The accuracy of touch

[DMcCoy]

A machinist friend remarked about the accuracy of a persons fingers in feeling the difference between uneven parallel surfaces-- .0015"!!!.  Sounded kinda nerdy but interesting.
I got out some shim stock and feeler gauges and placed them on my table-saw.
Rubbing my finger from surface to surface-
.001"  I couldn't feel the difference.
.0015"  This I could reliably feel.
.002"   Super obvious.
I'm now "calibrated".

[Magicman]

@doctorb once said that the hand has the most nerves than any other body part.  I figured it would be the feet because it seems that I can feel a grain of sand inside of my boot with my socks on.  

[LeeB]

Pictures are not needed to prove this point.

[SwampDonkey]

I'm with MM on the feet. I can't walk barefoot any distance unless it's pure sand. If I could hand stand, I could walk over angular pebbles no problem. :D

[maineshops]

Was a machinist for 40 or so years and still have a small shop. I relied on feel and hearing a lot. Now that I'm partially blind with macular I depend on those senses even more. When I crank the handles on the lathe or mill I can easily tell what the cutter is doing. After Carpal tunnel surgery on my right hand the left hand is slowly taking over some of the duties. The body is truly an amazing thing. Dan

[thecfarm]

I use to sort leather for shoes. After a few years I could just about tell the weight, thickness, of the side of leather.

[Jeff]

This isn't accuracy to that degree, but after years of sawing at the mill, I could tell if an 1 1/8" was right on or off as I walked past the pile and just grasp one as I walked by. It was my job for it to be right. My hand was more accurate than a board pilers tape. I say that because it was usually me that discovered discrepancies and not the guys that were supposed to letting me know if there were any.

[SwampDonkey]

It's sorta like pacing distance and using that to estimate area. Had a fellow GPS the perimeter of a piece, and I just paced off distances to do samples. I could fit in 16 points as it turned out. I said to the guy on the GPS, it must be close to 16 ha. Yes, he said, it was very close.

[scsmith42]

About 40 years ago I went to really great Chiropractor in Austin Texas.  One day he remarked that his final exam from Chiropractic school involved locating the position of a human hair placed in-between the sheets in the middle of a 4" thick phone book.  

A human hair is typically around .0007 thick!

[beenthere]

 :D :D
Was he a brother to WV Sawmiller? 

[SwampDonkey]

I bet he could bend spoons. ;D

[Hilltop366]

A auto body guy told me that a long time ago, he would work on a spot that looked good but would keep rubbing his hand over it and working it. Other tricks were to spray some primer on it and look at it while the primer was wet and shiny then the next step was to spray a coat of red primer then grey over that and lightly sand so the high spots were red and low spots grey.

[Magicman]

phone book

What is a "phone book" ??  You gotta be gettin' old to remember those!!  :D

[SwampDonkey]

Hey, I still get an annual phone book. Got my 2024 two weeks ago. I'm on land line. ;D The phone company does not issue them, Yellow Pages does these days. And their books are also all online where you can flip through like a book. I know lots of people that don't use cell phones.

[Magicman]

Yup, my reply was "tongue in cheek".  Phone books are sorta like pay phones.

[firefighter ontheside]

yellow pages have gotten very small.  Most businesses aren't interested in paying to have their business in the phone book anymore.  My wife(audiologist) still has her number in there because older folks are a big part of her customer base and they still want to use a phone book.  When she opened her business in 2002 the phone book for this county was about 1" thick.  Now it is 1/4".

I'm not a very good drywall taper and apparently my hand accuracy is not very good.  When I taped my bathroom drywall years ago, I sanded and then felt with my hand and decided I had done a good job and it was ready for paint.  After I painted I realized how badly I had done.  It's still that way today.  I haven't felt the need to re-do it in 21 years.

[SwampDonkey]

Of course only residential land line numbers are listed in YP. I did notice that not all auto dealers advertise now. The schools, telephone company, emergency, government numbers are all listed. Our phonebook was never very big, low population density. We have two area codes now because of the cell phones, otherwise wouldn't need two. And the cells are confusing because on land line, a 278 number tells me they live in Holmesville. A 391 cell number I would think Florenceville, but could be in Juniper, where land line is 246. :D

[scsmith42]

phone book

What is a "phone book" ??  You gotta be gettin' old to remember those!!  :D

Well, the event in question did take place before the popularity of cell phones and before Al Gore invented the internet....

[Broncman]

I used to do some high end auto work and painting. I could feel the body work better than I could see it! Even for large flat areas, I could feel waves that took a very large flat board to do the guide coat.   

If I could not feel it, you could not see it!

[WV Sawmiller]

:D :D
Was he a brother to WV Sawmiller?

>:( >:( >:( >:( >:(

   I would not have thought the human hand was the most sensitive body part but I figured if someone went around testing shims with the most sensitive body part he'd end up in jail or the psych ward. ;)