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I have a metal component on a project. The holes are countersunk for use with M3x16 flathead phillip screws. The problem is, due to torque requirements, these screws are consistently stripping out and require drilling to remove(they need removed periodically so I can check/maintain the component). I considered switching to a M3 flathead hex, but my previous experience shows that they strip out at similar rates to the phillips.

I would like to switch the screws out with bolts or Socket Caps. Unfortunately, due to clearances I cannot use a full size washer, so the fasteners without countersinks do not achieve the necessary contact to create a firm grip. The slightest gap causes the component to fail (this component has very tight tolerances).

Is there a washer or other device I can use to overcome this? I know they have finishing washers for using flathead screws in locations without countersinks, but have not had any luck in finding the inverse.

Note: The metal component with the countersunk holes is prohibitively expensive, so remaking it without the countersunk holes is not an option.

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  • A photo may help to understand the clearance issues.
    – Ed Beal
    Sep 2, 2016 at 9:19
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    If the threads are stripping, doesn't that suggest you need a bigger screw? substituting a harder screw (ss?) may prevent the screw threads stripping but won't save the threads in the hole. If the problem is cam-out damaging the Phillips recess in the head, switching to a better drive type (roberts, allen/hex) should help. Maybe you can drill and tap the expensive metal component for M4?
    – RedGrittyBrick
    Sep 2, 2016 at 9:55

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Conical washers M3 seems to get some of the kind you don't want, and some of the kind you do want.

3mm Conical Washers image from http://store.rc4wd.com

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