It's Monday

[Randy P]

I'm dealing with a project engineer a program manager and a GD&T expert!
They tell me I'm tolerancing true position all wrong. I have a diametric true position hole locating Y,Z with 1mm tol. So I true position the hole with Y and Z and 1mm in the TP.
First they tell me I have to show X in TP, (ok if you want to see you got it). Next they tell me That the the tolerance on this diametric hole is +/- .5 in all axis. And do it htis way from now on.
It's Monday with a long weekend is coming.......................
thanks for the vent

[JamesMannes]

Posta jpg or other forum friendly picture of your print area in question describing your datum structure. Something smells in Denmark.

[kbotta]

Is the diameter symbol inside the feature control frame?
Could you post a pic of the FCF in quesion?

Technically, yes - it is 0.5mm in all directions - but RADIALLY. You cannot simply offer the conventional tolerancing mehtod. that would take away the benefit of using GD&T (Round hole, round pin, round tolerance - not square)
kb

[bob mappes]

+-.5 in all axis?????

NO

the total deviation can be a maximum of.5mm in any direction,
so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
TP is a CIRCULAR tolerance zone, not SQUARE.

your GDT guy don't know pooh
bob

[dwade]

If the FCF has the diametrical symbol in front of the 1mm tolerance, ask your GD&T expert what he's been smoking this morning. Only if the diametrical symbol IS NOT in front of the 1mm tolerance would you be allowed to have +/-0.5mm.

[JamesMannes]

+-.5 in all axis?????

NO

the total deviation can be a maximum of.5mm in any direction,
so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
TP is a CIRCULAR tolerance zone, not SQUARE.

your GDT guy don't know pooh
bob

And if you want the cartesian tolerance for a 1mm TP it is .3536

[#2#]

I've found a good way to win these type of arguments is to draw a picture. Make it 2d so it is easier to understand. Draw a point. Tell them this point is the nominal location described by the basic dimensions. Now draw them a circle around the point and centered on the point that has a diameter of 1mm. Tell them that is the tolerance zone described by the FCF - assuming
the fcf is |TP|Ø1.0|A|... Now and here is the good part... Start making theorhetical examples. put an x and y axis on the drawing. Give them a theorhetical point that is +.5 in x and +0 in y. That part is good right. Next give them a theorhetical point that is +0 in x and +.5 in y. That part is also good. Now kick them in the butt and draw a point that is +.5 in x AND +.5 in y. That point should very clearly fall outside of your circle.

±.5 in all directions is not the same thing!!!

[Randy P]

this is section cut / basicaly frt a view.

[why me]

+-.5 in all axis?????

NO

the total deviation can be a maximum of.5mm in any direction,
so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
TP is a CIRCULAR tolerance zone, not SQUARE.

your GDT guy don't know pooh
bob

I SECOND THIS. DO WE HAVE A THIRD FOR THE MOTION TO CARRY!

[Cumofo]

The True position Formula ANSI Y14.5M Pg. 81

Here, let them check this out:

The True position Formula ANSI Y14.5M Chapter 5

The true position formula, and a calculator in a spreadsheet. If you can't tell them they are cave men, call me & I will.

Gabriel Ortiz
(949) 863-0560

[CGoode]

I'm dealing with a project engineer a program manager and a GD&T expert!
They tell me I'm tolerancing true position all wrong. I have a diametric true position hole locating Y,Z with 1mm tol. So I true position the hole with Y and Z and 1mm in the TP.
First they tell me I have to show X in TP, (ok if you want to see you got it). Next they tell me That the the tolerance on this diametric hole is +/- .5 in all axis. And do it htis way from now on.
It's Monday with a long weekend is coming.......................
thanks for the vent

The first two OK this really is not their field. But if you got an "expert" telling you this, you are doomed!!!

[Randy P]

An EXPERT thats never ever wrong and he'll tel ya so.

[Don Henger]

I've found a good way to win these type of arguments is to draw a picture. Make it 2d so it is easier to understand. Draw a point. Tell them this point is the nominal location described by the basic dimensions. Now draw them a circle around the point and centered on the point that has a diameter of 1mm. Tell them that is the tolerance zone described by the FCF - assuming
the fcf is |TP|Ø1.0|A|... Now and here is the good part... Start making theorhetical examples. put an x and y axis on the drawing. Give them a theorhetical point that is +.5 in x and +0 in y. That part is good right. Next give them a theorhetical point that is +0 in x and +.5 in y. That part is also good. Now kick them in the butt and draw a point that is +.5 in x AND +.5 in y. That point should very clearly fall outside of your circle.

±.5 in all directions is not the same thing!!!

Very good way to explane it Goodluck

I SECOND THIS. DO WE HAVE A THIRD FOR THE MOTION TO CARRY!

I third this for the motion to carry

[kbotta]

Well......he's wrong!

[bw_bob]

+-.5 in all axis?????

NO

the total deviation can be a maximum of.5mm in any direction,
so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
TP is a CIRCULAR tolerance zone, not SQUARE.

your GDT guy don't know pooh
bob

I really have nothing new to add. The answer is pretty straight forward.
I just had to comment on the harsh lauguage being used..............