Separating spot-welded body and frame parts

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moparmat2000

moparmat2000

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moparmat2000 submitted a new Article:

Separating spot-welded body and frame parts

Some of you know how to do this, some of you don't, i am going to show you the easy way to do this, especially if you need or want to save both pieces that are welded together.

Typically if you have one piece you need to save and the other you are discarding because of rust, you drill and separate from the side you are discarding, or grind down the spot weld with a grinder on the side you are discarding, and use a chisel to separate the pieces discarding the bad metal.

In my case i am separating a rust free transition pan from solid rear frame rails and need to keep both pieces. Logic dictates drilling the spot welds on the transition pan side, and then there's already holes in the pan to rosette weld it into place into the car its going into. This leaves the frame rails hole free, or with divots from a drill that can be filled with weld and ground flat prior to being installed in a different car.

The start of the spot weld removal after determining the side you are drilling on is to clean up around the weld to find its exact center, then using an 1/8" drill bit spot drill the center of the spot weld, but not all the way through. This will help center a larger bit. I removed the floor pan to frame rail spot welds. These are fairly big and require a 3/8" drill bit to drill out. Other body spot welds may not be as beefy and smaller bits can be used to drill them out. I determined these at 3/8" because the spot was about the size, or slightly smaller than a 3/8" bit shank diameter.

Here's first 4 pix in chronological order. Notice the drills don't go all the way through the frame rail at the spot weld, only far enough to remove or severely weaken it.

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The next step is separating the pieces once you have the spot welds drilled. I have some special made heavy duty spot weld chisels i made from .050" stainless steel sheet stock with sharp forward edges, and handles that can be smacked with a hammer. These are what i use to get between the sheets that are spot welded together. The long one is about 2.5 foot long and about 3" wide. This one is perfect for running up the frame rails after drilling welds to pop em free. The .050" stainless is thick enough with a sharp edge to cut, and thin enough to be flexible to follow the frame rail curvature when tapped in with a hammer. Pic #5 you can see it tapped in all the way to the handle and the welds are popped free.

The smaller chisel has seen better days. I am in the process of making a new handle and new longer chisel. The handle on the smaller chisel is made from 2 pieces of 1/4" aluminum plate bolted together. I made this one 20 years ago. It used to have 6 fasteners holding the handle together back then. The blade was about 3" longer then as well. The longer chisel i folded over the stainless multiple times over itself, then beat it flat on an anvil. used monel steel aircraft rivets in it to keep it from separating.

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A word of caution. When using the chisels to slice thru the weakened spot welds, if the chisel stops in the middle of a drilled weld, if you try to keep driving it in, you could tear the metal at the drilled hole because some of the metal is still attaching both pieces well enough. If this happens where the chisel stops, try to run it in 180° from the other direction, or at least 90° from the sides and drive it back in. 9 times out of 10 you can break the rest of the weld loose this way.

To give you an idea how easy it is to do this, i removed 2 frame rails, a rear cross member, and a shock cross member from the transition pan in about 3.5 hours. The last rail, the RH side took me only about 1 hour to remove. No damage to the rails, , transition pan, or cross members. The pan will clean up nicely, and already has holes in it to weld it into the car its going in.
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Read more about this article here...
 
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Thank you,
Finally a common sense write up instead of starting with "you need sheet-metal cutter".
I have found common drill bits are way faster than the sheet-metal cutters, just buy jobber bits at your local fastenal, they seem to stay sharp the longest, and are about the same price as hardware store bits.
Also I use two drills, one for the pilot bit and one for the 1/4" bit or in your case 3/8" bit, it always seems you miss a spot weld or two and changing bits consumes more time.
 
Yes, i had the pilot bit in my air drill, the bigger bit in my electric. Some welds can be seperated with a 1/4" bit. The floorpan ones are big welds. A 3/8" just about does it with those. On floorpans that are rusted out that i am trashing, i dont use the drill method. I cut the sheet metal out around the frames, then grind down the spotwelds and chisel off the strips of metal thats left from the old floor. In this way theres no drill divots in the framerails to fill and grind down.
 
I did this write up because i have had people tell me it was a ***** in a half to drill spotwelds out and cleanly seperate the pieces. With the RH rail i went into the shop at 3:30pm, and had it apart from the floorpan by 4:30pm.
 
I chuckle at guys who think they need a 220V welder to do unibody work when most of it is 18G with the frame being maybe 14G.
 
