Torque?

Shipper · Jan 11, 2021

Making pretty good progress on the rebuild - big time thanks to this forum. Finally found a new long screw for the starter motor and will be installing it to the bottom case soon. Who can tell me the torque on the 10mm bolts that hold the gear cover inside the left engine cover. Only torque not listed in the manual. Searched the Garage forum to no avail.

Thanks,

Jim · Jan 11, 2021

Those are 6mm bolts. 7 ft. lbs. is standard torque for a 6mm bolt.

Shipper · Jan 11, 2021

Jim said:
Those are 6mm bolts. 7 ft. lbs. is standard torque for a 6mm bolt.

Not usually one to question the expertise on this site - in particular yours, but nothing but a 10mm socket fits on these bolts.

RustiePyles · Jan 11, 2021

6mm is the thread diameter 10mm is the hex diameter, bolts are measured by thread diameter. :cheers:

Shipper · Jan 11, 2021

Duh...sorry guys.

Jim · Jan 11, 2021

You don't measure a fastener by the head size, you go by the shank. It's 6mm. All 3 fasteners below are torqued to 7 ft. lbs. Yet only one uses a 10mm wrench. All have a 6mm shank though...

jetmechmarty · Jan 14, 2021

Shipper said:
Duh...sorry guys.

Nope! It was a good question and I expect you're not the only one who doesn't understand this.

Also, torque specs are usually for clean, dry threads. Anything slippery that you apply to the threads will increase the torque.
(My Moto Guzzi manual specifies "lube torque" in the introduction pages, so it's good to read the manual.)

Steve C · Jan 14, 2021

In other words, for a given torque spec, for example 10 ft lbs,
when you lubricate the threads they will be tighter (more force on the threads) than if they are left clean and dry.
which (counterintuitively) means you run a greater risk of stripping out the threads or popping off the fastener head when they're lubed.

I believe thread locker fluid counts as lubed?

Good times.

jetmechmarty · Jan 14, 2021

Steve C said:
In other words, for a given torque spec, for example 10 ft lbs,
when you lubricate the threads they will be tighter (more force on the threads) than if they are left clean and dry.
which (counterintuitively) means you run a greater risk of stripping out the threads or popping off the fastener head when they're lubed.

I believe thread locker fluid counts as lubed?

Good times.

Yes, you are correct on all counts.

Consider when you torque a bolt, you are stretching it. With lubricant, you stretch it farther for a given setting on your torque wrench. That concept helps with understanding, I believe.

So, be careful honking on that steel bolt against aluminum threads!

arcticXS · Jan 14, 2021

jetmechmarty said:
Nope! It was a good question and I expect you're not the only one who doesn't understand this.

Also, torque specs are usually for clean, dry threads. Anything slippery that you apply to the threads will increase the torque.
(My Moto Guzzi manual specifies "lube torque" in the introduction pages, so it's good to read the manual.)

I MAY be wrong, but think I have seen old British Standard (Whitworth) spanners that were marked with the thread size, not the actual gap of the spanner. Something like 1/2" BSW would then be a spanner with a gap of maybe 7/8".

Jim · Jan 14, 2021

arcticXS said:
I MAY be wrong, but think I have seen old British Standard (Whitworth) spanners that were marked with the thread size, not the actual gap of the spanner. Something like 1/2" BSW would then be a spanner with a gap of maybe 7/8".

No... you're right. Forgot about that
Here's a quick (and rather obvious) way to find the size of your fastener, that I used to teach my students.... find the smallest open end wrench that fits the shank. Here's an 8mm bolt. An 8mm wrench just fits...

xjwmx · Jan 14, 2021

Good video about torque, starting at 3:27

DaveO · Jan 15, 2021

As an ex lecturer, I always used to tell my students, "There are no stupid questions. There will always be several people who who will be grateful the question was asked. Either because they were too timid to ask it, or because they now have their misunderstanding of it corrected without the embarrassment of having to ask."

Good post. I, at least, have learned something from Jim.

Jim said:
Here's a quick (and rather obvious) way to find the size of your fastener, that I used to teach my students....

Every day is a "school day".

Torque?

Shipper

XS650 Addict

Jim

Beyond the edge is the unknown. Here be Dragons

Shipper

XS650 Addict

RustiePyles

"Pocket sand! Sh-sh-sha!'

Shipper

XS650 Addict

Jim

Beyond the edge is the unknown. Here be Dragons

jetmechmarty

Project collector

Steve C

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jetmechmarty

Project collector

arcticXS

XS650 Guru

Jim

Beyond the edge is the unknown. Here be Dragons

xjwmx

XS650 Guru

DaveO

XS650 Addict

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