Counterbore callout help 1

[vlg426]

So I need to callout some counterbore holes on the drawing. However, the drilled surface is not perpendicular to the holes. Therefore, the depth of the counterbore is different for the 2 holes. Even for individual hole, the counterbore thickness varies due to sloped surface. How do I call out these holes so that they will have a 9mm "uncounterbore".

Thanks in advance

 

[drawoh]

vlg426,

Your section view works for me.

The standard callout with depth, implies that there is an obvious flat, orthogonal surface to work down from, and clearly, there isn't.

--
JHG

 

[BrianE22]

What I've used is "Counterbore to depth shown".

 

[racookpe1978]

Is the back side (the unfinished interior of the casting) flat enough to measure accurately enough for your measurement? You're calling out 1/10's of a mm as your controlling dimension - the reference surface needs to be at least that smooth and consistent!

Plus, you're requiring the machinists to measure "back from" the other side of their part: Can you make a jig or fixture so the stop depth is automatic? It will be more error-proof.

 

[MikeHalloran]

The part is actually dimensioned in the preferred way for the extant situation.

The depth stop on the milling machine's spindle is set so the cutter face is the specified dimension from the machine table to which the part is clamped.



Mike Halloran
Pembroke Pines, FL, USA