Naming decimal places in the shop

Oh yes, let's not forget about unit called a "damnit" which can exist in any of the decimal places.

This is the unit that starts out at some value and mysteriously changes... usually something like a shaft diameter that that was decreasing gradually and supposed to stop at say 1.2500" but suddenly disobeyed user commands and stopped at 1.2499. Damnit! I find the best way to change the value of the damnit is to use a different mic or leave the part under the halogen worklight for a long time..


Ray
 
jwalkerwade said:
See foot in mouth!! I wonder why they teach us in school that .1 is a tenth!!!! Oh well, understood... Thanks!
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What you were taught in school is correct. .1 is 1/10 of 1. In the shop we deal in thousandths, Now 1/10 becomes .0001.

"Billy G"
 
Or you have the half way conversion to metric in Canada where most temperature, weight and volume for sales is in SI units but housing lumber went back to inches and most machine shops still work in thousandths. Work around the home or at business is complicated by the need for both metric and imperial tools and the need to determine what the parts measured in.
 
I named all my sons but their friends call them something else. I always call the smallest measurement a _- hair, but i digress.

We had a substitute teacher for Mrs. Kasso one day in 5th grade (1968-69) and to her great misfortune we were discussing lines and rays that day, We all know a line travels infinitely in either direction from any point along it and a ray travels infinitely in one direction from a specific starting point. Seeing a cul de sac of logic i asked the substitute if a line was then half as long as a ray and she took the bait allowing that the ray must be half as long as a line, then i asked if ray was then half infinity the class had our fun as other challenged on the same subject she lost control, of course she told Mrs. Kasso and I got another day facing the back of the coat closet. Mrs. Kasso liked me but she never took any crap. nothing from nothing leaves nothing

sorry bob
 
A bit off subject but I work in .0001" (s) all the time....and when I am scoping out wear on a part instead of writing .0012 I write 12 or .0023 I write 23. I just think in tenths and write it that way. A lot less writing when your measuring a way that's 10' long and your making measurements every 6". When I work oversea's and everyone uses metric I have a cheat sheet conversion sheet from .00012" = 0-003 mm. I am an old dog and hard to teach new tricks especially when my math skills never were any good in the first place....lol
When I spend 3 month in Taiwan teaching I have metric mastered pretty good....but when I come home for a few days my memory chip on metric burns out. LOL
 
So is a tenth in metric the same as .0001 MM or is it somehow different since metric is much smaller to begin with? The reason I ask is a tenth in Inches is pretty small, a tenth in Millimeter is really really small and may be over kill. Any input on what regular tolerance machinists normally work to in the metric system? In inches we work to thousandths and tenths what is the regular tolerance that is comparable in metric? I hope that makes sense.

Bob
 
Ray C said:
Oh yes, let's not forget about unit called a "damnit" which can exist in any of the decimal places.

This is the unit that starts out at some value and mysteriously changes... usually something like a shaft diameter that that was decreasing gradually and supposed to stop at say 1.2500" but suddenly disobeyed user commands and stopped at 1.2499. Damnit! I find the best way to change the value of the damnit is to use a different mic or leave the part under the halogen worklight for a long time..


Ray
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CRAP!!! I wish I had known about this a long time ago .... I think all of my tools are in the Damnit scale :( Well, at least now I can blame all my screw-ups on the tools and not me :)
 
Hey Bob;

.0001mm is .000003937007874 inches. Is that 1/10? :lmao::lmao: Call it payback for the lady with all the face lifts Bob. Just had ta do it. :lmao::lmao::lmao:

"Billy G"
 
Rbeckett said:
So is a tenth in metric the same as .0001 MM or is it somehow different since metric is much smaller to begin with? The reason I ask is a tenth in Inches is pretty small, a tenth in Millimeter is really really small and may be over kill. Any input on what regular tolerance machinists normally work to in the metric system? In inches we work to thousandths and tenths what is the regular tolerance that is comparable in metric? I hope that makes sense.

Bob
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I work in inches here at home, but in Taiwan they work in metrics and gives me a headache. In my trade of Scraping we need to hold a tight tolerance in tenths .0001" because we get multiplication of the error as we build out. So we try to scrape a conventional machine which would include standard mills like a Bridgeport or a SB lathe we shoot for an accuracy of .0002" error over 12". In a Super Precision machine like a Moore Jib Bore or Precision scraped cast iron straight edge we shoot or scrape for an accuracy of .00005" (1/2 of a tenth, or 50 millionths of an inch) error in 12". If you have a 36" scraped cast iron straight edge or Jig Bore machine our allowable error would be 3 x .00005" or .00015. If your South Bend lathe is 36" center to center the allowable error is 3 x .0002" = .0006". I hope that makes sense. As someone is bound to point out those tight tolerances can only be help is temperature controlled rooms. In a Taiwan where they use the metric system. I have Engineers who are my translators and I let them translate that to Metric for my students. :phew: Rich
 
Some industries in the US did the metric conversion years ago. The automotive industry started changing products from English to Metric back in the late '70's, starting out with just converting fasteners. All new products were designed in metric, but we retained tooling in English dim. Needless to say, we had to become fluent in both Metric and English. As far as relative tolerances, 2 place dim. in metric (+/- .03) are roughly equal to 3 place dim in English (+/- .001).
 
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