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What you illustrate is called a “binder-head” screw. They have the thinnest head among the common screw types. Due to the shallow head few have Phillips or cross-head driving recesses. They were developed to hold wires to terminals, called “binding”. They are commonly found in the electronics industry, especially on barrier-type terminal strips.
Slightly thicker and more rounded are “pan-head” screws. The thicker head allows, in addition the common slot, use of Phillips or cross-head driving recesses.
Next up in head thickness is the common “round-head” screw where the head is nearly hemispherical.
There are many other types. The more common include:
“stove-head” screws (sometimes called" truss-head”) that have a larger diameter thin head. The name comes from their original use in assembling sheet metal heating and cooking stoves.
“fillister-head” screws (sometimes called “cheese-head”) have a thick cylindrical head, usually with a slightly convex top surface. These are found mostly in machine assembly. Some of the Kadee plastic screws have this head.
Most of the thicker head styles are also available with “Allen” (hex socket) driving recesses, and nowadays “”Torx” or similar star-shaped recesses.
Complicating the issue is that every make uses slightly different shape and proportions, plus many commercial large-scale users specify their own designs.
I keep running into a difficulty of the draft gear box wanting to rotate if the screw isn’t really TIGHT, which can be obviated by making sure there is a continuous contact between the back end of the box and the center sill, or, of course, by some adhesive. I really prefer the very flat headed screws I mentioned before as it reduces the side profile of the screw head. They look something like this:
But have an even flatter head
When I got the dozens I have, they were only available with the slotted head. I see now that there are some which are cross-headed screws.
It is exactly for this reason that I prefer brass screws - they are relatively easy to cut to a custom length (much easier than steel screws), but since they are metal they are stronger than plastic screws
----- Original Message -----
Sent: Friday, July 10, 2020 8:31 AM
Subject: Re: [RealSTMFC] Coupler Mounting Screws
I use the Kadee screws for cases (hoppers and flats) where the length of the screw causes it to emerge
and become visible - or if it interferes with something inside the car, like a weight. I install it, and then cut it
off flush. If you're snapping them, you're over tightening them. Use a tiny drop of Loctite if you're worried
about them coming out.
On 7/8/2020 1:12 PM, Benjamin Hom wrote:
Wayne Cohen wrote:
"In the distant past, I tried Kadee’s 2-56 Delrin screws to mount couplers. Many of the heads snapped off in normal use and I quit using them. Slot or Phillips head - same results."
Slot or Phillips is irrelevant - why use plastic screws if electrical shorts are not an issue? Use metal screws instead.