r/Tools • u/L0UDLlF3 • 2d ago
Is this 10 mil?
I'm trying to measure plastic film thickness. I believe this is .001 mm which is 10mil?
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u/_lavxx Technician 2d ago
Precision measuring tools are no longer precise after getting rusty.
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u/svideo 2d ago
My man that's a Browne and Sharpe which is probably older than most people reading this and has a few more lifetimes to go. Anvil is clean and that's most of what matters. Surface rust on the body won't make a difference to your measurement.
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u/L0UDLlF3 1d ago
Is it special in any way other than being an old quality tool? It is my dads but they just lay around now unless I use them.
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u/Onedtent 1d ago edited 1d ago
It's a quality tool whether new or old. Properly looked after that will still be a quality tool in 50 years time.
Edited to add: If it is currently in good working order.
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u/SomeGuysFarm 2d ago
While I wouldn't want to allow precision measuring tools to acquire even surface damage, given that it's visually clear that the anvil and spindle are perfectly fine, what part of the precision (though I expect you actually mean accuracy) would you argue is affected by the surface rust on the thimble and frame?
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u/Shot_Investigator735 2d ago
I would want to disassemble and inspect the threads. Usually they're oiled, so it's possible they're OK. I'd (t)rust this over the average digital caliper.
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u/SomeGuysFarm 2d ago
Same. If the threads are good, the anvil and spindle are good, and the bore isn't sloppy, surface rust on the frame and thimble really are an eyesore, not a problem for accuracy.
If the rust is sufficiently extensive that the dimensions of the frame change -- residual stresses released/etc -- then rust would affect something, but if we're going to hold micrometers in our warm fingers, we're not worried about the kind of dimensional change that would result from surface rust.
Ironically, it's likely that on mildly-abused (occasionally dinged into something) instruments, some amount of surface rust actually relieves surface stresses created by micro-dents, resulting in greater, rather than lessened accuracy.
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u/Onedtent 1d ago
Ironically, it's likely that on mildly-abused (occasionally dinged into something) instruments, some amount of surface rust actually relieves surface stresses created by micro-dents, resulting in greater, rather than lessened accuracy.
Very thought provoking. I'm not so sure I agree with you but don't have sufficient facts to disabuse this.
What I do know is that stress corrosion does exist because I've had it happen to me.
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u/rnaka530 1d ago
This is an intersting observation, and I donāt know if Iām 100% sold on the thought of going out to purchase Iron Oxide just yet.
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u/Onedtent 1d ago
One does not purchase Iron Oxide. Iron Oxide takes up residence of it's own volition.
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u/Zirconium_Clad 2d ago
Also should never store with anvil's closed
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u/Onedtent 1d ago
The reason for this?
Serious question.
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u/Deywalker105 1d ago
The anvil faces are more likely to corrode if you store them closed.
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u/Onedtent 1d ago
Ok. Fair point. I was always told to oil the faces of the anvils. (and make sure they are clean before using them as the oil film can lead to incorrect measurements)
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u/L0UDLlF3 2d ago
So the r/machinists reddit helped very fast. They said it's 0.01 inch which is about 10mil thick plastic. And eventhough it's rusty it's been sitting in a garage for like a decade and was barely used before that, it still gets tight right at 0 and this isn't precision fabrication or anything cray accurate. It's just plastic film from a Sony warehouse that was sold when tvs stopped being made of glass and its just for a greenhouse.
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u/Pumbapoo 2d ago
Yep. Itās needlessly confusing. But 1.0 Mil is the same as 0.001ā. Itās rarely used and causes confusion every time I see it.
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u/xmastreee 1d ago
Some say 1 mil is 1 thou, others say it's 40 thou. Until recently I'd never heard of a mil meaning a thousandth of an inch, it's always meant a millimetre for me.
