Thread Engagement length in Fluid power ports 1

[Channo]

Hello everyone!!!

The minimum length of engagements in threaded joints can be taken as 1*Dia. of thread. Then, how does the fluid power port connections like ISO 6149 have threaded connections that are less than 1D? What is the rationale behind the engagement length provided in fluid power port standards?

 

[dtimberlake]

The "1 plus diameters of engagement" "rule" is mostly to allow developing the full strength of the fastener.
For high strength steel bolts in aluminum ( or worse ) threads the recommended/required engagement can be more than two diameters.

The working loads from a few 1000 psi hydraulic pressure //might// translate into relatively wimpy forces (and resulting stress) trying to spit the fitting/port connection onto the floor beside the bed.

 

[CWB1]

The ISO standard is based on testing and reasonable tolerances. Your rule of thumb is based on nothing, its likely extremely conservative in many circumstances but guaranteed to fail in others.

Good engineers abhor rules of thumb as lazy, unethical, and/or dangerous.

 

[MintJulep]

A hydraulic fitting has a hole through it.

 

[ghostdigital]

Look at how the thread works - there will be minimal axial shear stress on the threads. Internal pressure will micro expand the fitting but there should not be much if any increase in force pulling the threads apart like in classic hold together applications for threads.