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MG MGA - Welding weld nuts

I've just replaced most of the floorboard rails on my roadster and now it's time to replace the captive nuts for the floorboard bolts. It first occurred to me to just tack weld ordinary nuts onto the drilled hole of the rails, but that is tedious at best, expecially holding the alignment while avoiding spattering onto the threads or welding the dummy bolt to the nut. So I decided in favor of originality and to use proper weld nuts. I have ordered the set of piloted projection nuts from Todd Clarke.

My problem is that I haven't a compression welder for making these kind of resistance welds. I have access to an ordinary spot welder, with two pointed electrodes. Barney notes on his site that a pressure head could be rigged up for this purpose, though:

" If you have a spot welder you can probably rig a pressure head to install these same as original, and much quicker than tack welding each one by hand. " < http://mgaguru.com/mgtech/frame/fr111.htm >

Has anyone ever made such an adaptor? If you know how to do this, please share.

Cheers,
Ken
Ken Korey

Yup, that's the link for the nut: http://mgaguru.com/mgtech/frame/fr111.htm
Here's a cheap spot welder: http://mgaguru.com/mgtech/restore/rt613.htm
Here is the offset tongs that may reach around the side frame (but may not be needed: http://mgaguru.com/mgtech/tools/pics/spot_welder2.jpg

The proper nut is a projection weld nut with three little contact points around the perimeter (see picture in link above). To resistance weld these things I would say leave the pointed tips off of the spot welder tongs, or grind the tips flat, or place a steel or copper plate at the tips. Welding current will then pass easily from tong to plate to frame rail on top, and from tong to plate to nut on bottom, and the high resistance welding will happen at the three projection points on the weld nut.
Barney Gaylord

You can also just put 3 fillet weld tacks around the outside of the nut. Holds it just fine.
G Goeppner

Thanks much, Barney! I THINK that I see what you've done. It's not my welder, so I'll have to improvise some attachment for the tips that's both removable and non-destructive. As soon as I receive it, I'll see how creative I can be with my modification.

Ken
Ken Korey

George--

What I know about welding fits in a very small thimble, but if I understand what you mean by welding the nuts with three circumferential tack welds then it misses my point. A competent welder with a conventional nut can surely do this, but my earlier efforts with a wire welder led frequently to displacement of the nut from the hole and splattering metal into the threads. A more practiced hand than mine is needed to do this with consistent success. (Fillet tack welds also can't be done with projection nuts very well, since the projections are left proud and standing off from the drilled rail.)

I decided to try the compression method because the pilots hold the nuts in place and keep splatter from their threads. I may discover that this method has its pitfalls as well, and that a profoundly inept welder should never borrow friends' welding equipment.

Thanks!
Ken
Ken Korey

Or you could hold the nut in place with a bolt. That would stop movement and weld on the threads.
Neil McGurk

Ken, just practice on some scrap sheet metal and spare nuts. You can turn the weld nut projections over so that the nut contacts the chassis channel on its flat side (although this isn't really necessary). Neil is correct, the nut is held in place by a bolt, and tightened. You need good metal contact for any weld, and a good ground on the chassis for the grounding clamp, remove any rust or paint where the ground clamp goes. Give it a try, you'll learn a new skill, ask your welder friend for help with the machine settings. You don't even have to move the torch, just squeeze and hold for a second or two. Try it, its not hard.
G Goeppner

Ken, Rather than go to the trouble of welding nuts on the rails why not try soft soldering them on if you can turn your frame upside down. I've recently been making soldered replacements for about twenty or so front and rear wing nuts turning down the circular 'nuts' from 1" iron rod and soldering them to 2"x1" steel strips. The only problem I foresee is if the screws rusted over time and the soldered joint giving way when dismantling but if you remember to assemble with copper grease you shouldn't have this problem...............Mike

m.j. moore

Thanks, all. I am going to give it a try, George and Neil, if only because the heavy spot welder is pretty ungainly to manipulate in much of the confined cockpit space. So this weekend will be welding school out in the garage for me. I've never had use of a welder long enough to acquire the least finesse, so it's probably time to master some elementary skills. If I arrive at the point where I can fillet tack a nut that I'm not ashamed of, I may also try to learn the compression technique for welding projection nuts.

Mike, I can't turn the frame over without making the body very unhappy. It would have been so easy to have done this while the frame was still naked on a rotisserie, but we're now dressed to the point where these nuts will have to be affixed below their frame members. I hadn't thought of soldering, but I suppose if corrosion fuses the bolt and nut together at some future time, then the soldered connection would be as easy to knock apart as any. (Besides, who doesn't enjoy lying beneath their car welding parts six inches above their nose?)

Best,
Ken
Ken Korey

I use a Snap on 120v MIG welder to attach the nuts. Easy as can be if welder is set up correctly. Mine has a spot weld setting. Set the correct heat and speed by trial and error on scrap. Each weld is then just put the tip where you want it and pull the trigger. You dont even need a welding helmet. Hold the tip solidly against the rail at a 45 degree angle with the wire touching the corner where the nut meets the rail. Then close your eyes and pull the trigger. If you have a "spot" setting it turns off automatically leaving uniform welds. If not you must be able to count to 2 or so before releasing trigger.
R J Brown

Thanks, RJ. Tell me if I have this right: You use a spot-weld setting, but actually you're using the MIG welder (presumably with flux-core wire in the feed) to tack-weld the nuts onto the rail? Do you hold the nuts in place by bolting from above? And the advantage of the spot-weld setting is that you have an automatic timer function? Could this be done without such a setting on the welder, merely by counting? Sorry to be asking such trivial questions, but I really am a complete novice.

The unpleasant part of the job will be welding the nuts on the center rail, since it's a U-channel and requires getting the welder tip into the space between the "legs." I would imagine that these nuts are the best candidates for two tack-welds instead of three.

Best,
Ken
Ken Korey

Hi,
I am an amateur at welding - took a night school course that was good for arc welding bridge supports! When it was time to replace the floor rails I used oxy-acetylene welding with the nuts held in place by their bolts. This worked well as there is very low chance of spatter. They are still holding firm.
Tom Heath

My wire feed welder uses an inert gas mixture to keep a clean spatter free weld. I don't use flux wire.
The answer to all your other questions is yes.
R J Brown

Thanks again, RJ--I do understand. Tom, years ago I nearly burned down a neighbor's garage in an early outing with an oxyacetylene torch, an event that, regrettably, the missus still remembers much too clearly. I have absolutely no chance to spirit a gas rig in unnoticed, and I risk a major breach of the peace if discovered. Thank you just the same.
Ken Korey

This thread was discussed between 19/08/2010 and 23/08/2010

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