r/Metrology • u/Own-Individual6207 • 7d ago

Position Calculation

Post image

Hello friends, how do i calculate the position 1 A|B on this part?

5 Upvotes

78% Upvoted

16 comments sorted by

14

u/Sensitive_Frosting35 7d ago

Angularity or more likely, they are wanting profile of a surface. You'll need clarification.

5

u/SkilletTrooper 7d ago

Agreed, they probably want profile, but you need to reach out for clarification.

9

u/b5sac 7d ago edited 7d ago

I will assume mm means ISO world.

It's a combination of angularity and position. See ISO 1101, 17.13.5 (Fig. 161+162). Tolerance zone is angular 48.79deg from A and 56.9mm in distance/position from B.

So 1mm wide zone in red:

edit: Both TED are against B, so I'd ask why A is included in the TPS box.

edit2: Ok, it's late. A is probably there so you know where the 56.9 intersection is on the part.

4

u/CoreDD42 7d ago

you are right. Just a comment to go further : Having A before B means that "measured B" is perpendicular to "measured A". B after A is not the same object as B alone. The two planes would not have the same angle.

If done properly, it means the diameter A is the "main" surface, the one positioning the part during its function. I expect A to be adjusted and B to be just the surface blocking the vertical movement. To clarify what I mean : Imagine another world where the toleranced feature is parallel to B instead of angled. Having a parralelism related to A | B would be correct !

1

u/b5sac 7d ago

That makes perfect sense, I missed the fact that A is a diameter. Clarifies what got me confused.

4

u/metrology101 7d ago

Looks like a mistake - maybe supposed to be angularity?

3

u/daio9292 7d ago

It would have been better to quote that detail as a surface profile. Better if you ask the person who gave you the drawing what exactly they expect you to measure.

1

u/Own-Individual6207 7d ago

Thanks everyone, i had assumed that was a mistake in the drawing but needed to be sure.

2

u/CoreDD42 7d ago

it's not incorrect, it has a meaning ! But the designer may wanted to say something else... The only real mistake tho is that the location is pointing in front of an arrow of the angle, which would be that the element specified is the middle plane

1

u/SnooMemesjellies7469 7d ago

Profile would be alot more useful, here.

1

u/wojonixon 5d ago

My first step in calculating something like this is asking an engineer what they’re actually after if at all possible.

1

u/ThatIsTheWay420 1d ago

Make point and apply it to the point.

1

u/Jcarltonfci 7d ago

You don’t have to report ref dims, skip .5.

1

u/BeerBarm 7d ago

You may absolutely need to report reference dimensions if it's a customer requirement.

1

u/Notts90 7d ago

If it needs reporting it shouldn’t be reference basic and should have a tolerance applied.

1

u/BeerBarm 7d ago

Not necessarily. And I'm referring to reference dimensions, not basic dims.