Calculating Hole Size For Odd Thread Sizes

[L98fiero]

L98fiero,
I have glanced at all the Machinery Handbook information on taps and threading until it fogs my glasses. This is good basic information but my concern was for unusually odd sizes such as making a nut (with any random TPI) for this 1.249" shaft. When I used the simple formula that danallen posted gave me a hole size of 1.199" and the more precise formula from Scott_M gave me 1.200 with using a 75% factor. These formulas aren't needed for "normal" threads - just look at one of the tapping charts that everyone has. I'm not dismissing your post as it is good "school learnin' " and needs to be understood.

One other question that came to mind as soon as I read your "L98fiero": Do you really have a Fiero with a Tuned Port engine stuck in it? Wow!

Yes, ~325 hp. it's a lot of fun when I can keep transmissions in it.

 

[lkrestorer]

I know this is the wrong place to discuss this but I'll make one more answering comment.

I caught that name because I own an NCRS Top Flight 1987 Corvette.

 

[ytrose2]

One reason why I love the Metric system. I used to work for a company who made rapid yielding hydraulic pit props for the mines. We had to screw the head casting onto the stainless barrel. There was no standard thread size for a 76mm barrel, so we created our own using the basic Metric concept. After a couple of trials, we finally found a thread pitch that gave us the right combination of coarseness and depth of thread that did the job for the application.

 

[Richard Hed]

One reason why I love the Metric system. I used to work for a company who made rapid yielding hydraulic pit props for the mines. We had to screw the head casting onto the stainless barrel. There was no standard thread size for a 76mm barrel, so we created our own using the basic Metric concept. After a couple of trials, we finally found a thread pitch that gave us the right combination of coarseness and depth of thread that did the job for the application.

The same can be said for all other systems too, however. We all know that the MS is far easier to use for just about any application (can't thimpfk of a single one that isn't). When the imperial system was invented, it was the beginning of the system and no-one knew what was to be expected. If someone had sat up and systematically designed the system, they should have designed it in 16ths of an inch. Then instead of saying such things as 5/8, 7/16, 3/4, etc, the things would have been: 1, 2, 3, 4, . .. . 7, 8, 9, 10 . . ....etc in 16ths. But no-one saw that far and instead invented two or three or more systems that went into a single system called "imperial". too bad. I still struggle with the pain in the . . .. . over number, letter sized drills, taps, and all the crap. once one gets above the number letter crap, the imperial system is much more like the metric but only in 16ths. If we had a hexadecimal system of arithmetic, ov course, 16ths would be the way to go. Then we would be complaining about metric, as if you halved 10, you come up with an odd number. If you halve THAT, you come up with a decimal number. But in Hexdecimal, you would not have that. Much easier to deal with in that way. Ounces, cup, pint, quart, gallon.

 

[mcostello]

I struggle with Metric. (and computers.) It's just what a person is used to.

 

[Richard Hed]

I struggle with Metric. (and computers.) It's just what a person is used to.

You just haven't had enough practice with it. Really, it's very simple. Thimpfk of it this way. Alex Hamilton managed to get US $$ to use the decimal system. Before, it used the British pound system which had a lb broken up into --come on my Brit friends, help me out--strange pieces including pennies which ARE NOT a cent. Even the Brits finally adopted the decimal system for their $$. How would you like to calculate your $$ in 20ths, 12ths and who knows what else?

Even WORSE were the Romans who used C, X, V, I, D, M for numbers and they way they put them together--to us a nitemare.

 

[Henry K]

How did the Romans multiply Roman Numerals?

 

[Richard Hed]

How did the Romans multiply Roman Numerals?

I wonder the same thing, and dividing would be even worse. They were probably limitede in their mathematical inventions because of this.

 

[awake]

We all know that the MS is far easier to use for just about any application (can't thimpfk of a single one that isn't).

