH> If I end up having to do this in-house, my question is: How far from JH> best is too far for reliability? I don't want to end up repairing this JH> thing every few months or worse having it break and cause an JH> injury. We'll have to warranty it to some degree, if we make it a JH> custom-built chair. (New chair, but too big a seat for the now JH> intended client -- The original client passed away before it arrived JH> from the factory.)

JH> As usual, the shop guys are in between the boss and the customer and JH> each wants something just different enough from the other to make it JH> interesting.

OK, thank you.

It might even be easier than that, since it's almost all square tubing.

What little round there is is butted straight up to the square tubing.

All the joints are butt joints or fillets. I'm beginning to think the most difficult parts of the project will be cutting everything straight and making sure to secure it well to a flat surface when putting it back together. That will be a matter of being careful when cutting and using enough clamps.

Sorry for being a bit of a nuisance, but I still lack some confidence when working on something that could get someone besides my own silly self hurt. I tend to try to get everything figured out before I start cutting things up and/or putting them together, cover all the bases as it were and get several opinions from those more expert than I ever expect to be in this life. I imagine my instructor gets a bit tired of all the questions too. :)

Again, Thanks, All.