How tight is 40-45 lb-in (electrical panel)?

[TomR]

In an earlier post of mine about adding a second neutral/ground bar to a
Siemens Main Load Center electrical panel, I posted the instructions for
doing that:

"Here is a link to the ECCNB16 Instruction Sheet which shows this neutral
bar
kit and how to install it:

http://www74.zippyshare.com/v/43794674/file.html ."

In Step 4, on the right hand side, it says to tighten the two screws using
40-45 lb-in of torque.

I don't have a torque wrench, and I would rather not buy one just for this
unless I need to.

My question is, about how tight if 40-45 lb-in when it comes to tightening
these screws?

I have to admit that in my mind I was thinking it said 40-45 FOOT-pounds at
first, which seemed like way too much. But, then I read it again, and I see
that it says lb-IN, not lb-FT.

I am guessing that 40-45 lb-in means tighten the screws so they are
definitely tight, but do not tighten so much that the threads strip. Does
that seem about right?

[tra...@optonline.net]

Bingo!

[k...@attt.bizz]

What sized screws? That seems awfully loose, though probably not for
something like an 8-32. 48 lb-in would be four pounds on the end of a
12" wrench (40in-lb would be 4lbs on a 10" wrench).

In any case, if you've stripped the threads, it's no longer tight ;-)

[Jon Danniken]

It's about half the torque of a regular nut, so it's probably a shear
nut (take a look at what the bolt screws into).

http://www.mechanicsupport.com/shear_nut_usage.html

You can convert in-lb to ft-lb by dividing by 12, so your 45 in-lb would
equate to about 3.5 ft-lb. For comparison, a 10-32 SS fastener, with a
regular nut, has a recommended torque of about 32 in-lb (about 2.5 ft-lb).

So make it snug but not much more would be my method.

Jon

[croy]

On Fri, 17 May 2013 10:43:23 -0400, "TomR"
<To...@tomrljp5.lhd> wrote:

>My question is, about how tight if 40-45 lb-in when it comes to tightening
>these screws?

If you were to purchase a torque-screwdriver (there are some
inexpensive ones these days), you could really get a good
feel for torque, with some positive feedback. Something
that could be beneficial for a lifetime (both the
screwdriver and the, "getting to know the feel").

I always wonder about the folks who write instructions
stating: "Do not over-tighten!" and give no torque values at
all. That's like putting up speed-limit signs that read,
"Don't go too fast!".

--
croy

[TomR]

TomR wrote:
> In an earlier post of mine about adding a second neutral/ground bar
> to a Siemens Main Load Center electrical panel, I posted the
> instructions for doing that:
>
> "Here is a link to the ECCNB16 Instruction Sheet which shows this
> neutral bar
> kit and how to install it:
>
> http://www74.zippyshare.com/v/43794674/file.html ."
>
> In Step 4, on the right hand side, it says to tighten the two screws
> using 40-45 lb-in of torque.
>
> I don't have a torque wrench, and I would rather not buy one just for
> this unless I need to.
>
> My question is, about how tight if 40-45 lb-in when it comes to
> tightening these screws?

....,

Thanks everyone for your replies. I think I now have a fairly good
understanding of what 40-45 in-lbs means, so I think I'm on the right track
by just tightening the screws so they are definitely tight but not
overtightening them

Using the concept of about 4 lbs of pressure on a 10-inch bar (or a little
less on a 12-inch bar) gives me a good idea of what they mean. I can do
that.

About the size of the screws -- the kit says it comes with two 1/4-28 x
13/32 screws. So, I think they are 1/4 inch screws, 28 threads per inch,
and 13/32 in long. They go into the same threaded holes in the neutral bars
that the rest of the regular neutral and ground wire attaching screws go
into.

[k...@attt.bizz]

On Fri, 17 May 2013 13:29:44 -0700, croy <ha...@spam.invalid.net>
wrote:

You've never seen a "slow" or "slow curve" sign?

[DD_BobK]

TomR-

You exactly correct... they are 1/4 inch screws with 28 threads per
inch (fine thread)

Think about the torque in an equivalent wrench or ratchet situation.

With your hand on a wrench or ratchet at ~12" from the screw center
applying 3-1/2 pounds would give you 42 in-lbs.
With your hand at 6" you'd need to apply 7 pounds to get 42 in-lbs.

These are pretty small loads.

The diameter is of the typical screw driver handle pretty small...less
than 1-1/2"?

