Off Topic What are tolerances

When I make gages they need to be to the tenth. A vision system and cmm verify it. Of course on a dmg mori nlx, I call that monday :D.
 
bhyde said:
Allowable deviation from the mean is a bit closer..the tighter the tolerance, the smaller the deviation from the mean can be.
Damn good though!

GD&T..
danbot danbot :thumbsup::cool:
Click to expand...
I've been working with and studying GD&T for quite a number of years now and I still don't have near a full understanding of it! I've also seen it misapplied by engineers more than once in the QC work I've done. Especially in the automotive industry!
 
b00n said:
"What are tolerances?" "The only thing keeping CRK in business...."

*cough cough* :p;)
Click to expand...

bmtwCxG.jpg
 
Here you go.
My beloved 710 in M390. So pretty, a good companion if she is in an amicable mood (feeling tolerant).
But flawed . . . I suppose we all have our kinks right ?

I pick her up off the table and the blade drops and swings and if I don't get too excited and squeeze her too hard she's just so fun to be with.
We hang out together; her in my front right pocket, enjoying a summer day.

I take her out for a bit of a swing, lock and then a lock release and . . .
she gets hung up there and says nope . . . not in the mood to drop . . . I need to be finessed she says.

What would you do at that point ?
Right !
Put her in the refrigerator for a few minutes.

She is ever so much more friendly now and a real swinger. Just releasing and dropping and very playful.

WHAT I am saying is there is a reason for a range of tolerance +/-. Too much plus and we get this problem. Too much minus and we get a knife that can still take some temperature change and still work even though those who sit and wiggle their blade might be all freaked to find some play.

In my case there was too much "-" (minus) they left out an entire spacer and screw between the liners but won't own up and mail me one.

Ambient temp can play a part. Missing parts can play a larger part.
I won't trade her for anything though . . . she's my little 710 . . . for better or worse.

(maybe one day I will get all excited and fix this for good . . . not today though)
IMG_4760.JPG

Some of my toys :
For the more coarse measurements (and for quite fine measurement in the right hands) the good 'O dial caliper.
IMG_4043.jpg

The blade tip was too minus; too near the surface of the handle not to snag on stuff.
IMG_4047.jpg

When I want to get more serious.
The little black thing with the steel dowel through it is a known standard for checking the micrometer for accuracy (the mic is adjustable and re-calibrates when ever it is turned off and back on)
There are some interesting inscriptions molded on the black plastic of the standard :
25mm
+/- one micron
@ 20°C​

(there's that ambient temp thing kicking in. The black area on the mic where it says Mitutoyo is a plastic buffer to handle the mic so body temp doesn't change the accuracy during use.
IMG_5066.jpg

And finally for gauging twist and out of flat over a larger area my good friend the Starrett Pink Granite surface plate. That DMT coarse / extra coarse doesn't teeter at all and was consistently very flat on the top side as well. I would have to look up that decade old post to tell you the specs but I was (am) HAPPY !
Take a bow.jpg
 
Last edited:
bhyde said:
Only made it about halfway through it..Will finish it later as I have time.
I will mention that he talks about calipers being able to measure .0005in.
There is a difference between resolution and measurement capability.
.002 is what the manufacturer of those calipers has listed. Most people that have used them for a decent amount of time are able to measure .001 accurately.
Otherwise, what I have seen looks pretty good..Will finish it a bit later though.
Click to expand...
I think you said this yourself. you would need a micrometer called an indicating mic. I wonder if they use one but just used that one cause it was there? Or maybe the place they out source does.
 
Mo2 said:
I think you said this yourself. you would need a micrometer called an indicating mic. I wonder if they use one but just used that one cause it was there? Or maybe the place they out source does.
Click to expand...

A caliper would work with anything that has something with a reasonable tolerance..I use them for a range of .002 or greater with a high level of confidence depending on what it was or the specific feature..Anything tighter than that, I go to micrometers, bore gages, gage pins..etc. Resolution determines method of measurement so whatever is appropriate.
We used the indicating mics to repeat measurements very accurately. Dial to zero and read the thimble..OR, set your specific mean and there are some hands similar to the ones on a clock face that you can set for your tolerance. Falls outside those hands, it's no good. I vaguely remember recalibrating that tool on a standard quite often as well as having frequent inspections by another individual. The everlong dayshift-nightshift battle raged on at the previous employer..I'm sure a few here can relate to what I am talking about.
 
While there is no accurate (or even precise) definition for a "tight tolerance", it usually means something you might use "special" processes to measure or hold. You might use a boring bar to finish a bore instead of just milling it. You might use micrometers or a bore gauge to measure it instead of just calipers.

A standard, everyday tolerance is +/- .005" or .004". Anything tighter you might call "tight".
 


This is our micro vu system. Excellent metrology tool, extremely accurate.

Tolerances like this are a regular thing, I can not show the entire print.

 
Last edited:
That one there is .0001 away from nominal, what's worse is when the part is long, has surface finish call outs, clocked features, has machined features on all sides, features that are toleranced off other features.. just to name a few.
 
shinyedges said:
That one there is .0001 away from nominal, what's worse is when the part is long, has surface finish call outs, clocked features, has machined features on all sides, features that are toleranced off other features.. just to name a few.
Click to expand...
Forsure! CMM's don't do well at measuring run-out!
I did about 2 years running the CMM at our shop. I learned a lot and I'm glad for the experience, but I'm also glad to not be overly involved with it anymore!!:)
 
danbot said:
Forsure! CMM's don't do well at measuring run-out!
I did about 2 years running the CMM at our shop. I learned a lot and I'm glad for the experience, but I'm also glad to not be overly involved with it anymore!!:)
Click to expand...
Absolutely, qc is for the ocd :D

More fun stuff is machining castings :rolleyes:, weldments, anything 46100 steel..
 
danbot said:
Forsure! CMM's don't do well at measuring run-out!
I did about 2 years running the CMM at our shop. I learned a lot and I'm glad for the experience, but I'm also glad to not be overly involved with it anymore!!:)
Click to expand...
Our cmm is a dinosaur. But works.
 
It uses qc5000, I'm not the qc guy by the way, Although I hop on it sometimes to "beep" stuff so I can make adjustments and check myself.
 
danbot said:
Actually, here are a couple of pics from our company website.

This is the Brown and Sharpe. This pic was taken before the climate controlled room was finished being built around it.
g0uRQwy.jpg


This is the Mitutoyo.
ViIhz9K.jpg

XCzknsQ.jpg
Click to expand...
Nice! What industry do you guys specialize in?
 
shinyedges said:
Nice! What industry do you guys specialize in?
Click to expand...
We specialize in designing and building machines and automated machining fixtures. But we do lots of work for GM, military and some nuclear power stuff too lately.

What do you guys mostly do?
 
You must log in or register to reply here.
Back
Top