GDT Callout 2

[waqasmalik]

Hi all
I am to drill a hole of Dia 4mm on CNC 3 Axis Milling Machine.Due to some limitations in accessing the location of hole i have to use an extension (Drawing attached). Dia 4 hole in the extension which is round bar as shown in figure is used for inserting the straight shank of Drilling tool in it and drill's motion will be blocked by a screw for which a hole has been provided at side in the extension.This right hand side of extension will be clamped in adopter of milling machine upto 35 mm and drill will be inserted in the hole at left hand side and then hole will be drilled.

Now i want that extension must have no run out when rotated without drill in it and when the drill is in it.I have applied GDT according to my limited understanding.

1) I have taken 35 mm length of cylindrical portion which goes inside the adopter as datum feature of size as A. Total run out of left end is given with reference tO A.

2) I have given concentricity of Dia 4 hole wrt Datum A.

Is it legal GDT Call out?? If not then what would be the other way depending on what i want?

 

[CheckerHater]

I don't see any GD&T on your picture.

 

[waqasmalik]

check hater
Really sorry for presenting my question properly.I have given it in theory i have written.There is a problem in applying at picture

 

[waqasmalik]

Really sorry for not presenting properly

 

[CheckerHater]

It's all OK.

I have my doubts about concentricity. It.s difficult to measure, but very powerful tool with very limited use.

I would specify runout on both features.

 

[waqasmalik]

1)Total run out of left end wrt to datum of 35 mm length?
2)Total run out of hole wrt to datum of 35mm length?

Am i ok?

 

[CheckerHater]

Yes, something like that.

But wait for more opinions to come in

 

[waqasmalik]

ok

 

[pmarc]

waqasmalik,
Since you are not new to the forum, some of us probably already know that you are working to ISO GPS standards. But for those who don't know that, I think it would be really useful if your threads started with such short information.

This is quite important, I would say. In this thread, for example, you want to apply concentricity callout to the hole. This is reasonable from ISO point of view (because ISO concentricity is just a special case of ISO position), but in ASME world concencentricity is something totally different than position, and in this application it would not be proper choice. As a consequence (without knowing that your drawings are governed by ISO GPS and knowing that most folks here work to ASME Y14.5), you may receive a dozen replies encouraging you to forget about concentricity (because it is considered to be a can of worms in ASME) and to apply position instead.

 

[waqasmalik]

pmarc

I am working on ASME Y14.5M 2009. Let me tell you what i know about concentricity.

Concentricity is actually controlling the axis formed by median points of diametrically opposed surfaces.It takes a lot of time to be verified because you have to examine the cross sections carefully.Also concentricity does not get affected by magnitude of form error, it gets affected by distribution of form error.A part having form error in such a way that its derived median points are congruent with the datum axis then it will pass concentricity test. So that why a run out is preferred because it controls form and location and also easy to check.

Position or coaxiality has all to do with the axis of the actual mating envelope.Actual mating envelope axis has to be in diametrical geometric tolerance specified wrt datum axis.

 

[waqasmalik]

My point of concern is that should i give total run out on both as checkhater mentioned earlier or there must be something else.

 

[pmarc]

Oh, in that case my apologies. Your inclination towards applying concentricity confused me.

What you are saying about ASME concentricity is correct.
Runout is one of possibilities, and position/coaxiality tolerance is another one.
As for form control, by default it is controlled by size tolerance, so if form tolerance does not have to be tighter than size tolerance, I would rather lean towards position/coaxiality tolerance.

 

[waqasmalik]

Pmarc

If form control would not be tighter then there will be run out due to form error, this run out will make my hole oversize.I think total run out would be a better option because it will control circularity, straightness,coaxiality. But im not sure.

 

[pmarc]

There are applications where form errors of a feature of size, by default controlled by size tolerance, does not have to be tightened by any additional callouts, like straignthness, circularity or runout. My understanding of your application (and I may be wrong) is that a cylindrical feature of size goes inside the dia. 4 hole. If mating of two features of size is all that is required, I do not think that additional form control of the hole is needed.