.. the screwdriver / nutdriver equivalent to a torque wrench is a
torque watch,
IIRC the max torques on these devices are pretty low...like 50 in-lbs
and they have bulbous handles.

You'd be hard pressed to over torque by hand with a nut driver /
square driver if it's handle is "screw driver handle sized"

I believe in this situation the torque is so low,
either because the ground bar is aluminum or they don't want to crush
the hell out of the conductors.

cheers
Bob

[micky]

On Fri, 17 May 2013 10:43:23 -0400, "TomR" <To...@tomrljp5.lhd> wrote:

I would think so.

I'm still looking for my 1/2 to 3/8" adapter so tht I can tighten my
trailer hitch to the setting the instructions said. So far the thing
hasn't fallen off.

I think if you ever really need to get this right, you can take the 45
inch pounds, divide by 12 to get about 4 foot pounds, and then using a
string probably, attach a four-pound weight to the wrench 1 foot from
the screw head.

If the screw goes in vertically, you'll need a pulley for your string.
to make it vertical.


Or you could just lift four pounds with a string or rope, get a feel
for how hard that is to do, and apply that same effort to the wrench,
one foot from the screw head. This is the way I did it at the JPL.

[DD_BobK]

On May 17, 11:37 pm, micky <NONONOmis...@bigfoot.com> wrote:

+1

[cl...@snyder.on.ca]

On Fri, 17 May 2013 21:45:06 -0700 (PDT), DD_BobK <rkaz...@gmail.com>
wrote:

It IS possible to overtorque a 45 in/lb fastener with a
"screwdriverhandle sised" nut driver.

[DD_BobK]

On May 18, 6:06 pm, cl...@snyder.on.ca wrote:
> On Fri, 17 May 2013 21:45:06 -0700 (PDT), DD_BobK <rkaza...@gmail.com>

>>>>You'd be HARD PRESSED to over torque by hand with a nut driver / square driver if it's handle is "screw driver handle sized" <<<<<

it is POSSIBLE.... but highly unlikely, unless, the nut on the handle
is an idiot.

[rep...@workshop.com]

Take a screwdriver and tighten it till the screws are tight. You dont
need no torque wrench. This is not a piece of fine machinery that
requires perfection. Even suggesting that you need to torque it is
stupid.

[DD_BobK]

On May 19, 1:09 am, repa...@workshop.com wrote:
SNIP

>
> Take a screwdriver and tighten it till the screws are tight.  You dont
> need no torque wrench. This is not a piece of fine machinery that
> requires perfection.  Even suggesting that you need to torque it is
> stupid.

>>>Take a screwdriver and tighten it till the screws are tight. You dont
need no torque wrench. This is not a piece of fine machinery that
requires perfection. Even suggesting that you need to torque it is
stupid. <<<

+1

[Bill]

In article <kn5ff1$cap$1...@dont-email.me>, To...@tomrljp5.lhd says...

>
> In an earlier post of mine about adding a second neutral/ground bar to a
> Siemens Main Load Center electrical panel, I posted the instructions for
> doing that:
>
> "Here is a link to the ECCNB16 Instruction Sheet which shows this neutral
> bar
> kit and how to install it:
>
> http://www74.zippyshare.com/v/43794674/file.html ."
>
> In Step 4, on the right hand side, it says to tighten the two screws using
> 40-45 lb-in of torque.
>
> I don't have a torque wrench, and I would rather not buy one just for this
> unless I need to.
>
> My question is, about how tight if 40-45 lb-in when it comes to tightening
> these screws?
>

Yes get an inch pound torque wrench! If you do not tighten main
electrical connections to the proper tightness, the connections will
work themselves loose.

High amperage connections which are not tight enough will heat up!

-So there is not tight enough (will cause future electrical problems).
-The correct tightness (a job done right which will be trouble free!)
-Too tight (You strip the lug and wreck your panel).

So that is the problem. People have different strength and may over-
tighten and strip the lug, but with an inch pound torque screwdriver or
wrench, you get it the correct tightness.

Look at all the posts on the internet about main electrical wires coming
loose. Loose neutral, etc. They never tightened the lugs properly to
begin with!

Note most electrical devices have tightening specifications. Even for
the screws on outlets and switches! This becomes more important with
higher amperage outlets/connections - like dryer, range, etc.

There are 12 inch pounds to one foot pound.

If you are going to do electrical work, do it right or not at all...