Hello Sir, I have Some questions, could you please clarify it. 1. Can it is compulsory to Show secondary and Territory Datum ? when we use to show Primary Datum ? 2. Can it is compulsory to show Feature Control Frame with Datums ? 3. Why we use Datum? can tolerance on dimension only can work ? 4. The Difference of AMSE vs ISO Standard for GD&T looking forward to hear from you. Thank you!
Great Sketching of the X-Y-Z perfect DRF constraining to the perfect CMM-world. Thank You! T J (Tom) Vanderloop, CMfgE, Author, Technology Instructor & Consultant. AWS & LSME Memberships
Can you show us how precision linear rails are properly bolted to datum planes. There is a lot of basic fundamentals thats needs to be know in order to install them correctly but no one shows what is the correct process.
I understand the 3 2 1 rule, but how would a designer determine which plane occupies primary, secondary and tertiary spots? In your example, why not use A/C/B instead of A/B/C in the control frame?
Hello Steve, thank you for your comment. We will upload a video soon on primary & secondary datums that I believe will answer this question for you. Stay tuned! Thank you, Your GD&T Basics Team
I'm a senior in highschool and I've taken Intro to Engineering class and a PLTW class and now I'm in manufacturing. This video made a lot of sense but I have one question, can datum C be on either side of the part? In doing this if would be the same perfect world just a different orientation and the datums would still be perpendicular.
Do I have to add basic dimensions to every feature which need to be inspected when the 3D model is provided to the inspectors? I mean we have so complicated injection molded plastic parts that only can be measured with laser scanner or classic CMM so the 3D CAD model should be provided to them to able to do it, and they could measure the dimensions out of the CAD model.
No, that is not necessary and does make for a very messy drawing when attempted. We simply add a note in the "General Notes" that tells the interpreter of the drawing to query the 3D model for all missing dimensions and that they are to be treated as "BASIC". Adding to also reference ASME Y14.41 is a good practice as this tells the interpreter the standard that covers the rules for "Digital Product Definition". Hope this helps!
Hello Dan, Thank you for your question. Section 4.11.2 of the ASME Y14.5 explains that if a datum feature has irregularities that cause the part to sit unstable (“that is, rocks”) when brought into contact with the datum feature simulator, we must stabilize the part in the “optimum” position. Essentially, we would shim underneath the part to cause the part to sit in the neutral position -- meaning that we would “equalize” the distribution of the shims so that all of our related features would stand the best chance at passing their own requirements. In that specific section of the standard, it states to seek further definition/explanation in the ASME Y14.5.1M standard. It does also state that if a different approach is desired for unstable datum features, such as Chebychev, least squares, translational least squares, etc., it must be specified on the drawing. We hope this helps!
hello sir i have a question, assume that on one part i have a hole on the top face of the part which is 0.1 mm positional tolerance with respect to datum A, B then C( assume these datums are planar on very basic rectangular block and ordering of datums are important) on the feature control frame. This means that when this hole is inspected first datum A is constrained from 3 point contact, then B from 2 point contact, then C from 1 point. I also have another hole on the same part which is placed on the left face or right face which is again 0.1 mm positional tolerance but this time with respect to datum B A then C on the feature control frame (ordering is important). This time time same datum B which is used for first hole is used to locate second hole but 3 point of contact is done on that datum. Then datum A for 2 point contact and for C 1 point contact. So same part and same drawing but according to my datum ordering, datum A can be used for 3 point of contact or 2 point of contact in inspection. Is my understanding true? if it is wrong pls help me understanding it. Thx for videos.
Yes, you have a good understanding here. If the feature control frame for the first hole is A|B|C, that hole will utilize datum |A| primarily to lock down the most degrees of freedom. Then B and C will lock in any remaining degrees of freedom. Then for the second hole, if the feature control frame lists B|A|C the hole will be located/oriented to |B| primarily and then A and C subsequently. If you were inspecting this part, the part would be completely removed from its setup, and re-set in its new order for these different features. Feel free to check out our video on datum reference frames if you still have any questions. ua-cam.com/video/D9U1YV_96kk/v-deo.html
Yes, you would have to construct a plane for each of them and you want to make sure that your settings are set to capture the three highest points for each plane (this is required for datum establishment). We have to have a minimum of three, but there is no maximum requirement. This does indicate that our sampling (number of probed points) is pretty high. We want to ensure that those high points are captures. Hope this helps!
Hello Sir, I have Some questions, could you please clarify it.
1. Can it is compulsory to Show secondary and Territory Datum ? when we use to show Primary Datum ?
2. Can it is compulsory to show Feature Control Frame with Datums ?
3. Why we use Datum? can tolerance on dimension only can work ?
4. The Difference of AMSE vs ISO Standard for GD&T
looking forward to hear from you.
