First TIG project and questions arising...

[Misterg]

I got myself a Sherman 206P AC/DC TIG set before the drawbridge came up at the end of last year, but unfortunately, the pedal didn't make it through. I've made a pedal mechanism which seems to work very nicely and want to make a cover to go over it. For a bit of practice, as much as anything else, I decided to try and weld one up from 3mm aluminium.

I did a couple of tests but welding 3mm:

Top one was a slightly hesitant 125 amps, bottom 130 amps with slower travel & pedal to the floor for most of the weld.

(AC 80Hz, 32% EP, 2.4mm 2%La tungsten, 6LPM Ar in each case)

Back sides:

Q1 - what is "normal" for TIG welding this thickness ali? Should there be penetration visible for the full length of the weld?

I cut a section from it, and while there was a definite groove that I wouldn't like in anything structural, I decided it was good enough for the job in hand:

Sides tacked together:

Welding the first seam went OK (IMHO!)

Blew a hole in the second (trying to be more bold and get better penetration|)

I thought the first side wasn't too bad inside:

Second side looked decidedly crummy.

Bit (quite a bit) of filing:

Fit-up poor in both cases.

Continued...

 

[Misterg]

...continued

For better or worse, I'd overlapped the sides with the top.

I tried just running over the corner, which gave a very nice, easy, joint, but there was almost no penetration or strength to it. I had slightly better results concentrating on the side, and just nipping the top, but still not convinced it has much structural integrity.

Q2: Is there a correct way to weld an overlapped corner?

Anyway, I went for it:

There's penetration through the side, but none through the joint - what should I have done?

Anyway, that old adage about 'grinder and paint..."

I needed to spark up again a couple of times to fill some low spots, but the metal went in beautifully - I absolutely love the process!

Reasonably pleased with progress, but more questions to answer!

 

[Barking Mat]

I'm no pro, but fair play, looking good!

Must get some more time in with the tig.

 

[Pigeon_Droppings2]

My 206p is still sitting in the loft...I'd be happy with what you achieved as a first project...well done.

 

[Misterg]

Thanks folks...

Any thoughts on the welds at the top of the first post:

'Good enough for government work', or 'must try harder'?

Thanks,

Andy

 

[addjunkie]

Id say more amps and travel faster. But the result is looking really good above, what you using to polish grind down the welds

 

[Munkul]

To use the amps you'd need to blow

Thanks folks...

Any thoughts on the welds at the top of the first post:

'Good enough for government work', or 'must try harder'?

Thanks,

Andy

To use the amps you'd need for full penetration, you'd have overheated those tiny little strips and melted them into some nasty shaped blobs. Sometimes physics is your enemy.

In that case, you'd have been better grinding a bevel on the edges - you'd have god full penetration that way.

 

[Misterg]

Id say more amps and travel faster. But the result is looking really good above, what you using to polish grind down the welds

Thanks. I got rid of most of the metal with files and a belt sander, then went over it with 120 grit on a DA sander.

 

[Misterg]

To use the amps you'd need to blow

To use the amps you'd need for full penetration, you'd have overheated those tiny little strips and melted them into some nasty shaped blobs. Sometimes physics is your enemy.

In that case, you'd have been better grinding a bevel on the edges - you'd have god full penetration that way.

Thanks very much.

(FYI - The little strips were sawn out after welding - they weren’t welded like that.)

 

[Munkul]

ah I see well you could up the amps then.

 

[Misterg]

I didn't intend this to be a build thread, but may as well finish it off...

The original plan had been to mount the gubbins in a diecast box, but I thought I could do better than that:

Base from 5mm ali extrusion and sides bent up from 2mm sheet:

It was somewhat challenging to tack the 2mm sheet to the 5mm base without melting through the thinner piece (given that I wasn't using a pedal). Blasting the 5mm with amps until I had a puddle, then walking it over to catch the 2mm and quickly dab it with filler seemed to work, but resulted in quite big tacks that weren't very pretty.

I'm sure that tacking it to the base would have been enough, but for the practice I tried to fillet weld the inside - I used a slow pulse for this, and bits of it eventually went well (not until I'd deposited goose-poop over much of the area though). It seems that if a big fillet builds up (or is there because of a tack) I struggle to reduce it again. I would really have appreciated a working pedal for this bit...

Internal corners are hard! (I think I need to learn to weld left handed as well.)

I only welded up one of my tapped holes by mistake.

For more practice, I went over the outside seam - It's not coming off!

Being consistent is hard!

I did go over the welds again to make them look (a little) more purty:

Settings used (for posterity).

I knocked the lumps off with the belt sander as before, then went over it with 125 grit on the random orbit sander and put the gubbins inside:

The switch is pressed by a plate on a second set of pivots before the toothed sector moves and turns the pot. (The pot looks weedy, but it's a sealed, long life industrial one rated at 1,000,000 cycles.) The return spring for the plate is the black one at the top of the photo.

After that, just had to put the lid on from part 1.

It works very well (IMHO) - smooth & the welder (Sherman 206P) fires up at whatever minimum current is set (5 amps).

I'm going to keep practicing, but any hints or tips gratefully received.

Andy.

 

[tom2207]

what did the gubbins come out of , handy looking springs set up.

 

[Misterg]

what did the gubbins come out of , handy looking springs set up.

Thanks - I found the gubbins in the shed - just had to scrape the swarf off

The springs are piano wire wound around a mandrel (the black one is a bicycle spoke because I didn't have any more thick piano wire).

(The 'arm' is a piece of 6mm ali plate cut roughly to shape and welded to a turned shoulder on a piece of ali round bar. The bar was then chucked in the lathe to turn the OD the arc true, clean up the welds, and put a hole through for the spindle bushes. The teeth are a length of T2 x 6mm timing belt wrapped over the aluminium and doubled back on itself around pins in slots in the arm. It meshes with an 18T timing belt pulley on a short spindle running in a couple of ball bearings in the welded ali bracket. The pot is connected to this with a short length of silicone tube. I had bought a flexible coupling for this, but it was too big & bulky. Other brackets are cut from 6mm ali angle with brass bushes pressed in - If you want details, just ask... )

 

[tom2207]

Very clever ,, well thought out an a fair sprinkle of ingenuity , looks like its been a great project with a very use able end result.
Thanks for the details and the pics.

 

[Misterg]

Thanks very much!

 

[daleyd]

Nice work Andy !!

 

[Barking Mat]

Superb work.

 

[chip]

nice job pal

 

[northwest]

If I may, you need to put a small wear plate under the spring ends where they rub against the ally housing. I could make all sorts of suggestions including heat treatments, the whole nine yards. Instead, I have often found that the semi-tempered steel of packing bands works just great as a rubbing strip, cut a bit off with a pair of snips and stick down with a glue of your choice and you are all set.

Or you could go down the Titanium wear strip route........

 

[Misterg]

you need to put a small wear plate under the spring ends where they rub against the ally housing.

A valid point, thank you!

(Don't have any titanium knocking around, so banding strap it'll have to be )