The instructions from Beneteau specified the use of a small amount of Never-Seez for each bolt and also provided table with min & max torque values for each size of bolt. The instructions are saved and available on the OneDrive cloud server.
Not sure where you read this but it sounds fishy. As bolt torque increases the friction on the threads and under the head of the bolt to the mating part increases dramatically. Having worked in aerospace manufacturing for decades I can assure you that thread lubricants were extremely common. Mo-lith No. 2 thread lubricant was a very popular engineering specification for fasteners and I recommend it for this application of keel bolts or nuts. Here's an outfit that sells single tubes at a reasonable cost. Might be a good addition to the SBO store! https://www.skygeek.com/lubriplate-...h-no-2-moly-lithium-lubricant-14-oz-tube.htmlI'm pretty sure I read on SBO that bolts to be torqued should have clean and dry threads for proper readings. Just say'n.
I’m quoting a Beneteau engineering doc with that statement.Minimum engagement depth for full structural integrity, will vary greatly depending on the materials in question (grade of the fastener) & the thread form.
I personally wouldn't be all that trusting of Beneteau' s specs. This is the info I received on keel boats torque for my boat, note the M20 have a min. of 94 ft. lbs. and a max. of 195 ft. lbs., 101 ft lbs difference, kind of a rinky dink scale,hahaI’m quoting a Beneteau engineering doc with that statement.
There are separate torque spec's for dry fasteners & lubricated fasteners. The numbers for the lubricated fasteners are lower. Torque spec's vary with fastener material & thread form. General recommendations for various fasteners can be looked up in charts. https://www.google.com/search?q=tor...WBwFMKHQ0TAWcQsAQIVw&biw=1280&bih=887#imgrc=_I'm pretty sure I read on SBO that bolts to be torqued should have clean and dry threads for proper readings. Just say'n.
It might be helpful for you to define that sort of thing when you make the kind of statement that you originally did. Within a specific set of parameters, using a specific bolt in a specific material, your original statement MIGHT be true. But if someone were to take what you originally wrote as a blanket statement & apply it in a different situation, they could cause a mechanical failure.I’m quoting a Beneteau engineering doc with that statement.
This still varies with the material in question. Not all fastener materials have a consistent ratio of tensile strength to shear strength. In the case of a machine screw going into a tapped hole in a material that is different from the material that the bolt is made of, this standard goes right out the window.For standard UNC threads three full threads engaged fully will give the full strength of the fastener. This is based on the cross section area of the root diameter compared to the cross section area of the thread at the pitch diameter for three threads. Another way of expressing what Jack offered
In the case of something like an aircraft, where everything has been engineered down to the last detail to save weight & there is a high expectation that only AFP's or other skilled individuals will be torquing fasteners, it is common to see torque ranges that are very narrow & even detailed instructions on torque intervals & patterns.I personally wouldn't be all that trusting of Beneteau' s specs. This is the info I received on keel boats torque for my boat, note the M20 have a min. of 94 ft. lbs. and a max. of 195 ft. lbs., 101 ft lbs difference, kind of a rinky dink scale,haha
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In my many years of mechanic/welding work it is very uncommon to see a range like this. Otherwise the instructions would be tighten until tighten. It's not uncommon to see a range of 2-4 ft lbs,variance but definitely not a 101 ft lbs .!In the case of something like an aircraft, where everything has been engineered down to the last detail to save weight & there is a high expectation that only AFP's or other skilled individuals will be torquing fasteners, it is common to see torque ranges that are very narrow & even detailed instructions on torque intervals & patterns.
In the case of less critical equipment that is likely to be worked on by less qualified individuals, it is common practice to oversize the fasteners by a much larger safety factor. In this case, a much wider range of acceptable torques may be appropriate. Perhaps that may be the case here.
A mechanic is most often a skilled individual. An engine is a highly engineered piece of equipment. Your example is one step below an AFP working on a Cessna or a Dart, but far from the bottom of the staircase.In my many years of mechanic/welding work it is very uncommon to see a range like this. Otherwise the instructions would be tighten until tighten. It's not uncommon to see a range of 2-4 ft lbs,variance but definitely not a 101 ft lbs .!
In the case of a bolt going into a nut how many "good" threads are in the nut? A quick check of a 1/4-20 nut shows it is 0.219" thick. So 20 X 0,219 = 4.38 threads. The first and last thread will be imperfect threads so if we assume about half of each thread is the full thickness of the thread form we get a little over three threads. For a 1/2-13 we get .427 X 13 = 5.5 again throwing out a full thread for imperfect form we end up with 4.5 threads. I can't argue that a bolt going into modelling clay will need a lot more threads engaged to develop the full strength of the joint. But the strength of the fastener is not effected by the modelling clay it is a property of the fastener.This still varies with the material in question. In the case of a machine screw going into a tapped hole in a material that is different from the material that the bolt is made of, this standard goes right out the window
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A common 1/4 -20 (UNC) nut & a common 1/4-28 (UNF) nut generally have about the same outer dimensions, but different numbers of threads in engagement. Same with 1/2-13 & 1/2-20.In the case of a bolt going into a nut how many "good" threads are in the nut? A quick check of a 1/4-20 nut shows it is 0.219" thick. So 20 X 0,219 = 4.38 threads. The first and last thread will be imperfect threads so if we assume about half of each thread is the full thickness of the thread form we get a little over three threads. For a 1/2-13 we get .427 X 13 = 5.5 again throwing out a full thread for imperfect form we end up with 4.5 threads. I can't argue that a bolt going into modelling clay will need a lot more threads engaged to develop the full strength of the joint. But the strength of the fastener is not effected by the modelling clay it is a property of the fastener.