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u/UnclassifiedPresence 1d ago
Yeah thatās throwing me off bigly here, I had no idea āmilā was anything other than an abbreviation of millimeters
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u/xmastreee 1d ago
Yep. It's an American thing apparently. Having said that, I'm British but I did an apprenticeship with an American company in the UK and we worked in inches mostly. I've still never heard of mil meaning anything but a millimetre. We always used thou to denote 0.001"
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u/hate_picking_names 1d ago
Mil is generally used for plastic sheeting and similar. I have also seen it used for garbage bags and plastic drop cloths. 1 mil is 1 thou.
That being said, as an engineer in the US, I generally use "mil" to refer to mm and thou for 0.001".
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u/TheRealTOB 1d ago
Exactly this! Plastic sheeting and occasionally thin coatings. The adhesive world often uses the mil designation for average thickness, although, coating weight is typically the controlled factor.
Now that Iām in metals, I rarely hear it used even with thin surface treatments. Only one paint shop says mil every now and then.
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u/3HisthebestH Weekend Warrior 17h ago
Coatings use mil extensively when referring to wet coating thickness on-line. Of course there is GSM (g/sq meter), grains, etc. but mil is an extremely popular measurement for coatings (adhesive, optical, visual, structured, so on).
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u/-sexy-hamsters- 15h ago
Yes in AMERICA maybe smart to say this since the rest of the world does not say or write it like this. Even if you do use the metric system you use it wrong
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u/dinosouborg 1d ago
It's used quite a bit in electronics engineering on the imperial side of things. We need to work on the order of magnitude of thousandths of an inch so I tend to talk about microns (.001 mm) or mils (.001 inch). Funnily enough I haven't really heard electronics engineers say "thou" that much.
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u/3HisthebestH Weekend Warrior 17h ago
lol itās not rarely usedā¦ itās HEAVILY used in industrial settings and Iād imagine more than just that. Itās actually what got me to learn the conversions between standard and metric to the point I can fire off calculations between one or the other instantly in my head.
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u/gatekeepr 2d ago
Seems to be what is called 'brown rust' which can appear in an atmospheric oxygen / low moisture environment, like a garage.
more here: https://www.armorvci.com/corrosion/types-of-rust/
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u/rnaka530 1d ago
You say that now mister but we all know you probably telling your friends you got the machine shop at the house
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u/L0UDLlF3 1d ago
Lol i wish, everything is so old and not taken care of you never know what you'll find or if it will work. It's so much (bc my dad horded tools) that's i feels impossible to properly sort and clean it all. And my grandpa's tools are so jerry rigged that I can't believe he made anything with them. My favorite is a band saw made from what looks like was once a sowing machine. But I've never seen it work
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u/APLJaKaT 2d ago edited 2d ago
Should mark that NSFW. That poor micrometer.
Mil is an almost slang term for 1/1000 or 0.001 and is likely based on the French word "mille" meaning 1000.
Probably not a good unit to use because of it's ambiguity.
However, mil is often used as a thickness measurement for various materials. Your micrometer appears to show 10/1000 or 0.010" so in that case it's "ten thousandths" or an inch or "10 mil". It would also be correct to say "one hundredth" of an inch, but for most people that would simply confuse them even more.
Fwiw, for measuring sheet goods like plastic, which are often labeled with their weight (thickness) in mils, this isn't really the correct tool to use. There is a micrometer designed for measuring sheet goods and it has a much larger anvil to prevent localized compression of the material being measured.
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u/CarpetReady8739 1d ago
Thank you for the cogent and insightful response to this person whoās just trying to ask a question and maybe even learn something. Those of us who actually think will benefit from this.
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u/sarlard 2d ago
As a Precision Measurement calibrator, this hurts me dearly to see.
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u/Badfootbarista 2d ago
Especially an old school Brown and Sharpe. Thatās a collectors item.
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u/L0UDLlF3 1d ago
Can you take these appart and clean them without damaging them? I actually think he had a couple of them but this one was in the best condition. I think it's all just surface rust. He used to take good care of his tools. And it spins like it's new, doesn't feel like there's any grit inside or anything.
