I have a rolling cart my wife uses for hobby supplies. Each leg is a rolled metal tube about 2" in diameter. In each leg, there is a disc of metal tack welded to the sides and a nut has been tacked to each disc so threaded casters can be installed. One of the nuts broke off because it was poorly tacked in only two spots. Unfortunately, I can’t measure the thickness of the metal disc, but it is fairly rigid.
Can I braze the nut back in place? I can get a pencil torch head for my propane cylinder for about $20 and several flux-coated brazing rods for about $5.
I don’t have any welding equipment. Even if I did, I understand that welding to sheet metal can be tricky and require practice. A couple friends suggested hauling it down to a welding shop, but I honestly don’t want the hassle and will probably end up giving the cart away if I can re-attach the caster. I can always use the torch head for other projects.
Mods, feel free to move this to IMHO if appropriate.
Thank, Moreau, but I tried epoxy and it snapped off. I can, of course, only get at one side of the disc and the nut sits in front of a slightly larger hole for the caster leg.
I can try MAPP gas, as the torch head I’m looking at is dual-fuel. But then I would have to buy a cylinder of MAPP.
There’s two types of professional tools to install rivet nuts. One threads in and pulls up on the nut, the other pulls the nut as it threads in. For home repait - use a bolt & a bunch of lubricated washers.
I’ve considered rivet nuts. That might be another option, though I suspect I’d get more secondary use out of a torch head than a rivet nut tool. I’m a bit concerned that the hole behind the nut for the caster is bigger than it should be for a rivet nut. I obviously didn’t get the chance to drill it myself. I’ll measure the hole and try to figure out if it will work with a rivet nut for the appropriate bolt size and go on from there.
Another option that occurred to me, if you can’t get a nut to hold securely …
Is there enough depth before you hit the ‘disc’ to use a fat piece of dowel as a plug ?
If so, you could taper the plug a bit by sanding it, and/or epoxy or screw the plug into place in the leg, and then drill the wooden plug for a T-nut into which you can screw the caster ?
You could even punch out the disc if need be, in order to get some depth for a ‘stout’ enough plug.
But a welding shop – if there’s one anywhere near you – is a pretty good option
Not a bad idea. Actually, I guess I could cut a disc of plywood the same size as the ID of the leg, put a T-nut through the center, and then glue/screw it into the bottom of the leg. It would take away 1/2" of the dept, but the disc of metal is recessed about that much anyway.
Brazing should make for a satisfactory mechanical result. But the temperatures needed will wreck whatever finish is on the leg. Moreover, be careful if the metals are zinc plated. Zinc fumes will arise and are toxic enough to make you quite sick if you don’t take appropriate precautions.
A wooden dowel is a good idea. I don’t think a plywood disk would have enough strength. There will inevitably be all manner of weird load directions applied, and plywood has poor resistance to some loads. You could laminate up a dowel from a stack of plywood disks. That may well provide enough strength. Just laminate the t-nut into the stack with an appropriate relief in one of the disks. I would want the dowel to have a height at least the same as its diameter.
The plug sounds like your best option but, what size is the thread and the hole in the bottom of the leg?
A few other ideas:
Maybe a dumb question, but is the top of the tube open, or could be opened? Could you feed a nut down from the top?
If not brazing, could you tin both surfaces with one of the new no-lead copper pipe solders and sweat the parts together?
If the hole is too large for a rivet nut, what feeding in a toggle bolt, more typically used for hanging things on walls.
If the thread is about 1/4-20, you might be able to retrofit one of those plugs used with “feet levelers”. the plugs I’ve seen are for square tubing for a desk leg, so you’d need to file a square hole. (The automobile industry uses something similar for adjustable hood bumpers.)
The top of the tube is not open, so I can’t feed a nut in from the top. It’s bent to form the top of the cart.
I might be able to sweat the nut on, but I suspect that brazing would be stronger.
The caster uses M8-1.25 thread. I could see if I can find a toggle that would work. Might need to enlarge the hole in the metal disc a bit. I could run the nuts up to tighten against the disc.
Thanks, Francis_Vaughan. The metal disc in the tube is recessed about 1/2" from the end, so I don’t have a lot of space (unless I try to cut out the disc itself). I was thinking I could use a 1/2" thick disc of plywood with a T-nut driven from the back. Fit it into the tube and then drive a couple self-tapping screws through it into the metal disc. The metal disc would give it strength and keep the T-nut from backing out.
How about filling the end with epoxy? Glue a nut in place (a T-nut would be a good option) to position it and seal it against the tube, then just fill the remainder with epoxy. It’ll cement itself not just to the disc but to the walls as well. Sort of a one-shot deal, though.
That’s what I’ve been thinking – although it would be very nice to see an actual photo of the tube and disk. A nut set in a disk of JB-Weld, adhered on its sides as well as one face, is not going to break off easily.
Even if you can, is it cost effective to? If it’s this type of cart they go on sale at Michaels and/or Joann Fabrics at least every other month for $30: it’s on sale at Michaels now. I think Sam’s Club always sells them for $30 when they’re in stock, and Target also sells one (but it’s round for some reason) for that price point too.
It’s a much nicer (all-metal) cart that might be compared to a mail cart at a business. As I mentioned, we might just give it away when it’s repaired as we haven’t been able to use it since it broke last year.
I’ve had some great suggestions, but I have continued to favor brazing because (a) it would keep all the casters uniform in position and method of attachment, and (b) a simple torch head would be something I would probably use again for projects in the future. Furthermore, if the braze doesn’t hold, I can always drop back and try one of the other suggestions, all of which will require a bit more effort or modification.
