Drilling holes in sheet metal

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Old 08-20-13, 11:28 PM
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Drilling holes in sheet metal

I've got a sheet metal cabinet I'd like to drill a few holes into. Guesstimating the sheet metal is ~0.06" thick. I've got a Milwaukee Thunderbolt black oxide drill bits - will that do the job?

Any tips? I figure I'll make a divot with a centerpunch and then use the drill. Would applying a little oil to the drill bit help?
 
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Old 08-21-13, 03:05 AM
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Center punching for the hole is a good idea. I doubt your drill will run long enough to cause any heat, but if you feel the oil is necessary, then use it. On thin metal, if you have the option, place a block of wood on the opposite side from where you are drilling. Drill into the metal and wood at the same time. Keeps your bit from blowing out the back side of the metal and leaves a smooth hole.
 
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Old 08-21-13, 05:39 AM
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16ga is easy to drill through but it's thinness causes some problems. How large a hole do you want to drill? First I drill a small (1/8") pilot hole which is easy to keep centered on your mark and easier to push and make that initial cut through the metal. For smaller holes in thin sheet metal I like to use step bits as larger diameter spiral bits like to grab as they break through thin metal which can wrinkle the steel.
 
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Old 08-22-13, 11:50 AM
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Thanks. The block of wood seemed to help. The holes I drilled were small - 1/8".

Next up, need to drill a hole large enough to pass a standard electric plug through (installing lighting in a cabinet made of sheet metal). Unless there is an easier alternative solution (would rather use outlet powered lighting over battery powered lighting). Largest drill bit I have is 1/2", which isn't nearly large enough; I have larger spade bits, but not sure if they would work for this application.
 
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Old 08-22-13, 04:17 PM
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Depending on the size of your electrical plug, spade bits with tips on the wings will cut through sheet metal. But you have to use the block of wood and go slowly with it. You'll still have to rasp or sand paper the boogers on the edge of the hole to prevent chafing. I'd also install some sort of liner around the hole to cushion it, like a rubber bushing. You can split the bushing and install it after the cord is pulled through.
 
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Old 08-22-13, 09:05 PM
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The spade bits I have do have tips on the wings, but I think I'll just drill a hole large enough for the cord, chop the plug off and attach a replacement plug. I'll sand the edge of the hole and seat a grommet on the hole to prevent the cord from being cut.
 
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Old 08-25-13, 05:37 PM
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I wouldn't have thought of using a spade bit, they aren't designed for that. But they are cheap, so you won't lose much, and not so hard to resharpen. Just be sure you use one with the prongs on the outside, so the whole blade doesn't try to cut the metal. That wouldn't work so well.

I use two blocks with a big bit, one on each side, clamped together. That way the metal can't wrinkle.

Of course, if you are doing this right, a good hole saw is actually made for this type of work. By good, I mean the type that attaches to the mandrel with shear pins, not tightens with a screw thread. They have bimetal blades made for metal. They are more expensive, but also cut deeper holes and stay sharper longer in wood.

Wear ear protection either way.
 
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Old 08-26-13, 10:17 PM
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To followup, I used a 1/2" drill bit to make a hole, which is large enough to allow the cord to pass through and fit a grommet to protect the cord from getting cut by the metal. I'll use a replacement plug to repair the cord.

Thanks for the suggestions everyone.
 
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