Countersunk vs pan head bolts for strength ?

[Boo2]

Hi,

I want to through bolt a plywood chain locker front to some 50x50mm square stock so that it won't come away under shock loads and I'm torn between pan head bolts and countersunk bolts. Intuitively the pan heads will be stronger because the head will lie outside the ply compeltely but they will be a pita to hide. Alternatively I could use countersunk head bolts but istm they will be weaker just because the heads might split the ply and pull though.

Can anyone tell me whether my fears are groundless ? Or should I definitely go with the pan head bolts ?

Thanks,

Boo2

 

[grumpy_o_g]

Hi,

I want to through bolt a plywood chain locker front to some 50x50mm square stock so that it won't come away under shock loads and I'm torn between pan head bolts and countersunk bolts. Intuitively the pan heads will be stronger because the head will lie outside the ply compeltely but they will be a pita to hide. Alternatively I could use countersunk head bolts but istm they will be weaker just because the heads might split the ply and pull though.

Can anyone tell me whether my fears are groundless ? Or should I definitely go with the pan head bolts ?

Thanks,

Boo2

I'd have thought pan head plus penny washer? The wood will be the weakest link and countersinking will only make it even weaker. Not sure what you mean by shock loads though - I assume you aren't attaching the bitter end of the anchor rode to the plywood?

 

[Tranona]

As it is wooden construction using suitable scantlings, adhesive (eg epoxy) would be fine. No mechanical fastenings needed for structural reasons. You can epoxy your square grounds to the ply bulkheads and your ply locker front to the grounds. Can't see any high loads on the front. If I were doing the job, I would probably use countersunk woodscrews to clamp the front onto the grounds as it is difficult to use clamps. You can counterbore the screw holes and plug them for neatness.

If you read the WEST book you could learn how to do such jobs with no fastenings at all - just epoxy fillets and do away with the timber grounds. Will give a nice clean radiused corner for the inside of your locker.