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'[EE] Measuring hole diameters in circuit boards'
2009\04\25@165235 by Forrest W Christian

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I occasionally need to measure holes in circuit boards when it appears
one is out of tolerance.   Mainly to be able to argue with the
manufacturer.   Typically it's an issue of a non-plated hole being the
wrong size, since I specify finished hole sizes in my gerbers, and the
non-plated ones screw them up at times.  

Regardless, it's really hard to tell if a hole is really .125 or .122 or
.128.... other than the fit.  My normal caliper has the issue that it
doesn't measure round holes well.  I thought a bit about getting one of
the tapered guages that fit in the hole and then you read the diameter,
but I don't think I've seen any that goes down to thousandths that
aren't really expensive as a set, since you need quite a few of them.

I've also been thinking of getting a set of drills, but again, not
really the right tool for the job of measuring, since it's really hard
to tell if a drill is bigger/smaller than a hole.

-forrest






2009\04\25@172749 by Alan B. Pearce

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>Regardless, it's really hard to tell if a hole is really .125 or
>.122 or .128.... other than the fit.  My normal caliper has the
>issue that it doesn't measure round holes well.

How accurately do you need these holes to be - especially if non-plated? I
would have thought a caliper could measure a round hole well enough - if you
can get the points in the hole satisfactorily.

>I thought a bit about getting one of the tapered guages that fit
>in the hole and then you read the diameter, but I don't think I've
>seen any that goes down to thousandths that aren't really
>expensive as a set, since you need quite a few of them.

We have a single taper gauge that measures as fine as you could want to go
(0.3mm in our case for via holes) up to 3mm dia. Above that we use calipers.

2009\04\25@173411 by Alan Schnittman

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The "right way" to do this is with a plug gauge (aka pin gauge).

For example, http://www.mcmaster.com/#plug-gauges/=1lpzq2

-- Alan

At 04:54 PM 4/25/2009, Forrest W Christian wrote:
>I occasionally need to measure holes in circuit boards when it appears
>one is out of tolerance.   Mainly to be able to argue with the
>manufacturer.   Typically it's an issue of a non-plated hole being the
>wrong size, since I specify finished hole sizes in my gerbers, and the
>non-plated ones screw them up at times.
>
> [snip]
>
>-forrest
>

2009\04\25@182136 by olin piclist

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Alan Schnittman wrote:
> The "right way" to do this is with a plug gauge (aka pin gauge).

Or design the system to that some slop in the hole diameter is tolerated.
If you design for +-4mil you'll generally not be disappointed later.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\04\25@182711 by Vitaliy

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Alan Schnittman wrote:
> The "right way" to do this is with a plug gauge (aka pin gauge).
>
> For example, http://www.mcmaster.com/#plug-gauges/=1lpzq2

Cool. It looks like they can go down to 4 mils.

Vitaliy

2009\04\25@185139 by Vitaliy

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Olin Lathrop wrote:
>> The "right way" to do this is with a plug gauge (aka pin gauge).
>
> Or design the system to that some slop in the hole diameter is tolerated.
> If you design for +-4mil you'll generally not be disappointed later.

Reminds me of a story.

=============
Shortly after the collapse of the USSR, NASA decided to save some money and
buy a Russian spaceship. After the Americans finished assembling it, they
realized that it is actually a steam locomotive. They complained to the
Russians, who urgently sent an expert to figure out what had happened.

After reviewing the assembly instructions, the expert said:

   -- Well, duh! It says right here, in black-and-white: "PARTS MAY REQUIRE
ADDITIONAL SANDING AND FILING"
=============

Chinese factories seem to have similar tolerance standards. "Design for
manufacturability" takes on a whole new meaning. :-)

Vitaliy

2009\04\25@201423 by John Gardner

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Vitaliy - Another case of delaying shooting the engineers.

Plug gauges are a good way to go - Mine are ancient, designed for
carburetor (remember those?) orifices. Can be had in metric as well
as normal sizes.

MSC Supply, J&L, have, or had, the right price on that kind of stuff.