I have no problem using the metric system, and routinely use metric dimensions, fasteners, bearings, etc. in many of my designs. That said, I can think of three places where the metric system is not as intuitive or easy to use:

1) Metric threading is easy to calculate in the sense under discussion, i.e., what size tap drill is needed for a given thread. (Actually, I find no difficulty in calculating imperial threads, but I digress). However, from what I understand, metric threading is much harder to implement on a typical lathe - not necessarily because of the particular dimensions involved, but because of how the system is designed, using the distance between threads rather than the number of threads per unit. As I understand it, threads-per-unit makes it relatively easy to generate the gear box and thread dial ... distance between threads, not so much. (I confess to knowing only enough to be dangerous on this topic, so happy to be corrected ...)

2) A topic about which I know quite a bit: implementation in computer hardware. Because of the binary system used in the vast majority of computers both historical and present, multiplying and dividing by 2 is much, much easier than by 10. Likewise it is far easier to store fractions-of-two (i.e., n/2, n/4, n/8, n/16, etc.) than it is to store decimals (i.e., .1, .2, .3, etc.). Where 1/2 and 1/4 and 1/8 can be stored exactly, .1, .2, and .3 are all going to be stored as approximations - very good approximations when you can use double-precision floating point, but if you are limited to single-precision, say on a microcontroller, you may see errors creeping into your computations.

3) Related to the above: One might argue that in many use cases, humans also find it easier to divide by 2 than to divide by 10. Think about spacing out the screws that will fasten one piece of wood to another - it is trivial to set screws at divisions of 2 by eye, with surprising accuracy: Identify the middle point and place a screw; then identify the middle point of each resulting half and place another screw, and so on. But if one were asked to place the screws at intervals of 10 ... it would be very difficult to come up with something by eye that was not noticeably "off."

How did the Romans multiply Roman Numerals?

At one level, the same way that you and I do. When you multiply 6 x 7, does the answer depend in any way on the notation used? Or simply on the answer we memorized back in 3rd grade? And if you didn't memorize it, how would you work it out - wouldn't you add up 7, six times, and see what the result is? 6, 7, 42, and (7+7+7+7+7+7) are the same values regardless of the notation used, and the math works the same way.

To be sure, if we are only multiplying by 10, then our decimal notation becomes very easy to use. But if you have to multiply 482 x 397, I don't think the notation is helping or hindering all that much. Keep in mind that Archimedes and Pythagoras and other brilliant mathematicians used the same sort of notation system. (Ancient Greek used letters for its numeric notation, just like Latin - or rather the other way around, since Latin almost certainly adopted it from Greek, which adopted its system from Phonecian writing.) And don't think for a moment that ancient money lenders had any trouble calculating the amount of interest owed!

But there is one issue that was a major hindrance for the Phonecians, Greeks, and Romans: while they certainly knew what "nothing" meant, they did not have a way to notate a zero value. This - the ability to write 0 - was the huge advance made by the Arabs - which is why today we use "Arabic numbers."

 

[Steamchick]

Nought is not worth nothing.
Nought is the most incredible mathematical location, where numbers change state.
It is unique in being neither positive, nor negative.
Nothing can be divided by Nought, yet Nothing is all that exists of Nought. Nothing else can be divided by Nought.
Without it, modern mathematics could not exist, yet nought does not exist, it is the absence of anything. So when we ask about "what came before the Big Bang?", Nought existed, but nothing else existed. Ergo it is the point from which all creation (Certainly in Mathematics) is derived.
Or have I been on the happy juice again?
(Please don't ask me to explain this, it is the point where I failed to cope with mathematics!).
K2

 

[Richard Hed]

Nought is not worth nothing.
Nought is the most incredible mathematical location, where numbers change state.
It is unique in being neither positive, nor negative.
Nothing can be divided by Nought, yet Nothing is all that exists of Nought. Nothing else can be divided by Nought.
Without it, modern mathematics could not exist, yet nought does not exist, it is the absence of anything. So when we ask about "what came before the Big Bang?", Nought existed, but nothing else existed. Ergo it is the point from which all creation (Certainly in Mathematics) is derived.
Or have I been on the happy juice again?
(Please don't ask me to explain this, it is the point where I failed to cope with mathematics!).
K2

You are not a knot but you are nought naughty. However, your erudite analysis is still not correct: Nought is a point on a number line, therefore it exists as a real number. The number "null" is considered to be the object that is "non-existent". This null is in EVERY set no matter what set it is.

