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#63456 - 03/15/06 06:49 PM Cutting Through KOs
SolarPowered Offline
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Registered: 07/05/04
Posts: 625
Loc: Palo Alto, CA, USA
I was reading the thread on panel preferences, and thinking about the comments about preferring a blank end panel, because the KOs are often the wrong size, in the wrong place.

It sounds like some folks just punch new holes in the pre-punch boxes, right though the existing KOs. Or I may have misinterpreted, and they're carefully placing the punch to cut virgin metal.

So, I'm wondering what it is people are really doing. Can you actually make a new opening that, say, takes out a third of a non-punched-out KO?

[This message has been edited by SolarPowered (edited 03-15-2006).]
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#63457 - 03/15/06 07:57 PM Re: Cutting Through KOs
electure Offline


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Registered: 12/24/00
Posts: 4259
Loc: Fullerton, CA USA
The difficulty with doing that is more with drilling the pilot hole for the KO than actually punching it. They always seem to end up right in the ring of a concentric KO. If you get past that part, the rest is easy
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#63458 - 03/15/06 08:20 PM Re: Cutting Through KOs
e57 Offline
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Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
When to KO's don't match the conduits that may already be in a wall, I often do this... Jamb the panel in the wall where it will be, find all the hole that can be used, or manipulated to be used, and then.... Very carefully holesaw the pilot for the KO punch, and try to position it so you can cover 2-3 of the offending prepunched KO's as much as possible. Then punch it, hoping that not too much of the un-needed KO came out around the hole you really need, if so reducing washers, and ground bushings. Big PITA!

Rather have a solid panel to work with and just use carbide hole cutters....

[This message has been edited by e57 (edited 03-15-2006).]
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#63459 - 03/16/06 06:50 AM Re: Cutting Through KOs
renosteinke Offline
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Registered: 01/22/05
Posts: 5316
Loc: Blue Collar Country
I have had reasonable luck using the Greenlee "High Speed Cutters." In technical terms, these are "rotary broaches," rather than hole saws.

Nevertheless, in replacing some panels I have had to resort to removing the bottom of the old panel and attaching it to the new panel. Or, when I simply need to place a small hole where there is a big knock out, I will make the "small hole" in a blank 4-sq cover, and attach that over the large knockout.
In either situation, pop rivets are my fasteners of choice.


By now, I sometimes feel that, if you're not fully equipped to make holes for pipe in a variety of materials- maybe you shouldn't be working on panels! A pox on panle knock-outs!
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#63460 - 03/16/06 04:59 PM Re: Cutting Through KOs
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
" if you're not fully equipped to make holes for pipe in a variety of materials- maybe you shouldn't be working on panels! "

My sentiments exactly - obviously not enough room to slam the trunk closed... A 1/2" -1 1/4 KO set (At least) is a standard issue item for anyone who takes themselves seriously.
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#63461 - 03/16/06 05:37 PM Re: Cutting Through KOs
resqcapt19 Offline
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Registered: 11/10/00
Posts: 2148
Loc: IL
Has anyone else used these hole cutters ?
Don
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#63462 - 03/16/06 05:46 PM Re: Cutting Through KOs
renosteinke Offline
Cat Servant
Member
Registered: 01/22/05
Posts: 5316
Loc: Blue Collar Country
Don, those are the type I was talking about. Cut metal real good, little burr.
Very important to keep RPMs low, and use cutting lube.
Also important to wear glasses...big sharp chips...and the chips are hot!
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#63463 - 03/16/06 06:56 PM Re: Cutting Through KOs
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
I have gone through a few different brands of them in 7/8", one in particular has a spring on the pilot that keeps the cutter from crashing into the surface, (and knocking off the teeth) which does really seem to prolong life...

Speaking of which, 'long life', I usually use them at high speed and lubed which gets me through 200-300 holes on a single sitting with the average un-caring underling assigned the task. (Except for the one with the spring, still going on over 800 holes...) Should they be at low speed?

FYI I seem to buy one every sizable job... And give away the nearly toothless item when it's over. (Except the one with the spring...)
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#63464 - 03/16/06 08:01 PM Re: Cutting Through KOs
resqcapt19 Offline
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Registered: 11/10/00
Posts: 2148
Loc: IL
John,
I tried the Greelee version and their is no comparison. They just don't do the job or last near as long as the Blair cutters.
Don
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#63465 - 03/16/06 08:03 PM Re: Cutting Through KOs
resqcapt19 Offline
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Registered: 11/10/00
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Loc: IL
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