Torquing Slotted Screws

N

nizak

Senior Member
Does anyone else find it difficult to torque slotted screws such as breaker terminations and equipment with slotted vs hex lug terminations?

Hard to get a good fit on the slot with a variety of different size heads.
 
I think the better question would be "Does anyone NOT find it difficult..." I hated having to use slot-only QOB breakers, and was soooo happy when my local house started getting the square-bit versions.
 
infinity said:
I have a variety of slotted tips for my torque tools so I try to find the tightest fit. I agree with you that the slotted screw design is not well suited for torqueing.
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Even a Phillips screw would be better as long as you use the correct bit.
 
And if the bit slides off center, your torque values are not accurate.

As a mechanic/millwright I've always hated torque as a measure of fastener preload. Too many variables to throw the readings off. Even the wrong lubricant on the threads. But for a lot of stuff it is the only practical way. Degrees of rotation or measuring stretch is much better, but for a lot of things that just isn't even remotely practical
 
Joethemechanic said:
And if the bit slides off center, your torque values are not accurate.

As a mechanic/millwright I've always hated torque as a measure of fastener preload. Too many variables to throw the readings off. Even the wrong lubricant on the threads. But for a lot of stuff it is the only practical way. Degrees of rotation or measuring stretch is much better, but for a lot of things that just isn't even remotely practical
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Definitely. In many applications torque is just about worthless. Especially for lots of electrical stuff which has low quality and inconsistent threads.
 
ModbusMan said:
I think the better question would be "Does anyone NOT find it difficult..." I hated having to use slot-only QOB breakers, and was soooo happy when my local house started getting the square-bit versions.
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I have had the square drive screws strip out frequently when torquing. Especially on ground and neutral bars. The manufactures need to use one drive type on screws. The combo square, slotted and sometimes Phillips makes the screw drive area very week. I think Torx would be best.
 
curt swartz said:
I have had the square drive screws strip out frequently when torquing. Especially on ground and neutral bars. The manufactures need to use one drive type on screws. The combo square, slotted and sometimes Phillips makes the screw drive area very week. I think Torx would be best.
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I remember having the bar screws strip like you describe, but 120v in a data center is thankfully becoming less common (apart from telecom provided endpoints, which their techs have an ungodly habit of plugging into 208v and providing escape routes for the magic smoke), so there are plenty of spare N/G connections on the panels to work with.
 
Many of the slotted screws on electrical components work with the Milwaukee ECX or Klein C combo bits, which I try to remember to use. The inner portion keeps the bit in place and the outer slotted "wings" help give good torque values.
 
How did we do it for so many years and almost never touch a torque wrench. I swear this is because everyone new coming into the trades is green as green can be and they have no mechanical feel
 
I had to change out the breaker in this last year. It was only 2years old at the time. The right top screw had never been tightened down. It burned up and welded the lug good and the breaker would trip from over heating when they used just the stove or furnace. The tourqe rules although not perfect are needed for people to have a fall back and say yes or no did you follow the installation instructions.1000004445.jpg
 
letgomywago said:
I had to change out the breaker in this last year. It was only 2years old at the time. The right top screw had never been tightened down. It burned up and welded the lug good and the breaker would trip from over heating when they used just the stove or furnace. The tourqe rules although not perfect are needed for people to have a fall back and say yes or no did you follow the installation instructions.View attachment 2579022
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No torque wrench in the world is going to stop a dumb dumb from missing tightening a fastener. It's not going to prevent cross threading, getting an incorrect reading from damaged threads, torquing it down till it clicks and having the fastener bottom out in a hole, or any other kind of contact the fastener makes to make the wrench click but not being tight in the right place
 
Joethemechanic said:
No torque wrench in the world is going to stop a dumb dumb from missing tightening a fastener. It's not going to prevent cross threading, getting an incorrect reading from damaged threads, torquing it down till it clicks and having the fastener bottom out in a hole, or any other kind of contact the fastener makes to make the wrench click but not being tight in the right place
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But it does show that it was without a doubt installed incorrectly and that my install with one is correct. We live in a time of lawyers and no common sense.
 
letgomywago said:
But it does show that it was without a doubt installed incorrectly and that my install with one is correct. We live in a time of lawyers and no common sense.
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But what proof is there that the numb nuts torqued it? Because he checked a box on a printed form? They all pencil whip those forms. I've proven it to corporate types by doing something that makes it impossible for them to do the actual procedure, and the little check boxes still come back checked off. (BTW corporate types will hate you for exposing their hired numb nuts for the idiots they are)

It's easy BTW, all you have to do is add check boxes for things that don't exist, or things that they don't have the equipment to perform.
 
Joethemechanic said:
And if the bit slides off center, your torque values are not accurate.
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That doesn't sound right to me. If the bit slides off center, the lever arm between the two ends of where the bit makes contact with the screw head will be shorter, as you won't be using part of the slot. But that just means the force will be higher at each of the contact points, the torque should still be the torque.

Cheers, Wayne
 
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