Misc. Tap sizes from a neighbor who passed away.

[Movin/on]

I cleaned out a small shop/garage for Bob's family after he passed away. Bob was a naval mechanic during the Korean War
He later became an aerospace mechanic someplace near San Franciso. His tools were mostly precession, dealing with mostly stainless steel.
Finally, I got to the taps and dies and decided to sort the taps by thread count. Most were between 20 TPI to 32 TPI but there were some I'd never run across before. A number were 40 one was 56 and a couple were 80 TPI. These were all less than #6. Are these common in fine machining operations? Bob lived a full and varied life from the stories he told. He also had a 1958 MG and a BSA from WWII. Both went to museums. I'm glad I knew him.

Movin/on

 

[liliysdad]

40, 48, and 56tpi are common thread pitches in the firearms world.

 

[Dave455]

40, 56 and 80 are the tpi for 6, 3 and O UNF respectively.

40 and 56 ditto for 4 and 2 UNC.

These will probably be Unified (or possibly American National, but I haven’t checked).

Probably not British, but 40 could be a 1/8 cycle thread, which the BSA might have used, or a 1/8 Whitworth, which I don’t think either the MG or the BSA would have used.

Used on all manner of other things. Anything that needs a small screw!

I’d always sort taps by diameter first.

 

[Steve_P]

If you look up inch sized threads in Machinery's Handbook, you'll find many hundreds of threads you never heard of, like 1/2-12, 11/16-18.... that are all "standard" threads.

 

[alfadan]

Did he do any gunsmithing by chance?

 

[T444e]

If you look up inch sized threads in Machinery's Handbook, you'll find many hundreds of threads you never heard of, like 1/2-12, 11/16-18.... that are all "standard" threads.

I have a handful of 1/2"-12 cap screws, no clue what they are from. Don't want to scap them as McMaster-Carr doesn't carry them. With my luck, as soon as I scrap them I'll find what they are for.

 

[woody 73]

A while back i had to buy a die thread for an airline, darn I never knew such a strange thread even existed, I forgot the size, but I had to order it from MSC. I have small batches sitting around for just such a day when they will come in handy.

You fellows have never seen watch thread taps, so fine they make your hair stand on end. My old eyes are not so good with those little monsters.

 

[Steve_P]

I have a handful of 1/2"-12 cap screws, no clue what they are from. Don't want to scap them as McMaster-Carr doesn't carry them. With my luck, as soon as I scrap them I'll find what they are for.

I have some ancient 1/2-12 taps from my dad. They're Pratt and Whitney, so maybe that was used on airplanes 50+ years ago. Dunno. But I doubt a 1/2-12 has been used on a USA made truck or car after the mid 60s, if ever.

Obviously if you say something like this here, the GJ crew is now searching for the exception. "Studebaker used it on one car model in 1953 on the outer clutch bell crank trunnion pivot bolt..." Ok, bring it on

 

[T444e]

These were in my dad's collection which is now my collection. I know they are not aircraft related and pretty sure not auto related. I was thinking an old piece of equipment (manufacturing, woodworking, etc). I don't have anything he disassembled except a John Deere tiller and I went the easy route and bought another one in operating condition to replace it.

Or he got them when cleaning out my mom's dad place, and he had all kinds of stuff.

The 1/2"-12 is definitely a head scratcher.

 

[RoninB4]

-There's a lot of thread sizes/designations that are uncommon to auto/motorcycles but rather common to bicycles, firearms, appliances, watchmakers, hinge/furniture hardware, lamps, and optical instruments. I've even cut some oddball threads for equipment that was proprietary so a replacement would have to be OEM. Each industry had preferred threads per diameter that I won't go into here.

-For the OP; The taps/dies from your neighbor are likely old and dull so I wouldn't trust using them to cut NEW threads. They may be ok for cleaning out existing threads but I wouldn't take the chance with a vintage plain carbon, especially one that's been used repeatedly on SS. I think Bob would even advise this. If you can't find answers to questions you can ask them here or contact me directly.

 

[Movin/on]

Thanks so far. I'll look at firearm sites and British Motor sites for more info. This helps but is intriguing.
Richard

 

[Dave455]

Thanks so far. I'll look at fire armes sites and British Motor sites for more info. This helps but is intriguing.
Richard

Aside from the sizes I quoted, they are not British.

Be careful with websites. An awful lot seem to be compiled by people who don’t really know their subject and are full of errors.

1/8 BSC is an obscure size. BSA used cycle threads up till the mid 50’s if memory serves, but 1/8 is really small. That’s the only real possibility from the vehicles you quoted.

The 1/8 Whitworth is very unlikely. It’s an unusual size you find on domestic hardware but seldom in vehicles. Smaller sizes are normally BA, which don’t use those pitches, and most threads on older vehicles are BSF.

 

[seber]

I used to run in to 1/2-12 on our really old machinery at work. Eventually I got curious and did a deep dive on it. Turns out that was the standard until just before WWII. We still had machinery that old on the production floor. It was gone by the time I retired, but the taps were still in the tool crib.

 

[tool_scrounge]

It depends a lot on the application.
1/4-80 screws are common for fine adjustment screws for optical components. 00-90 threads are available for really small stuff I. The old days.

 

[larry_g]

When I started working most of the fasteners on the tooling was in the #2 to #10 size. If you went over that you got out the big tools for the 1/4 and 5/16" fasteners....

lg
no neat sig line

 

[RTM]

Old Stanley planes have a lot of weird sized fasteners, but not a 1/2-12.

I grab all the weird taps I can find for potential fixes.

 

[Movin/on]

Not a tap or die but this was in with the things I got he left for me. I asked in the HAMB "What's it worth" section and no one had seen one of these.
Richard

 

[The Cobbler]

some of that stuff may be useful to the scale model builders

 

[kbuhagiar]

Not a tap or die but this was in with the things I got he left for me. I asked in the HAMB "What's it worth" section and no one had seen one of these.
Richard

I responded to you when you inquired last year:

Indian Shock absorber sales/countertop model

Got this today from a neighbor and wonder the age and if it is unique. It's cast iron 13" wide and 4.5"tall probably 3"deep, It's in exceptional condition. The leaf spring actually works. Is this from the same company that produced the motorcycles? The "Indian" script looks similar. Movin/on

www.garagejournal.com

 

[Movin/on]

Forgot that I also posted it here.

 

[BORING HOP YARD]

Worked in a aircraft factory for 40 years, some of your odd ball taps could be for oversized bolt threads or Heli-coil threads.
One example a 1/4-28 STI heli-coil tap is much larger than a normal 1/4-28 tap because its sized for the o/d thread of the heli-coil that will be inserted. Normal hole size for tapping a STI 1/4-28 is 17/64 or .265 a normal size hole for a 1/4-28 is 7/32 or .218.
I have seen oversized STI taps double oversized and triple oversized. if you had to go larger than triple STI you would be looking at a Keensert.