How to patch hole in duct work and drill new one? - DIY Chatroom

Studly · 03-02-2009, 11:17 AM

Okay, I'm a duct work/sheet metal newbie here.

I'm replacing an old manual Aprilaire humidistat with a new digital one. I took the old one off, and there's about a 3x4 inch hole in the return air ductwork where that was mounted. What's the best way to patch that hole?

My new humidistat requires a 3/4 inch round hole in the ductwork that I'll have to cut. Can I get metal drill bits that big and is that the best way to make the hole, or should I go with one of those hole cutters that you use with an angle grinder? I don't want to spend a lot on tools, if I can avoid it, since this will likely be the only time I use them.

It would be nice if I could get buy a square of sheet metal with a 3/4 hole premade, and then I could use that to patch the old larger hole, and have the new 3/4 inch hole already there so I don't have to buy any extra tools. Is there anywhere I could get something like this, or would a hardware store make that for me for cheap?

If you have ideas on how to patch the old hole and the most economical way to create the new one, w/o having to buy a bunch of new tools, that would be appreciated. Thanks for your help!!

DangerMouse · 03-02-2009, 11:31 AM

you can bang a coffee can flat (tin snip it to size and remove edges) and drill holes in it and use a rivet gun to attach it. they're cheap enough. for the hole, draw your hole on it, then use a smallish chisel to tap out 'pizza slices', then pull them up like Jughead's hat in the old Archie comics and snip them as round as you can, then tap them back flat. a dremel tool will help finish rounding the hole.

DM

hvaclover · 03-02-2009, 01:17 PM

Quote:

Originally Posted by DangerMouse

you can bang a coffee can flat (tin snip it to size and remove edges) and drill holes in it and use a rivet gun to attach it. they're cheap enough. for the hole, draw your hole on it, then use a smallish chisel to tap out 'pizza slices', then pull them up like Jughead's hat in the old Archie comics and snip them as round as you can, then tap them back flat. a dremel tool will help finish rounding the hole.

DM

DM has a good economic approach. But if you want a finished look to the patch i would buy a small piece of sheet metal from a hardware cut it to size
and bend the edges flush.

And you'll need this to make the 3/4" hole.

Studly · 03-02-2009, 01:22 PM

Thanks for the advice. I think I'll go with the sheet metal to cover the hole, although the coffee can idea is certainly economical

.

HVAClover, with that bit you show, do I need to use a center punch or something similar first, to get it started?

DangerMouse · 03-02-2009, 01:28 PM

well sure, if you want to do it the RIGHT way! sheesh.... with as much as i visit my local hdwr store, they'd just GIVE me a small piece of scrap like that. you may want to go and ask....as you're buying that tool....or take the side from an old computer power supply...that's about the right size. (or similar junk you may have laying around.... be creative!) but i'd run a bead of sealing caulk before you attach it with the pop-rivets.

DM

mjbxx · 03-02-2009, 06:05 PM

You could purchase one of those sheetrock hole repair kits that utilize sheet metal. I am sure they make a size that will cover a 3"x4" space. Just a thought.

hvaclover · 03-02-2009, 06:54 PM

Quote:

Originally Posted by Studly

Thanks for the advice. I think I'll go with the sheet metal to cover the hole, although the coffee can idea is certainly economical

.

HVAClover, with that bit you show, do I need to use a center punch or something similar first, to get it started?

It's self starting. Called a step bit. We use them for sheet metal work all the time.

yuri · 03-02-2009, 09:13 PM

Made by Greenlee for about $50. Wish I could afford those nice tools and a set of KO cutters. My stuff comes from WalMart. I guess I need to charge more $$

hvaclover · 03-02-2009, 10:09 PM

Quote:

Originally Posted by yuri

Made by Greenlee for about $50. Wish I could afford those nice tools and a set of KO cutters. My stuff comes from WalMart. I guess I need to charge more $$

You can get a step bit for $25-30 at lowes.

Studly · 03-03-2009, 11:21 AM

Quote:

Originally Posted by DangerMouse

....or take the side from an old computer power supply...that's about the right size. (or similar junk you may have laying around.... be creative!)

Hey DangerMouse, well my local store wanted $10 for a larger piece of sheet metal than I needed, so in scouting around the house for some scrap metal, I did exactly what you suggested ... took the metal from the bottom of a power supply box from an old PC. Works great, looks pretty good ... thanks for the idea.

Also I found that drill bit pictured above to be pretty pricey, as others have suggested, so I found a hold cutter with auger that attaches to the drill for about $5. It worked fine.

Thanks everyone for the advice!

hvaclover · 03-03-2009, 11:26 AM

You got it don that's the important part.