I have used spotweld cutters, however they leave a little nub in the center of the piece you are keeping that needs to be ground off, plus my chisels slide thru the weakened spot welds better when its a partially drilled hole without that raised nub from the spotweld cutter.
 
moparmat2000 said:
To give you an idea how easy it is to do this, i removed 2 framerails, a rear crossmember, and a shock crossmember from the transition pan in about 3.5 hours. The last rail, the RH side took me only about 1 hour to remove. No damage to the rails, , transition pan, or crossmembers. The pan will clean up nicely, and already has holes in it to weld it into the car its going in. View attachment 1715312230 View attachment 1715312231

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They say, necessity is the mother of invention ---------
 
sireland67 said:
Thank you,
Finally a common sense write up instead of starting with "you need sheet-metal cutter".
I have found common drill bits are way faster than the sheet-metal cutters, just buy jobber bits at your local fastenal, they seem to stay sharp the longest, and are about the same price as hardware store bits.
Also I use two drills, one for the pilot bit and one for the 1/4" bit or in your case 3/8" bit, it always seems you miss a spot weld or two and changing bits consumes more time.
Click to expand...
Cobalt is where its at. Took 2 of em to get all this apart
 
I drilled out the spot welds on the tail light panel and trunk floor of my 70 Duster. It can be time consuming, but with patience, it can be done cleanly so you don’t have a bunch of prep work before you put the replacement parts back in.
 
Being a newbie at rust replacement and alot of work in that department coming up on my dart, I appreciate you guys taking the time to "spell it out for us" ! THANKS for the very helpful step by step info Matt !
 
Matt, have you ever tried these? Picked them up at a swap meet years ago. Center pin is spring loaded. If the saw blade gets dull just un-screw it and turn it around. Works pretty good as long as you center punch the spot weld.

20190331_095334.jpg
 
Hi Rory,

Yes, i have spotweld cutters. The ones i have are called rotabroach, made by Blair manufacturing. They range from 1/4" up to 3/4" in my kit. They work pretty well. My kit of cutters cost me about $65 a number of years ago. However i have found that drilling eliminates the nub in the middle that you have to grind down after using the cutters. With the drill bit method, my chisels cut cleanly thru the centers with the drill holes and dont get hung up on a nub left from a spotweld cutter, plus the drill bit method is a cheap way to do this for people who dont want to spend the money for dedicated spotweld cutters. I cut the first half of this car apart with my spotweld cutters and my chisels. The latter half with my chisels and the drill bit method. I think the drill bit method is actually better, faster, and cheaper.
 
Blair cutter kit. $70 vs a couple of 3/8 cobalt drill bits at about $7.00 each. Most people will go for the drill bits lol.

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I've got several 5/¹/16" and ⅜' bits I've changed the angles to around 150° to keep from drilling too deep into the underlying material.
How did y'alls swap meet go?
 
Just checked. Well so it is this weekend. Had i known i woulda hauled my unneeded mopar stuff up there and would have been a vendor. Yesterday was windy as heck. Its only 45° currently. Woulda been a little cold hanging out and keeping stuff from blowing away though.
 
moparmat2000 said:
To give you an idea how easy it is to do this, i removed 2 framerails, a rear crossmember, and a shock crossmember from the transition pan in about 3.5 hours. The last rail, the RH side took me only about 1 hour to remove. No damage to the rails, , transition pan, or crossmembers. The pan will clean up nicely, and already has holes in it to weld it into the car its going in. View attachment 1715312230 View attachment 1715312231

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Awesome job Matt, as usual. I'm sure this nice write up will help a lot of people who will have to do this type work to their projects or for needed parts. No disrespect meant at all, but I hope I don't have to practice this on my Barracuda (crossing fingers).
Keep up the nice work when you have time. You do a great job of writing up the process and of course, the pics help too.
 
Hey Matt, I moved this thread to "how to" articles. It should be at home there.
 
moparmat2000 said:
Just checked. Well so it is this weekend. Had i known i woulda hauled my unneeded mopar stuff up there and would have been a vendor. Yesterday was windy as heck. Its only 45° currently. Woulda been a little cold hanging out and keeping stuff from blowing away though.
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Wow, this guy has been busy! [FOR SALE] - Dart body parts
 
He sure has been busy. Looks like lots of pieces for somebody wanting to clip a frumpy 74-76 darts tail feathers and put on a 70-73 *** end. Look at all the front framerails he has stacked up like chordwood.
 
Made me a new spot weld splitter knife. .050" thick stainless and some 1/4" aluminum plate handles. Old one was worn to a nub.

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I went a little extreme on it however the holes aren't perfectly spaced or in an exact straight line. I figure this thing is going to get hammered on, dropped, stepped on, etc. over its lifetime so I didnt get really super crazy with it. My old original one in the pix at the beginning of this thread was pretty nice looking like this one is, but was nice about 20 years ago when I originally made it. It's been used and abused.
 
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