I'm welding in new floor pans and I'm getting to the point where I need to spot or plug weld the pan to the floor braces. Can I just drill a hole and weld it ? What size bit should I use? I Por 15ed the floor braces will this be a problem?

Thanks,
Carl

You need to have BARE metal or at the least a weld thru primer to weld to. Your POR is NOT weld thru and it will create a heck of a contaminant in the weld. Probably not welding at all it will be so bad.

Yes, you can just drill holes for plug welding. Make them about 5/16".

However, the first thing is GET THE METAL CLEAN and the pieces fitting tight. Nothing but nothing will aid more in welding than clean metal and a tight fit. When I say clean, I mean bare metal. Not even traces of paint or primer should remain. This includes the BACK of the metal that you will be welding. That’s right, the back of the metal. Remember, the metal is going to be melting when you weld, right? Well, when the metal melts as it is welded it will bring into the molten area the impurities from the other side of the metal. THIS CLEANING IS VERY IMPORTANT. Don’t use a grinder (unless it is absolutly nessisary)to strip the metal. It takes off too much metal. Use something like a 3M “Roloc” disc (#07485) or a “Clean and strip” disc (#07466) In hard to reach areas I do use a cut off wheel or carbide bit. But this is a last resort and only used because there is no other way. Just don’t cut too much metal off. On a long “pinch weld” for instance, you should have the entire length BARE METAL (with only weld thru primer if it is going to he between two sheets). Not just where you will be welding, but the whole area where metal will mate. I say this because if you start “cheating” and only striping right were you are welding, you will soon get into a situation where you are welding up to that dirty metal and WHAM you have a contamination problem. So, if you clean it ALL you will never have a problem.
Yes there are some times when you leave primer there, but only when you KNOW what it is. What I am referring here is “weld thru” primer. This could be an existing primer found on the new parts you bought in the form of an “E” coat. Or one that is specifically made for this purpose. “Weld thru” primers come in aerosol cans (3M # 05913) and brush on. They are made by a number of manufactures. They should be lightly applied over the metal after it has been THOROUGHLY cleaned as described previously. Put a light coat, some are even transparent so don’t think it has to cover like regular primer you would paint over. It is simply a zinc coating similar to galvanizing. So look at it like an at home galvanizing job. Look at a piece of galvanized metal like chain link fence, you can see right through the coating to the metal. It should be totally dried by the time you weld. If it has any unflashed solvent it will burn and your welding will be negatively effected.


And for God's sake, wear a welding resperator when welding these floors. The zinc in the primer can KILL YOU.

your gonna have to get that por off the braces before you can weld the pans on. and yes all you need to do is drill a hole and plug weld to the brace. oh and you might want to use some weld thru primer between the pan and the brace.

I cannot overemphasize the use of a respirator, especially if there's any Por 15 in the vicinity. It'll get hot and smoke if it's close by, even if your weld area is clean. Por 15, according to the manufacturer, is very nasty stuff when heated to the point that it starts to smoke, and a respirator is mandatory!! You don't want it in your lungs.

The weld-through primer they're talking about is made by 3M, and it's available at any body shop supply store. There may be others, but I've had great results with the 3M primer.

For god sake wear a mask under your welding helmet, even if you dont use a weld thru primer.
Click on the link in there it stats a 3M approved welding mask that FITS under probably 99.9% of welding helmets
http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=3;t=008203;p=2
It should be 3M part number 071892 I believe

Welding fumes is NO LAUGHING matter, it might not KILL(eventhou in can) you from just welding in the floors but IT sure as hell can leave you with perment side affects for the rest of your natural life and believe me it will graemlins/hurray.gif

If you feel like having a constat cough, shortness of breath and a lung capacity of a 93yr old smoker then please all by means DONT WEAR THAT MASK.

I suffer from zinc oxide poisoning(welding fumes) every day and will continue to suffer from it. It attacks the air pockets that make up your lungs decreasing their size. Also because of this humdity really likes to HELP OUT :rolleyes: , if you ever been to Iowa in July or Augest then you know its about 100 degrees and 85% humidty. I can say theres been days when I wish it WOULD have KILLED me, cus the pain is unbelievable. Think its a joke call me at home at around 7:00am when am stepping out of the shower and coughing up my right F@%$ing lung, hopefully that sound will scare ya into spending that 20 bucks for a welding mask.

Other then that a 5/16 hole size will do just fine. Have a nice day smile.gif ...Eric

Thanks for all your help guys. I will invest in a respirator, I have one for buffing brass that has screw on filters, do you think I need a a special on for welding?
Welding supply store?

Carl

Carl, Yes I highly believe you need a mask JUST for welding. Its only 15-20 bucks. Trust me 20 bucks in NOT worth the BS I go throu day after day.

You can get them at any place that sells 3M products. Click on the very top link, in the second page there is a BIG picture posted. SOmewhere in that post I give the 3M welding mask part number. That mask is what I use and what was recommended I use by the 3M REP.

I believe the part number is 071892. The way 3M works is that the last number is the size, so a small is 071891, med 071892 and large is 071893. Its a great mask with removable filters, uses the P100 screw on filters

Thanks,
I'll get the 3M mask for welding. I've repaired musical instruments for 25 years and the first 10 didn't use a dust respirator when buffing brass, not too smart! When your 16 and your boss thats your "Teacher" said you don't need that then you don't use one. Things are changing for the better, people are more informed. Thanks to people that have learned the hard way and took the brunt of the suffering and now are helping others with what they have learned.

Thanks to all for your help and knowledge.

Carl