slot call out 2

[proEdj]

What is the best way to call out a slot? I have used basic dimension to reference the true center of the slot from 2 perpendicular datums. Then I called out the width of the slot and the height (the length from one tangent line off the full radius to the other tangent line) using standard dimension with tolerances. Then I called out the "2 X Full Radius" and also had a positioning block calling out diametric position of the center of the freature. Does this sound correct?

 

[wgchere]

Just to be clear, in a case where there are two sides to go thru I say THRU, BOTH WALLS.

There is a stong possibility there will be a literalist interpreting it and feel that thru only applies to the wall indicated.

 

[smcadman]

The slots were on a front view, and there was a top view because of a hole on the top view. The slot lines on the front and back were clearly visible because hidden lines were shown (using Solidworks 2006). If it was faxed to our vendor, then it would be possible that some clarity in the drawing could be lost, but since a PDF was sent, I know the hidden line were clearly visble BUT I guess it wasn't clearly notated.

Flores

 

[microdesign]

Hello all!

I wish to GDT a continuous (looped) slot, below a surface, which does not need special (tight) control on its location, but mostly needs control of the width independent of location.

Is there a control for one wall of the slot relative to the other, when neither wall is a datum?

Can it be done independent of the location?

Do I have to use a basic dim. with a centerline and a control based on center?

Can I dim. one side of the slot and then have a GDT control on the slot width relative to the side wall location?

Thx,

Davin

 

[ewh]

If location isn't that important, I would just control the width with a tight dimensional tolerance.

 

[microdesign]

Yes, that was my thought also, but in the interest of using only GDT on the part, I wonder if there is a proper way to do it.

What if I DID wish to closely control the location of the slot feature? Could I GDT it without using centerline?

 

[drawoh]

microdesign,

Dimensions with +/- tolerances are a part of GD&T, and are described explicitly in ASME Y14.5M-1994. If that is what you want, that is what you should call up.

JHG

 

[ringman]

drawoh,

What is the section of the std that describes +/-
tolerances?

 

[ewh]

Most of section one and para 2.2a.

 

[microdesign]

Quote drawoh

" Dimensions with +/- tolerances are a part of GD&T, and are described explicitly in ASME Y14.5M-1994. If that is what you want, that is what you should call up."

True enough. My issue with that is that my drawing is dimensioned with basic ordinate dimensions. If I were to place a direct dimension on the slot, I would also have to use non-basic dimensions all the way back to the datum.

 

[drawoh]

microdesign,

It depends on what you want to control. You can apply GD&T controls _and_ +/- tolerances. The part must conform to both specifications.

How about you apply a profile tolerance of 1mm around both edges of the slot and a +/-0.1mm tolerance across the width?

The inspector will verify that the slot lies within 0.5mm of nominal position with respect to your datums, and he will verify that each side of the slot is positioned to within 0.1mm with respect to the other side. If this is what you want, the specification is correct.

This works the other way too. I can tolerance the top surface of a block to +/-.050", and apply a GD&T parallel tolerance of 0.005". It gives me a sloppily located but very parallel surface, which could be exactly what I want.

The whole principal here is that you should be specifying the exact controls that you need. If you do not need to locate your slots accurately, don't. Just get the width right.

JHG

 

[microdesign]

Thanks drawoh,

Can I use a single positional for the slot such as in figs. 5-14, or 5-43 of ANSI 1994, or is that only usable in ref. to a centerline?

Can the GDT parallel symbol be used for one side rel. to the other without a datum ref?

or

Can flatness be used for one side rel. to the other side?

I don't suppose a composite is appropriate, as the features are not identical and are coaxial.

Ideally, I would like to use one control for one side of the slot, and then another to base one side of the slot on the other.

 

[ewh]

You can't use flatness relative to another surface. Flatness is a "stand alone" control. I suggest using flatness for one side of the slot, and control the other side with parallelism or profile relative to the first side. You can also add a flatness control to the second side if it is critical (you just can't make it relative to another feature).

 

[drawoh]

microdesign,

My assumption about positional tolerances is that you are locating the feature itself, and calling up everything about its form, elsewhere. The positional tolerance works from whatever datums you specified. The centrelines are only relevant to the specific examples in the standard.

The GD&T parallel symbol requires a datum. That datum need not be one of the datums used to fixture your part. You can define one side of your slot as a fourth datum.

If you apply a tight +/- tolerance to your slot, this controls parallelism. A parallel tolerance is a strategy for controlling parallelism, while tolerating a sloppy width.

JHG

 

[microdesign]

Thanks ewh and drawoh.

My "problem" is that my continuous slot is in a way, 2 separate features.

Imagine a plane with a rectangular projection. Now imagine a rectangular slot around the base of the projection. That is what I have, a radiused rectangular slot. As it is continuous, it has 2 separate surfaces.

If I place a direct dimension on it, I would have to do it for all segments seperately, wouldn't I?

If I place a +/- tolerance on it, It connot be dimensioned with basic dimensions, can it?

 

[ewh]

If the dimension is the same for all segments, you only have to dimension it once and note how many instances.
You can use basic dimensions to locate it and +/- to define
the slot, or visa-versa. You can't use +/- on a basic dimension.

 

[drawoh]

microdesign,

Use basic dimensions to call up the sides of your projection. Apply a profile tolerance to the outline. How about .020?

Pick the slot on one side and apply a dimension something like...

4X .500+.005/-.000.

The outline of your raised surface is controlled with respect to your primary datums. The width of each of your four slots is controlled with respect to sides of your raised surface. The outside edge of the slot winds up where it winds up. If you did not care about this, everything is fine.

One of the main ideas of good drafting is that you do not control features that do not matter.

JHG

 

[microdesign]

Thanks again,

drawoh,

That is the conclusion I had come to also, but still some issues. The slot is radiused also, so I guess I should do 4x the straight segment, and 4x the raduises, or should I say all around, or can I use an "all around" circle on a dimension?

 

[wgchere]

It would have to be 4X, because you have 4 separate radii.

I'm glad you finally described the feature you were talking about. Personally, I would call that a groove. A slot, in my mind, is a thru-hole with two parallel sides and a full radius at either end. A pocket would be a slot that isn't through. Before this explanation I was wracking my brain to try to visualize this slot you were describing.

Instead of a profile tolerance, I would use a linear true position tolerance on the length and the width of the rectangular projection (unless there are corner radii to control), than use a regular ± tolerance on the groove width, assuming its inside edge is contiguous with the rectangular projection. I would only use position because it seems to be understood by more people than profile is.