[nick7251]

This may seem like a dumb question to some. I can't say too many details about the project as it is subject to confidentiality. For my application it needs to be strong and hold up to wind (105mph 3 second bursts) and snow loads (40psf). The plan is to have j bolt anchors in concrete. Then I can bolt the baseplate down. Similar to a light pole, or larger basketball hoop.

Just wondering best practice for welding the 6x6 tubing to the base plate? Should I cut a 6x6 square hole all the way through the baseplate so I can weld the inside of the tubing to the base plate?

If so... Should I push the pole all the way through to be flush, or stop short from flush so I can be lap welded on the inside and the weld won't protrude beyond the bottom.

At first I was thinking of a solid base plate and butt welding the pole to it. I like the idea of cutting the hole in the plate to receive the pole and have a lap weld on the inside. Seems like it would be stronger. Just want confirmation. I'll ask welding process questions next.

[JayWal]

The way it was explained to me, as long as your fillet weld is the same size, or exceeds the wall thickness of your tubing then that's all you need, your tubing is now the weakest link.

I'd make a flat solid base plate, and butt the tubing square onto it, and depending on the process, wrap a 3 pass weld around it. Your tubing will break before the weld if done right.


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[Poland308]

Snow load and wind are going determine how big of a base plate you will need. The direction the loads are applied to the pole will change where and how much it will need to be welded. If you weld the tube directly to the plate I’d recommend leaving a gap between the two parts. This will help mitigate warpage, ( pre stress the base plate) ensure full penetration and help avoid stress from shrinking. Base plate thickness and size will determine the amount of side load stress.

[nick7251]

Snow load and wind are going determine how big of a base plate you will need. The direction the loads are applied to the pole will change where and how much it will need to be welded. If you weld the tube directly to the plate I’d recommend leaving a gap between the two parts. This will help mitigate warpage, ( pre stress the base plate) ensure full penetration and help avoid stress from shrinking. Base plate thickness and size will determine the amount of side load stress.

How would I "pre stress" the base plate? I assume you don't just mean pre heat it...

[Poland308]

If you bolt the plate down to something with a few washers under the center you can pre bend it. Leave it under tension while you weld it to the post.

[nick7251]

If you bolt the plate down to something with a few washers under the center you can pre bend it. Leave it under tension while you weld it to the post.

Ah, thank you. That is a good idea. Now to figure out what to bolt it down to. haha

I'd like to know if there is any draw back to doing the hole in the plat, and welding it flange style like pipe work?

[LtBadd]

I'd like to know if there is any draw back to doing the hole in the plat, and welding it flange style like pipe work?

Only drawback is it would be more work, which may or may not be an issue depending on your circumstances, I would set the tube back some (stop short from flush as you wrote in your original post) so a fillet weld could be done on the back side , and then weld the top as well

[nick7251]

Thanks for the responses. I gather that either method would work. I was hoping you experts would tell me something like: "absolutely do not do it that one way". haha.

So, Which method is perceived as stronger in this situation? The extra work is worth it if the end result is stronger/safer. Also it wouldn't be too much extra work for me because I am having the 3/4" plate cut at a local shop. Maybe just extra cost in more cutting. There is some advantage of doing the open tube concept on the bottom to pass electrical through if desired. Still waiting to hear back on that one.

Some more background: I will be welding with a Hobart Handler 210MVP. It is a great little unit, but I do worry about getting good enough penetration into the 3/4" base plate, so inserting into the base plate and doing the fillet weld in my mind seems stronger. But like previously said if welded right the week point becomes the 1/4" pole, which is plenty strong for my application.

[Poland308]

I’ve done it both ways. But I only do the hole method if there’s a reason too,( like you mentioned wires).

[sbaker56]

Can you get a roll of .035 Lincoln 71M outershield? If not you'll still be fine mig welding it, but you'll probably want to be up in the globular voltage range, which means welding it in the flat or horizontal position.

I have the exact same machine, and I've done a lot of cut and etch tests as well as weld bending. You can crank it up to around the chart settings for 1/4 or 3/8 and burn it in on a single pass, or you can drop it down a little and run a 3 pass weld thus making sure you get adequate fusion into the 3/4 plate. Either will work what matters is how comfortable you are with the settings and that you're not too cold to melt into the thicker base plate. Make sure if you do a multi pass weld you don't let the piece get too absurdly hot, a moderate preheat would do you good, but you don't want the whole thing glowing when you finish so let it cool a little in between passes.

