Removing stamped knockouts

[JazzBlueRT]

I have some under cabinets light I bought on clearance a long time ago. i finally found a use for them.

I opened them up and found the knockouts were only stamped slightly and there is no way to "knock" them out.

Is there a special tool for this or do I simply drill them out?

 

[driftpin]

Find one of your sockets that fits just-outside the stamping, and use another socket, and an extension, socket sized to the dia. of the knockout, slightly-smaller of course. Make sure everything is aligned, use a decent ball pein hammer on the extension/socket, and it should "open" after a blow or two, use your linesman's pliers to open it. Twist it back & forth to break the tab connection.

Or, drill a small pilot hole in the center, and use a decent quality holesaw to drill it out. Back it up on a 2x4 or something.

Drilling accurately in metal always seems to work better when you dimple the location w/a center-punch.

 

[zmaxmotorsports]

Picture?

 

[matt_i]

Other tools are a chassis punch or a uni-bit. I recommend deburring with rat tail (round) file or a Shaviv/Vargus-type deburring tool if that was in your arsenal.

 

[manwithtools]

Stepped drill (Uni-bit) will work well for this. I've seen some fixtures that the knockout was purely for decoration purposes as you describe. You don't have to use the knockout location if there is a more logical spot for cable entry with sufficient room for the bit to operate and a wire and clamp to fit.

 

[Muzzy]

If you want to buy a special tool, use a knock out punch.
They are expensive.
Drilling is a better option if there are only a couple of them to do.

 

[Norcal]

As mentioned by others a step drill (Unibit®) would work, if they are a slim profile under cabinet fixture a standard KO punch will be too large.

 

[couch67]

To expand on Driftpin's great idea, use the sockets and if you can get it in there, use a C clamp to press out the knockout.

couch

 

[DJL1967]

Step drill bit was my first choice when I had installed my electric garage heater. Same thing with my punch outs. They were not stamped well at all so rather than attempt to bang away at it and possibly damage the body of the heater, I just used my step drill and drilled it out to the size I needed. Very easy and fast too.

 

[Crazyjake8493]

Step drill bit or 7/8" carbide hole saw

 

[reader2580]

I bought a brand new Kohler transfer switch as surplus a few years back. It looked perfect when I got it, but I found out the reason it was surplus is because the knockouts were not punched properly and could not be removed.

Anyhow, I happened to have a hole saw the right size and drilled them out. The transfer switch works just fine.

 

[zmaxmotorsports]

Still waiting for picture of the problem knock outs.

 

[rburke65]

Drill them out...easiest n least cost.

 

[JazzBlueRT]

I used a 1/2 hole saw. Hole ended up begin pretty wonky. Cleaned up with Dremel (nextec rotary tool). Way too much time to drill a hole. Maybe the (cheap HF) hole saws are not intended for metal. Time for an upgrade.

I presume uneven pressure caused the wonky hole. I had a block of wood behind where I was drilling. Would this be avoided with a step bit?

 

[moserjj]

I used a 1/2 hole saw. Hole ended up begin pretty wonky. Cleaned up with Dremel (nextec rotary tool). Way too much time to drill a hole. Maybe the (cheap HF) hole saws are not intended for metal. Time for an upgrade.

I presume uneven pressure caused the wonky hole. I had a block of wood behind where I was drilling. Would this be avoided with a step bit?

Yes, step bit would have been a breeze. Few seconds of drilling and you're moving on. Super handy, I use mine all the time

Sent from my ONEPLUS A3000 using Tapatalk

 

[matt_i]

There's also Blair cutters and Hougen Hol-cutters which are sort of precision sheetmetal holesaws, cleaner cut than with a bandsaw-blade-based holesaw like Lenox/Starrett/Bahco/etc, if you are looking to acquire some new tools

 

[zmaxmotorsports]

I used a 1/2 hole saw. Hole ended up begin pretty wonky. Cleaned up with Dremel (nextec rotary tool). Way too much time to drill a hole. Maybe the (cheap HF) hole saws are not intended for metal. Time for an upgrade.

I presume uneven pressure caused the wonky hole. I had a block of wood behind where I was drilling. Would this be avoided with a step bit?

Hit them 90 degrees from the spot that isn't punched on each side,they'll come out.