Dimensioning Hole Depth

[dmiller327]

We have been dimensioning our blind holes from the start surface to the drill point. This is being done at the request of our machine shop. I was told that the reason is,the cnc operators want be be able to compare the depth readout on their cnc's with the value inthedrawing note.


Every standard I have seen calls for holes to be dimensioned to their full diameter depth.


Has anyone else dealt with this issue?Should thecnc operators really needthe bind holesdimensioned to the drill point? We are going thru our company standards andI would like to know if we should join the 99% of companies that dimension to the full diameter depth or not.





Thanks,

 

[appinmi]

It has been the standard for a long time to dimension hole depth by the full diameter. If you were to dimension the tip, you would also have to dimension the drill point angle, and tie the tolerances of both to control the actual depth of the full diameter. Doing so would make machining very impractical,


In every machine shop that I have worked, the depth of the hole is controlled by the full diamter, not the tip. The only exception is when the tip might break thru. It still has a dimension for the full diameter, but also has a "max" depth for the point.