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# What does .0001" look like

##### Aluminum
Seems like a simple enough question, yet the visualization of what 1 ten thousandth of an inch might look like is difficult to grasp. We recently had some discussions here and we talk about it all the time…we make it sound like it’s close to a mile long. What I mean is out by .0001" is OUUUUUUUUUT. So we set on a journey to discover what .0001" might look like. Below is what we discovered:

In March 1944 Popular Mechanics attempted to answer this same question. What they used for suggestions included: The tip of the HOUR hand on your watch takes hardly more than one second to move .0001". You would have to split a human hair into 30 equal slices to divide it slivers .0001" thick. This helped, yet it was still difficult to visualize.

So we decided that maybe the concept of time would make it easier to understand. 52.56 mins = 1/10,000 of a year. During that same year, you will spend approximately 175,200 minutes sleeping… about 122 days.

Say we live for 100 years… .0001 of our lifetime = 3.6525 days or 87.66 hours or two 10 minute breaks per work day for a year.

Hmmm...closer... I still couldn't "see" it though.

Money ALWAYS solves everything, so we decided to try that. How about a stack of pennies scaled so that 1” = 567 inches or 47.25 ft.
1.0” = 10,000 pennies
.1 = 1000 pennies
.010 = 100 pennies (+-.005)
.001 = 10 pennies (+-.0005)
.0001 = 1 penny

Ok...I can hold a penny in my hand and look at it from the side, that is what one ten thousandth of an inch looks like... so what does 10,000 pennies look like? It's the copper colored line to the left of the person in the photograph (her right). There are eight 6 foot long clear lexan tubes containing 10,000 pennies.

#### Winterfalke

##### Stainless
Interesting, I always thought .0001 looked like an engineer that didn't know how to use appropriate tolerances.

##### Aluminum
HAHAHAHHAAHAHA...that is the best one I've heard! I'll snip it out and send it to engineering...you just made my day!

#### CountryBoy19

##### Stainless
Interesting, I always thought .0001 looked like an engineer that didn't know how to use appropriate tolerances.

Who decides if the tolerance is appropriate? The engineer that knows the system and what the requirements are or the machinist that reads the print and makes the part as the print shows?

Just to be clear, many engineers don't have a clue when it comes to proper GD&T, but many machinists don't either... I wouldn't say any one group is at fault...

That being said, I don't want to derail the thread, it's a good concept to try to get a grasp on.

#### hanermo

##### Titanium
Nah..
3 microns is a std bore tolerance for P9 bearings, == 50 mm.

1 micron is so-so for amateur telescopes, and good ones are 10-100x better.
You can hand-make them with pitch laps, abrasives, time.

One micron over/under sized, easy to see and test by hand.

Lapping will get anyone to 1-2 microns, if they build a proper jig/tools.

#### JNieman

##### Titanium
HAHAHAHHAAHAHA...that is the best one I've heard! I'll snip it out and send it to engineering...you just made my day!

As someone who's been both a designer and machinist... it gets old. Engineers assume I'm tapping into the machinist side when I say "That's unreasonable, expensive, and beyond the design requirements, so should be revised." Machinists assume I'm tapping into typical engineer mindset when I require something that makes their job hard.

Sorry, I need X located within Y over a distance of Z, thus these locating features must be within .002(M) TruePosition, get over it and double check your work before the finishing passes. And yes, I really did mean .0003" parallelism.

...of course sometimes that's what you have to do to make the job work because someone bid a job with requirements that were underestimated... *sigh*

#### JNieman

##### Titanium
On-topic:

Neat visualization. I kind of like seeing those comparisons, when it's to something tangible, with a 'human for scale'. Just kind of neat. It helps when trying to explain to the laymen during shop tours, what it is we accomplish, too. Some of them actually can then get an idea of what it is to 'split thousandths of an inch' when machining, when you talk about it like that.

#### Danny VanVoorn

##### Titanium
I always use the "seeing a hair" and "splitting a hair" example when people ask what I do. Optics are brought up but really to hit a size all we need besides the skill set to make it is something suitable to compare it with. Funny thing is how accurate the human eye can be if focused on the right things.
Dan

#### conant

##### Stainless
I always used the reference to people for what a tenth of a thousandth represented to imagine 30 sheets of paper in a stack equal to one sheet of copy paper.
Seems to work.

#### John Welden

##### Diamond
View attachment 178244

Money ALWAYS solves everything, so we decided to try that. How about a stack of pennies scaled so that 1” = 567 inches or 47.25 ft.
1.0” = 10,000 pennies
.1 = 1000 pennies
.010 = 100 pennies (+-.005)
.001 = 10 pennies (+-.0005)
.0001 = 1 penny

Ok...I can hold a penny in my hand and look at it from the side, that is what one ten thousandth of an inch looks like... so what does 10,000 pennies look like? It's the copper colored line to the left of the person in the photograph (her right). There are eight 6 foot long clear lexan tubes containing 10,000 pennies.

What?

Were you going for the worst visualization ever?

