Thread callout, 1/4-20UNC or 1/4-20 UNC (space)
4

Question

Thread callout, 1/4-20UNC or 1/4-20 UNC (space)

jake98 (Mechanical)

(OP)

7 Mar 08 10:33

Hello,
Had been taught years ago not to put a space between the thread size, and class: 1/4-20UNC, but have lately been having some drawings criticized for not putting the space: 1/4-20 UNC. Which is the ansi standard, and are both acceptable?

looslib (Mechanical) · Answer 1 · 2008-03-07 15:41:40

ASME Y14.6-2001, page 8, shows the thread callout WITH the space.

"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

JLSeagull (Electrical) · Answer 2 · 2008-03-10 10:03:18

Looking at examples in ASME B1.1 Unified Inch Screw Threads I see examples on the same page that differ such as the following:
2.0625-12-UNS-2A
0.5000-13UNC-SE2B
0.3750-24UNF-SE2A
Just before section 6.2 a legend includes the hyphen such as between UNC-2A. This appears to be the preference in B1.1.

gibsonb (Mechanical) · Answer 3 · 2008-03-12 16:10:14

Interesting - I've typically used "1/4-20UNC". However, in scanning ASME Y15.100, the book depicts "1/4-20 UNC"

fcsuper (Mechanical) · Answer 4 · 2008-03-14 09:25:26

With space.

BTW, this is a question for Drafting Standards, GD&T & Tol Analysis forum: http://eng-tips.com/threadminder.cfm?pid=1103

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

jdaddy (Mechanical) · Answer 5 · 2008-04-07 12:53:21

I am trying to locate specs for threaded fitting ends as called out for a restrictor fitting in accordance with
AND 10056 Style E for 1/4 & 3/8 diameters. Does anyone know where I can find this info? Thanks.

KENAT (Mechanical) · Answer 6 · 2008-04-07 13:23:00

jdaddy, start a new thread with that question, it's not particularly related to this one.

As regards the OP ASME Y14.6-2001 "Screw Thread Represenation" shows the space as looselib points out. As well as page 8 all the other examples appear fairly consistent in showing the space.

Section 6.1 of B1.1 - Basic Method of Deignating has the space. However, as JLSeagull points out there are examples that don't follow this, I see several in section 5 with a "-". That said most examples appear to have the space.

There are other minor inconsistencies I'm aware of between these 2 specs, not ASMEs finest work.

I'd go with the space.

KENAT, probably the least qualified checker you'll ever meet...

Come Join Us!

Posting Guidelines

Related Projects

Thread callout, 1/4-20UNC or 1/4-20 UNC (space)
4