 

[Steamchick]

Thanks Richard. This explains why I failed Maths at Uni. "Despite my endeavours it all came to nought",
K2

 

[Thread man]

Of course knowing the bore size for an internal thread is important but there's a bit more to it than that. All threads have a tolerance on the bore (minor) diameter on an internal thread. If you know the thread profile height then it's twice that height from the OD. As was pointed out in the second post it's easy for 60º threads.

Getting the pitch diameter correct (within tolerance) is the most important but a bore diameter above tolerance gives a weak thread that will probably strip.

On this link I give the nominal pitch diameter for common profile threads. To get the bore diameter subtract twice PDn.
https://flexiblemeasuring.com/wp-content/uploads/pdf/support/manual/2 nominal/2.03.1.pdfand the same for inches
https://flexiblemeasuring.com/wp-co...rt/manual/2 nominal/2.03.2 - inch version.pdf
The PDF file covers several types of threads.

Probably easiest is just to ask someone that knows ☺ There seems to be several that are members.

To the first poster. There isn't as such a single formula. It depends on the thread profile.

Back to the original first post. Assuming a standard 60º thread with a 2B tolerance then for .800" x 32 TPI max .776" and min .774".

 

[Nikhil Bhale]

The first recorded zero appeared in Mesopotamia around 3 B.C. The Mayans invented it independently circa 4 A.D. It was later devised in India in the mid-fifth century, spread to Cambodia near the end of the seventh century, and into China and the Islamic countries at the end of the eighth. Zero reached western Europe in the 12th century. Arab merchants brought the zero they found in India to the West. After many adventures and much opposition, the symbol we use was accepted and the concept flourished, as zero took on much more than a positional meaning. Since then, it has played avital role in mathematizing the world.

Above taken from Scientific American website.


Regards
Nikhil

 

[Thread man]

I struggle with Metric. (and computers.) It's just what a person is used to.

I went from Scotland to Denmark (at the age of 22) and from inches (imperial) to metric. Took less than a week to get the hang of the metric system. I'm sure it would have taken much longer going the other way. Re the dislike so many have of the metric system then what do you do when you want to cut 1/8" on a machine. Dont ever remember ever seeing a machine with fractions. Back in those days I knew every 1/32" fraction in decimals.

Hmm how many cents in $1?

Sure 12 inches in 1 foot, 3 feet in 1 yard, 22 yards in 1 chain, 10 chains in a furlong and 8 furlongs in a mile.

1,000mm in a meter and 1,000 meters in a kilometer.

Within the industrial world then almost all dimensions are in mm, m and km.

Temperature. Water freezes at 0ºC and boils at 100ºC. Yeps, metric is complicated LOL
A cubic meter of water weighs a metric ton.
How many lbs in a ton? Depends on whether you are in the USA or the UK. How much is a gallon? Same problem.

Three countries in the world do not use the metric system as the official system of measurement: the United States, Liberia, and Myanmar. The United States' reluctance to fully adopt the metric system stems from when the British colonized the New World, bringing the Imperial System with them.

The US is however going metric. Inch by inch.

I think we're well away from the thread title.

