Perpendicularity

[Enrico Urru]

Hi everyone,

I am drafting a drawing of a toggle lever with a threaded hole for an insert. I set a control frame to control the perpendicularity of the hole with respect to datum A.

Should the dimensions for locating the threaded hole be basic dimensions? I am referring to 20 and 12, see the picture attached.
Thank you.

 

[Burunduk]

There should be basic dimensions for the location of the hole. But these basic dimensions would not be related to the perpendicularity tolerance, but to a position tolerance that should control the location of the hole.
The basic dimension that would be related to the perpendicularity requirement is an implied 90° angle.
There should be a datum reference frame established from sufficient datum features to fully define the hole's location. The basic dimensions for location need to originate from the datum features.

 

[Enrico Urru]

Thank you for the feedback.

I have made changes to the drawing in order to fully constrain the location of the hole.
By using a position control frame, am I still able to obtain perpendicularity? Is there anything I should change in the drawing? See update.
Thank you.

 

[3DDave]

Is this per ASME Y14.5-???? or ISO GPS standard?

Locating a feature from an intersection of two surfaces that are not both datum features is not appropriate.

 

[Enrico Urru]

Hi Dave,

Thank you for the reply.

ISO standards.

What surfaces are you referring to? I used datum features C and B to locate the hole.

How should I locate the feature in the best way?

 

[pmarc]

Enrico,

Just add a basic angular dimension between surfaces B and A and this will make the position callout correct.

A thing to remember is that in order to establish a datum system in a repeatable way, the datum features used to establish the datum system should be toleranced with respect to each other. (e.g., in this case B should be controlled with an orientation tolerance with respect to A, and C should be controlled with an orientation tolerance with respect to A primary and B secondary.

 

[Enrico Urru]

Thank you so much for your help!

 

[3DDave]

The 12 mm dimension is to an edge that is the intersection between two surfaces, only one of which is a datum so there is no true origin for that dimension to locate the true position of the hole.

 

[Enrico Urru]

Hi Dave,
Yes I see, I mistakened the surface where the datum A was referenced. The drawing as it is, shows that edge to be part only of datum B.

Thank you.

 

[pmarc]

Yes, you are right, 3DDave. A is not the surface in which the hole is made. I misread the print.

Enrico,
Is there a functional reason for that? Shouldn't A be the other surface?

 

[pmarc]

Okay, so with A corrected, my initial response holds water.

 

[Enrico Urru]

I mistaken the two surfaces, I should have put it on the surface where the hole is located.

I made all the changes that you suggested. Thank you for your help.

 

[Burunduk]

Add angularity of B relative to A.

 

[Enrico Urru]

Burunduk,

I got confused, I thought that it was enough to define a basic angular dimension.
Thank you again for the help.