USA bolt sizes - Withworth - Metric

3.6rs

3.6rs

Well-known member
Can anyone provide me a list with most current US bolt sizes and the TPI ? or a good link on the space wide web.
And is there a difference TPI between these and the Whitworth ? (Both Imperial ?)
I can use some explanation on this. (Metric is no problem)
 
The main difference between the British Whitworth and the Unified Screw Threads in the thread angle, 55 degrees and 60 degrees for the Unified (and metric as well). The threads per inch as similar between the Unified and the Whitworth, and with a long enough cheater bar they might be forced together. My Machinery's Handbook, 17th edition (1966), has well over one hundred pages covering screws and threads. 3 pages dedicated to the Whitworth. Spending 6 decades under an auto hood and over 5 decades in the tool & die business, I have never seen a Whitworth thread.
 
slammin said:
....Spending 6 decades under an auto hood and over 5 decades in the tool & die business, I have never seen a Whitworth thread.
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How fortunate you are Slammin!! Over here working on prewar Austins, MGs ,Model A Fords and post war MGBs I never know what thread is going to appear!!!... and the MGs are the worst .. prewar a mix of metric, BSF, Whit with different hex heads, and the MGBs shifting from UNF/UNC to Metric halfway through their production.
 
interesting thread here , When I worked in aviation while in Alaska we had a small class on fasteners, if I remember correctly aviation threads all have a 100 degree pitch. there is so much information it is intriguing
 
Then in 60's and 70's there were the Yamaha dirt bikes (RT-1, DT-1,CT-1 and etc) with ISO threads on SOME parts with metric on the rest of the scooter. Shock mounts and SOME front fork fasteners were ISO as I remember. Same same on SOME internal engine and transmission parts.
 
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Back in the late fifties, I worked in the Sears tool department. We always knew who was working on a Jag as that person would buy Standard, Metric AND Whitworth tools.
 
If I remember the Triamph motor cycles had the whithworth thread. It is hard to find those fasteners in our area.
 
It doesn't stop at just the difference between SAE and Whitworth for imperial sizes. From 1/4" up to 1/2", SAE and Whit have the same TPI, only a different thread form (55 or 60 degrees). A nut from one can be put on the other but won't fit or perform at its best. At 1/2", Whit is 12 tpi and SAE, 13. Why is anybody's guess. For anything smaller than 1/4", there is no whitworth thread. Joseph Whitworth, the designer made none smaller than 1/4". Others have added ******* threads since and called them Whitworth but the intention was that for smaller than 1/4", the BA (British Association) system would be used. I think that is similar to the American system where they use 4,6 or 8 (for example) gauge screws (which are a mystery to me). I wonder if there is any correlation between those and BA
UNF is the fine thread version of SAE (UNC) and BSF, the British fine thread system (British Standard Fine).
As for the different sizes of the hex nuts and bolt heads, the Americans quote a simple measurement across the flats (AF) whereas, there is a formula in Whitworth to calculate the size of the hex and it is based on the diameter of he thread.
Then there is Metric! Oh so easy. I am nearly finished restoring a French car from 1928 and all of the threads are standard metric. That makes things sooooo easy. IMO, the best thing to have happened in the world of engineering is the (almost) universal adoption of the metric system. As far as I know, only one country in the world persists with the antiquated imperial weights and measures system and even then, it is not the imperial system that the rest of the world used to use. A real oddball!
 
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Just about ANY thread of common use, past & present, is shown on the compilation at http://webcache.googleusercontent.c...BSgXK4J:www.watchman.dsl.pipex.com/thread.xls

The table starts out a little slow - all those small sizes like camera and precision instrument threads. But scan down a few pages and find BSW, ASME, NC, Metric and just about anything you might want. All arranged in order of increasing size.

A forgotten thought is that machine screws - shown on the table as "ASME" sizes - and which can be found at most hardware stores beginning with a No. 2 (possibly) and ended with No. 12 (possibly) but the number system goes on beyond No. 12, all the way up to No. 30 (0.450 basic diameter.)

I owned a lathe made in 1874 which used No. 28 screws in the headstock bearings.

Joe K
 
Synchro909 said:
As far as I know, only one country in the world persists with the antiquated imperial weights and measures system and even then, it is not the imperial system that the rest of the world used to use. A real oddball!
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That's not really true, America uses the metric system for anything that really matters, in science and industry, and has for a long time. Complaining about this is a kind of virtue signaling with some I've noticed, oftentimes the same sort that likes to claim "Science!" when they aren't really very scientific about too many things. If they were, they'd know this. It is true that Americans still use statute miles, yards and feet. Having used different standards it turns out that the "English" system of measurement is actually very well suited for human sized measurements.

Interestingly spark plugs have been Metric for almost as long as they've been around iirc. There were some other early Ford parts - maybe in the differential? That have always been metric. In a (sort of) similar vein, iirc American firearm ammunition cartridges were/are Berdan primed - a European invention, while European ammunition cartridges are all Boxer primed, an American invention. Hm.
 
If you own an older British motorcycle many of the threads were BSC British cycle engineering also called CEI threads ( cycle engineering institute). 1/4 inch and above were all 60 degree 26 tpi. That is close to 1 mm pitch (25.4 inch)so a certain metric size screws on with a class B fit from memory. Heads are smaller than Whitworth. Are they SAE A/F sized heads? I will have to go to my workshop and see.
7/16 and 1/2 inch were sometimes optionally 20 tpi, still at 60 degrees.
SAJ in NZ
 
I noticed that no one has mentioned UNEF, which is used on some fasteners in aviation. I've worked on British, American and Italian aircraft, so I have been exposed to three different thread standards. I have also worked on American, British, European, Japanese, Australian cars and bikes, so have also been exposed to different thread standards there as well. This means my toolbox has many odd ball spanners. All this just adds to the fun of spinning spanners.
 
If I could only tell what to "expect" when I try to take something apart. Is it this or is it that. Then the real fun starts when this is this and that is that, SAE here, metric there.
 
Crankster said:
..... America uses the metric system for anything that really matters, in science and industry, and has for a long time. Complaining about this is a kind of virtue signaling with some I've noticed, oftentimes the same sort that likes to claim "Science!" when they aren't really very scientific about too many things. If they were, they'd know this. .....
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Whoa Crankster,:) Isn't it true a Mars Orbiter failed because one engineering department was using "English" measurements and one was using metric??!!
 
Same here!



slammin said:
The main difference between the British Whitworth and the Unified Screw Threads in the thread angle, 55 degrees and 60 degrees for the Unified (and metric as well). The threads per inch as similar between the Unified and the Whitworth, and with a long enough cheater bar they might be forced together. My Machinery's Handbook, 17th edition (1966), has well over one hundred pages covering screws and threads. 3 pages dedicated to the Whitworth. Spending 6 decades under an auto hood and over 5 decades in the tool & die business, I have never seen a Whitworth thread.
Click to expand...
 
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