pinch weld trimming rust issue?

[meatball18]

has anyone had any issues with their pinch weld area rustin after hammering it or cutting it off? just wondering to see whats going on out there as i will be doing this soon.

also which do you prefer

the way of the hammer....

or the way of the grinder?


i will probably have to do the hammer for i do not have a welder.

[MEvang]

Have some pics so we know what your talking about?
Mike

[Tundradrenalin]

ahh the pinch weld...

Hey meatball,
The hammer will obviously take more elbow than the grinder. But whichever option you do, I'd recommend taking a wire brush to it after it cools and then hitting it with some WD40 or brake cleaner, let dry, then hit it with some black primer. Sean (Devinsixtyseven) has written a dozen reply-posts on this subject, maybe he'll chime in here again.

Take some reference pics for us too!

[meatball18]

well i have not done it yet to take the pics, i was just wondering if anyones has started to rust after cutting it off or hammering it down. ive been talking to Sean here lately hopefully he will put in his 2 cents

[eurobro]

I beat my pinch with a hammer for a few min.'s . . . . its a little better now but i still rub with my 35's. But yes mine is rusting a little bit.

[meatball18]

any pics? also how long ago did you do this modification? is the pich weld actually on the cab part of the truck or located somewhere else?

I beat my pinch with a hammer for a few min.'s . . . . its a little better now but i still rub with my 35's. But yes mine is rusting a little bit.

[Tundradrenalin]

Here are some of Sean's photos. Keep in mind he likes to use the Sawzall more than the average man.

[meatball18]

anyone else have any input on this

[MEvang]

Ahhh, you got me there I take it this is a modification for bigger tires? I don't read the big tire threads much since that not my bag.
But since I restore cars I may be able to help with this. I have done many of floor board repairs.
This is all about prep and the proper sealant. Using body filler is the wrong thing to do. This will not seal a thing and if not prepared properly the bondo will not adhere long and water will seep under it causing a big rust problem.
All looks good till this point. After welding and grinding the area should be sprayed with an epoxy primer or a rust inhibiting primer as sold by Eastwoods.(Eastwood # 50242ZP and #50243ZP or a spray can alternative is 16060Z) Next use a body seam sealer around all the weld areas. (On both sides if possible) Eastwood has this in a calking tube or brush on. (Tubes 31024Z or can 31028ZP) It is also available in calking form by 3M at most body shop suppliers. Do Not use silicon based or household calking. These don't adhere well to metals and can't be painted.
After this, being this is in an area that can get wet I would use a good under body paint like Eastwood's Ceramic Chassis Black #50544ZP and 50545ZP or 11175Z.
Top the area off with a good undercoating to prevent rock chipping and a final seal.

If you simpley beat over a pinch weld you have likely broke off most of the paint, If you can get it flat enough try painting the exposed metal with epoxy primer then sealing the bent over area with seal sealer, paint and under coat. This is about the best you'll do.
Odiously the more expensive products are the best and the more time you spent pre pairing the area the better chance you have of not seeing rust here.
Hope this is helpful,
Mike

[DevinSixtySeven]

Having done this a couple times now before I got it right...

This is all about prep and the proper sealant. Using body filler is the wrong thing to do. This will not seal a thing and if not prepared properly the bondo will not adhere long and water will seep under it causing a big rust problem.

100% correct. I didn't find this out until later. Whatever I used the second time was not the same as the 3M stuff from the first time around.

Next use a body seam sealer around all the weld areas. (On both sides if possible) Eastwood has this in a calking tube or brush on. (Tubes 31024Z or can 31028ZP) It is also available in calking form by 3M at most body shop suppliers.

That's what's in the pictures Andy linked, it worked well...never had water penetrate, on that trim job. I also tried a construction adhesive/gap filler...waste of time.

The first time around, inside and outside were sealed with the 3M product and the edges of the replacement plate were sawtoothed for more linear weld and to make fitment easier. This never leaked.

Second time around the cut was much deeper, harder to fit and weld the new pieces, the top coat wasn't the same, and the finish sealant was completely rushed. The undercoat was cheap and porous. In short, it was a mess. There were pinhole leaks exacerbated by winter conditions and ice buildup where it clung to the undercoat, rust pockets started forming like cavities in teeth during the winter season, just garbage. Take Mike's advice...prep and finish is very, very important.

I did fix it later, more on that in a sec.

If you do this (and I highly recommend it!):

Clean the area down to bare metal. Use a steel wire wheel on a corded, low rpm drill. I use a massive DeWalt, the thing's just a monster, 600rpm max or something, Fibertex wheels also work well. Don't bother with anything on an angle grinder, too much mess, hassle and risk for this, unless you're just taking off the factory undercoat before you get down to really cleaning the area around the cut.

Once it's bare metal, you're ready to cut. Make sure you're not gonna cut anything on the inside like the 4WD ECU (RHS) or the airbag sensor lines (LHS). Mark your line with a sharpie, doublecheck inside and outside measurements. Start conservatively with a cutoff wheel and etch your cut. Wet towel on the inside helps catch sparks, but once you've cut through it's time to work with a small saw (or a sawzall if you're comfortable).

Every weld needs at least an inch of bare, clean metal around it. Use the wire wheel and finish with acetone. If you sawtooth your new pieces, that's an inch away from the ends of the "teeth".

Use the right welder and wire for the job. 0.023, low voltage, low feed. The first round worked fairly well since we used John's 110v with probably 0.023 or 0.030 wire. Second time was rough since it was a gigantic Lincoln with 0.035 wire and a gun about the size Dirty Harry would use. I'll be doing a bit more sheetmetal work on the truck later this year and it'll be with a Miller M-10 gun (small) and 0.023 wire.

Wet towel on the inside is good here again, so you're not lighting the OEM body filler/glue on fire (often, anyway).

When you're finished welding, start with the chipping hammer, go to a larger wire wheel, finish with a small wire wheel.

You can etch, you can skip the etch, whatever. Next get a small tub (liter? half gallon? dunno...small tub.) of Herculiner. Herculiner is gap filling, does not dry porous, sticks to everything (watch your hootus!), etc...you'll end up using about a half dozen thin coats. I used six or eight, don't remember. You'll notice any pinholes from the inside, where the Herc seeps through and plugs the hole.

By the time you're done with the Herc you'll have a smooth finish (within the chunky limits of Herculiner) around all your welds, completely sealing everything, somewhat pliable, strong, weatherproof, durable...it's great. Much better than the body filler, seam sealer, undercoat, and whatever else I've tried to finish the cut.

If you don't go that far, go with Mike's suggestion on the primer around any areas you beat back.

If you trim off the pinch weld completely, sew it back up with the welder.

-Sean

[MEvang]

Eastwood and others also sell a weld through primer. I've used this with much success. It is very good for areas that get boxed in and you can't get back behind them. I don't know if you run into this in this case.
I also find that using a bright light on one side will help you find pin holes that are easy to miss.
Mike

[trfytoy]

Here is my pinchweld...or lack there of

I used sheet metal to box it back in after I cut everything out, then rubberized undercoating.

[DevinSixtySeven]

Eastwood and others also sell a weld through primer. I've used this with much success. It is very good for areas that get boxed in and you can't get back behind them. I don't know if you run into this in this case.
I also find that using a bright light on one side will help you find pin holes that are easy to miss.
Mike

Great suggestions. I looked at Eastwood's site, are you using the Bloxide or the cold-galv zinc stuff?

If you tub through the lower body channel as I did, there will be a few areas near-impossible to cover later.

My pinch weld looks like Trfytoy's but more so (or is that less so ).