ORIGINAL: DarZeelon
ORIGINAL: Broken Wings
Allow me to correct you. The American Unified Standard Thread Series classifies UNC Unified National Course as the 1/4-20 size NOT UNEC
UNF is Unified National Fine 1/4-28 and UNEF Unified National Extra fine as 1/4-32
There is NO UNEC Unified National Extra Course designation for American Threads...
BW,
You are right about the nomenclature.
I could not find the UNEC thread title...
But between the UNF of 28 tpi and the UNC of 20 tpi, there is another tpi of 24... 1/4''x24 bolts, nuts and appropriate taps and dies do exist.
Here are [link=http://www.google.com/products?q=thread+tap+1/4%22+24&sourceid=navclient-ff&rlz=1B3RNFA_enIL241IL243&um=1&ie=UTF-8&ei=mC9YSoCXFI6InQPdiOXdCQ&sa=X&oi=product_result _group&ct=title&resnum=4]some taps[/link], for example. This size is quite common in Harley-Davidson motorcycles.
Common it is, even in hardware stores, but there seems not to be a title for it in charts... It is commonly called NS (National Standard)
Because of the huge difference between UNC and UNF, I was under the impression that the 24 tpi is worthy of the title UNC and that the 20 tpi is the UNEC...
I must have been wrong...
You're mistaken. You need to look up the difference between NS (National Standard) and UNS (Unified National Standard)
Common it is NOT!
The ONLY use of the 1/4-24 in a Harley Davidson Motor Cycle is to hold the lifter/tappet blocks to the engine case and the last year Harley used the 1/4-24 was 1972 on the Shovel Head 74 cubic inch engine. Previously the Pan Head 61 and 74 cubic inch engines used the same screw and the last year Pan Head was made in 1965.
They used a 1/4-24 Twelve Point head by 1" long screw.
You will NEVER find a 1/4-24 stocked in a hardware store in the USA, PERIOD...