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u/HeioFish 1d ago
Some gentle rubbing with steel wool and a very light coat of oil will help this guy from developing further rust. Back in the day we used to toss an unwrapped camphor oil cube into the tool box. And that'd keep the tools from rusting.
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u/buildyourown 2d ago
That is .010" Mil can be used to mean 1mm or .001" when talking about thin films. So yes, it's 10mil if you are measuring thin film
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u/MannyCoon 2d ago
The only people I've heard use "mil" to mean millimeter are graphic and industrial designers who can't even measure using a banana. A mil is one thousandth of an inch, used in the film industry to describe thickness, and I'm not talking about movies.
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u/Evening-Green-791 21h ago
I deal with metric and mil means millimeter. Don't measure anything sub a mil. But is how it's spoken
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u/MannyCoon 6h ago
What industry? I deal with sub millimeter all the time, and sub .001". If someone says "mil" in my industry, I correct them because it has a double meaning, so I have to insist we keep it a singular meaning to avoid confusion. The people I correct are typically non-engineers/machinists. As I said, they're typically graphic and industrial designers making shorthand and misunderstanding the meaning of "mil" to be .001", typically used in the films industry (as in thin-film plastic sheeting, not movie-making). In this case, OP converted .001mm to .010", which is incorrect in either usage.
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u/Evening-Green-791 6h ago
Civil engineering. Construction. Everything is in mils. Canada mil is mm using si. Ya in this particular case, sure mil to YOU means a thou. Hear we'd generally use thou. They aren't wrong, they are just speaking a different language. Ya either which way he was wrong in his conversations
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u/Evening-Green-791 6h ago
On my industry we use 5mil-10mil poly/geo but it's generally listed as .125 -.25mm / 5mil-10mil. Our sheet goods are labeled as both on drawings and specs
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u/dippedtungsten 2d ago
As a millwright, when we do jobs that are strictly metric we'll normally refer to a millimeter as mil as long as everyone is aware.
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u/TryTop9572 2d ago
10.0 millimeters? Or 0.10 mirco meters?
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u/Deckpics777 2d ago
Nobody yet has mentioned directly this is not metric at all. Lots of correct answers though.
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u/L0UDLlF3 1d ago
Idk exactly tbh, plastic film is measured like this here. It's not mm. 1 mil is = about 39mm
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u/Obvious_Tip_5080 1d ago
You can actually take it apart and clean it, machinists do this yearly btw. Found a YouTube video for you, be very careful not to,lose any pieces, keep your work area immaculate. https://youtu.be/4v4oKTkfHHk?si=f8d9u3n1GFEK4D0Y Machinists have stick gauges for checking the calibration on their micrometers.
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u/Whitey_RN 2d ago
I always wondered what disk mics were really for. We just used them for places a regular mic canāt reach
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u/TryTop9572 2d ago
From my experience, they are designed for specific types of measuring of shapes a typical anvil will not reach.
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u/w1lnx 2d ago
Ignoring the visible rust on the micrometer, which will greatly affect its accuracy and reliability, let me answer your question with a few questionsā¦ have you
zeroed the micrometer (zero it), and
were you using the thumb spindle to set the pressure on the part being measured and while zeroing (technique and process are critical), and
is the part being measured not prone to being compressed (if it can be compressed, the measurement wonāt be correct) ?
And, quite importantly, have you measured the film thickness with a far more suitable tool like an isoscope (right tool for the job)?
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u/ulfbjorn987 1d ago
That is reading .010" This is a 0-1" micrometer. The decimal conversions on the arm is your first clue.
As stated by others, .010" = 10mil. In standard units 1mil equals .001".
.001" is (very) not the same as .001mm.
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u/Least-Monk4203 1d ago
I understand your confusion. When I was grinding precision round stock a mil was a thousandth of an inch, 0.001. I asked one of the engineers who calibrated our tools if it could cause confusion with metric mm. He said we donāt do metric here. Thought that was odd as it was a Canadian based company, but a US facility.
