[How-To] Fill (weld) holes in 1" steel plate

[keeena]

Was wondering if anyone had tips or setting recommendations for filling holes in 1" thick steel plate. Holes vary in size; largest is about 5/8" or 3/4". It's a mild steel workbench/fabrication table. I'd like to fill these holes up because their locations would interfere with fixturing holes I plan on drilling. Since some of these filled holes could end up being partially drilled out I'd need to tie to the full plate thickness vs. using the plug with a shallow weld on top. Not rocket surgery nor a critical part, but figured I'd ask before going the trial & error route.

• I assume wire feed would be the best process. Would GMAW, FCAW, or dual-shield be the most appropriate?
• Settings? Machine is a MM252, 28v (38v OCV) and up to 700ipm.
• I read that it can be better if welding from both sides (e.g. half the depth from each side). Accessing the bottom side in my case would be a bit tricky; would have to flip a ~1,200 lb plate of steel which is welded to 300lbs of table frame. But if its far better to tackle from both sides: let me know. Don't know if this would be practical to weld overhead, but if yes: tips?

 

[Janderso]

I'll be watching for the responses. This is a bit tricky.
I can see why you would want to keep the heat down to reduce the chance of warping the plate.

 

[RJSakowski]

I would think that accurately positioning a MIG wire 1" down a 5/8" or 3/4" would be tricky. I couldn't do it.

I would consider tapping the holes for a larger bolt and inserting a bolt. Cut it flush or slightly below and lock it with a surface weld. Grind flush and you should be good to go. Bonus, no warping issues. If you don't want to tap, interference fit plugs should also work.

 

[keeena]

Hey Jeff - yeah, the top/bottom approach would probably be better from a distortion standpoint.

Pretty sure I saw a post a while back that you were looking to upgrade a welding table yourself (or maybe found a bigger piece of plate); you tackling a similar project?

I did a small fixturing table to first get an idea of how much work this large bench would be. TBH I'm a bit on the fence; the smaller table was more of a PITA/time consuming than I expected and accuracy not quite where I wanted. That said: very glad I did it because I learned a bunch of things which was the whole point. I didn't do a write-up but here's a pic part-way thru. I feel like there's already info on these builds (this vid is more/less the approach I followed), but if you're interested in more let me know.

 

[NCjeeper]

Since you are just plugging holes as you say, I would put a copper backer under the hole I was welding and go to town welding it up.

 

[keeena]

I would think that accurately positioning a MIG wire 1" down a 5/8" or 3/4" would be tricky. I couldn't do it.

I would consider tapping the holes for a larger bolt and inserting a bolt. Cut it flush or slightly below and lock it with a surface weld. Grind flush and you should be good to go. Bonus, no warping issues. If you don't want to tap, interference fit plugs should also work.

I was hoping it would just be a matter of using an extended stickout at first and give 'er all she's got.

I wanted to avoid using plugs since the filled hole may end up overlapping a newly drilled hole. But I totally agree that if this wasn't the case: a plug would be easiest for this situation.

 

[Just for fun]

I would do like NCjeeper said a copper plate and start welding. Maybe not all at one time, weld for a bit let it cool and go at it again. Can you get to both sides for welding? If so, it should be a piece of cake to get a good job.

The plug idea is good also. If I did the plug thing, I would plug weld the top 1/4" then it wouldn't be a problem with the new holes.

Tim

 

[keeena]

Can you get to both sides for welding?

For most holes: yes. But as stated: either means flipping 1500lbs of table upside down or learning to overhead weld. I generally understand principal and that certain filler materials are better suited...but as a noob it frightens me thinking about molten metal wanting to fall on my face .

 

[graham-xrf]

I have to agree about not trying to flip over a 1" thick thing to casually weld onto the underside.
If one doesn't care about the underside remaining with a fat bolt head, then maybe tap the hole, fit a bolt from under and tighten.

If the bolt-plug is made with the last 1/8" chamfered to form one side of the standard weld vee, then countersink the topside a little to provide the remainder of the vee. You can make the weld quite small, All it's going to do is lock up an already tight bolt. Add permanent join LocTite or epoxy on the threads if you like. You might even make it topside flush, and leave out the weld and it's distortions and stresses altogether. The threaded anchorage, and lack of ability of the plug to rotate, more or less guarantees that you could drill a new hole through, even intersecting much of the plug.

The special case is if the new hole amounts to only a small re-location that takes out most of the plug bolt. Even then, what is fixed into the thread shapes would probably still remain in place. A tiny weld onto the side of the bolt-head underneath guarantees electrical conduction to the plug. I have noticed that LocTite can distribute in threads so evenly that it makes an electrically insulating layer, so omit it if this is a concern.

.. is what I would be thinking.

 

[Just for fun]

I have been welding a long time, I'm not a professional and I can't say that I am the best at it. I agree about the overhead welding, I have done it and it turned out ok, but I don't like it.

I guess the only problem with not welding the bottom would be if you needed a flat surface on the bottom.