I want to dimension two planes so that no matter where the depth of the first counterbore falls, the tolerance zone or relationship between another counter bore will be the same. I looked up symmetry gdt and it says i need a seperate datum to reference my two symmetrical planes. If you look at my print i am using two planes to reference my symmetrical planes. Is this right? Or how would you guys go about achieving this?
attach is a picture.
Symmetry need a center line or plane.
Two planes on same level is not symmetry.
hello frederick, so what would you call this?
Hello,
If I'm understanding correctly, you want the two depths to be identical within some tolerance.
If so, I believe profile is what's required.
Kevin
the depth between the two counter bore is .001(.025mm). I want to give it a tolerance zone so that no matter where the first counterbore falls(datum a) then the other counterbore should fall within the same tolerance zone.
for example, if the counterbore falls at .036 then the relationship between the smaller countebore should still be .002,
if the counter bore falls at .038 then the second counterbore should still fall within .002. Does that make sense?
thank you kevin.
Roger Fuentes wrote:
the depth between the two counter bore is .001(.025mm). I want to give it a tolerance zone so that no matter where the first counterbore falls(datum a) then the other counterbore should fall within the same tolerance zone.
for example, if the counterbore falls at .036 then the relationship between the smaller countebore should still be .002,
if the counter bore falls at .038 then the second counterbore should still fall within .002. Does that make sense?
thank you kevin.
Yes, it does. GD&T Profile, I believe, is what you require.
Kevin
thank you for the clarification kevin, does this drawing seem more accurate in what i am trying to achieve?
better.
but you need to remove the .038 dim and replace it with a basic dim from datum A to that surface you are trying to control.
thank you jim that is exactly what we are trying to achieve.
Roger Fuentes wrote:
thank you for the clarification kevin, does this drawing seem more accurate in what i am trying to achieve?
At only 0.001 difference, I can't tell without guessing which dim applies to which feature. And I'm sure others will be guessing.
Rearrange to remove extension lines crossing other dimensioned features and to eliminate guesswork.
Remember, you're much more familiar with this part than most other people who will be involved with it. Look at the drawing from their perspective.
The profile arrowhead is better placed on the dim's extension line, whichever one it may be.
Kevin
Jeremiah,
how does this look?
Original print, let me know if there is anything wrong thank you
Which CB does .038 apply to?
Same question for .037.
Also, if they're supposed to be on same plane why different dimension?
Should be same reference to Datum A.
crappy.
you still don't have any basic dims.
and your second line in the profile callout just repeats the requirement from the first line. a second line is only used to refine or loosen the tolerance given in the first line.
frederrick,
cb .038 applies to the left cb and .037 to the right . they are not on the same plane. they have a .001 difference. I am trying to follow the rule JIM SCULLEY posted about coplanarity.
I did remove the .038 dimension like you mentioned as to what basic dimensions you are referring to? can you clarify please?i thought the .037 is the basic dimension .
I think you are looking for something like this:
The 0.02 dimension is in a box, to denote that it is a 'Basic' dimension, which is to say that is what the dimension would be if everything was on nominal.
John
The other thing that I would point out is that, if you are going to use profile in this instance, the depth of the hole that is being profiled needs to be a basic dimension.
It is still not clear if 0.02 is added to 0.95 or subtracted.
Roger
The counterbore's coplanarity is not the same as their depth, and that could get you in trouble. If your datum A counterbore surface is tilted, coplanarity may require the other counterbore to be a very different depth.
I expect you want to make the top surface a datum and to place a profile tolerance on both counterbores.
Dwight
Dwight Livingston wrote:
Roger
The counterbore's coplanarity is not the same as their depth, and that could get you in trouble. If your datum A counterbore surface is tilted, coplanarity may require the other counterbore to be a very different depth.
I expect you want to make the top surface a datum and to place a profile tolerance on both counterbores.
Dwight
Hello,
With only a +/-.001 depth tolerance, would the tilt just before a size violation be enough to materially vary the depth of the other cbores?
Kevin
Kevin Chandler wrote:
Dwight Livingston wrote:
Roger
The counterbore's coplanarity is not the same as their depth, and that could get you in trouble. If your datum A counterbore surface is tilted, coplanarity may require the other counterbore to be a very different depth.
I expect you want to make the top surface a datum and to place a profile tolerance on both counterbores.
Dwight
Hello,
With only a +/-.001 depth tolerance, would the tilt just before a size violation be enough to materially vary the depth of the other cbores?
Kevin
Kevin
If they are right next to each other, then you double the depth tolerance to +/-.002 for the second counter bore. If they are farther apart, then more, which is the issue. It just seems to me a poor approach to the problem if you are interested in matching the depth. Why not make them both +/-.001 depth? You then limit the depth difference to .002, whereas using cooplanarity it could be a lot more than that, like .004 if they are only one diamater apart.
Dwight
if you do not understand how the .037 dimension is not a basic dimension in the images you posted, you NEED to attend a GDT class BEFORE trying to use it in a drawing.
makes sense thank you John.
I am taking a class in gdt, i am in training in for this.
GD&T Tips - Profile - Coplanarity