Butt weld panel fit - missing a trick?

[jb2000]

I notice quite a few people doing butt welds and the panel fit is not "daylight proof". The problem is compounded by the cutout 'ole usually being somewhat imperfect.

Those wonderful zirconium flap discs?

Buy a drill mandrel to suit the flap disc hole - 14-16-22mm etc.
Fit it into a 1000-1300rpm cordless drill - not a mains drill or angle grinder.
Lay it on your leg and with the lower RPM you can shape that patch with incredible precision to get a ridiculously perfect fit in the most bizarre hole.

Do not try it with an angle grinder, edge on it will throw 0.8-0.9-1.0mm auto body steel around the room, too fast, too aggressive. You want a slow cordless drill, the zirconium flaps are quite superb compared to hit-n-miss knibblers & snips in rounding, dipping, shaping. Very quick n easy, just watch the heat on your fingers (& panel).

Found out the car uses 0.8mm skin, but 0.7mm wheel arch liner - now that is annoying because it is the one area where you get pin-worms which means it is very easy to literally "bang" a 1/4" hole before you blink. If the welder will not weld, it may not be the tool, it may not be the user, you just need to cut a bit further :-) How true it is "if you can see an inch you have six to weld".

 

[Coo]

Any pics to show what you mean ?

please

 

[Delgado]

Why not just use a Flap wheel on a drill/die grinder/angle grinder?

 

[troppo]

I`ve always tried to make the patch before i cut out the damage. I probe to find the extent of the damage and make a patch to cover that and more, then scribe around the patch and cut INSIDE the scribe line and then trim the patch to fit with a flap disc. Unless you`ve got mega rust damage in which case you buy patch panels and then you still scribe to fit.

 

[jb2000]

Flap wheel on a grinder would be fine too.

Dropping RPM via a cordless drill or speed control to about 1000-1300rpm makes the flap disc a superb tool for rapid yet very precise patch shaping.

It comes down to how accurately you cut the hole.
Hand nibblers are very good - but double wall areas may prevent clearance for the jaw on the rear.
Drill nibblers might be better - if the clearance on the rear is less, but they need a large hole for access.
Dremel are good but hard to stabilise - you absolutely have to use reinforced cutoff discs not the exploding junk, about £8 for 4-5 from Dremel delivered (!) or a mere £8-12 for 100 from China. The China ones have the reinforcing mesh miss-applied quite often so 30% junk, 40% usable, 30% quite ok - cost wise you save a lot.
Angle grinders need a speed control - they are easier to control than a dremel which likes to climb out too much for my liking.
Cordless drill with a dremel-copy reinforced disc is good - it has enough weight to give stability from climb out although a side-handle would be good.

Air cutoff tools seem really attractive, the discs are 3" so last longer and fibre reinforced, they are smaller so with a worn disc can get into the smaller places. A dremel is a good backup but their consumable prices remind me of colour lasers, £80 for the printer, £110 for the toner 1000-1600 pages & £100 on top of that for the developer drum (!).

I think we should ban car makers from using 0.7mm steel, it pinholes too easily. A note about Japanese cars (Honda, Mazda, Toyota), they seem to be using a very thin paint around the outer inside edge of the wheel arch with single-sided zinc coated steel of 0.7mm, the zinc being on the inside of the arch. That thin paint just lifts and flakes after a few years and there is bare steel. Likewise some are using very few spot welds on the upper part of the arches and relying on the bonding sealant further up on the arch. Well worth examining this area on any car (including Ford/GM) much earlier than people used to. I believe stone chip protective paints are overcoatable and relatively easy to remove, might be worth using. The stone protected chip area ends a good 3-inches or so before the outside.

Cars like RX8 appear cheap, but are being plagued by rust problems - Ford/GM made it legendary often from multiple sheets of unprotected steel just spot welded. Disposable car industry with non disposable prices.