# M6 roll tap hole size?

We need to make about 250 special nuts for a specific application at work. As an exercise, we've decided to use a punch and die to flange the hole into
mild steel sheet, .04-.06" thick.
I need to know the correct ID for the hole before roll tapping. I'm sure it can be calculated (Cliff) but I don't have time and I need to get the design done.
Thanks for any help.
Regards,
Robin
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my msc chart says 5.5 mm...i usually end up a little smaller than that chart
Robin S. wrote:

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I understand that small deviations in diameter can have a very significant effect on the thread. By a bit under, something like 5.4? Perhaps 5.45 (inch equiv.)?
Regards,
Robin
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.213" or a number 3 drill will put you smack in the middle of the pitch diameter for a 6H thread. BTW, you didn't mention the pitch. M6x1 is what we're talking about here, right? 5H or 6H tolerance? What percentage of thread do you need?
Dan
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Sorry about that. It has been my experience when talking metric threads, it is assumed coarse unless the pitch is specifically stated (certain sizes have more than three fine pitches).

I'n not really sure. This isn't a *really* critical issue. The reason I wanted confirmation on the hole diameter is because I will have to grind a punch and I'm too lazy (efficient) to do it twice.
The nut will be used to attach light structural members together (the Bosch framing version of 80/20 extruded aluminium.) More thread would be better for strength, but I don't think our design will have a great issue with that.
Thanks for the suggestion.
Regards,
Robin
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I've often wondered if calling out a thread as an M6 alone is a standard way of calling for a coarse pitch thread. I see that on metric drawings a lot. You would think it would say M6 ISO Coarse or M6x1 just to be sure.
Dan
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Dan, Coarse is always assumed if not specified, as is a 6H class (internal) or 6g (external), although it is not incorrect to specify.
Greg
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Thanks. Like I said, I've often wondered about that. I've always taken it to mean a coarse thread, but every time I do, there's a nagging little doubt in my mind as to whether or not I'm doing the right thing. Good info on the class of the thread too. BTW, I hate metric prints. I don't mind working in metric at all, in fact if anything it's easier. But the drawings suck.
Dan
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Metric is (mostly) all I use (I'm in NZ), and the only dealing I have with "imperial" prints it when I have to convert to metric. Our machines & measuring equipment are all metric, I'ts all we know :-) This country metricated long ago, it's a far better system IMO.
Greg.
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If we woke up in the morning and gremlins had swapped all our prints to metric, it would be fine. It is the conversion that is the mess. All our machines and dros are one button away from metric, hell, half the people use digital calipers.
Now the US is like a 40 year old virgin, you can try to talk her into it, but the odds are slim....
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The metric system is horrible for construction and manufacturing. The Inch or Imperial system is far more managable. First off the scale is an inconvenient size. Second industry for the most part "grew up" around the inch system. Many of the standards for things like class of fit, tolerancing, and size in general were developed around the Imperial system. Quite often I find that when I'm converting a metric print to inches, the multi digit metric numbers convert neatly into standard "inch" sizes. The resolution is also off for manufacturing. .001 mm or 1 micron is too small to be practical. There are no .001 micron resolution conventional micrometers because the scale is too small to read. Even most digital micrometers have a disply resolution of one micron, but the accuracy and repeatability of them is several times that. Here is a good explanation of some of the disadvantages: http://www.abc.net.au/rn/science/ockham/stories/s11563.htm
Dan
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What size is the scale? What does that mean?

So that's a good argument in favour of teaching me a system which has no relationship or continuity?

What does that mean? Imperial shaft-hole classes aren't *round* numbers and neither are metric classes. The major difference is that the metric shaft-hole fit system can be extrapolated using a simple chart. For instance, if you know the spec for an H7 and an L9, you can easily figure out an L7, H9, l7, h9, l9, and h7 without a calculator (of a similar nominal size of course).

Perhaps talk to the engineer? I build heavy stamping dies for OEMs from Europe and NA and they are built in metric (using round metric numbers) and I build tools and tooling for my European apprenticeship (designed in Germany) and they use round metric numbers... Not really an issue with the metric system (or imperial system).

