Thoughts on joining plates welding through holes?

[FlyFishn]

I have a small project coming up where I intend to lay plates together. It is a table for a variable angle miter gauge and/or sled for a saw - which requires the accessories to travel through a track slot. I haven't decided how exactly I want to do it, but the composition of the track will require 3 plates - one laid underneath the track slot and the two sides of the track slot secured to the bottom. Whether or not I want to do a whole plate bottom or just a thin bar with sufficient overlap I am not sure, however I think I can maintain better table flatness and rigidity with a full bottom plate.

To secure the plates I want to drill the top ones and weld through the holes.

My thought right now is to use either 6010 or 6011 rod as they penetrate and have low slag. The arc can keep the metal below building up through the slag building up on top at the same time (I think). I need to be careful of heat because the more I heat the plates the more they will warp. I am not wanting to be super precise - IE I don't need to surface grind the table for absolute precision. However, I want to use straight metal to start with and end up with a straight table.

I thought about chamfering the top plates to create a V on the sides of the bottom of the track slot then filling that with weld. However, that would create a longer heat affected zone = potential for more warping. The other problem is that if the bead is too thick I loose the straight dimensions of the cut steel and have to grind it. The whole idea of forming the table this way with the plates is to keep the straight edges of the plates so the accessories fit nicely and slide nicely.

If I had access to a mill I'd get a thicker plate and mill the slot. But I don't have access to a mill that will work for the task so the alternative is using some creativity with fabricating and material selection to make do. That's half the fun on this one. I will try some miter gauges I have first. Down the road I may make a different one depending on what I want. I also want to look at making a sled - perhaps gravity run (pulled by a falling weight on a cable) or pneumatic (with a long stroke cylinder) for automatic feeding of work.

Ideas?

[CAVEMANN]

What you describe is a plug weld, I 've had guys tell me they'll never hold, but I disagree. I think they will be fine for your use. I personally would go with 7018, I think it will lay in better, you didn't mention how big the holes are, that wil be a concern, you will also need to watch warpage.

[albrightree]

Plug welds are usually best done with mig on light gauge sheet metal, because it puts the least amount of heat in the weld, for less distortion/warpage. Commonly used method in auto body work. Often used to replace body panels ie door skins.

3/32" 6011 or 6013 would be the best choice for stick electrode(unless you have some 5/64" 6013), as they would run the lowest amps, for least amount of warpage. Aluminum backer plates can help with burn through , and warpage also.

Note : many mig welders have spot and stitch settings for sheet metal repairs.

HTH

[BD1]

Mig as stated is probably the best procedure but stick is fine. As for rod, 6010 is DC and 6011 best on AC. 7018 will provide the easiest slag removal.

What is material size and thickness ? Posting a picture would help in determining hole size.

[Meltedmetal]

I think I'd cut the holes in the bottom plate so there is no ugly problem with the top surface or holes to fill with shavings. Just me. I do have a mill but if a single piece table was too big for my mill, I'd probably mill the slot in a piece of flat bar 4" or so wide and construct the rest of the support table around that.

[Kelvin]

I make similar jigs and fixtures for table saws, woodworking and sharpening equipment, etc., and in all honesty (and without actually knowing what exactly you're making) I still think I'd find a way to fasten the stuff together without welding. It'd be a heck of a lot easier to unglue and reposition if and when you oops it on assembly. Even brazing would be preferable to welding since you can unglue a braze joint...

If I did weld it, I would keep the welding to an absolute minimum, and if tacks would cut it, I'd use tacks. I know this is a welding forum and all, but...

[FlyFishn]

What you describe is a plug weld, I 've had guys tell me they'll never hold, but I disagree. I think they will be fine for your use. I personally would go with 7018, I think it will lay in better, you didn't mention how big the holes are, that wil be a concern, you will also need to watch warpage.

7018 produces more slag and the concern that hits me right off the top is slag inclusion in the weld. Building up metal in the hole means pushing up the slag on top and that tells me on 7018 getting through the plume of slag would be a problem. Maybe not?

Plug welds are usually best done with mig on light gauge sheet metal, because it puts the least amount of heat in the weld, for less distortion/warpage. Commonly used method in auto body work. Often used to replace body panels ie door skins.

3/32" 6011 or 6013 would be the best choice for stick electrode(unless you have some 5/64" 6013), as they would run the lowest amps, for least amount of warpage. Aluminum backer plates can help with burn through , and warpage also.

Note : many mig welders have spot and stitch settings for sheet metal repairs.

HTH

Thanks for the comments. OK on mig and the smaller rods. I can get what ever rods - I intend to stock up on small rods anyway. Right now I have only 7014 in 1/16" and 5/64", but can get what ever. I've been looking for small 6010 - I think the smallest is 3/32". 6011 is more likely to find smaller I think. I want to say Hobart makes a 1/16" 7018, but aside from that the smallest is 3/32" elsewhere.

Mig as stated is probably the best procedure but stick is fine. As for rod, 6010 is DC and 6011 best on AC. 7018 will provide the easiest slag removal.

What is material size and thickness ? Posting a picture would help in determining hole size.

See comments above for concerns on slag with 7018.

As for material size and thickness - I don't have the dimensions yet. I am open to any ideas. Overall dimensions would probably end up being somewhere around 15" square on top. But I may increase that with extra supports so I can run longer pieces on the saw. That could end up being a table big enough to make 2-3 foot work piece runs (not saw mounted, would definitely need legs and the saw in the middle). For now I just want a small plate table that is saw mounted.

An idea I have on thickness is the top plate thick enough to have a miter gauge drop in to it completely. This may be around 3/8". However, that is some really beefy plate. If I can keep the assembly rigid enough it would be conceivable to use a thinner plate on top then stack metal to build up the depth of the slot. However, that might be asking too much.

What I can't do is reinforce the table on either side (front/back) of it and block the slot. If I make extensions the slot has to be unobstructed so the miter gauge or sled can travel through.

I suppose I could do the same thing with spacers on the front and back - use angle reinforcement with enough of a block on the ends to get up to the top plate bottom.

If I used the angle reinforcement idea (cross bars, if you will) I could even use thinner wall angle or maybe C channel (if it has a sharp enough inside radius to be nearly a point) to form the track out of.

As for hole size - my thought there was big enough that the weld pool would wet to the edges of the hole all around. I was not thinking so big that I would fillet weld around the inside of the hole and not so small that the rod would have trouble getting down to the base before arcing just to the rim of the hole before getting down to the base. Numerically what that equates to I don't know - and surly would vary by rod size/type.

I need to draw this out so it makes more sense....

I think I'd cut the holes in the bottom plate so there is no ugly problem with the top surface or holes to fill with shavings. Just me. I do have a mill but if a single piece table was too big for my mill, I'd probably mill the slot in a piece of flat bar 4" or so wide and construct the rest of the support table around that.

Good point about the holes on the bottom. That could be done.

[walker]

Just jig it up and clamp everything together, then drill through the whole mess with a 13/64” drill bit, then run a 1/4-20 tap through it. You can use a countersink and flat head screws, or use bolts.

[FlyFishn]

Just jig it up and clamp everything together, then drill through the whole mess with a 13/64” drill bit, then run a 1/4-20 tap through it. You can use a countersink and flat head screws, or use bolts.

You're taking out the challenge of welding it by bolting it. That's half the fun.