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Measuring thread flank angle on a screw


Not out of the crisis
Staff member
Super Moderator
Hello metrology experts. I have a situation here that I have yet to run across.
My background: I've spent a number of years in different organizations measuring threaded parts - metals and polymer - on optical comparators.

I have a screw in my hand that has a special flank angle - 48 degrees. Here's the drawing from the product literature.

I have the screws in hand and when I put them on an optical comparator I'm measuring 60 degrees, with the axis of the screw perpendicular to the lens.
The supplier states that to measure this angle you need to turn the screw at an angle to the lens and you will find 48 degrees.

I maintain that the drawing shows the measurement with the axis perpendicular to the viewer.

I've never cocked a screw or other threaded part to measure it, but I've also never purchased a 48 degree screw before.

thoughts on this?
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