Thread resistance reference

[gersen]

Hi,
I'd like to make my calculation sheet more formal.
Some one has a reference for the calculation of non-standard-thread resistance?
I use some basic formulas but I don't have a reference of some norms, textbook,...

Thank you

 

[drawoh]

gersen,

Are you talking resistance to being torqued down?

This would be massively affected by the material, the finish, the fabrication method and by the clearances in the thread. Is a formula even possible?

--
JHG

 

[Sparweb]

My belief is that the values for running torque (assuming Drawoh has guessed right) are determined by test with controlled conditions.
I don't remember seeing a way to calculate it, other than extrapolate the test data for a thread size not in the table but all other conditions being met (material, finish, lubricants, etc).
But usually a thread torque table is very thorough and doesn't leave out any of the common sizes.

Can you tell us what thread form you are using? It is possible that a running torque table already exists, but we can't find it unless you tell us what it is.

STF

 

[Screwman1]

Can you give us a little more information on exactly what you are trying to obtain for outputs and what you will be able to provide for inputs? This group will likely be able to tell you what formulas are in existence and if what you are hoping for is even feasible.

 

[SandCounter]

The Machinery's Handbook has formulas for calculating thread friction in the Torque and Tension in Fasteners chapter.

I used to count sand. Now I don't count at all.

 

[gersen]

I'm referring on the shear strenght of the thread.
I find the shear area of the thread, calculate the stess in the area and check against the tensile strengh of the material.

I'd like to know if there is an official source about how to calculate the shera strengh of the thread.

We build hydraulic cylinder, we use the thread for the head. We use thread from the small M6,M8 up to M400 and bigger, with pitch up to 12 mm.

 

[drawoh]

gersen,

That is a completely different question. Thread stripping is discussed in the Machinery's Handbook. Look under Fasteners, Torque and Tension in Fasteners, and Length of Engagement.

--
JHG