[NC Cams]

13/64" = 0.203125"

How to derive? Divide 13 by 64.

DUH

[tajord]

Dang, each day you learn something new :withstupi .

[x6xtyx9x]

Just thought I would point out something... I don't know if it’s been said or not... but let’s go deeper than just machining and look at engineering and science. How volume transfers to 3D and how when you know how many cubic centimeters a box has you automatically know how many liters will fill the box and so on.

Science may be the illegitimate step child of math... but you still gotta support the lil booger.

[DomB]

OK that was an easy one for starters.

Question 2: The next dimension on the drawing is a tiny clearance. The dimension is 1/72nd of an inch. What do I enter into the computers???


Answers please.

Good Luck
(chair)

[tajord]

13/64" = 0.203125"

How to derive? Divide 13 by 64.

DUH

1/72" --> Divide 1 x 72 = ???

Give a man a fish, he eats for a day, teach a man to fish, well...............

[OCNC]

I god had meant us to us the metric system, we would have been born with ten fingers

...ten fingers and two hands...that's three sets of four (and definetly not four sets of three)...the right four fingers, the left four fingers and the combination of the two thumbs and the two hands. Twelve has 1,2,3 as prime factors and ten has 1,2,5 ...so isn't it obvious.......we should be working in the 'unified sexigesimal system' Any elegant system of measurement will be based on a proportional and not an absolute reference. That meter stick sitting somewhere in France is about the funniest thing I can think of.:violin:

Chris

[NC Cams]

Surely you jest and can't be serious?!?!?!?!?

Let me try this again:

1/72 = 1 divided by 72 = divide 1 x 72 where x equates to the "by" in 2x4 or, ultimately 1/72"= .013888888888888"

EDIT To address the inevitable next question for the metrically confined/limited members, multiply the quotient of 1/72 by 25.4 and you'll get mm or 0.01388888888" = 0.352777777mm or 352.7777777 microns END EDIT

If you don't know how to fish by now, perhaps you really do need to starve.....

[x6xtyx9x]

Are we talking metric or standard entry... if it was metric... follow the usual formula ... or such... if it is standard in a drawing.... why are you even using fractions. Any machinist will tell you that using fractions on a drawing is not a good idea for a number of reasons.

One of which being a fraction is a perfect number and could NEVER I be achieved in full. Their will always be some infinitely small number that will exist to break that measurement.
The other being... the last time I checked a FANUC did not work on a fraction system going from 1/10000 to 9999/10000.......why would you draw in a format other than what you plan on using.
The third being that when machining all sorts of factors would eliminate the need for 0.013888888888888888888888888888889
A chip could kill off a dimension to begin with... on top of that I am sure that tool pressure could even eliminate that.

I don't know what I am talking about..... But these are the thoughts I get....... and I don't understand why it would matter if you just programmed using the same structure for both. A number is a number and when machining most machinists won't even try to achieve a tolerance tight enough to not hit by rounding up half a thousandth... the part requires grinding or such... or at least this is what I have seen.

I'm interested in seeing the rest of the answers.... I may learn something valuable..... You guys really have me thinking.

[DomB]

Well theres plenty of sarcasm floating around now.

I think you mean
1/72 = 0.01388888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
888888888888.......

Where would you like me to stop.

So if I buy a 1/72nd inch tap or reamer or any tap that is a multiple of 72, what size is it

Is it

0.01389
or

0.013888889
or

0.0138888888888889
or

0.01388888888888888888889

I dont know, and it depends on what machine shop decides to use for decimal places.

So what clearance do I give it? I don't know because we cannot actually get a finite number for its size.

Anybody ever seen that pi calculator that calaulates pi to several billion digits and it just keeps going and going.

Discuss

Dom

[dertsap]

I. A number is a number and when machining most machinists won't even try to achieve a tolerance tight enough to not hit by rounding up half a thousandth... the part requires grinding or such... or at least this is what I have seen.

