×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

What is wrong with my Nut (K) factor calculation?

What is wrong with my Nut (K) factor calculation?

What is wrong with my Nut (K) factor calculation?

(OP)
I'm trying to calculate K factor, following the guidelines of the Machinery's handbook (I have 29th edition paper copy, and 27th edition electronic copy) but I'm not real confident in the results I'm getting.
The machinery's handbook lists the CoF for stainless steel/stainless steel as .14 - so that is what I've input.
However I'm getting a calculated K factor of -.02 for un-lubricated stainless steel fasteners, which just can't be right.

I've tried other CoF's from the chart on engineer's edge, but none of them seem to yield a resulting K factor that makes sense to me.
I think there has to be some mistake in the equations I'm using, but I don't know where. Hoping some more experienced eyes can help me out here.

Also, I'm open to different equations or methods of calculating the K factor. Preferably with source cited so I can justify in my reports.
Attached is my excel spreadsheet and below are screenshots in case you don't feel like downloading it.

Thanks for any assistance.

Inputs/outputs:


Formulas:


Machinery's handbook references.
CoF's:


K factor equations:


RE: What is wrong with my Nut (K) factor calculation?

Hi

I think the formulae part in brackets after the 2*d is dividing into the number 1, try it this way round:-
(p/*****)*1/(2*d) and i think you will get the right answer.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: What is wrong with my Nut (K) factor calculation?

Change your alpha prime and Beta to radians instead of degrees. Row 21 and 23

Doing that, your nut factor comes out to 0.1672

RE: What is wrong with my Nut (K) factor calculation?

(OP)
@desertfox - I tried playing with order of operations - getting no difference using additional parentheses or changing placement.




@ehbadger - I'm getting a different result than you just changing those to radians. Was there another change you made possibly that I missed? With just that change I get a nut factor of .5432.


RE: What is wrong with my Nut (K) factor calculation?

Hi cbrf23

Oh sorry that it didn't work I'll try and work through the calculation and see what result I get.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: What is wrong with my Nut (K) factor calculation?

(OP)
@Ehbadger - I see what you did.
However, those results would be incorrect I believe.
Excel returns Radians by default for all the trig functions (AFAIK)

including ATAN.


So using the RADIANS function is unnecessary and is actually taking the ATAN result (already in radians) and multiplying by π/180.


Using radians, I get a nut factor of around .54, which seems really high to me.

RE: What is wrong with my Nut (K) factor calculation?

Ah right.

Ok looking closer, your alpha you use (B22) is in degrees. Change that to radians. Doing that and removing the =RADIANS from alpha prime and beta, and you get 0.1778 nut factor.



RE: What is wrong with my Nut (K) factor calculation?

Hi again

Calculating the nut factor by hand I get the value to be 0.177796 which agrees with the post ehbadger, so modify the spreadsheet to the one ehbadger used.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: What is wrong with my Nut (K) factor calculation?

(OP)
Excellent!!
Than you gentlemen, I really appreciate the help!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources