Cap screws (allen head) vs, machine screws; thread size.
If I want to replace a cap screw, must I use a cap screw?
I have one of those DIY screw seletions and it's usually enough but this time, 6-32 x 3/4" screws screw in but loosely like they can probably wiggle out a thread at a time. (Can they?)
OTOH, 8-32 screws go in 2 or 3 turns and then jamb up. If I had just the right length, that might work pretty well too, but are 3 threads enough?
Since neither fit, one too small and one too big, I suspect that cap screws use a different measuring system? Surely it's not metric ??? since it's Black & Decker. But if it is metric, it seems like it's between M3.5 and M4!!!
This is a Black & Decker GrassHog XP**, version 2, model GH1000 or GH2000, and the screws hold on the guard so rocks won't hit me in the shins, as much, and the after market parts companies sell them, at $3/per, with added shipping $12 for two of them, but (on purpose?) don't say what threads they use.
Black and Decker refers users to
So it's discontinued and they still don't tell what size it was. "Qualify for free shipping on orders over $150!"
Or I think I can stand in the aisle at Home Depot and try various screws, if they're not sealed in their wrapper. They sell a lot of cap-screws (assuming I really need a cap-screw) but I can't find a size betwween 6-32 and 8-32! FWIW this is 6-32:
2) With some devices, engines? other car parts? is it not true that the threaded hole is made of harder material than the bolts and screws will go in it? Is this generally followed? Almost universally? I'm curious for this case and others: Could I just force in the bigger screw as far as it would go with confidence that if I later removed it, the threads in the hole would still be good for use with the proper screw? Or can I ruin the threads in the hole by twisting in an 8-32 machine screw.
I came across this page, with interesting background, while looking for an answer. I don't know how many of you have believed what.