How to drill 3/4 inch hole into sheet metal?

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Old 10-13-12, 05:54 PM
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How to drill 3/4 inch hole into sheet metal?

The instructions of my Aprilaire 600 humidifier ask to drill a 3/4 inch hole into the sheet metal to install the control unit.

I don't even have a drill bit that big. Do I need to buy a drill bit that large, or is that another way to do that?

Thanks
 
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Old 10-13-12, 06:23 PM
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You'll need to use a hole saw or variable step uni bit. I use a uni bit and I stick an HD magnet, below the bit, on the duct and it attracts and holds the metal chips. The bits are a little costly but a great tool to have around. The link is just to show you what it looks like.
Irwin Unibit #4 High Speed Steel Fractional Self-Starting/Hole Enlarging Step Drill Bit, Model# 10234 | Step Drill Bits| Northern Tool + Equipment
 
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Old 10-13-12, 06:25 PM
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Non-pro way is a 3/4" bi-metal hole saw. Pro way is a chassis punch. The latter is expensive. The former will only cost about $15.
 
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Old 10-13-12, 06:40 PM
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If you're near a Harbor Freight you can get those step drills (unibit) for less than $10 for a set and they're pretty good. I've gone through some pretty heavy sheet metal with no signs of dulling.
 
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Old 10-14-12, 03:39 PM
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Thanks, I got a 3/4in spade bit at home depot and used that. The step drill bits are probably better, but the cheapest one at HD started at $35, too much for the one hole I needed.
 
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Old 10-14-12, 03:42 PM
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Spade bit ?!?! You actually used a spade bit to drill metal. How did it turn out ?
 
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Old 10-14-12, 03:46 PM
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Spade bits are for wood, not metal - how did it work?
 
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Old 10-14-12, 03:57 PM
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Actually, worked okay, no problem. Made a nice round 3/4 in hole.
 
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Old 10-14-12, 04:09 PM
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The wings on the bit probably did the cutting. Just like cutting the 3/4" hole for the latch on an aluminum storm door. They sometimes provide you with a spade bit to cut the hole. Course, you usually throw it away afterwards... lol
 
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Old 10-14-12, 04:09 PM
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Spade bits work fine......for one hole....in thin sheet metal (aluminum is better)...and if you never intend to use them for a another project requiring good cutting.
 
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Old 10-14-12, 04:20 PM
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The step drill bits are probably better, but the cheapest one at HD started at $35,
Which is why I suggested a bi-metal hole saw.
 
 

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