zzr1100rick2
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| posted on 3/3/07 at 11:47 AM |
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welding to mot standards
Hi can anyone help iv got a transit to weld and
was just wondering if there is a web site that
says what is acepatable or can any one tell me
also would you underseal it before or after its been tested cheers Rick
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nitram38
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| posted on 3/3/07 at 11:54 AM |
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What part are you welding?
Most plates on structural parts have to be seam welded. (this includes sills on monocoque cars)
Whereas, wings and things like battery trays can be spot welded.
If the examiner failed it on a previous MOT, best to leave the underseal until after he has seen it.
[Edited on 3/3/2007 by nitram38]
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mark chandler
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| posted on 3/3/07 at 12:00 PM |
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I,ve seen some appalling 'MOT quality' repairs by some garage's I do not believe there is a standard as such.
As the previous post if its structural then you need to seem weld, ie all edges of the patch plate, if its just filling a hole (transit bonnet edge,
wheel arch) then you can tack weld and fill.
Say you have a structural hole you do not have to cut out the area, its okay to simply plate over, although obviously a better job is to cut out the
rot, step the edges and weld a flush plate.
Once welded, paint then MOT.
Regards Mark
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zzr1100rick2
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| posted on 3/3/07 at 12:42 PM |
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its gone on sill under side door step and rear panel under / behind bumper
think i will seam weld it where possible althou its more than a foot from suspension point
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BenB
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| posted on 3/3/07 at 01:05 PM |
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Did an MOT welding job on my Micra where the sill had gone... Seam welded it, painted it but left the underseal off until after MOT so they could
inspect the work properly.... They were perfectly happy with that...
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mad4x4
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| posted on 3/3/07 at 03:12 PM |
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All chassis welds need to be seam welds with good penatration into both parts (plate & Chassis).
Repair has to be welded onto good metal no point in welding a plate onto rust. (yeah but some people do).
Tip use thick plate to patch this 2mm plus. This will be able to take the heat where a thin bit of plate will melt.
Don't try and cover a postage stamp hole with a bit of metal the size of a postage stamp. Grind round the hole and make the plate big enough to
reach good metal this may need to be 6" square if thats the case thats what it needs.!
If the weld looks good & is good then the MOT tester should accept it. I would at minimum paint it to protect the bar metal. before presenting it
to tester, I usually under seal over patches no probs.
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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Simon
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| posted on 3/3/07 at 04:37 PM |
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A friend boorowed my welder as his Merc van was rather rusty - read both sills, doors bonnet.
He bought a load of sheet and seam welded the lot straight over the old (cut the crap out).
You can clearly see where it's been welded, but it's strong and passed. So....
ATB
Simon
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Peteff
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| posted on 3/3/07 at 05:23 PM |
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Disconnect your battery first.
I leave mine bare till it's been seen then zinc it and paint or underseal with bitumen. If it's for someone else I let them paint it  I
use 18g or 16g because it's easy enough to beat into place if it lifts due to the heat yet thick enough not to blow away. Fetch all the paint
off where you are welding, bend it to shape roughly before you start and tack the corners.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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britishtrident
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| posted on 3/3/07 at 07:26 PM |
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Always use the same thickness as the panel you are repairing.
Where you are replacing/repairing at a point that was originally spot welded --- for example the bottom seam of a sill you can puddle weld through the
panel with a MIG but you must at least a number of good puddle welds equal to the number of spot welds. Just stitch welding at he edge every inch or
so is not good enough.
Where you join at a point that wasn't originally a joint you must seam weld.
Somewhere out the web is a site with instructions on how to produce really good puddle welds using an alloy backing block as heat sink to prevent
burning a hole.
[Edited on 3/3/07 by britishtrident]
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froggy
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| posted on 3/3/07 at 08:52 PM |
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welding repairs can be as good or bad as you want to do them as a tester cannot remove any coating applied to a repair but would have to make an
advisory that the quality of the repair cannot be inspected. 
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