sealing openings and equipment in outer walls.

Ok I'm no expert, I'm not done yet, I have to fill the void with polyurethane insulation, and I also want to add sheet metal around the opening and seal it with silicone caulking.

myredracer wrote:
It's hard to say without being there, but maybe the reason for having a little trouble with the cutoff wheel is how you are using it. You should do a "plunge" cut and sink the wheel about 1/4" - 1/2" into the sheet metal near the start of the cut and move the wheel forward in front of you. Keep a firm grip on the grinder.

With the wheel sunk into the cut, it keeps the cut in a fairly straight line. You can steer the wheel a little to keep it going straight. If you run the wheel just touching the surface until it cuts through will result in a cut that isn't straight and wider than the wheel.

If you do it right, the cut should be really clean and straight and just the width of the cutoff wheel. When you get the hang of it, a quick zip and it's done. There is a guide available for an angle grinder that allows you to set the depth of the cut.

I think you are right, I wasn't pushing hard enough, I don't feel comfortable working with metal, lack of experience I guess, I used the grinder with the cutting blade on the inside panel and I followed your advice, things went much better, thanks.

It's hard to say without being there, but maybe the reason for having a little trouble with the cutoff wheel is how you are using it. You should do a "plunge" cut and sink the wheel about 1/4" - 1/2" into the sheet metal near the start of the cut and move the wheel forward in front of you. Keep a firm grip on the grinder.

With the wheel sunk into the cut, it keeps the cut in a fairly straight line. You can steer the wheel a little to keep it going straight. If you run the wheel just touching the surface until it cuts through will result in a cut that isn't straight and wider than the wheel.

If you do it right, the cut should be really clean and straight and just the width of the cutoff wheel. When you get the hang of it, a quick zip and it's done. There is a guide available for an angle grinder that allows you to set the depth of the cut.

myredracer wrote:
If it were me, I'd be using an angle grinder with an ultra-thin cutoff disc. You can make very nice clean and straight cuts that way and because you can make cuts fairly quickly, there isn't a whole lot of heat generated. If you had a big enough compressor (5HP, 60 gal.) a pneumatic die grinder with a thin cutoff blade is great on sheet metal, especially for smaller cuts since the blade is quite small in dia. A pneumatic shear, cutoff tool or nibbler are other options, but again, you'd need a big enough compressor.

If using a cutoff wheel, you'll be left with burrs along the cuts that can easily and quickly be cleaned up with a file. Cutting through two adjacent but separated layers of the sheet metal at the same time may or may not be difficult and the cutoff disc could potentially get away on you. Without seeing it in person, I think cutting each layer separately would be better.

I've used a sawzall on car bodies before but only for carving a shell into pieces or salvaging large sections. They're not really suitable for cutting neat holes and openings. I jigsaw can work with a metal cutting blade. Both a sawzall and jigsaw can vibrate and jump around a lot and be hard to control A plasma cutter will work but would be way too expensive for just a few cuts, but they sure are fun to use. An ultra-thin cutoff wheel really is the way to go.

If heat is causing problems, you could try some thermal paste that is used when welding thin sheet metal to prevent warpage. Goes by a variety of names and Eastwood has Cold Shield.

Drilling holes will work but man, that's gotta be so slow and painful... :( Then you still need to cut the metal between the holes and you're left with really jagged edges that need to be cleaned up somehow.

I tried a 4.5" diam angle grinder with a thin cutting blade and look at the top horizontal cut I did, you can see the white became yellow/beige and started to crack/peel off so I stopped.

I don't have a big compressor :(

I guess I'll need more patience... lol
But drilling holes is not that slow, I'd say it takes around 3 seconds each holes.

I've never used one myself, but it seems to me that a nibbler would be the tool of choice for this sort of work. (As with most things, you can find better and more expensive ones than the Harbor Freight version.)

duplicate...

If it were me, I'd be using an angle grinder with an ultra-thin cutoff disc. You can make very nice clean and straight cuts that way and because you can make cuts fairly quickly, there isn't a whole lot of heat generated. If you had a big enough compressor (5HP, 60 gal.) a pneumatic die grinder with a thin cutoff blade is great on sheet metal, especially for smaller cuts since the blade is quite small in dia. A pneumatic shear, cutoff tool or nibbler are other options, but again, you'd need a big enough compressor.

If using a cutoff wheel, you'll be left with burrs along the cuts that can easily and quickly be cleaned up with a file. Cutting through two adjacent but separated layers of the sheet metal at the same time may or may not be difficult and the cutoff disc could potentially get away on you. Without seeing it in person, I think cutting each layer separately would be better.

I've used a sawzall on car bodies before but only for carving a shell into pieces or salvaging large sections. They're not really suitable for cutting neat holes and openings. I jigsaw can work with a metal cutting blade. Both a sawzall and jigsaw can vibrate and jump around a lot and be hard to control A plasma cutter will work but would be way too expensive for just a few cuts, but they sure are fun to use. An ultra-thin cutoff wheel really is the way to go.

If heat is causing problems, you could try some thermal paste that is used when welding thin sheet metal to prevent warpage. Goes by a variety of names and Eastwood has Cold Shield.

Drilling holes will work but man, that's gotta be so slow and painful... :( Then you still need to cut the metal between the holes and you're left with really jagged edges that need to be cleaned up somehow.

You have a lot more patience than me.

The newer, battery powered reciprocating saws are a god send. They allow an opening to be cut in just about all materials and are fairly precise.

Round holes, I cut with a hole saw mounted on a drill.

Quick question, I've been making holes on the outside panels of my van, using a drill and self taping metal screws.

What do you guys use?

I tried a grinder (heats the metal and the paint changes color and starts to crack and flake off)
I tried a jigsaw/sawsall with masking tape around the opening, since the shell of a van is made of 2 panels (inside and outside) the blade hits the other panel and kicks back or breaks/bends the blade

This is the biggest hole I have to make for my fridge lower vent.