ko,s

Status
Not open for further replies.
L

liquidtite

Senior Member
Location
Ny
whats the best way to figure out what size knockout it is with concentric kos, ive put the locknut up to the ko and tried it that way .or to take a hole saw,or dye to the ko that way .i was just woundering some diff ways to see what size it is.
 
liquidtite said:
whats the best way to figure out what size knockout it is with concentric kos, ive put the locknut up to the ko and tried it that way .or to take a hole saw,or dye to the ko that way .i was just woundering some diff ways to see what size it is.
Click to expand...


Just measure it with your tape measure.
 
The reason why I asked is bc we have an apprentice that punched out the wrong size and we had to use reducers ,I explained how I do it I wanted to see if their was a diff way I could tell him
 
liquidtite said:
The reason why I asked is bc we have an apprentice that punched out the wrong size and we had to use reducers ,I explained how I do it I wanted to see if their was a diff way I could tell him
Click to expand...

Use a ruler and a loose rule of thumb:
Trade sizes 1/2" thru 2" add 3/8" to the trade size for the KO size. (For example 1/2" KO=7/8" hole)
Trade sizes 2.5" thru 4" add 1/2" to the trade size for the KO size.
 
The next time you get the chance, work carefully and save the knocked 'outs'.

Label them and give them to your apprentice.

Once he masters concentrics, ease him into eccentrics. Those are much trickier.

FWIW, I am with the crowd that hates KOs. On one box they practically fall out, on others you need a sledge hammer and a chisel to get them out and the one you want to remain is always the one that is the easiest to become dislodged.
 
liquidtite said:
The reason why I asked is bc we have an apprentice that punched out the wrong size and we had to use reducers ,I explained how I do it I wanted to see if their was a diff way I could tell him
Click to expand...
Sad but true there is a learning curve for the apprentice. It may be a pain but if the KO that is removed is too small they can always carefully remove the next larger one. Seeing how much work it adds to the job but messing aroid removing the next larger ring without ruining the others hopefully the apprentice's learning curve will ramp up very quickly.
 
One EC I worked for had a great system. He would use a red sharpie and mark the KOs he wanted out. Saved on left / right errors, too. At least if there was one, it was his fault, not the employees!

Same EC would rather a hydraulic knock out set be used to make the holes. I think that's a much better system than guessing and pummeling.

Said EC used a fitting to choose the KO to be removed. He has the process down pat.
 
infinity said:
Use a ruler and a loose rule of thumb:
Trade sizes 1/2" thru 2" add 3/8" to the trade size for the KO size. (For example 1/2" KO=7/8" hole)
Trade sizes 2.5" thru 4" add 1/2" to the trade size for the KO size.
Click to expand...

I'm pretty sure the 3/8" is just up to 1-1/2". I think the 1/2" starts with the 2".
Most hole cutter sets are gauged that way that I've seen.
 
K8MHZ said:
One EC I worked for had a great system. He would use a red sharpie and mark the KOs he wanted out. Saved on left / right errors, too. At least if there was one, it was his fault, not the employees!

Same EC would rather a hydraulic knock out set be used to make the holes. I think that's a much better system than guessing and pummeling.

Said EC used a fitting to choose the KO to be removed. He has the process down pat.
Click to expand...
I guess then it takes two people to a job one person should be able to do, one to mark the ko's then another to knock them out. Sounds like government work to me, job security.
 
Little Bill said:
I'm pretty sure the 3/8" is just up to 1-1/2". I think the 1/2" starts with the 2".
Most hole cutter sets are gauged that way that I've seen.
Click to expand...


You may be able to use a 2-1/2 inch hole for 2 inch conduit, but a 2-3/8 hole fits better, the OD of 2 inch pipe is 2-3/8.

The OD of 2-1/2 inch pipe is 2-7/8. 3 through 4 inch is 1/2 inch larger.
Here is a link to pipe dimensions:

http://www.harvel.com/piping-systems/harvel-pvc-pipe/schedule-40-80/dimensions

Note that is not a chart of electrical raceways, but RMC, IMC, PVC schedule 40 and 80, are all same OD, as well as all fittings for other raceways that use national pipe threads.
 
kwired said:
You may be able to use a 2-1/2 inch hole for 2 inch conduit, but a 2-3/8 hole fits better, the OD of 2 inch pipe is 2-3/8.

The OD of 2-1/2 inch pipe is 2-7/8. 3 through 4 inch is 1/2 inch larger.
Here is a link to pipe dimensions:

http://www.harvel.com/piping-systems/harvel-pvc-pipe/schedule-40-80/dimensions

Note that is not a chart of electrical raceways, but RMC, IMC, PVC schedule 40 and 80, are all same OD, as well as all fittings for other raceways that use national pipe threads.
Click to expand...

This chart doesn't agree with you.

http://www.mrelectrician.tv/conversioncharts/pipeconduit.html
 
Little Bill said:
This chart doesn't agree with you.

http://www.mrelectrician.tv/conversioncharts/pipeconduit.html
Click to expand...

Actually if you compare the diameters of RMC in your chart to the ones I posted a link for, the pipe diameters are exactly the same.

What is different is the "size opening needed into box" which probably corresponds to common KO punch diameters. My chart was not intended for electrical pipes/tubing so that kind of information was not provided - but the diameters are the same. Notice though that IMC is generally slightly smaller than RMC but sch 40 and 80 is generally same diameter as RMC.

If hole is exactly same size as the pipe it will fit but will be be tight. The fact that you will be inserting threaded ends or fittings of very similar dimension will make it easier than inserting a solid wall pipe.
 
kwired said:
Actually if you compare the diameters of RMC in your chart to the ones I posted a link for, the pipe diameters are exactly the same.

What is different is the "size opening needed into box" which probably corresponds to common KO punch diameters. My chart was not intended for electrical pipes/tubing so that kind of information was not provided - but the diameters are the same. Notice though that IMC is generally slightly smaller than RMC but sch 40 and 80 is generally same diameter as RMC.

If hole is exactly same size as the pipe it will fit but will be be tight. The fact that you will be inserting threaded ends or fittings of very similar dimension will make it easier than inserting a solid wall pipe.
Click to expand...

Also, if you look at any "electricians' hole saw/cutter kits", they start the 1/2" increments at 2".
 
Status
Not open for further replies.
Top