need to make hole in sub-panel box


Old 06-24-04, 07:25 PM
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need to make hole in sub-panel box

I am adding a circuit to existing wiring. I need to add a hole.. Iknow there is a tool to punch holes, I think I am talking about a knock-out tool. I have seen them iin store but I have no idea how these work. can someone explain the process to me. thank you "fire"
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Old 06-24-04, 07:47 PM
Join Date: Sep 2000
Location: United States
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Do you need to make a new hole through solid metal? Or are you just punching out a manufacturer-provided knockout? If the latter, almost anything can be used. A sharp blow on a screwdriver will work.
Old 06-25-04, 04:44 AM
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holes in metal

thanks for answering , I need to make a new hole in solid metal. There are no pre=fab punch-outs that are accessable. I have seen what the tool looks like. It has a wratchet type handle and cutters that attach to it by screwing on to the threaded part. I assume you have to predrill a smaller hole to start it but I have no idea. I would like to do this week-end. thanks again "fire"
Old 06-25-04, 05:40 AM
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Location: Eastern USA
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Turn the power off to the subpanel, drill a pilot hole and use a step up drill to finish it.
Old 06-25-04, 10:55 AM
Join Date: Sep 2001
Location: Yorktown, VA
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Hellrazor's approach will work. However, you may be thinking about a "Greenlee" punch, or chassis punch. You may be able to rent one, not sure. Take a look at this link.
Old 06-25-04, 04:40 PM
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Just for perspective, here's how one amateur (me) did it:

I used a felt-tip pen to draw a circle on the metal the size of the needed hole. Then used a power drill with a small bit (1/16 inch I think - designated for metal) to make about 10-12 holes tracing the circle I had outlined by pen. Then used a hammer and screwdriver to knock out the hole. This seemed to work fine. Was a little time consuming - 20 to 30 minutes - but this was not a factor as I was only doing this one time. Hole was not perfect, but I used a water-tight conduit connector that had a fairly robust rubber seal that more than covered the imperfections.
Old 06-25-04, 09:53 PM
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holes in metal

I think it is the greenlee punch Randy is talking about. It looks like you have to drill a hole big enough for the draw stud to fit and put cutter on other side of metal .I think I will try this or the step up drill bit. Thanks to all who contributed. on a related topic would anyone like to comment on the best tool to have for checking voltages and/or see if wires are live. I amm using my old multi-meter which works,but is awkword to hold and check at same time. What's best? and thanks again for the hole info all."fire"
Old 06-26-04, 07:58 PM
P Michael
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There are numerous ways to make a hole in the sheet metal.
1- Step drill.
2- Hole Punch [Greenlee]
3- Hole Saw.
4- The above mentioned technique of drilling a lot of small holes around the circumference and then enlarging them thus connecting them together. This is rather crude.
5- Plasma cutter.

You didn't say what diameter of hole you need but I'll assume it is for a 1/2" connector which requires a 7/8" hole
altho 13/16" will work.
1- A step drill or UniBit will cost about $20~30.
2- A Greenlee Hole Punch is the professional method. A 1/2" kit is available at THD for ~$20. For a 3/4" hole [1 1/8"], then you need a 3/4" clearance hole and then about $40~50 for the stud, punch and die.
3- Hole saw. For your situation, this is probable your best alternative. You must use the bi-metal saws -- not the wood drilling ones. The mandrel is about $10~15 and the saw itself about $6.
Think of this as an excuse for buying a tool. Once you have the mandrel, you can add more saws to your arsenal.
Old 06-27-04, 07:56 AM
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thank you

Thanks again for all the advice. I opted for the uni-bit. I had bought one years ago. Finding it was harder than getting the hole drilled! But I did locate it and it worked just fine. This is a great site and I am sure I will keep my eye on it. I have quite a remodel project going . I would like to get a better tester . What is the Ideal tool to use to check voltage,see if wires are hot,ect.... I didn't have to put any money out for the uni-bit and now I have the itch to upgrade and I would feel safer knowing I am using a good tester. What do the pro's use? Thanks "FIRE"
Old 06-27-04, 08:18 AM
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Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Thumbs up

If you are going to mess around .Go for a good amprobe. That way you can read Volts-amperes - Ohms.


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