Jack

2009\04\25@203223 by Forrest W Christian

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Olin Lathrop wrote:
> Or design the system to that some slop in the hole diameter is tolerated.
> If you design for +-4mil you'll generally not be disappointed later.
>  
These are for snap-in connectors, so the hole size is fairly critical.  
Too small, problems with insertion.  Too large, the connector doesn't
stay tightly attached to the board during the wave process.   But,
usually we're ok.  BUT when they get it wrong... they need to fix it for
free, or make sure it isn't done next time.

I'm also picky about plating on non-plated holes.  Because the wave
solder machine will fill a plated hole in, and sucking solder out before
assembly takes time.

-forrest

2009\04\25@203354 by Forrest W Christian

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That is exactly what I was looking for.. but didn't know what to ask
for.   And I had a picture of it in my mind, but assumed that a set
would be prohibitively expensive.... looks like the set I'd want is only
$222.06, which is perfectly acceptable.

-forrest

Alan Schnittman wrote:
{Quote hidden}

2009\04\25@205341 by Jinx

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>  Well, duh! It says right here, in black-and-white: "PARTS MAY
>  REQUIRE ADDITIONAL SANDING AND FILING"

There used to be similar labels on sow's ears until someone complained
that you can't actually make silk purses from them

2009\04\25@224139 by Vitaliy

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John Gardner wrote:
> Vitaliy - Another case of delaying shooting the engineers.

Not sure what you mean, sorry..

2009\04\25@224622 by Vitaliy

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Jinx wrote:
>>  Well, duh! It says right here, in black-and-white: "PARTS MAY
>>  REQUIRE ADDITIONAL SANDING AND FILING"
>
> There used to be similar labels on sow's ears until someone complained
> that you can't actually make silk purses from them

Apparently, you can:

libraries.mit.edu/archives/exhibits/purse/purse-lg.html

2009\04\25@230932 by John Gardner

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> Not sure what you mean, sorry..

My apologies. A doubtless faux Russian proverb has it that
"in every project the time comes to shoot the engineers and
begin production".

First time I heard that might've been 40 years ago.

One mingles with a rough crowd in the military.

Ourah pobieda!

Jack

2009\04\26@002607 by Jinx

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> Apparently, you can:
>
> http://libraries.mit.edu/archives/exhibits/purse/purse-lg.html

Haha. They actually extracted glue from 100lbs of sow ears to
make a silk-like thread. Amazing

Still, that's what innovation's all about

2009\04\26@015154 by Vitaliy

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John Gardner wrote:
>> Not sure what you mean, sorry..
>
> My apologies. A doubtless faux Russian proverb has it that
> "in every project the time comes to shoot the engineers and
> begin production".

I bet I'm just too young to remember. :) The proverb does make sense,
though..

2009\04\26@114344 by Peter

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Forrest W Christian <forrestc <at> imach.com> writes:
> I occasionally need to measure holes in circuit boards when it appears
> one is out of tolerance.   Mainly to be able to argue with the

There are two ways to measure small holes: Hole caliper and optical comparison.

The hole caliper set is a set of steel rods of different diameters, each turned
down to the next lower diameter say 5mm from the end. You push the caliper into
the hole to be measured starting with a good guess. The one that goes in but
stops at the lip (where the turned-down-to-the-next-size edge is) is the correct
one fotr the hole you are testing. This is a standard machine shop item, look at
suppliers for such for a source.

The optical comparison device is a specialized magnifier with a reticle that has
various holes drawn on it. It is used by holding it against the part in good
lighting and aligning the holes until one matches. This can also have Torx and
other special tool hole markings on the slide. You can probably make your own by
printing a high resolution set of circuit board 'donuts' on a transparent film
(repro) slide and using it with a magnifier that has a built in transparent
'spacer'. The same tool can be used to gauge trace widths. I had a commercial
one and also made my own. E.g. one of these would work:

 http://www.magnifierplace.com/magstore/index.html?loadfile=itemco-lt-30.html

Just cut out and glue the printed slide in the lower (reticle) rectangle.
Technically, this would be an optical comparator (of sorts).

