Agree with all of this. It does get very heavy, very quickly, but as neither the welder or the tips are water cooled, I only do a few welds at a time anyway. Generally with restoration work, that's not nearly the faff that it sounds. On the whole you can do some welds, tweak the fit, do something else for a bit, and then do some more welds.911hillclimber wrote:Not intending to answer for Barry, just my take having been there on several restorations:
I used to hire my spot welder as cost was so high to buy new.
It came with a timer and the hire shop said that this was the only one to hire because so many got damaged manually 'timed'
I got great consistency from the timed unit. The hire kit came with stacks of arms and electrodes and I needed them all.
The hardest bit was holding the flippin' thing as it was SO heavy.
Worst part was you could easily think you had a good spot weld but in fact you had a very very weak one, just looked good, but that is true of many welds (and welders)
I tend to make up arms to fit whatever I'm doing, and my (second hand) welder came with three sets. I was able to cut one set up and adapt it, and that gives me everything I need. The 'tips' are simply a weird copper alloy round bar, which are cut to length and then a tip profile filed on. I've got a proper tip-shaping tool, but they are quite expensive for what they are. They look as though they should be £25, and are actually £80-90. Does a good job though. I was interested to see on 'MegaFactories: Bentley', that even there they made a point of saying they re-shaped the welder tips every few welds. I was rather under the impression that if running a full-on industrial welder the tips would last for ages. It would seem that might not be the case, and therefore there's no shame in running a welder that requires frequent tip re-shaping.
When I end up in a workshop with three phase, I'll certainly buy a big industrial machine, but in the meantime, the hand-held welder will do just fine. The reason is below ....
The bottom line with any spot welder is that it very much depends on the state of the metal it's welding, and the way that it's clamped / touching. My experience is that all of the time you are welding new metal to new metal, and assuming the fit is good (so you're not asking the welder to actually pull parts together, just compressing two parts that are already a tight fit) and the tips are well profiled, they will produce a very good weld. What I find on restoration work though (and this might just be me, but I suspect not) is that when you try to weld new to old, you often run into problems:
i) The old metal is too grubby (don't forget that both sides have to be perfectly clean, and primed with a true (highly conductive) weld-through / spot welding primer).
ii) The old metal is too porous: lots of sparks, often with the welder burning through the old metal.
iii) (This is the worst one), trying to weld through two layers of old metal to attach one new layer: outer sills on 911's, A-post door seal holders, engine bay seal holders etc. There's always old paint / corrosion / particles between the layers, and time after time the welds just fail.
Frankly, all of the above are going to apply whatever welder you've got. Even if you've got the very latest weld-testing machine, all it's going to do is tell you that weld after weld has failed. Pragmatically, the solution is plug welding. I know from experience that these are pretty bullet-proof once you've got the method sorted. O.K. if you get it wrong, you might end up with a weak weld, but you're much more likely to be aware of it at the time. If you suspect you've done a duffer, simply drill alongside it with a 6mm spot weld drill, and pop another plug weld in.
So, although I'd love a big commercial machine, I don't think that in the real world it would gain me a huge amount of time, as many of the welds you might imagine doing in reality probably wouldn't be sensible anyway for the above reasons. The advantages for me would be the lighter 'business end', the various programs, water cooling and the variety of arms and accessories.
As for timer, yes most of them have them fitted, and for good reason. I certainly use my timer.
Oh yes, when you look at a lot of bigger spot welders (like the Tecna's), many of which can be adapted to run on single phase, the single-sided gun looks very tempting. My experience is that these are absolutely lethal. They produce incredibily weak welds as there's no real clamping, and of course the return current is not directly behind the weld as is normally the case. Even Spanesi's in Chatham (who are big importers of Italian machines) say not to trust these, and to back them up with plug welds. Shame, as they would be very useful indeed if they were strong (kidney bowls, bottom and front seams of outer sills etc etc).
Oh dear, I've done it again: got a bit carried away .... I'll get me coat
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