Question for you regarding how I see drawings frequently in my shop: ASME Y14.5 paragraphs 6.4.7, 10.4.1, and 10.4.1.2 all cover how projected tolerance zones can be interpreted in orthographic views with chain lines when necessary. I assume chain lines are only unnecessary in that lens when a hole is blind like you mentioned. They also state that in MBD that the surface the leader arrow of reference frame attaches to, that surface is the one that a projected tolerance zone will extend from. What if I have projected tolerance zones listed on head-on views (axis of a hole is going in-out of the drawing)? ASME doesn't seem to specify what the default interpretation should be in drawing format, not when it is "necessary" to utilize a chain line.
How do you know what value to use for a Projected Tolerance Zone. You stated that it doubles with every plate. Am I correct in thinking that if I have three plates with the same thickness it triples? So, for example the first hole (lowest in the stackup) has a PTOL of +/- .015; then my second plate must have a PTOL of +/- .030, and the third having +/- .060? What if I hade three mating surfaces where one of them was 1.000in and the mioddle one was .675in and the third .375in. Would I then multiply my PTOL by 1.675 and 1.375 respectively? I forgot to mention I am speaking 3X clearance holes through a 3X tsack bolted joint (nut & bolt).
Hi, it’s unlikely that a fixed gage would be effective. Normally projected tolerance zones apply to threads, or holes that will receive a press fit pin, ergo no MMC. If there was an MMC symbol, it’s possible to figure out what the tolerance zone inside the part should be taking the projected tolerance zone into account (depends on the thickness of the parts) In that case a normal gage with fixed pins could be used.
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.
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Question for you regarding how I see drawings frequently in my shop:
ASME Y14.5 paragraphs 6.4.7, 10.4.1, and 10.4.1.2 all cover how projected tolerance zones can be interpreted in orthographic views with chain lines when necessary.
I assume chain lines are only unnecessary in that lens when a hole is blind like you mentioned.
They also state that in MBD that the surface the leader arrow of reference frame attaches to, that surface is the one that a projected tolerance zone will extend from.
What if I have projected tolerance zones listed on head-on views (axis of a hole is going in-out of the drawing)?
ASME doesn't seem to specify what the default interpretation should be in drawing format, not when it is "necessary" to utilize a chain line.
Great series of videos
Thanks so much!
How do you know what value to use for a Projected Tolerance Zone. You stated that it doubles with every plate. Am I correct in thinking that if I have three plates with the same thickness it triples? So, for example the first hole (lowest in the stackup) has a PTOL of +/- .015; then my second plate must have a PTOL of +/- .030, and the third having +/- .060? What if I hade three mating surfaces where one of them was 1.000in and the mioddle one was .675in and the third .375in. Would I then multiply my PTOL by 1.675 and 1.375 respectively? I forgot to mention I am speaking 3X clearance holes through a 3X tsack bolted joint (nut & bolt).
Could projected tolerance zone been inspected by fixed gage method? If yes, how the fixed gage look like?
Hi, it’s unlikely that a fixed gage would be effective. Normally projected tolerance zones apply to threads, or holes that will receive a press fit pin, ergo no MMC. If there was an MMC symbol, it’s possible to figure out what the tolerance zone inside the part should be taking the projected tolerance zone into account (depends on the thickness of the parts) In that case a normal gage with fixed pins could be used.
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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.