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quick welding question


callum

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slightly off topic, but there lots of people iwth lots of welding experience here and something i dont understand.

was welding some threaded rod this evening, two bits of m4 side by side, for a model at uni.

i thought i'd do it at home rather than filling out 16 health and safety forms and waiting ages to do it at uni.

was just going to tack it together and wound the current down (arc welder) from what i had been using for welding 2mm steel...

blob, blob, drop i'd managed to cut it in half by mistake and had barely touched it. i managed to weld them together buy being ultra delicate and not without chopping two little end bits off though. it also looks really carp.

is there something odd about threaded rod? really carp heat distributor or something, or made of poor steel? was using the 1.6 sticks i had been using on the 2mm sheet steel, i thought i would have been able to turn it up a bit, not have to turn it down and still be able to do lightsabre impressions.

i'm just kind of learning to weld so anot at all experienced, but have welded up plenty bolts and captive nuts before without fuss.

i think i'll stick to the uhu for this stuff though.

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Threaded Rod is used extensively in the construction industry, i.e. suspending pipes from the roof etc, if you have got some of that then typically its monkey metal.

Usually (but not always) threaded rod sold in 1m lenghts is decent 8.8 grade, the 3m stuff is just carp.

Was it Zinc coated? Thats not going to help either.

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Threaded Rod is used extensively in the construction industry, i.e. suspending pipes from the roof etc, if you have got some of that then typically its monkey metal.

Usually (but not always) threaded rod sold in 1m lenghts is decent 8.8 grade, the 3m stuff is just carp.

Was it Zinc coated? Thats not going to help either.

hmm, no idea of its origins, nicked from the pile o' scrap in the workshop. its pretty dull in colour so either not bzp or really old. it seems reasonably soft, so perhaps as you suggest, just cheap carp.

thanks for the info at least it seems i'm not (tooo) ham fisted with the welder.

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hmm, no idea of its origins, nicked from the pile o' scrap in the workshop. its pretty dull in colour so either not bzp or really old. it seems reasonably soft, so perhaps as you suggest, just cheap carp.

thanks for the info at least it seems i'm not (tooo) ham fisted with the welder.

Mr Warne "Warne-O-Matic CooooCoed Welder Extrordinaire" will be along I'm sure soon, ...

......so just be patient :ph34r:

I'm just go and go and hide over here.......................

peek-a-boo.gif

Nige

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I suspect ......

Disclaimer

I'm not holding myself up as any kind of welding expert, just as someone with a bit of knowledge of the underlying physics. :)

......that it is a mixture of the problems outlined. Remember that when heating sheet, the heat will be dissapated in all directions so the effective volume to sink the heat is very big compared to a rod, even if the rod is twice as thick.

The residual zinc on the surface will burn, further increasing the temperature and contaminate the resulting weld.

If you were to clean off all the zink around the area to be welded and use a very low power, I suspect it would be fine!

Si

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CooooCoed

eh?

so...thorough cleaning, followed by decrease in power + increase in skill = success

anyhoo, its now sitting amongst bits of balsa card and plasticine. to top it off when it got assembled in the model i realised, that as is so often the case, i'd made it the wrong way round, with snotty welds which should have been on the bottom sitting proudly on the top....ho hum

thanks for the input si, the singular dimnesion of heat dissipation vs 2 dimensions with sheet was kind of what i was thinking, but wasn't so sure it would have such a marked effect.

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