original size of rocker cover screw

[hdhikaru]

hi there, working on the 52 panhead. just got the new screws (1/4-20..? ) but this is different thread from old one came from the head....
which one is correct size? please advice. tks Shin S__53633128.jpg

[BigLakeBob]

The original thread size is 10-24. Hope that helps.

[hdhikaru]

thanks! so.. its metric?

[BigLakeBob]

No, a #10 is a UNC (unified national course) screw size. .190 O.D. or major diameter with 24 threads per inch. In comparison, a 1/4-20 is .250 major diameter and 20 threads per inch. The '54 parts book says part # 2675.

[Arley]

thanks! so.. its metric?

not metric, more like archaic
Its designation was National Standard.

[exeric]

not metric, more like archaic
Its designation was National Standard.

I wouldn't call SAE standards archaic, just a different standard. Both systems are very good depending on your application, or intended end user. Accuracy has nothing to do with standards, but everything to do with how precisely a manufacturer uses those standards.

[BigLakeBob]

Using the word archaic on an antique motorcycle forum is quite funny!

[hdhikaru]

great !! thank you guys!!

[Jerry Wieland]

I wouldn't call SAE standards archaic, just a different standard. Both systems are very good depending on your application, or intended end user. Accuracy has nothing to do with standards, but everything to do with how precisely a manufacturer uses those standards.

Well I would agree with archaic. I like the Standard system only because I grew up with it. After working in industry for 30+ I find that the Metric System is far superior to the Standard System. The metric system is very easy to understand and use. My brother used to work for a company that made packaging equipment and they needed to have 2 assembly lines. One for Standard (domestic use) and one for Metric (export). Costs of production were approximately .05 to 1% higher on the Standard line and a lot of it had to do with the use of Standard.

20 years ago when my youngest son who has a learning disability was in high school it was all I could do to convince him that 9/16 was not bigger than 5/8. He easily understood that 15 was bigger than 13.

Jerry

[exeric]

I recall a quality control guy telling a tool & die man that metric was far more accurate than NS. The tool & die man told the QC guy to stay out of his shop until he could prove that. The QC guy never came back.

[pisten-bully]

I was talking with a 30-something engineer this week about micrometers and he asked "do you have metric or dumb units" (...dumb units on mine!)

[Arley]

I wouldn't call SAE standards archaic, just a different standard. Both systems are very good depending on your application, or intended end user. Accuracy has nothing to do with standards, but everything to do with how precisely a manufacturer uses those standards.

My point was no it isn't metric. It is National standard not National Course or National Fine. Metric is not without its problem it also has multiple thread pitch available. HD used NS on any place going into cast aluminum the last HD used NS was on lifter blocks and oil pump until late 79 I think.