Ah yes, the numbered sizes 0 through 12 (I think that's the biggest)  Perhaps related to wire and sheet metal gauges?  And the thickness isn't independent of the metal involved either.  Maybe we're stuck with it because after you go to all the trouble to memorize it all you're reluctant to give it up.

Started a new job in 1972 and one of the first training sessions for new hires was about our transition to the metric system.  I left there 10 year later and there hadn't been a lot of metrification going on for the average employee.  I only heard about new product parts designs being in metric.

---
----
You said "tomorrow" yesterday.

The above comments or recommendations are SWAG. Use at your own risk.
John, W9DDD
On 11/25/2022 3:03 PM, sean wrote:
Forgive my ignorance,  but say 4-40, the 40TPI I get, but 4 what exactly? Not inches, or thousandth.....

M3, M4, M5, yup, makes sense, okay two or three thread pitches might be confusing....

But the instrument screw system as used with American equipment is.plain confusing,  even for a Brit that is used to BA, Imperial, and even Whitworth.....

Cheers
Sean
M1ECY 



Sent from my Galaxy


-------- Original message --------
From: "John, W9DDD" <[email protected]>
Date: 25/11/2022 20:51 (GMT+00:00)
To: [email protected]
Subject: Re: [GreenKeys] Weird hardware size

How do you think us yanks feel about the weird metric thread nomenclature?  Diameter and threads per inch seems simple enough to me.

---
----
You said "tomorrow" yesterday.

The above comments or recommendations are SWAG. Use at your own risk.
John, W9DDD
On 11/25/2022 2:45 PM, Tomas Larsson wrote:

For me, and us on the other side of the Atlantic, imperial sizes is a great mysterium, and we do not understand it at all.

 

With best regards

Tomas Larsson

Borås

Sweden

 

Från: [email protected] <[email protected]> För [email protected]
Skickat: den 25 november 2022 20:36
Till: [email protected]
Kopia: [email protected]
Ämne: Re: [GreenKeys] Weird hardware size

 

I believe you will find your answer here:

 

https://grandbrass.zendesk.com/hc/en-us/articles/201711490-What-is-IPS-and-Why-Do-We-Use-These-Size-Threads-for-Lighting-Parts-

 

Tom Tillson

---------- Original Message ----------
From: Nick England <[email protected]>
To: Greenkeys <[email protected]>
Subject: [GreenKeys] Weird hardware size
Date: Fri, 25 Nov 2022 14:21:27 -0500

Well, Teletype is kind of weird in using 5-40 and 6-40 where most folks would use 6-32. 

And using 1/4-32 instead of 1/4-28. 

But who in the world decided on 1/4-27 for lampshade finials? Where did *that* come from?

--

Nick England K4NYW
www.navy-radio.com



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