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u/Uniturner 1d ago
Iād clean it up, zero it, and see if you can calibrate it. Thereās not much to lose other than a bit of time.
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u/HeyItsDizzy 1d ago
Say USA so itās definitely imperial, I also see it has 32nds this refers to super small fractions of an inch
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u/TrainingParty3785 19h ago
Terminology is key. The micrometer you are showing is in very bad condition btw, it is made for Imperial units, not metric. The confusing part is when you are measuring MILS which sounds likeāmillimetersā, but it is referring to thousandths of an inch, 10 mils is .010 of an inch. When the two surfaces are touching, not forcefully, the barrel should read 0, if not you need to either cal the mic or compensate. Good Luck
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u/CaerbannogsOffspring 1d ago
Note the conversion scale stamped on the body showing that a reading of 9 equals to 0.2812 32nds or 0.2812/32 = 0.00879in which approximates to 9mil of an inch which translates to 0.22mm.
Same goes for 11: it converts to 0.3437/32 = 0.10741 =Ā 11mil of an inch = 0.27mm.
Run the math for 10, and you find it results in 10mil of an inch or 0.254mm.
Apologies if I am wrong, last time I saw it was in trade school back in 1989 and havenāt really use this model ever since.
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u/myniwt 2d ago
10 mil would be a metric measure of 1cm, which it really isnāt. Perhaps you mean thou?
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u/kirill9107 2d ago
Mil is a unit used to describe the thickness of plastic sheeting, confusingly a mil doesn't indicate a millimeter, but is actually equivalent to a thousandth of an inch, as you mentioned.
So a ten mil sheet of plastic is ten thou thick.
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u/clambroculese Millwright 2d ago
Ok so youāre right (I looked it up) but in machining it is also short for a mm.
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u/ImReallyFuckingHigh Millwright 2d ago
Yup, I am a millwright at well (UBC in the US), am currently taking my first shaft alignment class this week and it was covered that a āmilā is a thousandth (.001)
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u/clambroculese Millwright 2d ago
Yeah Iām not American which is probably why it confused me. Dual ticketed millwright/machinist.
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u/TryTop9572 2d ago
Red seal machinist, I have never used the term'mil' to reference one thousand of a inch. It's one thousand of a inch.. not 'mil' . I was only in the trade for 32yrs. So maybe they changed the wordage.. there is the term 'milspec' which was typical for military specifications
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u/clambroculese Millwright 2d ago
I think itās an American thing, Iām red seal millwright/machinist and today is the first time Iāve heard it.
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u/ImReallyFuckingHigh Millwright 2d ago
It stems from the Latin prefix āmilliā and the French word āMilleā which both mean 1000. Could just be a millwright thing though.
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u/TryTop9572 2d ago
Possibly we never used the word Tram when dialing in the head of a milling machine. But my buddy who is a millwright used the term.
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u/RegularGuy70 2d ago
It all depends upon context. As an engineer with machinist background, I speak in thou or fractional inch. But my circuit card designer colleagues speak in āmilsā which means to them thousandths of an inch. Millimeter is something else entirely.
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u/Seroseros 2d ago
If your units depend on context, they suck.
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u/RegularGuy70 2d ago
Not going to argue that point, except that none of what Iāve said, save āinchā and āmillimeterā, is a unit. A āthouā isnāt a unit, nor is a āmilā. Theyāre all colloquialisms for units. Which is where the context makes sense.
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u/bbbermooo 2d ago
10 mils equal .010"
10mils does not equal 10mm
That looks like .010" of an inch, which is 10 mils.
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u/GeniusEE 2d ago
10mils IS 10mm in metric countries
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u/bbbermooo 2d ago
Didn't know that, they shorten millimeter to mils?
In the US it means one thousands of an inch.
Since the mic was not metric I assumed we were talking US stuff.
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u/Deckpics777 2d ago
I agree to a point, since Iām from a metric country. In this case, itās slang, being its measuring in thousands of an inch.
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u/BobT21 2d ago
You have a welding clamp.