.

to say that is rediculous
a good machinist always aims to make the dimensions of the parts dead nuts ,many parts that i have done had dimensions within a thou ,and on a good machine it is no problem to achieve those dimensions unless it s a pretty funky part
5 decimal points is best for tapping ,otherwise added pressure is on the tap due to the fact the teeth arent following the other ones perfectly ,especially so on deep holes
throw in two decimal points the next time your tapping and see what you get

[Jason Marsha]

Surely you jest and can't be serious?!?!?!?!?

Let me try this again:

1/72 = 1 divided by 72 = divide 1 x 72 where x equates to the "by" in 2x4 or, ultimately 1/72"= .013888888888888"

EDIT To address the inevitable next question for the metrically confined/limited members, multiply the quotient of 1/72 by 25.4 and you'll get mm or 0.01388888888" = 0.352777777mm or 352.7777777 microns END EDIT

If you don't know how to fish by now, perhaps you really do need to starve.....

I really think he is pulling your leg.

Jason

[DomB]

to say that is rediculous
a good machinist always aims to make the dimensions of the parts dead nuts

Dead nuts to what?
The number that you decide to round the error to or the number that the customer rounds to or the number that another subcontractor rounds to........


Next question.

On a thread of 1/72 inch pitch. How deep a rigid tap (assuming the rigid tap is perfect for arguments sake)..can a 1/72" pitch tap be threaded, rounding the decimal measurement of 1/72" to 4 decimal points, before it breaks due to the error making it misalign.

Who will take the challenge to work it out.

Have inches of fun.

[dertsap]

Dead nuts to what?
The number that you decide to round the error to or the number that the customer rounds to or the number that another subcontractor rounds to........


Next question.

On a thread of 1/72 inch pitch. How deep a rigid tap (assuming the rigid tap is perfect for arguments sake)..can a 1/72" pitch tap be threaded, rounding the decimal measurement of 1/72" to 4 decimal points, before it breaks due to the error making it misalign.

Who will take the challenge to work it out.


Have inches of fun.

how can anything get more simple , i dont decide the numbers , the customer decides the target dimension and gives a +- tolerance , dead nuts is the target dimension
a FOOL would try to work within the tolerance rather than aiming for the target number because you are minumizing your room for error ,which is what the tolerance is for to begin with

as for a 1/72 pitch tap ,i"ll let you figure that one out for yourself

[x6xtyx9x]

Woops... I didn't mean the Dertsap.... I meant rounding up the tenth of a thousandth based on the answer going out infinitely... I left out the HUNDREDTH OF before the thousandth. I was going back into the rounding bit. HAHA boy that sure made me look dumb..., need to look at how I word it before I send it(nuts) to myself.

IE

.013888 being rounded up to .01389
would be rounding up causing an increase of 2 hundredths of a thousandth
.013885 being rounded up to .01389
would be the equivalant of rounding up 5 hundredths of a thousandth which is equal to half of a tenth

That make any sense?? Or am I still missing something? I was trying to say that is it near impossible to fight over the hundredths of a thou. when a machine is capable of mass production for the most part in the tenths. Would you agree with that? Aircraft parts go to a tenth according to a programmer I just got off the phone with.

Having never programmed in metric...I am curious as to whether or not someone programming a machine in metric would be able to create a readable machine movement smaller than a tenth of a thou. I thought I read this somewhere.

Also... what are you running that will allow you to program to the hundredths of a thousandth. I am used to the FANUC 0M and it just stops at .0001 and at that movements made by the machine can only be regulated by hand control to the tenths. You may be programming in hundredths of a thou. but I seriously doubt you are acheiving them. Tool pressure alone on the most stable of tools would begin to set in at that point. Its just like when drawing in CAD..... I might tell that line to start at x0y0 and end at x0 y2.34567864580932850858325098350980958395890589385 0975892380840
499959584 ...but that isn't going to happen, the software has its limitations.

Nothing is perfect... and never will be. Besides a fraction is an imaginary number... it is not even a number it is an imaginary placement of a number between a number at a set point based on the use of two integers as a numerator and denominator. Just as a thought. So... I really think the answer for the whole form is there isn't a right or a wrong.

