Hawk1061

Since I have no experience yet, I'm looking for advice regarding spot welds and drilling them out.

Is it best to use a standard metal drill bit? Or is there a specialized bit I should use?

If using a bit, do I simply find one that is slightly larger than the weld and go through both pieces of metal? Or do I drill out the weld on the 'junk' half and try to not drill completely through the part I want to re-use from the donor?

Once the donor part has been removed, how do I go about attaching it to the vehicle? Seems that if I lap weld the donor part I'm asking for moisture/corrosion to start between the two pieces... something I really want to avoid. So what's the trick to avoid that issue?

Thanks,
Steve

oldsbucket

as far as paint use weldable primer in the weld areas but its a no win situation you are going to burn the paint its just less exposure with the primer and a dp primer elsewhere.
use a spot weld cutter made for this purpose if used properly you only cut through the first layer which leaves something to weld to on reassembly a plug weld vs. triggering a hole up much neater.. but if you have a hole to fill i keep a small piece of copper plate that backs up the weld and keeps the metal from falling out when i can.
after wards use seam sealer on the joints and primer over

oldcutlass

There are a multitude of bits for drilling out spot welds from inexpensive to expensive.

http://www.bing.com/images/search?q=...it&FORM=RESTAB

ziff396

You can use a regular bit but is quite tricky and you will end up going through both pieces. Do use one of the spot weld cutters already listed. Cost is more, but well worth it in the long run. Either way, it still takes a lot of time to drill out all of those pesky things.

oldsbucket

i center punch each weld first. i have also drilled a small pilot hole to keep the cutter in place if i having problems with that

Lady72nRob71

Use the special spot weld drill bit - you will thank yourself later!

Hawk1061

Thanks for all the responses.

Ok, it makes sense to get a specialized spot weld drill as opposed to using just a drill bit, I'm sold. For those of you with experience, can you recommend a specific brand/model that you've had good success with? I'd hate to buy one only to find there are other better ones... is cost a measure of quality (the more I pay the better the bit)?

Regarding the avoidance of corrosion, how did the factory get away with it when they spot welded these cars originally? I know I see seam sealer on all their joints, was that all they did? And if seam sealer is that effective at preventing corrosion when spot welding, why do people seem to recommend butt welding instead of lap welding? Seems to me if seam sealer is effective with spot welding, then shouldn't it be just as effective when lap welding?

Can I use high temp paint between the two mating surfaces and then scuff up the area where I intend to weld? That way the high temp paint should not burn off and most of the area would be protected. Then add a seam sealer (can anyone recommended a quality brands based on your own experiences) and finally prime.

Hope these aren't stupid questions, I just am learning and want as much info before I start.

Thanks,
Steve

coppercutlass

Keysco makes a killer spot weld drill bit. The spot weld drill is very expensive and not worth it. You can find that drill bit through autobodytoolmart.com . I like to use transmission fluid to lubricate the cut just like you would with any cutting machine cutting metal. You can use an air hammer with a cutting bit to cut the extra sheet metal so to speak between channels and welded areas and just leave the sections with the spot welds to drill out and take off. That way insetad of taking out a huge panel you take it out in sections. I like to clean the area and use rustoleum or some other good paint like por 15 on interior areas and I use self etching weld through primer in the welded areas.

http://www.autobodytoolmart.com/coba...t-p-12259.aspx

http://www.autobodytoolmart.com/38-c...r-p-12256.aspx

Btw I have had my spot weld drill bit for 2 years now it's starting to get old but I have drilled thousands of spot welds with it.

MX442

Steve, I'm not a body man or painter, but here is a forum thread that shows there are several accepted practices on this subject.
http://www.spiuserforum.com/showthre...ight=spot+weld
In the next week or two, (or month), I will be plug welding fender braces back into the fender and will document my process.

oldsbucket

the spot weld cutter i buy is more expensive but all of the components are replaceable and the blades are reversible so in the end the more expensive is actually cheaper to run. i'm not so lucky and usually need new blades at the beginning of a job as it doesn't take much to brake a tooth and then it will want to walk.
I've noticed that the Factory uses seam sealer on joints prior to assembly the spot welder they use is able to weld through this being a clamp type. which a mig welder will not do, so mig welding is not a factory procedure but can have satisfactory results if you put in the effort.
I have less than satisfactory experience with the dedicated spot welders so i cannot say if the small shop machines can duplicate the welders the factory uses in this ability to weld through sealer

coppercutlass

The keysco spot weld cutter will not walk if you center punch the spot welds and start your drilling slow then speed up once you established your cut where your cutter will remain in place ., same goes for cutter oldsbucket speaks of which sounds like the blair style spot weld cutter. Imho opinion the keysco cutters are more hobbist friendly as its very hard to break them. Correct speed and pressure are key with Any of these cutters to make them last. A little trick I learned to mimick spot welds when mig welding a panel in is after you plug weld in your floor grind the weld flush. Grab a flat point round punch and hammer it down. It will create an imprint very much like a factory weld.