#### Monarchist

##### Banned
View attachment 178244Seems like a simple enough question, yet the visualization of what 1 ten thousandth of an inch might look like is difficult to grasp.

Anyone who has ever encountered a flake of failed chrome-plating - many of us, I'd wager - might also find it dangerous to grasp.

Platings can be far thinner yet, even to exhibiting a degree of transparency to light.

That sort of visualization needs no 'scaling', and is easier than building columns of copper pennies.

Bill

#### fmari --MariTool-

##### Titanium
Story time.

When I first started making tool holders (just for our own internal use, not for resale) I was able to consistently get .0002 or better runout. This is runout between the tool holder taper and whatever feature on the other side, collet pocket, endmill bore, arbor diameter, whatever. To get better runout I redesigned some clamping fixtures and processes to get .00015 and better. Almost a decade later we are consistently making tool holders .00006-.00004 runout and maybe .00008 every 30th pc. To get to this level we redesigned every operation, modified machinery, established a lint and dust control cleaning method, made custom tooling, changed methods of inspection, etc.etc.

In the future to get to the 3rd improvement I will have to design and make my own machine. I think I can do it, but its going to take lots of time and money. Also I will need to improve air, water, coolant filtering. Temp and light control (no more skylights). That will get me down to .00003-.00001 runout. But if it makes my obsessive cumpulsive nature happy it is worth it. If you aren't reinventing yourself/company you are falling behind.

#### i_r_machinist

##### Titanium
Man, This is just what I needed! "They" decided we needed all of our planners,(the people that write the instructions in the work orders), to be in a pool and not be specialized. So, now I have guys that spent the last 20 years telling people how to build scaffolds telling me how to machine parts.I was tasked by the head of planning with giving the planners a "cheat sheet" on tolerances this morning and had no idea where to start. I think I'll just write a wordy response that incorporates that picture in it with a conclusion of CALL THE ENGINEERS.
Then the engineers can call me.
have fun
i_r_machinist

#### SteveBausch

##### Stainless
My WAG is a thumbprint on a mirror.

##### Diamond
Work a little math based on iron's atomic diameter of 0.28 nanometer and you get roughly 10,000 atoms per 0.0001". I don't know if that comparison holds water but is kinda places things on a scale. Does that that work?

Some things cant be translated to man-in-the-street human terms. Some people simply can't grasp basic concepts in physics. I sure don't understand relativity except in the popularized science sense even though I read Steven Hawking's books until my eyes burned. My grandma couldn't understand television to the point she covered the screen when the set was off so "the people couldn't see her." My neighbor covers the hood of his car in cold weather so the engine wont get too cold. There are people in this country who argue against demonstrable fact as though it was not only right and reasonable to do so but expect their misconceptions to be enacted into law to govern the behavior of others.

When simple explanations are futile you either have to give up explaining and leave the questioner in ignorance or fob them off on wiki. Used to be "Look it up in the dictionary."

#### PegroProX440

##### Cast Iron
At least engineers don't tolerance things in smoots.

#### JRIowa

##### Diamond
Who has 10,000 pennies? How about 2 boxes of printer paper. That 20 reams @ 500 sheets to a ream. Way easier to stack than pennies.

Us engineers only spec tenths just so we can hear the machinists tell us they can't do it.
Yep, I got that big spoon out so I can stir the pot.
JR

##### Diamond
At least engineers don't tolerance things in smoots.

Or:

List of humorous units of measurement - Wikipedia, the free encyclopedia

Speaking of units and standards, how often have you heard the call: "Come left about an RPH"? Fr those who don't know, out of the infinite varieties of PH available from half the population, RPH is the most consistent and finest to be found. Also the rarest because of the scant population of authentic redheads of a gender to grow RPH..

I once had a fabulously attractive redhead girlfriend. One spring when she barbered for the bikini season I siezed the bounty. I made on my computer suitable window cards enscribed "NBS Laboratories - US Standard - RPH - Intrinsic Standard - No Calibration Required" and there were phony serial numbers, dates, citations, and authorization signatures. It was all very official looking. I assembled about a hundred window cards, each with a curly red hair in the window and passed them out to co-workers, visitors, and salesmen much to the delight of their recipients who had a lot to say about certifying the source etc. Needless to say Marleen was never made aware she sat on a de facto national standard.

#### DMF_TomB

##### Diamond
.0001"

when i want to remove .0001" i mark it up with a magic marker and when i remove .0001" the mark is still visible just starting to get transparent.
.
i use to sand a emulusion coater slots to millionths parallelism. i had a capacitance gage measure then i made a 6 foot long printout laid side by side with part.
.
i used 600 and 400 grit sand paper stuck to precision ground blocks sanding pressure based on 6 foot long graph printout. then reassembly and measure slot width to millionths of a inch
100 millionth is .0001"
.
does not take long to remove .0001" with 600 grit..... by the way thickness of finger prints often is over .0001"...... we had to wipe bars with alcohol using lint free wipers. water when dry unless demineralized leaves residue often more than .0001"

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