Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floor

M

markro

I've attached a print for a part we are machining. I'd like to make an attribute gage to check true positioning on the shop floor. If a plate was created with pins in the positions described with the basic dimensions on the print and with the positions verified, could I make the pins the smallest diameter/smallest minor diameter of each of the 11mm holes/threaded hole and the ?54.4 hole since each true position callout uses maximum material condition?
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Stijloor

Leader
Super Moderator
Re: Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floo

A Quick Bump!

Can someone help?

Thank you very much!
 

Paul F. Jackson

Quite Involved in Discussions
Re: Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floo

The ? 54.4 (datum feature you cannot because it is referenced RFS.

The M10 position and perdendicularity MMC allowances for will be difficult to address in your attribute gage since they are applied to a threaded feature. They will provide rotational DRF mobility only since the secondary datum feature is referenced RFS and it constrains translations in X and Y.

The pin size in the two ? 11.0 +/- 0.3 holes will be ? 10.4 (10.7 - 0.3 Position Tol) and they will serve to check the perpendicularity conformance simultaneously since it is the same tolerance as the position (which means perpendicularity is redundant "unnecessary").

Paul
 
Last edited:
M

markro

Re: Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floo

Thanks, Paul.

Does that mean I'll only be able to check the position of each of the holes to each other and will have to leave the ?54.4 out of it?
 

Paul F. Jackson

Quite Involved in Discussions
Re: Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floo

No You must use ?54.4 to check the position requirements because it must establish the DRF (coordinate system) for measurement regardless of its size (without looseness). In physical gauges balls activated by a cone under spring force can be used or hydraulically expanding arbor or other devices. In analytic gauges the center established by least-squares fitting or maximum inscribed circle etc. is used.

Paul
 

Stijloor

Leader
Super Moderator
Re: Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floo

No You must use ?54.4 to check the position requirements because it must establish the DRF (coordinate system) for measurement regardless of its size (without looseness). In physical gauges balls activated by a cone under spring force can be used or hydraulically expanding arbor or other devices. In analytic gauges the center established by least-squares fitting or maximum inscribed circle etc. is used.

Paul

Great responses Paul!

I just hope that the poster understands how datum features called out at RFS are simulated. MMC lends itself better to functional gaging.

Threads are a pain because of the default rule (axis of the pitch cylinder).

Thank you for your help!
 

Paul F. Jackson

Quite Involved in Discussions
Re: Proper Gauging - GD&T - Attribute gage to check true positioning on the shop floo

Thanks Stijloor,

MMC lends itself better to functional gaging.

I would say that... MMC lends itself better to attribute gaging... and if the datum feature selection and the material condition modifiers truly reflect the function then the gauge is functional regardless of the modifier used. Otherwise it is just an attribute (discreet) or variables (continuous) gauge.

Paul
 
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