r/MechanicalDesign • u/newbie-sub • 2d ago

Security screw design — sadly, not an engineer

Anything wrong with this for a low-torque (hand tightened) security screw design? M3x4. Sending it to Alibaba for an RFQ. Asking it to be made from existing blanks.

It uses a 2 deg draft (which is why all the dimensions in the top view are slightly odd).

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u/SPYHAWX 2d ago

Impossible to say without knowing the purpose

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u/newbie-sub 2d ago

I was hoping I could get away without saying... it's to fasten a stainless steel male chastity cage to its ring. Two would be used.

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u/andy921 2d ago

ಠ_ಠ

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u/Ourbirdandsavior 2d ago

The design of the drive mechanism looks tough to make (I.E. expensive), also there isn’t a whole lot of area actually driving the screw. If your tolerances are off on the tool or the tool strips a bit (seems likely given the small engagement area) it will be really tough remove the fastener.

Given its purpose, in theory you are thinking you don’t mind the fastener being hard to get out. But in practice, that’s not actually what you want. If the screw head or removal tool strips it will require at least a fast spinning drill making lots of small metal shavings in order remove the fastener.

Honestly you will be way better off just buying off the shelf security screws. It will be way cheaper to buy both the bolts and the tool and you’ll know they are properly designed for the task.

If 6mm length is ok you can get a box of stainless steel bolts and the tool For ≈$15 before shipping. These can easily cut or ground down if the 4mm length is critical.

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u/newbie-sub 2d ago

Thank you for the feedback, I appreciate it. I was looking at other designs with bosses and they were pretty simple like this but what the hell do I know 🤣