Datum

[VD2108]

Hi everyone,

We have these triggers that are dimensioned and toleranced as shown in the attached image. Recently we have switched the supplier and received parts that are not good. The main problem is that the center of the ears (slot) does not align with center of the tab (0.43 dimension) at the bottom. The part is not straight. The goal is to have centers of slot and tab to have controllable alignment.

I am thinking to add Datum A to slot (0.416 dimension) and location/position tolerance to tab (0.43 dimension) referencing Datum A.

Am I doing this right?

Thanks,
Vadim

 

[VD2108]

Do we know the size and tolerance of the holes in the trigger?

0.203 +0.005/-0.000

What is the size and tolerance of the pin that goes through those holes?

0.194 +.005/-0.000

What is the size and tolerance of the width of the tab that mates with the .416 opening?

0.38 +/-0.015

The size of the slot that 0.43 handle feature fits into is 0.50. This is sand casted handle.




-Vadim
Design Engineer

 

[pmarc]

Thank you, Vadim.

Knowing these values, I agree that the holes in the handle should be selected as primary datum features. Their coaxiality could be controlled by datumless position callout or by using CONTINUOUS FEATURE concept (if you follow ASME Y14.5-2009). The .416 opening should be secondary datum feature, controlled by perpendicularity callout relative to A. The .430 tab should then be controlled by position callout to A|B. I would personally define both A and B at MMB (MMC, using Y14.5M-1994 terminology).

Dave,
Actually, I did consider your reply to my inquiry about fig. 4-2 in my last post, although not directly. Last part of your reply was about customization of orientational degrees of freedom, which lead me to the conclusion that you really did not consider any other feature beside holes as orienting feature.

This is also where the over-constraining issue came from in your reply to powerhound, I believe.

 

[greenimi]

pmarc,

Re:" the holes in the handle should be selected as primary datum features.................The .416 opening should be secondary datum feature"

I said exactly that a week ago or so..... That is called beginner's luck ....Thank you for agreeing with me.
If I have you on "my boat" I am not afraid of anything