As was mentioned as long as your fillet is the same size as as the wall thickness on the tubing and you don't have any discontinuities your tube will be the weak link, and probably the bolts as well. So what I like to do is figure the most likely causes of failure when determining how to weld something, In this case the most likely problem would be lack of fusion into the much thicker base plate, so you just need to ensure that.

[Oscar]

Can you get a roll of .035 Lincoln 71M outershield?

Another good option is Kiswel 706M 035 diameter metal-core wire. It can go into spray transfer at about 160A with a 90/10 Argon/CO2 mix for a hot weld that really drives into joints, and the beauty about it is it doesn't need heaps of voltage to do so. I'll have to check my notes to see the operating parameters again, but they were very favorable. The downside is that you have to run it in the flat position due to the very fluid puddle.

[sbaker56]

Can you get a roll of .035 Lincoln 71M outershield?

Another good option is Kiswel 706M 035 diameter metal-core wire. It can go into spray transfer at about 160A with a 90/10 Argon/CO2 mix for a hot weld that really drives into joints, and the beauty about it is it doesn't need heaps of voltage to do so. I'll have to check my notes to see the operating parameters again, but they were very favorable. The downside is that you have to run it in the flat position due to the very fluid puddle.

Funny, when you first mentioned it I searched high and low for that wire and couldn't find it, I just tried again and found like 3 sources, guess I'll pick up a roll later.

But yes, .035 metalcore could also be another good way to weld it with a single pass if you can get the gas cheap. I've achieved spray with solid .025 and .030 wire, and 92/8 gas using the same machine although .030 wasn't stable I'm also sure it would've ran better if I had been able to get 95/5 Ar/O2. So I can't speak for exactly how .035 metal core would run but It typically reaches spray at a lower voltage and amps than does solid wire.

[Oscar]

Well the passes is inconsequential, as he could run multiple passes quite easily.

I forgot the first part of the model #: KX-706M is the complete model, which falls under the class of E70C-6M. Being a 70-series wire, its only meant to be ran in the flat & horizontal positions, unless you can run pulsed-spray, then it becomes an all-position wire

But my main point really is that short-circuit vs spray transfer, for a given amperage the spray transfer mode will have a deeper penetration profile due to the small droplets being pinched and propelled at the joint with greater arc energy. It does take more voltage, but metal-core isn't as demanding as solid wire IF you have the right gas mixture. Under very specific conditions, and with a very specific ternary gas mix, I can spray that kiswel metal-core wire all the way down to about ~128A .

[sbaker56]

Well the passes is inconsequential, as he could run multiple passes quite easily.

I forgot the first part of the model #: KX-706M is the complete model, which falls under the class of E70C-6M. Being a 70-series wire, its only meant to be ran in the flat & horizontal positions, unless you can run pulsed-spray, then it becomes an all-position wire

But my main point really is that short-circuit vs spray transfer, for a given amperage the spray transfer mode will have a deeper penetration profile due to the small droplets being pinched and propelled at the joint with greater arc energy. It does take more voltage, but metal-core isn't as demanding as solid wire IF you have the right gas mixture. Under very specific conditions, and with a very specific ternary gas mix, I can spray that kiswel metal-core wire all the way down to about ~128A .

I definitely don't prefer short circuit for fusing to 3/4 plate either, although I'm not sure how easily OP can get different gases. If he doesn't have a WPS or any specific weld size requirements, I would absolutely do multi pass regardless of the method though, even on 3/8 plate I've found a triple pass short circuit weld I'd done on 120v to be stronger than a single pass 1/8 7018 weld, it's just the best way to make sure you have enough material fused into both sides.

@ OP As Jody has said, 1 test is worth a hundred opinions, why not do a sided T joint with some 3/4 and 1/4 scrap and do the old BFH test or a cut and etch to get a rough idea if your preferred welding method is adequate? Since I have the same machine, If you tell me what size wire wire and gases you have or are willing to purchase I can do some experimentation and write up a suggested procedure, but I REALLY don't want to test every option