Material around internal threads - again, new scenario
Material around internal threads - again, new scenario
(OP)
I'm attempting to identify the miniumum material required around an internally threaded hole to maintain thread/material integrity. The advice from the other threads I've read has been to use the AF size of the fastener, however the scenario I'm considering is slightly different and the standard part I'll be modifying already doesn't meet this rule. The part is a wheel hub/flange with threaded holes for the the wheel bolts. The bolts are M14x1.5 and there's about 3mm clearance to the OD of the hub as https://www.carpartsdiscount.com/auto/archive/pict... . Rather than using offset bolts (wobble bolts) I am planning to re-drill the hubs to the new PCD (114.3, old was 112) but naturally this will take the thread outer diam just over 1mm closer to the outer edge.
The hub is 12mm thick steel (not sure of the grade yet) and naturally the joint interface will be with the large wheel back-side face but in either the original or new configurations the outermost section of the threaded hole is likely to be unsupported due to the large clearance used for wheel bolts in alloys.
I've not found any guidance in the machinery's handbook or a few other books I have access to, nor any online resources. Can anyone point me in the direction of the information?
The hub is 12mm thick steel (not sure of the grade yet) and naturally the joint interface will be with the large wheel back-side face but in either the original or new configurations the outermost section of the threaded hole is likely to be unsupported due to the large clearance used for wheel bolts in alloys.
I've not found any guidance in the machinery's handbook or a few other books I have access to, nor any online resources. Can anyone point me in the direction of the information?





RE: Material around internal threads - again, new scenario
http://www.welding-advisers.com/
RE: Material around internal threads - again, new scenario
To the left it's clear to see that the loads spread out into the supporting plate, not just taken as a discrete shear anulus around the thread.
RE: Material around internal threads - again, new scenario
But doesn't that same FEA analysis show almost all of the stress is concentrated in the base material at a distance of less than 1 thread root depth? That is, it looks like you'd need 2x - 3x thread depths around the tapped hole to prevent pullout axially.
RE: Material around internal threads - again, new scenario
RE: Material around internal threads - again, new scenario
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.g... page 21.
Ted
RE: Material around internal threads - again, new scenario
RE: Material around internal threads - again, new scenario
In my past life I used 1.0D edge distance to tapped hole. But with testing and proof of application.
Ted
RE: Material around internal threads - again, new scenario
In other lightly loaded situations I've just worried about the remaining wall thickness being something sensible - less than about .050" and I'd start to be concerned for my typical applications.
If you have the time and skill set to actually analyze it, and no industry standards directly apply, then why rely on rules of thumb?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Material around internal threads - again, new scenario
original number and size of the tapped holes?
RE: Material around internal threads - again, new scenario
I'm a bit confused as to why, but yes - are you considering destructive testing?
I suspect that in comparison with many applications an M14x1.5 torqued to ~100Nm to hold a wheel on is relatively low load, especially considering the application of spigot rings to take the primary shear load.