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Countersink with M3 and bigger only?

jmsaltzmanjmsaltzman Member Posts: 5 PRO
edited September 20 in Community Support
I'm trying to make M2.5 countersunk holes, but I don't get the chamfer on them (or smaller), while I do get it on M3 size and bigger.


The dialog for M2.5 here shows the same value for "Diameter" and "Countersink diameter," but the latter is greater for M3 and larger hole sizes.

Is there a reason for this? I could enter a reasonable value myself but am curious why it's not setting it automatically.

M3: showing the countersink diameter of 6.72:

M2.5 showing the same countersink diameter as the normal diameter:



(edited for grammar)

Best Answer

  • philip_thomasphilip_thomas Posts: 1,355
    Accepted Answer
    @jmsaltzman - Your curiosity shall be rewarded. I spoke to the keeper of the standards (Jason) - yes we really do buy the standards (they are ridiculously expensive if you were wondering), and the answer is that there is no specification for chamfer on fasteners less than 3mm (ISO). Because the value in the table (and subsequently shown in the dialog) has to be something, we set it to be same as the pilot diameter (why 2.9 for an M2.5 i do not know). Can you override it? Of course!
    I hope this helps :)
    Philip Thomas - Onshape

Answers

  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,355
    Accepted Answer
    @jmsaltzman - Your curiosity shall be rewarded. I spoke to the keeper of the standards (Jason) - yes we really do buy the standards (they are ridiculously expensive if you were wondering), and the answer is that there is no specification for chamfer on fasteners less than 3mm (ISO). Because the value in the table (and subsequently shown in the dialog) has to be something, we set it to be same as the pilot diameter (why 2.9 for an M2.5 i do not know). Can you override it? Of course!
    I hope this helps :)
    Philip Thomas - Onshape
  • jmsaltzmanjmsaltzman Member Posts: 5 PRO
    Aaah... that makes sense. Interesting reason too: we learned something!
    I overrode the diameter myself, works fine of course.
    Thanks for digging and reporting back!
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