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Sharpness/Dullness Evaluation/Testing of non-standard cutting geometry

BiPolarMoment

Mechanical
Mar 28, 2006
622
We have some custom stainless steel tools with hole saw type geometry where the cutting 'tips' are not of a standard geometry--it has a scalloped leading edge which creates two sharp 'peaks' at the innermost and outermost edges:

View attachment 8604

These items are intended for limited re-use, but we would like to be able to determine (in-between uses) when they are no longer "sharp enough" without requiring complicated/time-consuming/expensive metrology such as was necessary when they were first manufactured. Presently there is a visual inspection (minor magnification only) that should weed out ones that are obviously damaged (e.g. fractured/bent edges) but can not reliably determine when it is simply 'dull'. Therefore, if I can find examples of various levels of dullness (determined subjectively), can we develop a way to 'measure' them somehow in a fashion that can be adapted for a relatively non-skilled technician to evaluate?

Curious to know what may already be out there to evaluate something like this. A thought thus far would be to somehow use pressure sensitive film (or similar) under a (non-destructive) controlled axial load to evaluate the contact patterns created... but my exposure (pun intended) to using said film is mostly tales of how knee replacement devices were developed/evaluated and nothing practical.

Any obvious ideas?
 
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I don't know if this guy has a video to cover your problem, but I can't think of anyone better - https://www.youtube.com/@OUTDOORS55/videos

He has made a full scientific analysis of how knife blades are actually sharp and how thing get dull and has microscopic evidence to support what he shows at the macroscopic level.
 
Can't see your attachment, so unclear what your edge actually looks like.

Nevertheless, the Youtuber that Greg cited uses a sharpness tester that uses the amount of force required to cut through a calibrated wire on the tester to determine absolute sharpness. Note, however, the tester is designed for testing knife edges, so other types of edges likely will produce drastically different results.

https://www.sharpeningsupplies.com/...JafIrDyzGw_9lM6c54oJcbzqkdkmZDLbho-MKBDhpbywA
 

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