If you wanted to simplify the datum structure some things you could do is:
Change the side plate mounting surfaces which are currently H & J to A1 & A2. In your drawing when you dimension the height of these mounting surfaces, use 2X along with the <CF> symbol to indicate that it's a Continuous...
The method you suggest over the principle engineer's simple 'Constrained' is more accurate and true to the design intent. It might require more time to validate and may require an inspection fixture vs someone just pushing down on the part to make sure the surface sits flush on the flat surface...
If you want to do it the easy way, just use the first ISO view you show and place a Datum A marker on one of the curved surfaces and a Datum B marker on the other, then you'd call out A-B as primary, C as secondary, and D.
This part sort of looks like a machined cylinder head with valve guides. On a part like this, since it's machined on all sides I would use the bottom surface as Datum A, the two surfaces you currently show as Datum A as Datum B, and the right surface as Datum C. Then use positional tolerancing...
I would use the large flat top surface as Datum A, the long surface that is perpendicular to that and that is flush with the end of the cells as Datum B, and the overall length dimension which touches off the the short ends as Datum C because this part is symmetrical. Then use a profile control...
Datum target lines don't have to be related to cylindrical features. Using the sharp edges as a secondary datum is perfect for the Ops scenario where there are no perpendicular surfaces. Just lay the bottom flat surface on either the mill table or inspection table and use either an edge finder...
I encounter this a lot as well. What those people who don't like too much tolerancing and GD&T on the drawing don't realize is that all the features generally have tolerances either way, in the title block, and they all need to be met. If the parts are being made in house then I think it is more...
Datums can also be lines (edges) and points so you could use the edge along the wider side of the draft as a secondary datum. If symmetry was important you could pick both edges on the wider side as secondary datum B-C.
My guess is that the connectors are floating on the sidewalls. If that's the case their position may not be that critical. What would be more critical is the location of the mounting holes in relation to the connector cutout. The connectors probably have a datasheet that may show tolerances and...
I wouldn't go to that extreme. I think it's better to try and keep the detail or section view on the same page as the view from which it is being pulled from if possible. If there's not enough room, at least try to keep it close like on the next sheet rather than further on in sheet number. At...
My opinion would be not to use the 4 hole pattern as a datum. Use the back surface then two of the edges, or the back surface, one edge, and the center hole. Whichever is more applicable to how the part will be assembled and function. Using a pattern of holes for a datum seems like a pain to...
I don't think there can be hard general rules. It would totally depend on the application and the requirements. Will it be a weldment? A large machined part? Multiple parts bolted together? This is where knowledge of various manufacturing processes and their realistic tolerance capabilities...
I'm not familiar with the ISO standard but does it have the same principle of datum hierarchy as the ASME standard?
Primary - 3 points of contact
Secondary - 2 points of contact
Tertiary - 1 point of contact
I think technically you'd have to have a collet that is almost 190mm long in order to accurately grab the entire virtual condition OD. Then you can run the indicator on the tapered surface. Depending on the fit and function of the part it may be more practical to use diametral datum zones or...
It seems your checker is suffering from the ole' "Missing the forest for the trees" paradox. I think he's one of those that get tunnel vision when looking at the standard not realizing that the standard can't cover every situation
Just a tip: you can upload an image by clicking the Image icon.
I agree that there is an implied zero basic dimension in the fore-aft features but I believe you still need to specify the qty. Every place I've worked always preferred it this way.
I don't have any hard numbers to give but currently (and in the past) I've worked on large weldments that have machined surfaces and holes. Often times with the Engineering team there's debate and resistance to putting GD&T on the drawings because the shop has no way to inspect them. Perhaps I...
