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cutting prop bolt threads

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morid(at)northland.lib.mi
Guest

Posted: Mon Feb 13, 2006 5:19 pm Post subject: cutting prop bolt threads

Rich, there's a problem with what you're doing.  AN bolts have "rolled"

threads which means they aren't cut, but rolled in with a machine.  The

reason for this is to eliminate stress cracks in the threads.  By using a

cutting die on your bolts you're changing the properties of them and what

you end up with is a bolt that does not have the tensile strenght or

predictability of a prop bolt.  It's possible that you will never have a

problem, but as important as prop bolts are, I don't think it's wise to take

that risk.

If I'm off base on this someone please let me know.

Deke



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donpearsall
Guest

Posted: Mon Feb 13, 2006 6:13 pm Post subject: cutting prop bolt threads

I absolutely agree with Deke. When you die cut the AN bolts to extend the

threads, the resulting threads are sharp and much thinner in cross section

than the rolled threads. The FAA AC's even advise against this. You could

not do this on a certified plane. If you look at them under a strong

magnifying glass, you can even see the stress cracks (that's because I have

done the same thing.) The threads will give way long before the rolled

threads will. 



Don Pearsall

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon Feb 13, 2006 8:20 pm Post subject: cutting prop bolt threads

Cutting threads like Rich is suggesting is fine if done for a 

non-stressed part on a ground-based vehicle, but for staking your life 

on...it's a bad idea. I've done work like Rich proposes on slow-poke 

cars, work benches, and house decks, but not on something that takes me 

and my loved ones up flying...don't do it!



Lynn

On Monday, February 13, 2006, at 09:11  PM, Don Pearsall wrote:



[quote] 

 <donpearsall(at)comcast.net>



 I absolutely agree with Deke. When you die cut the AN bolts to extend 

 the

 threads, the resulting threads are sharp and much thinner in cross 

 section

 than the rolled threads. The FAA AC's even advise against this. You 

 could

 not do this on a certified plane. If you look at them under a strong

 magnifying glass, you can even see the stress cracks (that's because I 

 have

 done the same thing.) The threads will give way long before the rolled

 threads will.



 Don Pearsall

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

rdarchangel(at)earthlink.
Guest

Posted: Tue Feb 14, 2006 3:34 pm Post subject: cutting prop bolt threads

Deke,

I agree with you.  Refer to Carroll Smith's book "Nuts, Bolts, Fasteners 

and Plumbing Handbook"published by Motorbooks International.  This a a 

great reference to theory and practice of high strength fasteners  It's 

written for the motor sport audience but applies to equally to aviation 

applications.

Dick

Fox5flyer wrote:



[quote]



Rich, there's a problem with what you're doing.  AN bolts have "rolled"

threads which means they aren't cut, but rolled in with a machine.  The

reason for this is to eliminate stress cracks in the threads.  By using a

cutting die on your bolts you're changing the properties of them and what

you end up with is a bolt that does not have the tensile strenght or

predictability of a prop bolt.  It's possible that you will never have a

problem, but as important as prop bolts are, I don't think it's wise to take

that risk.

If I'm off base on this someone please let me know.

Deke



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rwill1(at)adelphia.net
Guest

Posted: Fri Feb 24, 2006 12:52 pm Post subject: cutting prop bolt threads

Ah ha.... thanks for the info, I had no idea!!!



Rich

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