Thank you!
It is so kind to share your knowledge
Great Sketching of the X-Y-Z perfect DRF constraining to the perfect CMM-world. Thank You!
T J (Tom) Vanderloop, CMfgE, Author, Technology Instructor & Consultant. AWS & LSME Memberships
Very good explanation. Thank you as I needed a refresher
Glad it was helpful!
Can you show us how precision linear rails are properly bolted to datum planes. There is a lot of basic fundamentals thats needs to be know in order to install them correctly but no one shows what is the correct process.
Thanks
GD&T Basics!
I understand the 3 2 1 rule, but how would a designer determine which plane occupies primary, secondary and tertiary spots? In your example, why not use A/C/B instead of A/B/C in the control frame?
Hello Steve, thank you for your comment. We will upload a video soon on primary & secondary datums that I believe will answer this question for you. Stay tuned!
Thank you,
Your GD&T Basics Team
I'm a senior in highschool and I've taken Intro to Engineering class and a PLTW class and now I'm in manufacturing. This video made a lot of sense but I have one question, can datum C be on either side of the part? In doing this if would be the same perfect world just a different orientation and the datums would still be perpendicular.
Perfect 👍🏻
Do I have to add basic dimensions to every feature which need to be inspected when the 3D model is provided to the inspectors? I mean we have so complicated injection molded plastic parts that only can be measured with laser scanner or classic CMM so the 3D CAD model should be provided to them to able to do it, and they could measure the dimensions out of the CAD model.
No, that is not necessary and does make for a very messy drawing when attempted. We simply add a note in the "General Notes" that tells the interpreter of the drawing to query the 3D model for all missing dimensions and that they are to be treated as "BASIC". Adding to also reference ASME Y14.41 is a good practice as this tells the interpreter the standard that covers the rules for "Digital Product Definition".
Hope this helps!
What happens if the surface that contacts datum A is convex and the part rocks on the datum?
Hello Dan,
Thank you for your question.
Section 4.11.2 of the ASME Y14.5 explains that if a datum feature has irregularities that cause the part to sit unstable (“that is, rocks”) when brought into contact with the datum feature simulator, we must stabilize the part in the “optimum” position. Essentially, we would shim underneath the part to cause the part to sit in the neutral position -- meaning that we would “equalize” the distribution of the shims so that all of our related features would stand the best chance at passing their own requirements. In that specific section of the standard, it states to seek further definition/explanation in the ASME Y14.5.1M standard. It does also state that if a different approach is desired for unstable datum features, such as Chebychev, least squares, translational least squares, etc., it must be specified on the drawing.
We hope this helps!
hello sir i have a question, assume that on one part i have a hole on the top face of the part which is 0.1 mm positional tolerance with respect to datum A, B then C( assume these datums are planar on very basic rectangular block and ordering of datums are important) on the feature control frame. This means that when this hole is inspected first datum A is constrained from 3 point contact, then B from 2 point contact, then C from 1 point. I also have another hole on the same part which is placed on the left face or right face which is again 0.1 mm positional tolerance but this time with respect to datum B A then C on the feature control frame (ordering is important). This time time same datum B which is used for first hole is used to locate second hole but 3 point of contact is done on that datum. Then datum A for 2 point contact and for C 1 point contact. So same part and same drawing but according to my datum ordering, datum A can be used for 3 point of contact or 2 point of contact in inspection. Is my understanding true? if it is wrong pls help me understanding it. Thx for videos.
Yes, you have a good understanding here. If the feature control frame for the first hole is A|B|C, that hole will utilize datum |A| primarily to lock down the most degrees of freedom. Then B and C will lock in any remaining degrees of freedom. Then for the second hole, if the feature control frame lists B|A|C the hole will be located/oriented to |B| primarily and then A and C subsequently. If you were inspecting this part, the part would be completely removed from its setup, and re-set in its new order for these different features. Feel free to check out our video on datum reference frames if you still have any questions.
ua-cam.com/video/D9U1YV_96kk/v-deo.html
@@Gdandtbasics thank you so much !
awesome video, thank you 🙏
How do I this on a cmm? Do I need to find the high points for each datum and construct datums?
Yes, you would have to construct a plane for each of them and you want to make sure that your settings are set to capture the three highest points for each plane (this is required for datum establishment). We have to have a minimum of three, but there is no maximum requirement. This does indicate that our sampling (number of probed points) is pretty high. We want to ensure that those high points are captures.
Hope this helps!
Axis of a cylinder cannot be a datum because it's a virtual(theoretical) thing
Hello, we will be uploading a video shortly on primary and secondary datums that I believe will answer this question for you. Stay tuned!