Icky Diameters

[operator1]

Ok, here's an interesting situation. I create a program that checks(amongst other things) a diameter. This diameter is supposed to be .7539 -.008. The tip calibrates fine. At the end of the program, the report says the diameter is over by at least anywhere between .003 and .0045. I check it with calipers and it measures (in metric) 19.15 or less--within tolerance. Can anyone see why it would do this?

[bw_bob]

Ok, here's an interesting situation. I create a program that checks(amongst other things) a diameter. This diameter is supposed to be .5739 -.008. The tip calibrates fine. At the end of the program, the report says the diameter is over by at least anywhere between .003 and .0045. I check it with calipers and it measures (in metric) 19.15 or less--within tolerance. Can anyone see why it would do this?

Are you using least sqr or max insc, min circsc & another thing is your tolerance on the diameter is only 8 microns. I would not use a cmm for this check. My .02

[operator1]

Are you using least sqr or max insc, min circsc & another thing is your tolerance on the diameter is only 8 microns. I would not use a cmm for this check. My .02

NOOOOOOO, not 8 microns, 8 thousandths(of an inch). The .5739 is in inches, and so is the tolerance. When I check it with the calipers, the 19.15 is in mm.

I take 2 rows of hits, create a cylinder, and check the diameter of the 2 circles and the cylinder. When I create cylinders, it's always least square. Maybe I should try some other setup option? What is max-inscribe and minimum circsc?

[operator1]

19.15 -.2 in metric

[Matthew D. Hoedeman]

None of those numbers work out right. 19.15mm = .7539"
19.15-.2 in metric = .7460"

19.15 (metric) (.7539") -.2" = .5539"

None of those options are even close to anything you posted for a size and tolerance.

[bw_bob]

My mistake......I saw metric on calipers & just assumed. Try the different kinds like suggested & see what results are.

[operator1]

Didn't work. The circles themselves are oversized. I take hits and create the feature, but the features are reported oversized. Both circles on both rows.

[Matthew D. Hoedeman]

You still need to give us correct numbers, your metric manually readins DO NOT match what you say anything should be, 19.15mm = .7539" OR more than 3/4 of an inch, your callout says 0.5739 or LESS than 9/16 of an inch. THese is a big size issue here OR faty-finger syndrome.

[operator1]

You sure? When I use conversion calculators, I get .5739. When I divide the inches by 25.4, I get .5739.
And for the .2 tolerance, I get .0078, or .008 in inches.

[bw_bob]

Are you checking plastic or sheet metal...Plastic is hard to check sometimes.
Make sure of your calibration
How many points are your using for your circles.

[Matthew D. Hoedeman]

Ok, here's an interesting situation. I create a program that checks(amongst other things) a diameter. This diameter is supposed to be .5739 -.008. The tip calibrates fine. At the end of the program, the report says the diameter is over by at least anywhere between .003 and .0045. I check it with calipers and it measures (in metric) 19.15 or less--within tolerance. Can anyone see why it would do this?

19.15mm / 25.4 = .7539370...." or more than 3/4 of an inch. NOT even close to 0.5739"

[operator1]

There is only a "minus" tolerance. The diameter can be no smaller than 18.95 and no bigger than 19.15.

In INCHES, the diameter can be no smaller than .5659 and no bigger than .5739

[Matthew D. Hoedeman]

There is only a "minus" tolerance. The diameter can be no smaller than 18.95 and no bigger than 19.15.

In INCHES, the diameter can be no smaller than .5659 and no bigger than .5739

19.05mm = 0.75" NOT 0.57"

[operator1]

SORRY. I'm having a dyslexic moment right now......it IS .7539. I typed it in backwards.
I a dum-dum. Sowwy

[operator1]

Yeah. It's supposed to be .7539 or .7459, but the CMM measures circle 1--the first row--as
.7575, circle 2--the second row--as .7569, and the cylinder--constructed at least sqr, max insc OR min circsc--measures over.

Sorry about that. I'm on another planet right now.