Torque wrenching
Thread Starter
Racer
Joined: Jul 2013
Posts: 385
Likes: 3
From: Leesburg VA
Torque wrenching
I was reading in one of my engine rebuilding books about using a lubricant on the threads of some bolts and decreasing the torque values by some percentage over the dry recommendations.
My question is, as I reassemble the suspension on my 74, should I be using some sort of lubricant on the threads of all the fasteners, or should I torque them to specs dry. I know that I should use Locktight Red on the control arm bushing bolts according to Vansteel (using poly bushings).
John
My question is, as I reassemble the suspension on my 74, should I be using some sort of lubricant on the threads of all the fasteners, or should I torque them to specs dry. I know that I should use Locktight Red on the control arm bushing bolts according to Vansteel (using poly bushings).
John
Race Director
Joined: Jul 2004
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From: Scottsdale Arizona
The only place that I've seen where lubricant is used on washers and threads are the head, main and rod cap bolts. In those cases, the specs specify that they are for lubricated threads, washers and bolt heads ( or nuts). Remember that these fasteners will always be in contact with lubricant. I wouldn't lubricate nuts and bolts on your suspension though.
Race Director
Joined: Apr 2011
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From: North of Toronto - Ontario
Dry vs wet torque is another one of those arguments that isn't going to be solved here.
In non-critical use, target torque values are usually only within about 25% of optimum. Factor in the questionable accuracy of the torque wrench (particularly the clicker style ones), thread condition (paint, rust, damage, etc) and you can see where the difference between wet and dry torque values quickly becomes negligible.
In critical areas (some motor work etc) most manufacturers of these precision/specialty type fasteners have tested their fasteners and provide conversion charts or values to allow for the use of torque values instead of the stretch measurement.
There are special tools for measuring the stretch of the fastener rather than the torque but not in most peoples tool boxes.
That being said, and in this case for the suspension, just try to compensate for any torque needed to turn the bolt and toque to whatever the factory numbers are.
My $.02
M
In non-critical use, target torque values are usually only within about 25% of optimum. Factor in the questionable accuracy of the torque wrench (particularly the clicker style ones), thread condition (paint, rust, damage, etc) and you can see where the difference between wet and dry torque values quickly becomes negligible.
In critical areas (some motor work etc) most manufacturers of these precision/specialty type fasteners have tested their fasteners and provide conversion charts or values to allow for the use of torque values instead of the stretch measurement.
There are special tools for measuring the stretch of the fastener rather than the torque but not in most peoples tool boxes.
That being said, and in this case for the suspension, just try to compensate for any torque needed to turn the bolt and toque to whatever the factory numbers are.
My $.02
M
Safety Car
Joined: Jan 2014
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From: Walhalla South Carolina
I was a former Mech. Instructor at a nuclear facility and we trained our tech. on this issue. We had a training aid with string gauges that showed the difference when using lubricant and not using lubricant on fasteners. I would always use lubricant on fasteners, the friction points will rob you of the true torque required for a given application. I even lub my wheele lug nuts before installing.
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From: New Or-leens Loo-z-anna
I use the "Next-time" Rule: If it was rusted tight this time---a dab of grease--for the next time.
(For those who switch to stainless nuts/bolts....a small amount of lube must be applied to mating surfaces---stainless-on-stainless is more than likely going to seize together)
(For those who switch to stainless nuts/bolts....a small amount of lube must be applied to mating surfaces---stainless-on-stainless is more than likely going to seize together)
Pro
Joined: May 2013
Posts: 672
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From: Rapid City South Dakota
I was a former Mech. Instructor at a nuclear facility and we trained our tech. on this issue. We had a training aid with string gauges that showed the difference when using lubricant and not using lubricant on fasteners. I would always use lubricant on fasteners, the friction points will rob you of the true torque required for a given application. I even lub my wheele lug nuts before installing.
I'll agree that torque values are an indirect representation of bolt stretch, and we probably only get a crude approximation. It's not a simple topic...
Safety Car
Joined: May 2008
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From: Lafayette Louisiana
torquing values for fasterners
I always thought you wanted to torque fasteners dry and have seen that reference in outboard engine building books.
If you do torque lubricated, here is a link that might be helpful on the amount to discount the torque values.
http://www.portlandbolt.com/technica...que-chart.html
If you do torque lubricated, here is a link that might be helpful on the amount to discount the torque values.
http://www.portlandbolt.com/technica...que-chart.html
