pinhole

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pinhole

(pĭn′hōl) [AS. pinn, pin, + hol, hole]
A small perforation made by, or the size of that made by, a pin.

pinhole os

A very small opening to the uterus from the vagina. It may be present in very young women.
References in periodicals archive ?
Water: Due to the many possible sources of water, hydrogen pinholing is often a major problem.
Mold Atmospheres: The more reducing mold atmospheres (those rich in |H.sub.2~ and having a higher CO/C|O.sub.2~ ratio) tend to promote pinholing. No satisfactory explanation for this phenomenon exists, due in part to a less than obvious correlation between defects and mold additives that affect the "reducing" nature of the mold.
Which, if any, of these gases actually affects pinholing tendencies remains to be determined.
Higher pouring temperatures also lead to longer solidification times that promote pinholing in thin castings and decrease them in thick castings.
Typically, however, only when slag enters the casting cavity can pinholing occur.
Some basic guidelines in daily foundry practice can be useful for reducing the possibility of reaction pinholing: