True Position of slots that have angles as basic dimensions

J

Joaquin S

#1
Hi everyone,
Can anyone hlep me to resolve this problem ?
I need to calculate the true position for a slot that have angles as basic dimensions, see attached part of the drawing, some people said that this can not be possible , other said this is possible and for me is becoming a headache, any help to this will be greatfully appreciated.
Thanks...
 

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Stijloor

Staff member
Super Moderator
#3
Re: True Position of slots

Hi everyone,
Can anyone help me to resolve this problem ?
I need to calculate the true position for a slot that have angles as basic dimensions, see attached part of the drawing, some people said that this can not be possible, other said this is possible and for me is becoming a headache, any help to this will be greatfully appreciated.
Thanks...
Hello Joaquin, welcome to The Cove Forums! :bigwave: :bigwave:

I looked at the attached drawing and there are a few issues that need to be resolved with engineering:

  1. I assume that this drawing is interpreted according ANSI Y14.5M-1982. (The datum feature symbols are from the 1982 standard.)
  2. I also assume that you're referring to the position of the ribs? 3x 90 degrees basic?
  3. OK. D is your primary (surface) datum, E is your secondary (axis) datum. This is not sufficient to establish the correct datum reference frame because the part is still be able to rotate and that would affect the position of the ribs. A tertiary datum must be specified.
  4. The feature control fame includes a diameter symbol for the 0.10" tol zone. That is incorrect. The tolerance zone is 0.10" wide at MMC and only applies in one direction.

My conclusion is that the part can be inspected if the corrections are made.

Please let me know if this makes sense to you.

Stijloor.
 

Jim Wynne

Staff member
Admin
#7
Re: True Position of slots

Hello Joaquin, welcome to The Cove Forums! :bigwave: :bigwave:

I looked at the attached drawing and there are a few issues that need to be resolved with engineering:

  1. I assume that this drawing is interpreted according ANSI Y14.5M-1982. (The datum feature symbols are from the 1982 standard.)
  2. I also assume that you're referring to the position of the ribs? 3x 90 degrees basic?
  3. OK. D is your primary (surface) datum, E is your secondary (axis) datum. This is not sufficient to establish the correct datum reference frame because the part is still be able to rotate and that would affect the position of the ribs. A tertiary datum must be specified.
  4. The feature control fame includes a diameter symbol for the 0.10" tol zone. That is incorrect. The tolerance zone is 0.10" wide at MMC and only applies in one direction.

My conclusion is that the part can be inspected if the corrections are made.

Please let me know if this makes sense to you.

Stijloor.
I'm with you. If a tertiary datum isn't added, there's no point in using GD&T--you could just use standard angle callouts (and tolerances).
 
J

Joaquin S

#8
Re: True Position of slots

Are you good to go with the inspection now? Please do come back if you're not sure. Happy to help.

Stijloor.
Well, I talked to Engineering CAD drafter about your inputs and he said that nothing is wrong with the drawing, but i think that you're right and the data in the drawing need to be revised and fixed ,
from your perspective what would be the correct call outs in the drawing to inspect this true position ?
thanks in advance...
 

Stijloor

Staff member
Super Moderator
#9
Re: True Position of slots

Well, I talked to Engineering CAD drafter about your inputs and he said that nothing is wrong with the drawing, but i think that you're right and the data in the drawing need to be revised and fixed ,
from your perspective what would be the correct call outs in the drawing to inspect this true position ?
thanks in advance...
Joaquin,

Well, for starters, your drafter is 2 standards behind, but let's go with the 1994 version. That'll be OK for a while.

A feature has to be selected to be the tertiary datum feature. What is the important relationship between the three ribs and another feature? based on your drawing that could be quite a few..... Slots? The 3-hole pattern? That other hole perhaps? Keep in mind: function and relationship.

The diameter symbol must be removed. See my previous post for an explanation.

Also, material condition(s) for datum features of size should be considered as well. MMC? LMC? RFS?

I'd be happy to have your folks in my GD&T course....;) Naahh, just kidding...

Hope this helps.

Stijloor.
 
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