ASME B18.6.3 machine screw heads

[fsincox]

Can all of the heads in the ASME B18.6.3 be used interchangeably for the same loading requirements? Providing identical material properties and identical thread specification?
Frank

 

[racookpe1978]

Are you asking if - for the same threaded diameter and material and machine thread size and spec - can a pan head or truss head screw or rounded head screw carry the same loads in the same metal as a flat head countersunk or oval head countersunk screw?

Why would you think the different geometries would resist the same load the same way?

 

[fsincox]

Our drawing specified a special length (extra long) slotted fillister head screw and the vendor sent a slotted pan head style screw. They are special length so they are not stock.
Frank

 

[racookpe1978]

This diagram is for sealing head screws - not your exact type certainly - but is adequate to show the difference between fillister head and (simple rounded) pan head machine screws.

The extra material reduces internal stresses in the head somewhat, but raised the height of the screw head above the surface and adds weight. Might cost more. If clearance or flow issues matter (outside head height), you may not be able to use these taller screws.

Did they charge more?

http://www.sealingscrews.com/images/screwheadstyle2.jpg

 

[fsincox]

Thank you racookpe1978,
This was an error of communication on our drawings. We are asking for a part made from another part previously made internally. They made a screw of 440A SST and it looks like a standard "#2-56 fillister head machine screw but 1.75 " long. The tolerances turned out to be slightly tighter for most features. (machined complete vs forged?)
The part was outsourced. The make from part(final part) is drawn as if it was a binder head screw and says cut to 1.420/1.410 length. The vendor sent something that looks like a "pan head". Looking through the ASME standard brought to mind that torquing specs seem more based on size and materiel, thus my question. I figured the thread root is the weakest spot on a screw.
Frank

 

[racookpe1978]

"torque" is transmitted from the driven "holes or indents" through the head down to the shaft-head interface.

A Phillips head indent, flat head notch is probably the worst/least consistent driver method.
Torx-head stars or hex key hole probably the best after a six-sided hex head top. (Impossible with a pan head obviously). The typical Phillips head interface (a manual screwdriver operated by a ???? qualified and trained person) is not likely to set ANY real-world consistant torque values: going from "Ooops I sheared the head" to "Ooops, I sheared the Phillips" to "Ooops, I didn't even tighten it."

Machine-automated assembly helps the initial assembly to provide some degree of standardization.

Nbr 2 thread is very, very tiny dia. Easy to foul up.

 

The Phillips screwdriver is responsible for more busted knuckles than any other tool (nearly including a few of my own).

Americans should have listened to Mr. Robertson. Well they did, but they expected him to give it to them for next to nothing, which he refused.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."