Thread cutters

[Leroy]

I was just going thru the thread taps and dies that I have acumilated over the years. Comming up with something that is confusing me, On the 1/2" taps I am comming up with the 1/2 x 13 NC that I understand is national course, 1/2 x 20 NF that is national fine but then I am comming up with 2 taps with 1/2 x 24 NS. What is the NS and why the 3 different thread sizes for fine and course?

 

[glennster]

ns is national special. it is a very fine thread.

 

[smallercrawler]

NS denotes a special, usually to customer specification.
Untitled URL Link

 

[Shoprat]

Can't say what the NS means (I should know) but I'm thinking somewhere along the line, someone needed a special thread size. I have screw machines in my shop and buy special taps on occasion. Even these days, manufacturers ask for non standard threads.

 

[Ian Beale]

Leroy

One you missed

1/2 x 12 Whitworth.

Can cause confusion!

 

[Cory Schmidt]

different hold (tightness/strip resistance) or for finer adjustment(finer thread, less movement when turned). Fasteners (and therefore cutters) can have infinite number of TPI, just depending on use. Can't forget about pipe threads as well, now that's another mess.

 

[Dr. Walt]

Don't forget the ACME Threads. lol

:>)

 

[pete 23]

National special is often used on firearms hardware. Even the old IH cream separator used NS on the adjustment screws for getting all the fat out of the milk. Yaa, I had to repair a few separators also. Jack of all trades in a dealership. Poured a lot of milk into them also at home.

 

[Leroy]

Looks like I have several to junk that I believe are brand new and bought at flee markets believing thay were normal fine thread. Also found some that are completely unmarked as to size and think they must be metric and thought they were either 5/16" or 3/8" fine thread. Would anybody want those NS thread taps?