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Countersink Screws and Holes Mating

DarK_AlximiKDarK_AlximiK Member Posts: 11 EDU

Countersink screws has a mating snap point right after fillet before tapping starts is making problem during automatic countersink hole population.

You can see that mated part is not flat to the countersink surface

Example bellow is overall view

I would suggest to add possible mating point for imaginary top of the cone inside the part or the center of the bolt hat should be made as mating point

Then it is almost perfectly mated, would be nice to have mated tops of the cones


  • Jason_SJason_S Moderator, Onshape Employees, Developers Posts: 162
    Hi @DarK_AlximiK ,

    The most important part about properly mating countersunk fasteners is ensuring that the conical surfaces match up. Mating to the planar surface of your part might look good for for CAD (and may match the conical surfaces up by chance),  but upon manufacturing and assembly you will find the tolerance of your holes and the tolerance of the fasteners themselves stacking. The end result will be you, in final assembly and QA, running your hand over your part all to find fasteners inconsistently sticking above and below the planar surface of the part.

    To properly DFM and DFA your holes to accommodate countersunk fasteners, there should be counterbored recess below the surface or a slightly over-countersunk hole in your part. This will ensure that your fasteners do not stick above the surface of the part. This z offset to the fastener is up to the designer and is specific to the fastener.

    The best Mate Connector point would be the point of the projected conical surface, on both the hole and the fastener. This would ensure proper fitment of the fastener to the hole and accurate recess information. Our hole feature, unfortunately, does not yet fully support inserting holes for standard content or inserting holes designed for specific fasteners. We already planned on covering this case, but I will write up this as a customer improvement request and attach it to our hole feature. Please look for improvements to our hole feature in the future. 


    QA Engineer - Onshape, Inc.
  • David_BoneDavid_Bone Member Posts: 21 PRO
    Has there been any update to this yet?  Mating fasteners of ANY kind should be a high priority feature, and all other CAD packages easily handle mating conical features.
  • Hendrik_Hendrik_ Member Posts: 22 PRO
    Also just came across this issue.  Kinda surprised that OS has not addressed this out of the box.  Not usable for design purposes. 

    Clearly the mate Z value is should be auto-adjusted to match the relevant countersunk standard content model. An offset in the case of countersunk would be useful - even if that is an interim solution.

    Trusting @Jason got round to writing up that improvement request?


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