Comment by mgdlbp
3 years ago
Re: Phillips drive, it's actually a common misconception that this was an intentional feature of the design. The original patent for the driver[1] specifically describes resistance to "camming out" (seemingly in the modern sense of the phrase). Omitting some of the verbose context:
> One of the principal objects of the invention is the provision of a recess in the head of a screw which is particularly adapted for firm engagement with a correspondingly shaped driving tool or screw driver, and in such a way that there will be no tendency of the driver to cam out of the recess when united in operative engagement with each other. (https://worldwide.espacenet.com/patent/search?q=pn%3DUS20468...)
And the patent for the drive (I don't know why under patent law several consecutive patents mostly saying the same thing had to be filed) uses the word to refer to the ejection of trapped debris instead of the driver:
> This same angular formation of both elements is especially designed to also create what might be termed a camming action during the approach of these angular faces toward one another with respect to any substances which might have become lodged within the recess of the screw. (https://worldwide.espacenet.com/patent/search?q=pn%3DUS20468...)
Edit: Wikipedia notes that a later patent acknowledged the tendency to cam out and its effect of preventing damage to screw heads...perhaps meaning that the head would be saved from snapping off--the drive itself surely isn't!
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