A special tool having a cross section of 'Reuleaux triangle' when mounted in a floating chuck can trace the shape of square..
Refer this for more details:
http://www.slideshare.net/Arahvinth/square-hole
The relevance is some fool drilled a hole in it.
A 3/16 inch pilot hole should be drilled for a 10 screw.
A pilot hole of 3/32 inch should be drilled for a 6 screw.
A counterbored hole in engineering is used to create a recessed area at the top of a drilled hole. This allows for a screw or bolt head to sit flush with the surface. It is different from a regular drilled hole because it has a wider diameter at the top to accommodate the head of the fastener.
The size of the hole drilled for a door knob should typically be 2 1/8 inches in diameter.
A 3/16 inch pilot hole should be drilled for a 12 wood screw.
A 3/32 inch pilot hole should be drilled for a 10 wood screw.
A 7/64 inch pilot hole should be drilled for a 8 wood screw.
About 20 dollars! Hey oh!
the hole was a dead end hole you drilled all the way thru and into the water jacket. depending on the model of head you just made sure you get to buy another and replace the one you drilled. Next time go to a mechanic that knows what they are doing.
A 5/32 inch pilot hole should be drilled for a 3/8 lag screw.
micro inces