[Elecraft] understanding screw sizes

[Don Wilhelm]

  Pf,

Most of the screws in the K3 are #4, and the thread size is in turns per 
inch (4-40).  These are standard sizes here in the US - no metric size 
hardware is used in the K3 as far as I know.
You have the reference link correct.

There is also some #2 hardware used in the K3 - it is the smaller 
diameter, and has 56 threads per inch (2-56).

#6 hardware has a larger diameter and will have 32 threads per inch (6-32)

The length of the screw threads will change depending on whether the 
head is flat or not.  For flathead screws, measure the entire length of 
the screw including the head.  For the others, measure from the head to 
the end of the screw.

The washers are designated by the size of the hole.  Other dimensions 
may exist if important, but often just the hole size and the washer type 
(flat, internal tooth lockwasher, split lockwasher) suffice for the 
description.

Sorry for those in "Metric Land" who do not understand the US hardware 
system.  We tried to go metric many years ago and failed.  Most of the 
auto industry is now metric, but for small hardware, the US sizes 
predominate here.  We have to keep two sets of wrenches if we are to 
have a complete set.

73,
Don W3FPR

On 4/9/2011 1:51 AM, Pierfrancesco Caci wrote:
> Hello,
> while lenght of the screws is given in the manual in mm also, I'm
> trying to figure out how to read the screw and washer diameters
> that are given as "4-40" and such. Is this the relevant standard?
> http://en.wikipedia.org/wiki/Unified_Thread_Standard
>
> For washers, the first number should be the size of the hole, right?
>
> Pf
>
>
>