Peter

Peter


2009\04\26@114505 by Peter

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Alan Schnittman <schnitt <at> mindspring.com> writes:
> The "right way" to do this is with a plug gauge (aka pin gauge).

Ah, ok, this is the proper name in English. I did not see your post before.
Sorry for duplicating.

Peter

2009\04\26@115007 by Peter

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Vitaliy <spam <at> maksimov.org> writes:
> I bet I'm just too young to remember. :) The proverb does make sense,
> though..

Unfortunately in Communist times they were aware of the implications and often
shot the engineers at the very beginning in an attempt to fulfill the plan with
as few delays as possible, with predictable consequences.

P.



2009\04\26@115506 by Peter

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I can't open this page:

> > For example, http://www.mcmaster.com/#plug-gauges/=1lpzq2

but the table on the page found by entering 'plug gauges' one can see tolerance
Z which is +/- 2.5 um ?! I don't think so, at least not in plastic or FR4 holes.
The pin collar would simply go through forcing its was on. I think that one
needs a 20um collar to feel it in plastic. 20um is only 5% of the diameter for a
0.5mm hole. Either that or these pin gauges are collar-less.

Peter


2009\04\26@140426 by John Gardner

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An interesting variation on the plug gauge was used in automotive
engine manufacturing - A slightly undersize plug was inserted and
regulated compressed air fed through the plug to holes around the
circumference of the plug. The actual pressure is a quite accurate
index of the difference between plug & cylinder.

Perhaps it's done differently these days - Compressed air is expensive
stuff.

2009\04\26@174811 by Alan B. Pearce

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>Chinese factories seem to have similar tolerance standards.
>"Design for manufacturability" takes on a whole new meaning. :-)

This was always a program with Japanese cameras, when the camera industry in
Japan was growing in the 50s & 60s. Holes were always tapped so that they
would take a grub screw that was made to maximum diameter tolerance, and the
grub screws were made so they would always screw into a hole of minimum size
tolerance and tapping.

The result was the screws were always sloppy in the hole, and there was
always a second one to act as a lock screw, and then there would be a touch
of cement to stop them both falling out ...

My father would always have a pile of screws that seemed to be twice as many
as there were holes to put them in, when repairing Japanese cameras.

2009\04\26@175514 by Alan B. Pearce

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>That is exactly what I was looking for.. but didn't know what to ask
>for.   And I had a picture of it in my mind, but assumed that a set
>would be prohibitively expensive.... looks like the set I'd want is only
>$222.06, which is perfectly acceptable.
>
>-forrest
>
>Alan Schnittman wrote:
>> The "right way" to do this is with a plug gauge (aka pin gauge).
>>
>> For example, http://www.mcmaster.com/#plug-gauges/=1lpzq2
>>

Hmm, I guess that would be fine where you are measuring lots of holes of the
same size, but the device I had in mind is the last one on this page, I
think.

http://www.mcmaster.com/#hole-gauges/=1m8rli

It has a tapered pin that slides in a tube. The pin is retracted, then
pushed into the hole while the tube is butted against the material. When the
pin has gone in as far as it can, the hole size can be read off a vernier
scale.

2009\04\26@181602 by John Gardner

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www.mcmaster.com/#hole-gauges/=1m8rli

How round can a hole drilled in FR4 be? I use plug gauges
because I have them, but what you describe should work.

2009\04\27@145908 by Edson Brusque

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Hello,

    what about using a regular flatbet image/picture scanner to
photograph the board and measure the internal diameter of hole with some
graphic/picture editor?

    Best regards,

    Brusque
--
---------------------------------------------------------------------
Edson Brusque                    Stagetronics Eletro Eletrônicos Ltda
Research and Development                   Blumenau  -  SC  -  Brazil
http://www.ryan.com.br/netiqueta.htm             http://www.citronics.com.br
---------------------------------------------------------------------

2009\04\28@041238 by Russell McMahon

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Moving this into tech - related to 'doing science'.

>> I bet I'm just too young to remember. :) The proverb does make sense,
>> though..

> Unfortunately in Communist times they were aware of the implications and
> often
> shot the engineers at the very beginning in an attempt to fulfill the plan
> with
> as few delays as possible, with predictable consequences.

