Rear Floor Cutting

K

kastlerock

New member
I will be replacing my rear cargo floor in a sii. Can someone suggest the best method for breaking the welds on the body cross members and how best to weld them back up? Should I cut out around the cross braces and drill holes before welding back up? Is the best tool for this a grinder with a cutting wheel? Any help would be greatly appreciated.

Thanks,

d
 
kastlerock said:
I will be replacing my rear cargo floor in a sii. Can someone suggest the best method for breaking the welds on the body cross members and how best to weld them back up? Should I cut out around the cross braces and drill holes before welding back up? Is the best tool for this a grinder with a cutting wheel? Any help would be greatly appreciated.

Thanks,

d
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I'm not sure about best method but whatever you choose to do remember about wiring, gas lines and the gas tank. You'd be surprised about how many people forget and cut into the tank or at least the sending unit wires. Not to mention the sparks or flames from cutting and welding. Course if it is just sitting there tank less no worries lol. For any long cutting I'm planning on trying a body saw or other small reciprocating saw next time. Grinding any long lengths can be annoying and tedious. I would definitely cut any excess bed material from the cross members so that you don't sandwich any old material between the new and old. I'm not sure how to recommend though especially if you aren't trying to cut the cross members out too. Oh and you might want to look at bracing the sides of the inner fenders at the bottom so that they stay in line but I'm not sure how important that is or isn't. Good luck.

Hth
Rich
 
1hc72 said:
for cutting I would use plasma torch no flames for welding it back I don't know
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I was also considering the flames from the stuff that will catch fire such as undercoating and paint if you do weld or use any hot cutting method. I can't remember if I ever actually caught anything on fire with a cut of wheel.

Rich
 
In my case, the body is removed. My only concern was how to remove the floor without cutting the cross braces and then how to weld it back together at each spot weld? I am a beginner when it comes to this stuff and I am limited on the tools I have - though I do have a good mig welder. I figured I'd cut the perimeter and then maybe use some sort of saw to cut the spot welds between the floor and the braces. Thoughts?
 
kastlerock said:
in my case, the body is removed. My only concern was how to remove the floor without cutting the cross braces and then how to weld it back together at each spot weld? I am a beginner when it comes to this stuff and I am limited on the tools I have - though I do have a good mig welder. I figured I'd cut the perimeter and then maybe use some sort of saw to cut the spot welds between the floor and the braces. Thoughts?
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Drill out the spot welds. A drill bit "cutter" for doing this is widely available or ya can use an assortment of hole saws also for sheetmetal spots.

Many of the so-called "spot weld drills" are pure shit and worthless. A spot weld locally hardens the materials and makes it tough to drill. If you invest in a spot weld drill, by a pro version and it will hold up to many uses!

If ya do this neatly, then ya can use the resulting hole as a location for a plug weld (from underneath) to re-attach whatever floor sheet ya end up using.

Another method is simply cut around each spot weld with a gizwheel and then pull all the rotten sheet out. Then the leftover spot weld/sheet can be easily ground flush...but that method is very time-consuming and it's impossible to get a gizwheel into the tight spots where some of the spot welds are located.
 
I 2nd mm's drill method. I could never cough up the money for a spot drill rig so I have used the dewalt pilot point drill bits many times to remove spot welds. Only leaves a small hole if ya stop at the first layer. Only the tip is pointed and the outer cutting edges are flat. I like the 3/8 bit for the large IH spots. Also rust kills drills so wire brush as much as you can before drilling ans use a drop of cutting oil. Buy them at hd and osh. Should drill out the floor without needing to be sharpened. A ra grinder and hard wheel will do to sharpen.
tool detail
 
Thanks for the "pilot point" tip bits idea Robert! I forgot to mention those! Probably even a better solution since they are so versatile for general shop work.

I use those bits nearly exclusively here. They work like a cross between a conventional drill bit and a end mill or spot facer. Unless they are badly abused, they will outlast and outcut any other conventional drill bit and are very much worth the extra cost. And for working out the spot welds, ya only need a few sizes anyway.
 
If you have a grinder you can grind what I call a "sheet metal drill" by hand. I start by grinding the end of the drill down to just a point and then grind from the point down the shank of the drill and just leave the cutting edges with a sharp edge. The point should extend slightly beyound the cutting edges so as to locate in a center punch Mark and then the only other contact between the drill and the sheet metal is the outer cutting edge. Once the outside edge is starting to cut, the web of the drill will start to make contact, but by then the sheet metal will be cut. It's a bit difficult to explain the grinding of the end of the drill, but the sharp edges will give a nice round hole as opposed to a three sided hole in the sheet metal.

Just a cheap way to make a pilot point drill.

Lyle
 
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