But I think I'm going to side with the metric guys. The system is much more useful in the broad scheme of things and standard is as dumb as can be. It is a sign of the need for a change of times. I mean cmon links furlongs..... heck most of you cant even tell how big one of those are and how many inches are in each... I sure can't. But ask someone how many centimeters are in a decimeter and they could pull it off the top of thier head if they use the system daily. More power to you my metric loving friends and congratulations on finding one the reasons the US has to fight to continue as a superpower.

[dertsap]

i hear ya man

[martinw]

I just wonder if manufacturers in China give a rat's a## about the measurement system on the drawings or files they are sent.

They must get sent tens of thousands every day, and I very much doubt that they care a great deal whether they are in imperial or metric units. They get on and manufacture. Meanwhile back west, we indulge ourselves with debates such as this.

Isn't it time to get real and admit that both systems work??

Just a thought

Martin

[x6xtyx9x]

Right on Martin.... but who is to judge what works. Again I go to the bigger picture........ Sure it works for the CNC programmer...and in other things...but why complicate the whole picture. Engineers find it easier to calculate scientific data in metric... machinists (here in America for the most) find it necessary to program in standard. Mostly because it is what we are used to. Amazingly the so called grease monkeys of society (mechanics) have found a way to adapt. So I am sure we too could find a way. No offense to mechanics anyway... I am just making fun of the ignorance of society.

So which is more efficient... a process that can be used efficiently from start to finish ... From engineering to final product. Or something that creates train wrecks and complication.

It all comes to commonsense versus tradition. For goodness sakes........We measure vehicle motors in Cubic Inches and then describe it in liters..... Ever notice that bike motors don't have the need to say 150cc and then liters.... it can be determined by using the tens process.

We have to face it... we are in a global economy ... with global trade... we have to learn to evolve as a country and quit trying to be the last piece of the puzzle to fit. From a philosophical view I see it just like global warming.... we know we messed up... and have to find some sort of way to feel in control.

[Glidergider]

Hey x6,
I've been in the engineering business since '82 and I remember vividly the US goverment proposal to switch to metric. It made since then and it still makes sense. I've had jobs where I worked on Italian and British designs. I can say it was very easy to understand the tolerances of the metric system. I think its called the DIN system of tolerances.

Then, all of a sudden the government's effort to switch to metric system desolved. Pooff it was gone.

I don't think anyone mentioned the Mass system differences between metric vs imperial. When doing calculations for acceleration us imperialist must cipher the differences of pounds mass vs pounds force. Or use Slugs in our calculations of speed and acceleration. I like them both, but I'd rather have metric.
Dave

[x6xtyx9x]

Would you please explain pounds/mass and pounds/force. Also, having the opportunity to experience metric at its most full, would you say that momentum and inertia are easier to equate in metric than in standard? I am curious of the metric system's traits.

I also am curious as to whether or not a machine can make a registered movement of less than the equivalent of one ten thousandth of an inch when using metric alignment

I believe the last question if true may be the answer to the alignment of the 1/72" pitch tap listed above? I would like to know the answer to that by the way. Help us young'ins help ourselves!

[FrankM]

Hey x6,
I've been in the engineering business since '82 and I remember vividly the US goverment proposal to switch to metric. It made since then and it still makes sense. I've had jobs where I worked on Italian and British designs. I can say it was very easy to understand the tolerances of the metric system. I think its called the DIN system of tolerances.

Then, all of a sudden the government's effort to switch to metric system desolved. Pooff it was gone.

I don't think anyone mentioned the Mass system differences between metric vs imperial. When doing calculations for acceleration us imperialist must cipher the differences of pounds mass vs pounds force. Or use Slugs in our calculations of speed and acceleration. I like them both, but I'd rather have metric.
Dave

When the big push to convert back then I worked in a lab next to a prototype machine shop with about 20 toolmakers old timers who could fabricate anything (no cnc) some of them legends . When the first Metric drawings came down from the engineers the place tunred into Kaos, you should have seen these guys converting every dimension in the drawing just to start cutting it sounded so rediculous then , it only lasted about 5 months .These guys knew what cutting 5 thousands on the lathe looked like, but had no idea what cutting .5mm looks like