Is there a method for measuring sharpness? - Router Forums
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post #1 of 13 (permalink) Old 02-01-2010, 06:01 PM Thread Starter
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Default Is there a method for measuring sharpness?

You can feel the edge with your finger. You can tap it on a piece of hard wood and note the depth of the cut. You can even put it in in your saw or router or whatever it may be and see how it cuts.

All of these methods tell you that it has an edge, but they do not tell you how that edge compares to a fully sharpened edge or to a used up dull edge.

Is there a way to accurately, or officially, measure an edges sharpness?
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post #2 of 13 (permalink) Old 02-01-2010, 06:22 PM
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It comes with experience with your tools. The material might be a little harder to push thru blade or bit. you could have more tearout than usual. After awhile you can tell by looking & feeling the cutting edge. It's like being able to reading a tape measure without all the extra measurements on the tape (1/16, 1/8, 3/8, 5/16,7/16,etc). It comes with use.

James
Whittier, CA.

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post #3 of 13 (permalink) Old 02-01-2010, 06:24 PM
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the answer is:
N per cm^3
now who knows what the hell that means *L*...Where's bigjim when ya need him *s*

I do believe that "cutting force" is the general measurement used.

do a google search..some interesting info available..just an fyi
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post #4 of 13 (permalink) Old 02-01-2010, 06:41 PM Thread Starter
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Yes, there is quite a bit about this subject on Google, but it mostly deals with high tech machines and industy I think.
Here is a link that I found that sheds some light on the subject that is on the level of us plain ol' folks...
Testing Sharpness

And there is much more interesting information (directly related to woodworking) at the first page of that website...
http://bladetest.infillplane.com/


Pictures...
http://bladetest.infillplane.com/htm...ker_tests.html

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post #5 of 13 (permalink) Old 02-01-2010, 06:47 PM
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James defined it well enough, but I guess there are two ways to look at it. One being "measuring" the actual cutting edge via any number of methods. I would suspect all relative to its application. and then there is James's method which I tend to agree with more so than not. I can spend an hour tuning a new plane blade and find it very relaxing. there's nothing like the "whisp" you hear when a sharp edge cuts through the grain. *S*
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post #6 of 13 (permalink) Old 02-01-2010, 08:13 PM
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I drag the blade accross my finger or thumb nail beforeat about a 90 angle. If it removes material, it is sharp. This works for HSS and carbide saw blades, drills, router bits, drill bits and lathe tools.
Dan

St. Louis, MO
Retired Welding Inspector and past Ind Arts teacher
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post #7 of 13 (permalink) Old 02-01-2010, 08:45 PM
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I have less hair on my *left* forearm. I am right-handed. Guess how I test for sharpness.
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post #8 of 13 (permalink) Old 02-02-2010, 04:38 AM
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The noise from the router is also a good indication if it should be sent for sharpening and of course the obvious burning smell.
Tom
(Template TOM)
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post #9 of 13 (permalink) Old 02-02-2010, 05:41 AM
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You have to be 1 with your senses. Touch and bleed, sight, see my reflection, sound, wrong note/pitch, smell of burning, do I need a new handbag, does my bum look big against this router table. Always check your tools before use. I clean and strop my bits before and after use. A shiny edge will show defects.A fingernail will detect roughness.
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post #10 of 13 (permalink) Old 02-02-2010, 07:07 AM
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there is a similar thread where someone suggested a strong magnifying glass or microscope is the best way.

LeeValley had a

Pocket Microscope 45K16.12 $9.50

available before christmas. according to the website it is "sold out for the 2009 holiday season." This leads me to think they'll have it xmas 2010.

Pocket Telescope/Microscope
45K16.15 $27.50

is a 30x pocket microscope. Much fancier but will still do the job.

Allthunbs
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