What Do All Those Zeros Really Mean?

Whyemier said:
Leave it to a Texan to get to the point in a round-about- way. :applause 2:Cactus (even sounds Texan...I like it:D) has made a good point. My micrometer and vernier caliper can read tenth of a thousandths (1/10000") but how sure am I of their accuracy in doing so...don't know. Also I too believe the local temperature can affect them adversely. Though the engineers at NASA supposedly work in hundreths of a thousandth (1/100000) or millionths (1/1000000) so somebody knows how to go there. Not me, I'm satisfied with + - .001 on my work. What are we trying to do? Rocket science?:grin:
Click to expand...

Thanks, I'm proud to be a Texan, although I was born in New Mexico, it was in the part that was part of the Republic of Texas before statehood.
And close enought to theTexas border to shell it with an 87mm mortar. Hobbs to be exact. Have a great day.
 
chips&more said:
In a machine shop, if you propose to have a part made with a bunch of 5 place and more 0’s, you are going to pay dearly for that part. Holding that kind of tolerance in a machine shop is not easy and it will cost you. And IMHO a DRO with 5 places is kinda silly, especially on a manual milling machine. You might as well tape over that last digit…Good Luck, Dave.
Click to expand...

I did exactly that and taped over the last digit with gaffers tape.
 
Many measurements are comparative and need to be read to the forth decimal place.
If the components are at the same temperature when the measurements are taken there is no problem unless one will have differing expansion rates.
Some bearings need a large press fit to expand the inner race to the proper DIM. and to keep them in place. Others need only a couple tenths to retain them and to be certain they are centered.
In scraping two surfaces to be parallel and flat or measuring a dovetail or.....
There are far too many examples to name where measuring a part or machining a part to within a tenth or two tenths or less than a tenth is needed and many people in the forum are capable of it.

I've met others who would only use three decimal places and that's OK for you.
Sorry it bothers you so much!
 
If four decimal places bothers you so much, switch the resolution to metric!:D

As stated before, resolution and accuracy are two different things.
 
OH this is good! And I aint no book writer either. So when I write my chicken scratches I write .5 not .500 or .50000 I'm saving ink. Then
I understand todays micrometers all have plastic on the frame for the .00000 readings cause of the heat of your hand ? wonder bout that.
Really I think its all about what you are doing( the job). Such as we deal a lot with something like .0015 to .002 like bearing clearances.
And then there is a machine shop 500 feet from here that does deal with the .000000000's they have contracts for the big guys
like Boeing and others... so its job related so is my oldest, a union carpenter with a 16th ruler & he can't read a mic. job related....
 
GK1918 said:
OH this is good! And I aint no book writer either. So when I write my chicken scratches I write .5 not .500 or .50000 I'm saving ink. Then
I understand todays micrometers all have plastic on the frame for the .00000 readings cause of the heat of your hand ? wonder bout that.
Really I think its all about what you are doing( the job). Such as we deal a lot with something like .0015 to .002 like bearing clearances.
And then there is a machine shop 500 feet from here that does deal with the .000000000's they have contracts for the big guys
like Boeing and others... so its job related so is my oldest, a union carpenter with a 16th ruler & he can't read a mic. job related....
Click to expand...

So thats what the lumps of plastic are for, you live and learn.

Saying about bearing fits, making nice press fits for small (10-12mm od) ball bearing races is a 0.0001" thing, i managed to get a couple to fit nice then realised i needed to change the design.

Surface finish starts to become more important with smaller tolerances.

Stuart
 
Yes Stuart, but don't you think Starrett would have found that out yrs ago. And then the logic, how long
does one hold a mic in hand to raise the temp. of a mic? So I think the plastic is for looks or maybe
an easy way to put their name on it.
sam
 
interesting conversation. I spent years working with close tolerances to .0002 ALWAYS in a temp controlled environment. The dimension is only good at that temperature and the part must be inspected NORMALIZED at that temperature. In a home shop environment, no you cannot consistently achieve these tolerances because the size will change several times a day with the temperature, but you can achieve that dimension at THAT moment ( and that may make some folks feel good).

I am guilty of adding all those zeros, only because I was used to it. I also know they don't really matter in my little shed of a shop in the back yard, but I keep using them. The little zeros are pretty and make the print look nice. And if i knew they bothered someone, I would add a few more just to watch them wind up and explode.

I have enjoyed reading this thread, Have a wonderful day in your shop
 
NO! NO! My head has a tendancy to EXPLODE! Don't do it!:eek:
Well...mayB not, interesting post anyway.
 
You must log in or register to reply here.
Back
Top