Udja
Military
- Jun 10, 2015
- 3
I'm trying to build a basic knowledge of geometric tolerancing in Y14.5. I'm very much out of my element, so apologies up front if I lack even the fundamentals; I'm muddling my way through this without instruction, which is very much not how I prefer to learn things. Regardless, I've got a drawing attached that I'd love to have someone review/critique. This part (and its mate) are currently being produced, but the drawings use symmetry and concentricity callouts - they're very much 'shop-style' prints. I understand that those callouts are both deprecated in 2018 since they are supposed to be rarely used. Consequently, I also understand that I fundamentally did/do not understand what those callouts meant since I used them all the time! All that said, I'd like to learn how to redo these prints to reflect best practices per the standard.
This sleeve is pinned to its mate using a 1/8" spring pin, as illustrated in these screenshots. The sleeve rotates on the mating part. All parts are Swiss-style machined parts; three place decimals on our prints means a default +/-.005 tolerance.
The features that I'm trying to control are the radial slot, the hole opposite the slot, two detent pockets, an offset axial hole (or groove, if you prefer), and the flats on the end of the OD.
Functionally, the slot locates a lot of these features (via the pin that rides in the slot), starting with how closely the sleeve sits near the shoulder on the mating part. The 'slop' in that gap needs to be minimal.
The hole opposite the slot is to allow removal of the pin if necessary. It has to be in line with the slot but is just clearance for a punch or similar removal tool.
The detent pockets are to give the sleeve open/closed positions. It's more important that they line up relative to the ends of the slot than that the pockets are perpendicular to each other. The depth from the OD is also important.
The position of the offset axial hole (groove shown at the bottom of sections C-C and D-D) is also important relative to the slot: the top of the slot must be opposite the axial hole.
The flats are used to turn the sleeve using a tool; it's a small part and it can be hard to turn by hand.
Questions I had were:
1) Which of these controls am I using incorrectly? I don't know if the profile tolerance should be used for the slot vs position, for instance.
2) Am I making my intent clear in regards to how this part fits with its mate by using the schemes shown here?
3) Do I need a plane that runs axially through this part to use as a datum for anything? I'm using -B-, but I'm not sure if there's an implied horizontal/vertical that I can use to clock features off of (like the 45deg angle in section A-A. If I do need an explicit plane, how should I define it?
4) Do the surface tolerances in section C-C ensure that the same features in section D-D are straight? For instance, I do not want the groove on the ID to walk and break through the OD - on the model, the wall thickness is .07825; if I could keep that to a min of .060 I'd be happy. Does the surface callout control for that at all, or do I need an additional callout in D-D for these features?
5) In reality, they might actually drill an offset .201 hole through the part first, before doing the main bore. If that's the case, would it be beneficial to use this as a datum and reference the bore off of it?
I hope I'm on the right track here, I know I've asked a lot of questions, and I am grateful for any input you experienced folks would like to give.
This sleeve is pinned to its mate using a 1/8" spring pin, as illustrated in these screenshots. The sleeve rotates on the mating part. All parts are Swiss-style machined parts; three place decimals on our prints means a default +/-.005 tolerance.
The features that I'm trying to control are the radial slot, the hole opposite the slot, two detent pockets, an offset axial hole (or groove, if you prefer), and the flats on the end of the OD.
Functionally, the slot locates a lot of these features (via the pin that rides in the slot), starting with how closely the sleeve sits near the shoulder on the mating part. The 'slop' in that gap needs to be minimal.
The hole opposite the slot is to allow removal of the pin if necessary. It has to be in line with the slot but is just clearance for a punch or similar removal tool.
The detent pockets are to give the sleeve open/closed positions. It's more important that they line up relative to the ends of the slot than that the pockets are perpendicular to each other. The depth from the OD is also important.
The position of the offset axial hole (groove shown at the bottom of sections C-C and D-D) is also important relative to the slot: the top of the slot must be opposite the axial hole.
The flats are used to turn the sleeve using a tool; it's a small part and it can be hard to turn by hand.
Questions I had were:
1) Which of these controls am I using incorrectly? I don't know if the profile tolerance should be used for the slot vs position, for instance.
2) Am I making my intent clear in regards to how this part fits with its mate by using the schemes shown here?
3) Do I need a plane that runs axially through this part to use as a datum for anything? I'm using -B-, but I'm not sure if there's an implied horizontal/vertical that I can use to clock features off of (like the 45deg angle in section A-A. If I do need an explicit plane, how should I define it?
4) Do the surface tolerances in section C-C ensure that the same features in section D-D are straight? For instance, I do not want the groove on the ID to walk and break through the OD - on the model, the wall thickness is .07825; if I could keep that to a min of .060 I'd be happy. Does the surface callout control for that at all, or do I need an additional callout in D-D for these features?
5) In reality, they might actually drill an offset .201 hole through the part first, before doing the main bore. If that's the case, would it be beneficial to use this as a datum and reference the bore off of it?
I hope I'm on the right track here, I know I've asked a lot of questions, and I am grateful for any input you experienced folks would like to give.
