DRILL & TAP A BUS

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infinity

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New Jersey
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Journeyman Electrician
If the bus is de-energized it doesn't involve much given you have the correct tools. Energized is a different story.
 

ron

Senior Member
Be sure you are not reducing the cross sectional area of the bus below the required current load. It is hard to know how to calculate that because of the varied heat rejection characteristics of bus in different orientations and configurations.

I believe that it requires the equipment to be inspected by a NRTL to ensure compliance with the appropriate standard.
 

infinity

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Location
New Jersey
Occupation
Journeyman Electrician
How the heck could you ever do it live??? Thanks

Back in the day before cordless and double insulated drills we would take laundry drop (or female end of an extension cord), safe off the ground (important) and connect the white conductor to the neutral bus and the black conductor to the same phase bus that you're drilling. Protect the surrounding area/bus with rubber mats and drill away. I did this 20+ years ago when I was stupid. I wouldn't do it today even with a cordless drill.
 

Okie Sparky

Member
Location
NW Oklahoma
VERY, VERY carefully!! NOT recommended for long term life expectancy. Would do it differently today than I did it back then 12 or more years ago. I see infinity beat me to the reply so I won't bore you with the details. Same basic idea only I used a cordless drill.
 
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Joethemechanic

Senior Member
Location
Hazleton Pa
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Electro-Mechanical Technician. Industrial machinery
Lots of stuff done hot

hotwork.jpg

Sometimes with good reason, and sometimes not.

I'd have to have a really good reason to drill and tap a hot buss, I'm too old to do it just to prove I can.
 

__dan

Senior Member
WHAT DOES THAT ENTAIL???? Copper bus of course

Most likely you are looking at a bad spec. I did it once, copper is very soft, malleable, and the busbars get pretty thick so i was able to get a good hold cutting, tapping, for coarse thread bolts, but I did not like it. I would only do through bolts with high quality hardware after that. Did drill, bolt, and electrically tap a live main busbar once with a cordless drill. Never again.

"Tap" may mean drill and bolt a lug on the busbar for an electrical tap.

It annoys me when I see guys bolting lugs on busbars with the same hardware they hang pipe with, mild steel coarse thead bolts. Hardware should be minimum high carbon steel with fine thread bolts, grade five or better, with very good corrosion protection plating. Busbar bolting specs usually include Belleville concave washers. If you see silicon bronze bolts in the spec, that's marine grade corrosion protection.
 

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
What do you guys think of a fusion welding process to attach a lug. Like thermite welding that can pretty much be done without too much hands on contact?

I just wonder if some of the combustion byproducts in the air or the heated (less dense) air might cause a flash-over.


Thin air can be a sucky insulator
 

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
VERY, VERY carefully!! NOT recommended for long term life expectancy. Would do it differently today than I did it back then 12 or more years ago. I see infinity beat me to the reply so I won't bore you with the details. Same basic idea only I used a cordless drill.

Lol...thanks
 

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Most likely you are looking at a bad spec. I did it once, copper is very soft, malleable, and the busbars get pretty thick so i was able to get a good hold cutting, tapping, for coarse thread bolts, but I did not like it. I would only do through bolts with high quality hardware after that. Did drill, bolt, and electrically tap a live main busbar once with a cordless drill. Never again.

"Tap" may mean drill and bolt a lug on the busbar for an electrical tap.

It annoys me when I see guys bolting lugs on busbars with the same hardware they hang pipe with, mild steel coarse thead bolts. Hardware should be minimum high carbon steel with fine thread bolts, grade five or better, with very good corrosion protection plating. Busbar bolting specs usually include Belleville concave washers. If you see silicon bronze bolts in the spec, that's marine grade corrosion protection.

Yes drill and tap means just that right.. Drill and apply lug
 
I had drilled and tapped a bus in a sewer treatment plant in Spring Creek Brooklyn NY in 1975. And as far as I can remember it was not hard, it was very easy. Had this receptacle with two alagator clips that we would clip on to the "BUSS". We called it the clip light. of course it also had a pigtail and lamp on it. S long as you are on the same phase its ok, but matt off everything around you. And as always......turn it off if you can.
 

renosteinke

Senior Member
Location
NE Arkansas
FWIW ...

Ordinary general purpose drill bits won't drill copper well at all. That have what is known as a 118 degree point. Look at the bit from the end, and you can see the letter "S" formed by the contours.

What you need to use is a 135 degree "split point" bit. This bit has a flatter point, and when you look at it from the end you see a 'bow tie.'

Drill with a slower speed and greater pressure.
 

Fulthrotl

~Autocorrect is My Worst Enema.~
FWIW ...

Ordinary general purpose drill bits won't drill copper well at all. That have what is known as a 118 degree point. Look at the bit from the end, and you can see the letter "S" formed by the contours.

What you need to use is a 135 degree "split point" bit. This bit has a flatter point, and when you look at it from the end you see a 'bow tie.'

Drill with a slower speed and greater pressure.

ya must have been a machinist in another life.... ;-)

as long as the existing bus has drilled and tapped holes, matching the same size and
thread count is acceptable, just make sure you use the correct pilot bit, so you get
a fully formed thread.

unless i can get a kit, with all matching nuts, bolts, and hardware that is OEM,
i use belville washers, and allen head cap screws, as the black ones with
knurling are grade 12. i'm also more partial if i can, to using grade 12 nuts on
the backside instead of drilling and tapping.

grading of bolts is not always "more is better". i've seen situations in off road racing
where a grade 12 engine mount bolt, thru bolted, will snap off in an hour of racing,
and the emergency repair piece of 1/2" running thread with two locnuts on it stayed tight
and didn't break for six months.....

same with torque. more isn't always better.... you want the bolt slightly stretched, a
percentage of the amount you can stretch it without failing, like 40% or so. that's how
the torque tables were developed for fasteners.
 
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