And .01mm is less than half a thou. I don't believe imperial micrometers are produced in .0005 increments (no vernier scale)?

At the push of a button they read to .00005". Can they be expected to be accurate to 50 millionths?
A cube has a volume of ten gallons (you pick the nationality). What are the side lenghts in yards (no calculator or reference text)?
A cube has a volume of ten liters. What are the side lengths in meters (can probably be done in one's head)?
Because I have been trained on both, I am comfortable machining parts using either unit. Given a choice, I would take metric because the mental math is so simple.
Regards,
Robin
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Well said ! http://www.infoweb.co.nz/free-articles-for-reprint/metic-system
Greg.
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It means that the imperial system evolved along with man. It is based on unit sizes of familiarity. Ever hear of a foot? What do you suppose that length approximates?

As a matter of fact it is. The other day the quill handle broke on our Taiwanese knee mill. Turns out to be a 3/8" thread. Same as on the U.S. made drill press which has three handles. So we borrowed one until the replacement arrives. What is the IC size of a CNMG431 insert? And on and on. Industry grew up with a system that grew up with mankind. The inch system of lengths has realationships, fairly easy ones that relate to everyday life. As far as continuity, the Imperial system beats the metric system hands down. Man has been counting by twos since he learned to count. The computer you're using is based on the very fast and efficient binary system. Thank god the French haven't insisted on applying the metric system to computers. Computers manipulate strings of ones and zeros in groups of four, eight, sixteen, thrty-two, etc.. The foot has been used as a unit of measure by every race on the planet. How many times have you seen someone measure a roon or space by pacing it off heel to toe? The division by twelve is also quite ancient. It comes from counting the knuckles on of your fingers on one hand. Did you ever notice in history the number twelve appears often? 12 tribes, twelve gods, etc.. It was natural for the foot to be divided by twelve, and easily divided by 1/2, 1/3, 1/4, 1/8, and so on, all easily visible by looking at your hand. Conversley, the metric system of the meter is based on a mistaken calculation of the diameter of the earth, and a division system of tens. Not very user friendly. All over Europe people have improvised systems to help them relate the scale of the metric system to every day life. So you end up with people using a system of two metric "feet", divided up into 24 pieces to end up with metric "inches" of a 25mm length. Stupid.

You're not quite getting what I'm saying, and I'm having trouble figuring out how to put it together in a better way. Read through Machiery's Handbook and I think you'll get it.

I started out much the same way, except in a U.S. based apprenticeship. As I recall the die heights, mountings, die bed dimensions, were all inch. Has that changed? What about a company with a twenty year old Minster? That press would be built all in the Imperial system.

Useless information in your every day life. Why would you ever need to know the length of a side of a ten gallon cube in yards? I do know that a gallon is 231 cubic inches off the top of my head, so you'll have to trust me that I can take the math from there without a calculator. I also know that most people don't need to know that info so they don't bother to learn or remember it. Not everyone needs to be able to design a coolant tank, and those that do have managed just fine for at least a dozen millenia (there's that damn number twelve again). Proponents for metrication always seem to posit these silly arguments. Where would I be or what would have happened to the world that I couldn't figure out your problem? The metric system falls apart in real world situations. Let's say you get up in the morning and want to make coffee. It takes 3/4 cup to make a pot. The measuring cup has gone missing. No problem, a handful is equal to a 1/4 cup. 3 handfuls and I'm done.

How's that? In most manufacturing measurement is carried out in a system where the inch is divided by tens, same as metric. However if I need to cut a plate to 7' 3-3/8" it's a real simple proposition to take a measuring tape and mark the plate. That equates to 2219.33 mm. How hard is that to keep straight in your head and measure on a Metric measuring tape?
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Dan

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<huge snip>
The Chinese, the Japanese, the Europeans all use metric.
You lose.
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Great point. So if everyone is jumping off of a bridge.... Idiot.
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Dan

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4ax.com:

The U.S.

