A thru hole, also known as a through hole, is a feature on a blueprint or drawing that identifies a hole to be machined with two open ends. The hole goes all the way through the part. In other words, the hole breaks through at two locations on the part.
In the picture below, the thru hole is on the right. The other holes are blind holes.
How to dimension a thru hole?
A thru hole is dimensioned by specifying the diameter of the hole along with a tolerance. Additional features can be added if needed such as a countersink or counterbore for the hole. No other features are required.
Thru hole examples
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