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I am asking here for your help and advice on how to read holes schematic notations.

On the attached picture I've marked with a green color part of notation that I don't know how to read / understand. And will be thankful for any advice on how to interpret this notes.

With the red color I've marked a holes with countersinks. But I'm failing to pick up necessary details from the sketch to understand the size/angle/depth of this countersinks. (I understand that they can be missing, but I tend to think that they might be in the notations that I don't understand)

Thank you for considering this question!

source: the drawing was taken from this youtube video - link

enter image description here

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  • $\begingroup$ The upside down T means the hole must be perpendicular to the surface. There is an annotation for "all holes" underneath your cursor, I presume that is about the countersinks. $\endgroup$ – ratchet freak Jul 11 '17 at 9:52
  • $\begingroup$ @ratchetfreak, You are very right. Chamfer details are clear for me now. And the details following the upside down T turned out to be 'perpendicularity tolerance'. Thank you! Now I am able to google through this farther. $\endgroup$ – AlStorm Prime Jul 11 '17 at 10:19
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The upside down T means the hole must be perpendicular to the surface. The stuff following it is likely the tolerance of perpendicularity.

There is an annotation for "all holes" underneath the cursor, I presume that is about the countersinks.

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Just to add.

The green is perpendicularity in respect to datum C. Meaning, the called out feature must be perpendicular to datum feature C within 0.003.

I'm also seeing the condition "45 degrees 0.030 - All holes". The countersink will be an additional 0.030 at 45 degrees from the thru hole values (since the countersink won't be thru). I'm not entirely sure if the larger hole callouts are pointing to the OD or ID of the countersunk hole but you'll simply add or subtract in accordance to the condition: "45 degrees 0.030 - All holes". Hope that helped.

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