[GreenKeys] 6-40 UNF and other wierd screw sizes

[Bob Camp]

Hi,

Also to the point - Our standard screw size system only dates roughly to the
early 1930's. Before that point there were many screw thread systems but no
one commonly accepted set of standards. Almost anything you come across from
before say 1910 or so will be full of weird threads. Instrument grade stuff
from before 1890 looks like they made each nut and bolt custom for the job.

The time line is a little different depending on the industry and even the
company you are looking at. Some groups did their own thing right into the
1950's and others standardized pretty early. Henry Ford was big on
standards. The crew at Rolls Royce seems to have thought they didn't need to
standardize much of anything ever.

The early Teletype stuff more or less spanned the period that most
industries went to standard screws. Obviously the 28's and 33's came well
after standardization was a given. The 14's, 15's and 19's all came off the
drawing board in an era that did not have a true standard to work to. A
Teletype is nothing if not a bunch of screw machine and punch press parts
done very accurately in high volume. It's still pretty amazing that they
could churn them out the way they did.

    Take Care!

        Bob Camp
        KB8TQ



----- Original Message -----
From: <jhaynes@alumni.uark.edu>
To: <W8MAQ@aol.com>
Cc: <greenkeys@mailman.qth.net>
Sent: Monday, December 23, 2002 4:33 PM
Subject: Re: [GreenKeys] 6-40 UNF and other wierd screw sizes


> Teletype mostly made their own.  I haven't tried locally, but have you
> looked at a company that specializes in screws?  I've bought other odd
> sizes from such a supplier.  In the yellow pages here they are under
> Bolts & Screws, and also under Fasteners.
>
> (turning on the philosophy mode) One could argue that Teletype's great
> manufacturing capability was both a strength and a weakness.  There was
> nothing to inhibit a designer from designing a new screw slightly
> different from anything in the book instead of figuring out how to make
> do with a size that was already being manufactured.  So there were a huge
> number of part numbers occupied by screws and nuts and washers.
>
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