Who cares?

Nope.
--

Dan

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Well, I could see your point if all our feet were the same (I imagine shoes would be significantly cheaper as well).

Our Taiwanese machines are built with metric fasteners. That argument is a no-go.

I have no idea. I would buy the insert by it's designation, not its IC. What does that matter?

Which industry? Go to Germany and see how many imperial fasteners you find. They don't count?

I find that .0001" relates to nothing in *everyday* life, and why should it?
What is the OD of a #12 thread (no calculator, no paper, no reference)? What about a #00?
My mind is nimble enough to think in meters without having to remove my boots...

Dial in 65/128" on a DRO for me.

What does binary counting have to do with manufacturing? You're grasping at straws.

Who cares? I have a tape measure and I know how to use it.

No, I haven't.

I was under the impression that the metric system is based on some wavelength of light through a vacuum. Meaning one can create a metric length standard anywhere in the universe.

I've never seen that. You're right, it is stupid.

It looks like you haven't convinced anyone here.

Read through the European equivilent to that book and you'll get it.

I am doing my Canadian apprenticeship simultaniously. It is both metric and imperial.

Yes. We build our dies in metric. Name and OEM...

Our old Hitachi press uses metric, as well as our British Clearing presses. The shut height readouts are typically digital anyway.

True, but steel is purchased by weight, which means volume.

Well, if you don't have an application to know the side lengths of a ten gallon cube in yards, I guess the metric system is not for you.

Whoa! Watch the *s* word.

What the hell does that have to do with the metric system? Are your hands a "standard" size?

So you should have no problem with either.

Is that scribble 73-3/8" or 7'3-3/8"?

The fact is that I can work easily in both. You're used to the imperial system so you don't want to change. Forget logic...
Have you ever used metric for any length of time?
Regards,
Robin
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http://www.cogsci.princeton.edu/cgi-bin/webwn2.0?stage=1 &word=Approximates
So you're telling me I don't know the specs on a mill that we import sell and use in our toolroom? Come on over and measure any part of it anytime you want.

It doesn't matter to me either. You were the one who disagreed that many industrial standards were developed in the Imperial system. I don't suppose you have any mills that take CAT tooling, or drill presses with Morse tapers, or knee mills with R8 spindles, or lathes with 5C collet chucks, or....

All of the plumbing for one.. Have you ever left your home town?

I know these dimensions off the top of my head. I've probably been in manufacturing longer than you've been alive. I don't think I need to pass any tests that you are giving. I find this question ironic coming from a guy who didn't know the pitch diameter of a metric fastener and got the size from me. Even more so that you have to use a standard Imperial size drill to get the hole size you need.

But you find fractions difficult?

12.889mm No problem.

Fractions are convenient. BTW, where can I buy 80mm floppies?
<snip>
Sorry, I just don't have it in me. So let me ask you a question.
The United States built the largest economy in the world, remains the largest manufacturer, is the largest exporter, as well as the largest market for the rest of the world's goods. How will converting to metric benefit this country?
We have the best of both worlds here in my opinion. We live in a dual use society where both Imperial and Metric are common. The benefit to the Imperial system is that it's built on a human scale and it's easy to visualize and approximate. The benefit to metric is the continuity between units of measure, which is useful in science, medicine, and some industries. As far as metalworking goes, what's the diff? It's all just numbers in a program or on a digital gage anymore. All of the imported CNC machines we sell take Imperial size tool shanks, people don't want to pay the cost of tooling up a machine that is not compatible with that which they already own. All of the manual machines are Imperial throughout, fasteners and all. The market governs what people are willing to pay for these machines, the builder in the "metric" country is the one who has to decide if they can build an "inch" compatible machine and compete with the native builders. Seems that quite a few can. I heard that Haas just sold their 50,000th machine. Many of those were exported. Seems that they can figure out how to work in both systems as well.
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Dan

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4ax.com:

http://www.prattandwhitney.com/pdfs/supermicrometer_external.pdf
No need to know anything about metrology if you can't make good parts?
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Dan