fasteners

[Ol'fogasaurus]

The question on fasteners came up and I posted this in the wrong place. Some thoughts based on my experiences with them.

https://www.astm.org/Standards/fastener-standards.html

And then there are Fed Spec'd fasteners (and other processes within some of the specs shown here) such as AN, NAS, AND, MIL and so on. Add to that you have the metric specs and (probably) specs from each country around the world plus fasteners made by companies that are also speced to their needs. I am not sure I have covered all of the problems either. It is all very confusing and what you get from off-shore (or even withing the states) can be very questionable.

Fed specs. have a lot of close tolerance fitting and testing requirements found within the specs applicable each batch of fasteners produced. Not sure about a lot of the other manufactures standards. The ones I worked on their design or worked with were tightly controlled (its hard to replace a bolt at 34K feet in the air ). There were grounded airplanes at times when the test (et al) data did not arrive with the fasteners or within the time allotment.
https://www.astm.org/Standards/fastener-standards.html

And then there are Fed Spec'd fasteners (and other processes within some of the specs shown here) such as AN, NAS, AND, MIL and so on. Add to that you have the metric specs and (probably) specs from each country around the world plus fasteners made by companies that are also speced to their needs. I am not sure I have covered all of the problems either. It is all very confusing and what you get from off-shore (or even withing the states) can be very questionable.

Fed specs. have a lot of close tolerance fitting and testing requirements found within the specs applicable each batch of fasteners produced. Not sure about a lot of the other manufactures standards. The ones I worked on their design or worked with were tightly controlled (its hard to replace a bolt at 34K feet in the air ). There were grounded airplanes at times when the test (et al) data did not arrive with the fasteners or within the time allotment.

Lee

[Ol'fogasaurus]

http://homepages.cae.wisc.edu/~me231/on ... andout.pdf

This is one of those things that you will probably forget about but just may come in handy at some time in your future. It talks about the detail basics of fasteners; "fasteners" this time meaning certain basic types of bolts and of screws. How to read the blueprints when pertaining to fasteners, and details on several styles of fasteners.

It does miss some of the "whys" but basically it is pretty good. One of the "whys" might be why are the flutes on the underside of the head machined away so not to be flat (it allows you to turn the bolt by the head of the bolt and not have the flutes dig in. The same for the nut.).

Lee

[Ol'fogasaurus]

On page 10 figure 9 of http://homepages.cae.wisc.edu/~me231/on ... andout.pdf the last of the three images is for spot facing. The picture isn't the best it could be as one of the uses for "spot facing" is in the situation where the head or parts of the fastener head is "riding the radius" (not clearly shown here) of whatever you might be up against, even thin metal (care has to be taken here). You have to accommodate body the outside dimensions of the fastener but also you may have to accommodate the tool that will be used to work the fastener or nut. Spot facing and counter boring also can be the same thing but usually spot facing only cuts into the radius of the area to be relieved.

There is some other things that should be shown especially to clarify how a nut and bolt work together and what happens when things "tighten up" and why "torqueing" is so important.

Lee (still got the "teaching bug" .