Dimensioning Inspection Gage

[Kinsrow]

I have an inspection gage that measure height position of a point with relative to a simulated datum line from 2 other points. This simulated datum line becomes a "zero" dimension and dial indicator read the reading at the inspected point. It's hard to explain this, so I attached the picture. Target 1 & 2 are gage pin pressed fit to the base plate. The tangent line between the two produces the simulated datum line "zero" and need to be pararrel to DTM A(.002 max). Target 3 is pressed fit carbide round that will be grind off until it reads zero relative to simulated datum line "zero" and become your target to for zeroing the dial indicator tip. This indicator would then move to any specific location(s) to read its height with respect to simulated datum line "zero".

I'm having hard time to dimension target 1, 2, and 3 so that functionally make sense.

Anyone has experience dimensiong this using GD&T and ANSI standard. I could explain what I want to machine shop and I'll get what I want, but I would like to learn to do it correctly.

Thanks

 

[drawoh]

Kinsrow,

It is hard to see exactly what you are doing. This drastically affects dimensioning and tolernacing. Can we assume your datum_A is a base that sits on your inspection table?

If the positon with respect to your inspection table is not important, your datum_A is not very good, especially as a primary datum.

How about using face_C as your primary datum? Assign the bottom faces of pins_1 and_2 as datum targets D1 and D2 to create your secondary datum, and face_B as your tertiary datum. If B is tertiary, you probably do not need to control perpendicularity.

Now, you can assign a profile tolerance to the top of your carbide round.

You can apply a sloppy profile tolerance to surface_A.

I am not sure of what you are trying to do, so this is only a suggestion.

JHG

 

[Kinsrow]

I'm afraid that I wasn't clear enough trying to explain what I was trying to do. Maybe my comment below will help.

Yes, DTM A will sit on granite table. I was going to assign D1 and D2 target dtms like you were saying, but not sure how to assign a seconday datum from these 2 dtm targets in the drawing and not sure if this is legal. I'm not very good at doing standard ANSI drawing and still learning it.

Thanks again.

 

[drawoh]

Kinsrow,

In my suggestion above, D1 and D2 are your secondary datums. You would not have to do anything. Your part's front face would locate to face_C. Your part's top edge would pick up D1 and D2. Your part's end would pick up face_C. I am assuming that the location of everything off the face of your granite block is not critical.

Datums mostly are a fixturing specification. You do not just stick them all over the place.

JHG