suitable torque wrench - PG11 Cable gland

[dogbural]

Hi,

I have been searching for torque wrench suitable to PG11 cable gland (Nut flat width 21.6mm), applying a torque of 7.5Nm.

I have no luck; I am wondering if there is any website/company I can contact.

Please advise

Thanks
MK

 

[3DDave]

Is this for a one-off use or for a factory? What wrenches have not been suitable and what is the problem with them?

 

[dogbural]

Will be used for factory. Cannot find any torque wrench (open ended) suitable for PG11 size and capable of a torque of 7.5Nm

 

[TLHS]

I don't know anything about this, but I went on a bit of a run around because I was curious whether there were wacky wrench sizes I was unfamiliar with. Glands appear to use pretty typical metric sizes for the actual nut portion, it looks like. I can't find any mention of your unusual size for that. There are lots of data sheets who have that size for things like the maximum cable dimension though.

Are you reading the wrong number on the data sheet or have you bought a very unusual part?

 

[3DDave]

At worst, get a 22mm width and glue in a shim. The torque wrench will work the same.

 

[dhengr]

Dogbural:
Why not use a 22mm open end wrench (that’s only .4mm clear across the flats) with a long enough handle so you can fashion a pulling force point at 12" (304.8mm), for a spring scale. I don’t work in Nm’s ever day, so, isn’t 7.5Nm’s = 66.38 "lbs.? That’s only 5.53 lbs. out at 12", and don’t forget to include the weight of the wrench, at its c.g., in the moment calc., with these small forces. Tighten that cable gland up, finger tight, and apply your make-shift torque wrench with 5.5 lb. force. I’ll bet that after a good mechanic does a dozen of these he will finger tighten that cable gland and know that it needs another quarter turn, or some such, to hit the mark. Isn’t this effort primarily intended to adequately compress the o-ring?

 

[BridgeSmith]

7.5Nm (66in-lbs) is in the typical range for a 1/4" drive torque wrench. If you can't put a socket on it, would a 22mm crowfoot wrench work? You would need a 1/4" drive to 3/8" drive adapter. All 3 are readily available.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Stick.]

A 1/4" drive torque wrench with a crow's foot wrench was my first thought as well. Either shim a 22mm wrench, grind out a 21mm wrench or use the 22mm and don't care about the slop (least desirable option). I suppose a fourth option is to have a crow's foot custom made with the desired opening and 1/4" drive so you can forego an adapter. Note that you'll have to adjust the torque value to account for the offset on the crow's foot wrench:

https://www.engineersedge.com/manufacturing_spec/torque_wrench_1.htm

 

[BridgeSmith]

use the 22mm and don't care about the slop

There's not much slop with a 22mm wrench on a 21.6mm nut. I'm fairly sure 21.6mm is within the tolerance for a "22mm" nut, anyway. A little 'slop' won't matter, especially with such a low applied torque value.

Update: I was able to access the ASME specification for metric bolts (B18.2.2M), and while there isn't a bolt size listed that has a 22mm head, the M12 has a 21mm head. The width across the flats is 21.00mm max and 20.16mm min. So, even for structural bolts, which in that size are routinely torqued to over 100 ft*lbs (135 N*m), the head is allowed to be 0.84mm under the specified size. 0.4mm under with 7.5N*m applied does not seem like it would be a problem.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Stick.]

BridgeSmith: good catch, shows how little I work in metric that I didn't immediately realize that's a negligible difference.

 

[3DDave]

You need to also consider that wrenches have + margin on their opening as well that adds to the potential clearance. It doesn't take a lot of gap to be rounding off the corners and it gets worse if the nut is plastic. The low torque helps avoid that but if the nut doesn't have sharp corners then it's back to being worse if there's a gap.

I do like the idea of grinding out a 21mm wrench vs shimming. A personal blind spot over mangling tools, even if it's useful.

 

[BridgeSmith]

I do like the idea of grinding out a 21mm wrench vs shimming.

If it's needed, I agree that's the more durable option. If it needs to be that exact, they should probably have several in different sizes, since there's bound to be some variation in the nut dimensions.

Rod Smith, P.E., The artist formerly known as HotRod10