holes for plug welds ?

[Paul-n]

Hi all

Is there a rule of thumb for the holes needed for plug welds ?

I have 2 tubes I need to join they are 1.5mm thick about 1.5" in diameter , I have a 3rd tube also 1.5 mm thick that is a cosy fit inside the other 2.

So the plan is to cut the inner tube to say 3" and plug weld it to both tubes first then do tacks around the centre joint till they are welded together.

What is the method used for a plug weld ? rods are 2.4mm

Start in the middle of the hole get the weld going and then move to the edges ?


regards Paul

 

[GeorgeB]

Start in the middle of the hole get the weld going and then move to the edges?

Yes, that's my approach, too. I start with a hole of 1cm. It may seem large but if you go any smaller (minimum 8mm) I find it's more difficult. I'd use a rod of 2mm- 2.5mm.

 

[Drains]

Paul, you can go even bigger - then you don't weld in the middle, but do a small donut shaped weld. Perhaps not necessary with 1.5mm thick stock, as that will weld up easily enough, especially with a 2.5mm rod - careful you don't burn through!

 

[GeorgeB]

Paul, you can go even bigger - then you don't weld in the middle,

Are you referring to the hole size when using an arc welding rod? I find 1cm to be more than large enough to avoid touching the edge when using a thin arc welding rod. I haven't tried with a MIG welder but, due to the bulky size of the torch head, I should think it's more difficult to get the positioning spot on.

 

[Wozzaaah]

George, you don't put the entire shroud in the hole, just the wire which is usually either 0.6 or 0.8mm diameter so I'd say would fit quite easily inside a 10mm diameter hole.
If plug welding using a mig the norm is to use a hole of maybe 5-8mm diameter, no bigger.

Paul, what I'd do is drill 4 holes at 90 degs, as big as you like, plug weld them leaving a decent gap between the two tubes then run a bead round the gap filling it and fusing all 3 pieces at the same time.
Don't butt them up as the weld will sit a bit higher and probably won't penetrate to the sleeve.

 

[Paul-n]

Hi all

Thanks for the replies , proceeding with caution.

Paul