It's 1/2"-12 Ya Dummy, Not 1/2"-13!

I have a 1/2-12 tap, I just don't have the die. The tap is marked "NS" for National Special. The following web page says "The NS series is a catch-all category for threads which have the American Standard form, but whose pitches are not in the National Coarse or National Fine series." As mentioned before, 1/2-12 was _the_ primary standard until the 1920's but was changed to 1/2-13 when the "Unified Series" thread standard was ratified.

American screw thread gauges

American screw thread series, with diameters of clearance holes, size of tap drills, and size of nuts.
www.sizes.com

Craig
I've also got a 1/2-27 tap! Gotta love auction box lots!!
 
projectnut said:
I have 2 drill presses purchased new in the 1980's that identical to the one you have. Both were produced in Taiwan by the same company under private labels. One is labeled "Rockford" while the other is labeled "Farm & Fleet". They were both purchased at our local Farm & Fleet farm store. The first one was purchased in 1982 and the second in 1984. The company that made them would put any name on them you wanted with a minimum order of 500 units. I suspect the same drill presses were made under hundreds if not thousands of private name brands.
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Actually, I've got a Rong-Fu style (RF-30) mill/drill. It was imported by Busy Bee Tools in Canada and labelled with their "Craftex" brand. Exact same process as your drill press.

Craig
 
1/2-12 BSW (British Standard Whitworth) threads. 55 degree angle thread flanks, rounded thread form instead of coming to sharp points and troughs, both externally and internally. Anybody who has ever dealt with older British cars knows Whitworth threads... Some things are still made with BSW threads...
 
England and America, two countries separated by a common language...
 
I ran into some 1/2-12 threads on my B&S universal grinder recently. I made the mistake of running a 1/2-13 tap through one before I checked the threads on another bolt. (we all know about assuming, right) :blue: At first I thought the threads were damaged because I could get only about 1 thread in before it got hard. I tried other sizes to make sure but none worked. It had to be 1/2". It's old American iron it couldn't be metric. So I checked with thread gauge, 1/2-12.
This machine was built around 1940 +/-. Must have had some left over fasteners from before they made 1/2-13 the standard, but that's another assumption. :face slap::cower:

Chuck
 
Jubil said:
I ran into some 1/2-12 threads on my B&S universal grinder recently. I made the mistake of running a 1/2-13 tap through one before I checked the threads on another bolt. (we all know about assuming, right) :blue: At first I thought the threads were damaged because I could get only about 1 thread in before it got hard. I tried other sizes to make sure but none worked. It had to be 1/2". It's old American iron it couldn't be metric. So I checked with thread gauge, 1om my 1/2-12.
This machine was built around 1940 +/-. Must have had some left over fasteners from before they made 1/2-13 the standard, but that's another assumption. :face slap::cower:

Chuck
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Until near WWII many manufacturers used proprietary fasteners and threaded parts to capture the replacement parts market. In most cases it was easier and less expensive for the customer to order a replacement part from the manufacturer than to try to figure out the profile and recreate it themselves. When I got my 1916 Seneca Falls Star lathe from my father in law it came with a box of spare parts, tools, and taps & dies. At the time I realized the taps & dies were obsolete and proprietary threads and almost threw them away. Instead for some unknown reason I put them in a drawer. 5 years later I was glad I did. It turns out they were all for repairing or making parts for the lathe.

With the threat of oncoming war (WWII) the defense (War) department was letting contracts for all kinds of military hardware and machinery. They insisted on standardized thread pitches on fasteners to minimize inventory and make replacing parts easier and faster. I'm sure this influenced the SAE and other standards.

However as far back as the 1980's these standards started to be ignored in favor of once again creating proprietary replacement parts that could only be supplied by the original manufacturer. The company I worked for made a lot of their own proprietary processing and packaging machinery. We found different hydraulic component manufacturers once again started using their own thread pitches, sealing surfaces, and tapers. All in the quest of trying to capture the replacement parts market. Fortunately our company was large enough to employ about a dozen engineers, machinists, and technicians whose sole jobs were to reverse engineer the more expensive replacement parts and fabricate standardized replacements
 
And on the subject of awkward threads, I bought some 5/16 UNC nuts from a supplier here in the UK (I was restoring my Elliott mill which dates back to when British industry used imperial fasteners). I'd single point threaded some external threads and tried checking if the nuts fitted. Some did, some didn't. Had me scratching my head until I looked closely at the problem nuts, marked.... LH!
 
1/2-12, I have several one pitch off taps, B & S automatic screw machines had a lot of this non standard stuff, HoneyWell used 5/16-17 screws to lock the casings of their gas valves togeather, the bolt could not be unscrewed
 
An afterthought, on Amazon there are Chinese companies as well as Japanese who will grind you a custom tap and die for under $20.00, that's what a .180 x 36 cost me
 
1/2" - 12 TPI was the US standard before WW-1, plenty of old machinery used it.
 
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