Thread protrusion - a measure of good workmanship

[Gerald D]

Looking at some of the photos, I often notice screw threads that are too long.....they stick too far past the nut. A shorter screw should have been used.

What's wrong with a lot of thread protrusion? Those threads are waste of material and can cause injuries or scars on the product. They wear out self-locking nuts before the nuts get to do any work. They waste elbow grease. They easily get damaged and make nuts hard to remove.

What is acceptable? It seems the popular American way is to allow up to 10 threads protruding (USNavy (http://www.submepp.navy.mil/jfmm/HTML/Volume%20V/V-I-05.htm)), but NASA (http://workmanship.nasa.gov/lib/insp/2%20books/links/sections/files/603.pdf) has seen the light: "Thread extension should not be more than 3.0mm (0.12 in.), plus 1-1/2 threads for bolts orscrews up to 25 mm (0.984 in.) in length, or 6.3mm (0.248 in.) plus 1-1/2 thread for bolts / screwsover 25 mm (0.984 in.) in length."

Our size of screws are typically sold in 1/4" (5mm) length increments. Use the shortest screw that will give at least one thread beyond the nut.

[Regnar]

Gerald, I know in the Aviation Field the tolerance is 3-5 threads of protrusion. Less than 2 we start looking for a longer screw or bolt. The vibrations, expansion and contraction of the aircraft will often loosen bolts 2-3 turns in a few weeks.

Another form of good craftsmanship is a use of a Torque Wrench. To often people under torque larger bolts and over torque smaller bolts. Loose bolts elongate holes and over tighten bolts will strip out fastners.

Here is a good chart to see what you should be torquing the bolt around.

http://www.imperialinc.com/pdf/A_FastenerTorqueCharts.pdf

[Gerald D]

I didn't realise that those looooong screws were for safety margin.

[Regnar]

10 threads is a little overkill. What is funny is Nasa says 1 1/2 threads minimum but shows a picture of 3 threads protruding.;)

[domino11]

And you guys really think they actually went to the moon? :)

[Jan de Ruyter]

Problem is, if you go to the screw shop (or nut shop), they only have three sizes:

1. Too long

2. Too short

3. Out of stock.

[Gerald D]

Hacksaw + file . . . . apprentices were taught how to use them :)

[tangocharlie123]

Here in Australia Casa (aviation Aurthority):D requires us to have only two threads showingand we use the american AN series.
There was rumors that they were going down to 1/2 a thread.

Cheers

[hennie]

And NASA used Pratley Putty also to the moon

[lumberjack_jeff]

Excess bolt length? Bend 'er over and you don't need locknuts. ;)

[Greg J]

Looking at some of the photos, I often notice screw threads that are too long.....they stick too far past the nut. A shorter screw should have been used.

This is why I'll never retire. :) Way too much time on your hands.

[Gerald D]

Greg, around here a long thread shouts out: Home-built, DIY or made in America . . . . . I thought that a lot of guys wanted to be aware of this. Let's say I am donating my time to a charitable cause. ;):o

[Greg J]

Too funny. :D:D:D

[Kobus_Joubert]

I am sure old BBB is HOME-BUILT here and there. :p

[lumberjack_jeff]

Greg, around here a long thread shouts out: Home-built, DIY or made in America . . . .

Then what does a microwave oven as a control enclosure say?

.... profitability. :D

With that tradeoff, I'll happily suffer the slings and arrows. Maybe I'll build the next one with less "shouting". ;)

[Gerald D]

Jeff, your system shouts "MacGyver"...and there is nothing wrong with that! :D

A lot of guys are building real show piece machines with top quality welding, paint & wiring jobs, but then have a few long screws sticking out. For years I shut up about that because that is apparently quite acceptable in the "inch-oriented" part of the world. Now that I can risk losing a few friends (since I am officially "retired" and thus senile), I thought it time to take a dig :D . . . . . see it in the same light as the swipes against the inch users :rolleyes:

[qroger]

I used to read a car magazine that covered a competition for Americas Most Beautiful Roadster, (AMBeR). When I read that the car builders "clocked" the nuts and bolts so they would all be oriented the same way, I found other places to spend my attemtion span. Who knows maybe the "Rat Rods" have a few out of place for that wild look.

[Gerald D]

My old man was a garage owner and as a kid I spent a lot of time in his workshop taking things apart. From a very early age I learnt to hate long protruding threads when they were rusty and the nut was in a bad spot that only allowed a 1/6th turn of the wrench. Exhaust pipe clamps immediately come to mind...

[qroger]

I remember a radiator attachment bolt on a Triumph TR-3. With an open end wrench I could get part of a turn, flip the wrench over and get another part. I think I was getting one face, (1/6 of a turn) from each two wrench flips. And it was a looooooong rusty bolt. I'm actually with you on the too long bolts. Besides the other considerations, those long bolt ends seem to collect dings, dents, rust and the odd piece of clothing or skin. My issue with the "clocked" nuts is that some have to be torqued too loose, and some over torqued for them all to line up the same.

[polishpickle]

10 threads is a little overkill. What is funny is Nasa says 1 1/2 threads minimum but shows a picture of 3 threads protruding.;)

1 1/2 minimum so 3 what is their maximum 3