Torque wrench

[onetrack]

I have 2 Warren and Browns and 1 Norbar. Probably what most owners are missing is the informative W&B instruction sheet, which is near-on impossible to find today.

 

Remember that clean threads are a must when torquing fasteners (I run a bottoming tap through all threads that aren't new) - and whether you use thread lubrication or not is critical.

 

Lubricated threads will make a difference of 10% or more to actual torque applied to the fastener shank. Some manufacturers will specify whether threads should be dry or lubricated, many don't.

 

Usually fasteners are installed dry, but occasionally you will be desiring to add anti-seize to threads where corrosion potential, or the likelihood of galling, is very high.

 

Adding anti-seize to fastener threads effectively makes them a lubricated fastener, and the recommended dry thread torque setting should be reduced by 10%, when threads are lubricated.

 

The same principle applies to threadlocking compounds, they also lubricate the threads.

 

Trying to get 100% repetitive accuracy in torquing fasteners with simple torque recommendations, is very difficult.

 

Thus the reasoning behind the introduction of the "torque-angle" method, where a low torque setting is used initially to "bed" the fastener, followed by an additional set amount of turn, measured in degrees.

 

Torque and angle explained

 

 

[old man emu]

?????? the recommended dry thread torque setting should be reduced by 10%, when threads are lubricated ??? I thought that a lubricated bolt would require higher torque, but I was wrong.

 

When a bolt is lubricated - less torque is required to achieve bolt axial load or tension. Reduction of torques for lubricated vs. dry bolts are indicated in the table below.

 

Lubricant Torque Reduction

 

Lubricant Torque Reduction (%)

 

No lube 0

 

Graphite 50 - 55

 

White Grease 35 - 45

 

SAE 30 oil 35 - 45

 

SAE 40 oil 30 - 4

 

The maximum tightening torque for a slightly lubricated 1" Grade 5 coarse bolt is 483 lb ft. Dry bolt torque is approximately 30% higher - or 628 lb ft.

 

Tdry = (483 lb ft) (1 + (30%) / (100%))

 

= 628 lb ft

 

If the bolt is lubricated with SAE 30 oil - the torque compared to a dry bolt is reduced with approximately 40%.

 

TSAE30 = (628 lb ft) (1 - (40%) / (100%))

 

= 377 lb ft

 

Note that if torque specified for a dry or slightly oiled bolt torque is applied to a lubricated bolt - the bolt may overload and break.

 

 

[facthunter]

All this is good gen.. Finer threads need less torque also . That you are trying to do is apply an axial force which the design needs to locate the parts firmly . In large applications the load can be applied by hydraulic means and the nut just located against the face to position it and the hydraulic pressure released. Where you are pulling a taper in, the nut may distort the outer part of the tapered hole and alter the fit by burring the end of the tapered bore. There's a lot to be said for tightening it to a low torque initially and then going through a stipulated number of degrees to get the figure you need.. Nev

 

 

[Jaba-who]

Find out who you are going to use to calibrate it and ask them what ones they’d recommend.

 

We have a guy in cairns who actually refuses to calibrate kinchromes.

 

Says they are frequently go out of calibration as soon as they first get used after a calibration.

 

 

[old man emu]

https://www.engineeringtoolbox.com/us-bolts-torques-d_2055.html

[M61A1]

Says they are frequently go out of calibration as soon as they first get used after a calibration.

That's what I'd say about Norbar wrenches. We had heap of them on a toolboard at one place, they were rarely in cal when put on the tester (we were required to test them prior to every use). The Norbar guy used to whinge that they weren't being returned to zero after use, but I know that to be false. He also said that we should exercise the mechanism several times before use, while it made a difference, most of the time they still weren't in cal limits.