... or used a shaman instead, with predicatble consequences.
Lysenko? May have wrong name. New genetic theory. Allowed them to fit in an
extra crop cycle per season.
Would have been a great idea if it worked.
Alas ... .

Gargoyles ...
Ah. Got it right:

 http://en.wikipedia.org/wiki/Trofim_Lysenko

Key points

... rejected Mendelian genetics in favor of the hybridization theories of
Russian horticulturist Ivan Vladimirovich Michurin, and adopted them into a
powerful political scientific movement termed Lysenkoism. His unorthodox
experimental research in improved crop yields earned the support of Soviet
leadership, especially following the famine and loss of productivity
resulting from forced collectivization in several regions of the Soviet
Union in the early 1930s.
... Scientific dissent from Lysenko's theories of environmentally acquired
inheritance was formally outlawed in 1948, and for the next several years
opponents were purged from held positions, and many imprisoned. Lysenko's
work was officially discredited in the Soviet Union in 1964, leading to a
renewed emphasis there to re-institute Mendelian genetics and orthodox
science.

The point being that bad science lead to bad theories BUT the ability to
question same was legally banned leading to ... .

ie the engineers were not shot but instead eliminated.
Risky business.


       Russell

2009\04\28@172425 by M. Adam Davis

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On Sun, Apr 26, 2009 at 11:48 AM, Peter <spam_OUTplpeter2006TakeThisOuTspamyahoo.com> wrote:
> Unfortunately in Communist times they were aware of the implications and often
> shot the engineers at the very beginning in an attempt to fulfill the plan with
> as few delays as possible, with predictable consequences.

Premature optimization is the root of all evil...

-Adam

2009\04\28@213440 by Vitaliy

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Edson Brusque wrote:
> what about using a regular flatbet image/picture scanner to
photograph the board and measure the internal diameter of hole with some
graphic/picture editor?

This is the most creative solution so far. :-)

Reminds me of a story I originally heard from a math professor ("On no, here
we go again!" ;)

===============
Angels on a Pin
A Modern Parable
by Alexander Callandra
Saturday Review, Dec 21, 1968.

Some time ago I received a call from a colleague who asked if I would be the
referee on the grading of an examination question. He was about to give a
student a zero for his answer to a physics question, while the student
claimed he should receive a perfect score and would if the system were not
set up against the student: The instructor and the student agreed to submit
this to an impartial arbiter, and I was selected.

I went to my colleague's office and read the examination question: "Show how
it is possible to determine the height of a tall building with the aid of a
barometer."

The student had answered: "Take a barometer to the top of the building,
attach a long rope to it, lower the barometer to the street and then bring
it up, measuring the length of the rope. The length of the rope is the
height of the building."

I pointed out that the student really had a strong case for full credit
since he had answered the question completely and correctly. On the other
hand, if full credit was given, it could well contribute to a high grade for
the student in his physics course. A high grade is supposed to certify
competence in physics, but the answer did not confirm this. I suggested that
the student have another try at answering the question I was not surprised
that my colleague agreed, but I was surprised that the student did.

I gave the student six minutes to answer the question with the warning that
the answer should show some knowledge of physics. At the end of five
minutes, he had not written anything. I asked if he wished to give up, but
he said no. He had many answers to this problem; he was just thinking of the
best one. I excused myself for interrupting him and asked him to please go
on. In the next minute he dashed off his answer which read:

"Take the barometer to the top of the building and lean over the edge of the
roof. Drop that barometer, timing its fall with a stopwatch. Then using the
formula S = (1/2)at^2, calculate the height of the building.

At this point I asked my colleague if he would give up. He conceded, and I
gave the student almost full credit.

In leaving my colleague's office, I recalled that the student had said he
had many other answers to the problem, so I asked him what they were. "Oh
yes," said the student. "There are a great many ways of getting the height
of a tall building with a barometer. For example, you could take the
barometer out on a sunny day and measure the height of the barometer and the
length of its shadow, and the length of the shadow of the building and by
the use of a simple proportion, determine the height of the building."

