This will put it in perspective

As another representative of the thickness of .0001", figure a swipe of a green or red magic marker on a sheet of glass. Black marker is about .0002, give or take a bit.
Sam

Real-life comparisons.

Paper is about 0.003" thick

Index card about twice that (used to be 0.007").

Cigarette paper about 0.001" - depending on the brand.  Machinists would know exactly as they'd use it to indicate how close an end-mill was to the work surface.

And, when comparing to hair you need to specify what color of hair!

George

Thanks for all that info. All true.  I was just posting the illustration. It shows the outside ring as a cross section of a human hair .0035”. Compare that to the black dot representing.0001”. As small as it is, it’s a lot when having to hold a .0002” tol. It’s really a good illustration and amazing too. Go back and take a second look.

Statesrights wrote on Jan 10^th, 2025 at 6:50pm:

Early in my career I hade 100 parts 12 inches long +\- .0002. I grind them up and they sat all nite. I checked one the next morning and it was about .0003 out of tolerance. Undersized. I was in a panic. These parts were $1000.00 each. I just scrapped $100,000.00. I went and got my Forman and just in the time of telling him what I did I checked that part again and it was .0005 oversize. Letting the parts set overnight they shrank. Hold them in my hand to show my foreman they grew. He told me not to worry about it.

it may but most likely not, you only have a clearance of .00005 per side. Most likely if you are able to slip it in, it will not come back out. Any oil on either part will take up some of that clearance and reduce it to  0.  FYI I spent a huge part of my life in a precision tooling shop, the normal tolerance on the tooling I worked on was 
+/- .0002" and sometimes less. One job I had the parts were tolerance d to a stack dimension of .0005 over a stack of 10 parts. Each part was right to size but the oil on the parts from stoning off burrs made the stack oversized. That one took a bit to figure out. A good cleaning and they fell into size but am pretty sure I added a few gray hairs in the process. 
As a general rule, .0002 will give you a slight drag on a hole. If its a blind hole, air pressure will push the pin back out, a through hole, if you block the other side will give a nice "pop" when you  pull the pin out. 
Sam

.0001 is so small, a couple wipes with a scotchbrite pad will change it, depending how you are measuring.I used to grind mold cores for plastic injection, even if the tolerance was 0/plus .0005" it was an incredible pita to nail it,without coolant and 20 year old harig surface grinders etc. i would have to let the piece cool off with a wet towel over it,and then if it was still oversize by like .0003,i would spin the scotchbrite over it and send it out. you cannot get back in there and try to kiss .0003 off there,,when the whell finally sparks out ,you took off .0005" ....ooops.   and when the boss says you are making love to these parts and taking too long?? thats the difference between made in the usa or send it to china, i said send it to china,see what you get then. Now we are fixing the molds made overseas on the cheap,because they are no better and no one wants to pay for nice work .

dave j wrote on Jan 16^th, 2025 at 1:41am:


Dave, got any video of that?

SBoomer wrote on Jan 14^th, 2025 at 7:14pm:

I have a small shop out in my barn. A mill and a lathe. Nothing near as precision as I did in my Job but I just can’t get away from machining. I love it.  The tenth part of my career was kind of boring to me. I love throwing chips. Not grinding dust

I think you’ll find most of your equipment gets smaller when it’s colder out. Empirical Observation #3

In the fine woodworking business .010" is called a whisker (red), .001" is called a whisper and a 
.0001" is called a concept.  Almost none of which are achievable 

Rick