Welding on nuts without damaging them

[joshuabardwell]

No, not my nuts. :laughing:

I'm making a toy for my 17-month-old son. He loves playing with wrenches and nuts and bolts, so I figured I would make him a plate of metal with some captive bolts and a box wrench on a chain, so he can turn the bolts but neither they nor the wrench could get separated. It's a pretty rudimentary project, and once upon a time, I would have made it out of wood, but I'll take any chance I can get to practice welding.

My idea was that I would drill holes in a plate, then weld nuts over the holes, then put bolts through the nuts, then weld washers onto the end of the bolts to prevent them from being removed. The problem I ran into was, after welding the nuts on, the bolts wouldn't go all the way through two out of the three of them. At first, I thought maybe a little slag or dust got into the threads, but upon closer inspection, they looked like they might be warped or distorted from the heat. For perspective, I used 3/32" E7014 at about 110 amps, DCEP. The base plate is about 3/16" to 1/4" thick and the bolts and nuts are 9/16" (3/8" diameter thread).

As a workaround, I am considering putting the bolts through the plate and then welding the heads of the bolts to the back of the plate, but I really like the idea of having the bolts being turned through the plate, compared to having the nuts being turned up and down the bolts, so I'd rather find a way to affix the nuts to the plate without damaging them. I suppose I could just break down and use JB-weld, but I didn't buy a welder just go turn around and JB-weld something, now did I!

 

[bcp]

Run a tap through the nuts.

Bruce

 

[Katahdin]

A couple thoughts, 1) use weld-nuts, which are designed to be welded on. Or 2) put a brass bolt through the steel nut that you're welding. The brass and steel won't bond and it may keep the nut from warping.

 

[gwdixon]

Run a tap through the nuts.

Bruce

Agree with bcp. Use a tap to ream out the nuts.

I have also had success using a impact wrench with larger nuts and bolts. Lube the bolt and run it back and forth several times.

Also, next time you do a project like this, leave the bolts through the nuts during the weld. That will support the nuts from getting so out of round due to heat warping. Just spot weld or tack three of the six faces to lessen the HAZ.

 

[RobertBrown]

You could try the heavy 3/8" nuts, for a 5/8" wrench.....might help. I've successfully welded nuts but never that small 5/8" thread and larger.

 

[joshuabardwell]

Here are some pics of the project.



One side weld. 3/32" E7014.



Other side weld. The second side is a lot neater, I think because the electrode had burned down shorter. If you look at the first side, you'll see it gets a lot better towards the end of the weld.



Top plate. I beveled the plates with a small landing to help with penetration. You can see where I undercut the landing on the top weld, whereas the bottom weld stayed entirely within the bevel.



"Bad" side -- after grinding flat. Small slag inclusion towards the end of the weld.



"Good side" -- after grinding flat. Some undercutting, but otherwise, I'm pretty happy with this bead.



After welding, I beveled all the edges, both for safety and because I thought it looked nice. Not sure how I should have done this if I wanted it absolutely flat. Maybe no bevel? Or another pass?



Finally, I drilled 1/2" holes.

 

[joshuabardwell]

Run a tap through the nuts.

Good suggestion! But I don't have a tap.

 

[gwdixon]

Good suggestion! But I don't have a tap.

Taps are not that expensive. In fact, if you are going to weld and fab you need a whole set. Harbor Freight has horrible ones for cheap but they work for a few holes if carefully done. They are better than not having any.

That opens another option - tap the holes in the plate instead of welding nuts on the back. One less step and guaranteed to work.

 

[k0ua]

Agree with bcp. Use a tap to ream out the nuts.

I have also had success using a impact wrench with larger nuts and bolts. Lube the bolt and run it back and forth several times.

Also, next time you do a project like this, leave the bolts through the nuts during the weld. That will support the nuts from getting so out of round due to heat warping. Just spot weld or tack three of the six faces to lessen the HAZ.

I agree, but also a couple of other things, The larger the nut the easier to weld and less likely to be so heat distorted. You can also tack one side let cool, and tack again. Also try just a little less heat (amps). A single tap and a tap handle is not a whole lot of money. You don't have to buy a whole set. Now the best solution. Dont stick them on, TIG them on.. much better control of the process and much better results.. NOT that you cant stick weld small nuts, because you can, and I have done it several times. But given the choice if I had the TIG torch I would use it. On your welds on the plate, you can weave across the puddle a bit and just touch the "toes" of the weldment. This will fill in the gap by making a wider weld bead. I applaud your efforts for tackling the project and getting better all the time.:thumbsup:

James K0UA

 

[Scooby074]

I cover a bolt's threads in grease then thread that into the nut to be welded. Weld the nut on going easy on the heat (enough so that the nut is well stuck however) then back out the bolt once it cools a bit. Works for me.

Most important thing is making sure the bolt is centred in the bore of the hole. If it's off centre, it will be a bear to get in and out.