"Fine," I asked. "And the others?"

"Yes," said the student. "There is a very basic measurement method that you
will like. In this method you take the barometer and begin to walk up the
stairs. As you climb the stairs, you mark off the length of the barometer
along the wall. You then count the number of marks, and this will give you
the height of the building in barometer units. A very direct method."

"Of course, if you want a more sophisticated method, you can tie the
barometer to the end of a string, swing it as a pendulum, and determine the
value of 'g' at the street level and at the top of the building. From the
difference of the two values of `g' the height of the building can be
calculated."

Finally, he concluded, there are many other ways of solving the problem.
"Probably the best," he said, "is to take the barometer to the basement and
knock on the superintendent's door. When the superintendent answers, you
speak to him as follows: "Mr. Superintendent, here I have a fine barometer.
If you tell me the height of this building, I will give you this barometer."

At this point I asked the student if he really did know the conventional
answer to this question. He admitted that he did, said that he was fed up
with high school and college instructors trying to teach him how to think,
using the "scientific method," and to explore the deep inner logic of the
subject in a pedantic way, as is often done in the new mathematics, rather
than teaching him the structure of the subject. With this in mind, he
decided to revive scholasticism as an academic lark to challenge the
Sputnik-panicked classrooms of America.
===============

2009\04\28@214924 by John Gardner

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> Angels on a Pin...

Perfect!

2009\04\29@005028 by Russell McMahon

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While this is dated

> Saturday Review, Dec 21, 1968.

This suggests it's origin is at least the best part of 10 years older.

> decided to revive scholasticism as an academic lark to challenge the
> Sputnik-panicked classrooms of America.

and it was probably something else before Sputniks.


     Russell


'[EE] Measuring hole diameters in circuit boards'
2009\05\12@204232 by Edson Brusque
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Hello Vitaliy,

> This is the most creative solution so far. :-)

    thank you. :)

> Reminds me of a story I originally heard from a math professor ("On no, here
> we go again!" ;)

    That's an interesting story, but the instructor would
have a better point saying that it was asked to use a barometer, not a
barometer and a rope.

    With the conventional answer, you use only things present in the
question's enunciation (barometer, building and the one that will
measure and calculate). If you're (really) good doing calculations in
your head you don't even need pen and paper.

    The student's answers implies the use of objects that the question
don't say he have at his disposal (rope, stopwatch, measuring tape etc).

    I really like when someone thinks not conventionally. But there's a
(sometimes big) distance from "different" to "usefull".

    Best regards,

    Bruque

--
---------------------------------------------------------------------
Edson Brusque                    Stagetronics Eletro Eletrônicos Ltda
Research and Development                   Blumenau  -  SC  -  Brazil
http://www.ryan.com.br/netiqueta.htm             http://www.citronics.com.br
---------------------------------------------------------------------

2009\05\13@091354 by Gerhard Fiedler

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Edson Brusque wrote:

>> Reminds me of a story I originally heard from a math professor ("On
>> no, here we go again!" ;)
>
>      That's an interesting story, but the instructor would
> have a better point saying that it was asked to use a barometer, not a
> barometer and a rope.
>
>      With the conventional answer, you use only things present in the
> question's enunciation (barometer, building and the one that will
> measure and calculate). If you're (really) good doing calculations in
> your head you don't even need pen and paper.
>
>      The student's answers implies the use of objects that the question
> don't say he have at his disposal (rope, stopwatch, measuring tape etc).
>
>      I really like when someone thinks not conventionally. But there's a
> (sometimes big) distance from "different" to "usefull".

Right... but think of the average barometer's precision and the
precision of the height of a building that you would get out of this;
possibly not that useful for the height of a building. (Barometers sold
as "precision barometers" spec e.g. 1.5 mbar. That's more than 10 m in
height difference.) Also, for the "conventional" answer you have to
assume that the atmospheric pressure remains the same while you move the
barometer up or down the building -- which is an assumption that wasn't
listed in the question. So you need to "add" something to the question
anyway, and, at least from a "useful" perspective, a rope and a meter is
a safer bet than two assumptions :)

Gerhard

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