Does it matter which way these bolts are fitted? It is certainly neater if the nuts, as opposed to the bolt heads, are behind the ball plate but on my car, it's impossible to get a torque wrench onto the nuts because of the proximity of the rear valence.
Tow ball bolts
- Thread starter oldagetraveller1
- Start date
I don't think it matters if you use the nut or bolt head for the torque wrench it should give the same reading or as near as it needs.
The truthful answer is yes it can make a difference, and it depends on the materials in contact with the underside of the head of the bolt, the contact side of the nut.
Presuming the nut and bolt are made of the same material then to maximise the clamping effect for a given applied torque you should tighten the whichever part of the nut or bolt is in contact with the material with the least coefficient of friction.
Where as in some circumstances these differences may be significant for example in some aerospace applications, the bolting of a tow ball to the towbar assembly whilst of course it is important, the normall appplied torques will drown out and minimise any differences in the coefficients of surface resistance of the steel tow bar and the cast tow ball.
In many cases there may only be enough room to use a torque wrench on one side of the assembly.
Presuming the nut and bolt are made of the same material then to maximise the clamping effect for a given applied torque you should tighten the whichever part of the nut or bolt is in contact with the material with the least coefficient of friction.
Where as in some circumstances these differences may be significant for example in some aerospace applications, the bolting of a tow ball to the towbar assembly whilst of course it is important, the normall appplied torques will drown out and minimise any differences in the coefficients of surface resistance of the steel tow bar and the cast tow ball.
In many cases there may only be enough room to use a torque wrench on one side of the assembly.
I have my bolts with the heads faceing aft, plain washer under the head, spring washers under the nuts, and thread lock, torque up to 250 Nm as per Tow Trust fitting pamphlet. I have a special torque adaptor which allows me to get to the nuts, a 2 inch extention, for off set torquing. Made by Snap On. During my apprentiship we were always told that if your torqueing a bolt by the head it was 10% more than the nut.
EH52ARH said:
You might need to use more torque to correctly tighten a bolt if its s close friction fit in the through hole, Otherwise and assuming all other factors such as materials are equal, then there should be no difference.
The use of washers can of course change the surface friction, usually reducing it thus improving the clamping force.
Tighten the nut, if not possible then add more torque when tightening through the bolt.
I had not heard of the 10% add on to torque if tightening the bolt, but I will adopt that as a guide for future.
Thank you Sir Were-Rabbit
I had not heard of the 10% add on to torque if tightening the bolt, but I will adopt that as a guide for future.
Thank you Sir Were-Rabbit
ProfJohnL said:
I think Prof you mean a close tollerence fit,
Also the 10 % is depending on the application of the bolts.
EH52ARH said:
Well it might be a close tolerance fit but I actually meant an interference fit, meaning the shank or thread of the bolt makes contact with the sides of the hole causing increased friction.
I know what you mean Prof, In Aviation a bolt is one with a plain portion, and a screw has a threaded portion all the way to the head. Even though a screw can have an a bihex or a hex head. . 
In Nigeria Screw nail. Is a wood screw. They fit it in with a hammer and can only remove it with a screwdriver or a claw hammer. WONDERFULL.
In Nigeria Screw nail. Is a wood screw. They fit it in with a hammer and can only remove it with a screwdriver or a claw hammer. WONDERFULL.
In Canada, in mining they have an adjustable spanner incorporated with a forged hammer head, so with a pair you can adjust any type of fixing Excellent bit of kit
Excellent bit of kit A simple question was asked and a simple answer relevant to a tow bar was given.
Does it matter whether you tighten the bolt head or the nut?
Normally it will not matter whether the bolt head or the nut is torqued. This assumes that the bolt head and nut face are of the same diameter and the the contact surfaces are the same (giving the same coefficient of friction).
Why do we have to complicate the answer?
Does it matter whether you tighten the bolt head or the nut?
Normally it will not matter whether the bolt head or the nut is torqued. This assumes that the bolt head and nut face are of the same diameter and the the contact surfaces are the same (giving the same coefficient of friction).
Why do we have to complicate the answer?
From my aviation engineering days I seem to remember there was a formulae to apply to torque settings if you were tightening the bolt, rather than the nut. Interesting article about how much of the torque applied is used to overcome friction and how the figure varies with lubricated or dry assemblies etc.
http://www.boltscience.com/pages/nutorbolttightening.htm
seems it's all very imprecise;-)
http://www.boltscience.com/pages/nutorbolttightening.htm
seems it's all very imprecise;-)
jignc said:
Sometimes the simplest answer may be appropriate but at the same time the over simplified knowledge can be dangerous in other situations.
Also you are not the only person who may read these threads, and others may want to know more than you do. You are not obliged to read all the comments. Provided the comments do not become personal attacks, dangerous or illegal, then the forum is not restrictive.
We all have the same rights to add material subject to teh forum rules.
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