Drawing callout

[surfit]

I have a part with a Ø2.000 counterbore that requires close linier tollerance but only up to Ø.900 what is the best way to dimension that? I put
2.7475 +/-.0002" (@ Ø.900).

[DareBee]

huh?

[mfgbydesign]

Check ASME Y14.5
This is the American standard for dimensioning drawings.
You will find examples and specifics for your situation.
If you are designing parts and want it interpreted correctly by the fabricator it is imperative that you follow the standard.
As you indicate there is opportunity for cost savings as well by allowing a dual tolerance on the same feature.

[RICHARD ZASTROW]

Is that .900 diameter (as dimensioned) or is it intended to be the first .900 depth of the counter bore?

Dick Z

[surfit]

The dimension is linier so in other words it's to the bottom surface of the bore not the diameter. It is for a fixture where a part will locate. The locating surface of the part that goes onto the fixture is Ø.875 so I only need to hold the close tolerance up to Ø.900 the rest is for clearance.

[mfgbydesign]

Sounds like a good candidate for a rest button. Counterbore the hole then attach a hardened rest button that can be dusted off to the correct depth.
Otherwise holding that tolerance on the bottom of a bore will be quite challenging.

[surfit]

Ok this might help explain what I am talking about. I added a flag note to the dimension how ever I wanted to know if there was another standard way of doing this