 

[Steamchick]

Ever seen Korean inches? 10 to the Imperial foot. They managed to Metricate by themselves, without "Imperial" rule..
The have 1 foot rules printed/engraved on both sides, "Imperial" inches one side and Korean inches on the other. Just talk to them and they are completely sure which unit when they discuss sizes. It is just "language". Not too difficult for anyone brought-up in multiple languages. Typically in India children learn 7 languages, then travel the country and use "English" as the universal language..
Our brains are all built the same (like Dell computers) but programmed with different software in different places.
K2

 

[Steamchick]

Of course knowing the bore size for an internal thread is important but there's a bit more to it than that. All threads have a tolerance on the bore (minor) diameter on an internal thread. If you know the thread profile height then it's twice that height from the OD. As was pointed out in the second post it's easy for 60º threads.

Getting the pitch diameter correct (within tolerance) is the most important but a bore diameter above tolerance gives a weak thread that will probably strip.

On this link I give the nominal pitch diameter for common profile threads. To get the bore diameter subtract twice PDn.
https://flexiblemeasuring.com/wp-content/uploads/pdf/support/manual/2 nominal/2.03.1.pdfand the same for inches
https://flexiblemeasuring.com/wp-co...rt/manual/2 nominal/2.03.2 - inch version.pdf
The PDF file covers several types of threads.

Probably easiest is just to ask someone that knows ☺ There seems to be several that are members.

Well I had never given it that much thought! Just use thread tables from any one on my many inherited "Engineering" almanacs that are full of thread tables. Many came from my grandfathers, both of whom travelled the world by ship, and one visited USA a few times including after being sunk in mid-Atlantic... but that's for another day. His "USA" books are as good as any, except for modern and Japanese Metric standards.
https://www.goodreads.com/book/show/24702141-a-nice-quiet-lifeK2

 

[Thread man]

The first recorded zero appeared in Mesopotamia around 3 B.C. The Mayans invented it independently circa 4 A.D. It was later devised in India in the mid-fifth century, spread to Cambodia near the end of the seventh century, and into China and the Islamic countries at the end of the eighth. Zero reached western Europe in the 12th century. Arab merchants brought the zero they found in India to the West. After many adventures and much opposition, the symbol we use was accepted and the concept flourished, as zero took on much more than a positional meaning. Since then, it has played avital role in mathematizing the world.

Above taken from Scientific American website.


Regards
Nikhil

Mathematical question for you and hope you have humour. If I multiply your post with 0 what do I get out of it?

 

[Thread man]

Ever seen Korean inches? 10 to the Imperial foot. They managed to Metricate by themselves, without "Imperial" rule..
The have 1 foot rules printed/engraved on both sides, "Imperial" inches one side and Korean inches on the other. Just talk to them and they are completely sure which unit when they discuss sizes. It is just "language". Not too difficult for anyone brought-up in multiple languages. Typically in India children learn 7 languages, then travel the country and use "English" as the universal language..
Our brains are all built the same (like Dell computers) but programmed with different software in different places.
K2

No I've never seen a Korean inch ☺ Until a few years ago many European countries had different values for an inch. A ton, gallon and probably other "units" vary depending on where you are. First time I drove in Sweden seeing distance signs in MILS was confusing. Thought for a short while Swedes didn't know how to spell mile. What MIL means is 10 kilometers and due to the size of the country. Tip Norway over and it reaches Italy!

I've been in India several time and have never had the impression kids learn several languages. My (Danish) wife speaks, apart from Danish of course, English, German and French and has also learned a little Chinese. She's HR manager at Legoland here in Denmark. ½ an hour from where we live.


At 3 mins. 20 seconds British kids often get it wrong by driving on the left hand side LOL

Kids here learn English from the very first year at school.

Do threads usually get so far away from the subject?

 

[Nikhil Bhale]

Typically in India children learn 7 languages, then travel the country and use "English" as the universal language..

I am from India and I think you erred a little in this assumption.
I know 3 languages Marathi my mother tongue, Hindi the national language and English the universal language. I don't think I am offending anyone by saying English is universal language.
I can understand Gujarati but cannot speak.
Some people take Sanskrit the ancient language in school and can understand it but it is not a everyday use language.
So I think the average will be around 3-4 languages including English.

Regards
Nikhil