Testing for sharpness

[Luke Maddux]

I'm not a terribly hairy guy to begin with, but I really have to stop shaving all of the hair off of my forearms. Someone actually asked me about it a couple of days ago...

So, pretty straightforward question here, but how do people test their edges for sharp? Is there a better way than the hair test?

I guess an obvious answer is to "hone" (get it?) one's skills to the point that there's no need to test. I'm almost there, but in the meantime, any ideas?

Cheers,
Luke

[powderpost]

Luke, the old trade test was to carefully put the edge onto a finger nail, if the tool "slides" on thr finger nail, it is still blunt. If it will not "slide", then it is sharp. Needless to say, I hope, is that a little commonsense applies.

Jim

[derekcohen]

Pare end grain Radiata Pine. If it tears, your edge could do with more work. If it is smooth and clear, your edge could do with some work. If the RP jumps off your bench and scaddadles out of the workshop begging for mercy, then it is just right

Regards from Perth

Derek

[Robson Valley]

+1 for derek. I have yet to see any constructions built with either hair or fingernails.
Instead, test the edges in the wood of choice. If it performs well, you're done.

End grain in wood carving can be a nightmare, the softwoods in particular.
However the ring count is an important factor.
Using local pine or western red cedar (Thuja plicata) as example:
12 or less rings per 25mm/1 inch, the early wood compresses and tears so easily that the mess is no fault of your own.
15-40 rings per inch should give you an honest evaluation of the tool edge.

I have seen absolutely beautiful WRC = knot free & straight grained, but 10 rings/inch.
Not a hope of carving, no matter what edge I can produce.

[hiroller]

If after cutting yourself and the wound heals quickly, then it was sharp.

[Simplicity]

I also agree with pine end grain testing
Save your hairs for warmth

[Gabriel]

If after cutting yourself and the wound heals quickly, then it was sharp.

Wouldn't a sharp, clean cut heal more quickly??


Alas, I suffer the same zero arm hair effect, that's sharp enough for my work/skill level

[Jone5y]

I do believe that's what hiroller was saying

[Arron]

Luke raises a point I have wondered about many times.
It seems odd that there is no universal but accessible measure of sharpness.
Something that would allow two people who have never met to discuss sharpening techniques without subjectivity.

Everyones idea of 'sharp enough to shave your arm' or 'slice end grain pine cleanly' is different.

Are there no DIY level devices for measuring sharpness objectively?

[Luke Maddux]

Are there no DIY level devices for measuring sharpness objectively?

Are there even any industry level devices for this? I guess sharpness could be quantified by the thickness of the blade at the edge relative to the steepness of the bevel, but how is that actually measured, even in a laboratory setting?

[Arron]

It's easy enough to design a homemade gadget to test sharpness - like this http://bladetest.infillplane.com/htm...sharpness.html . With a bit of attention to detail it's probably easy enough to get it measuring reliably. It still falls short though in that it's not using a universal scale, and it only provides a common medium if I can be sure the person I'm talking to has constructed the same device to the same standard.

Still it would be useful for refining your own methods. Learning to sharpen is a long journey which would go better with a way to measure results and track progress, I think.

[derekcohen]

When testing blade steels, and documenting the results for all to read, the Radiata Pine method was always my preference. This offers a Real World test that anyone can replicate.

There is no such thing as "sharpest" It is always relative .... relative to cutting angle, the steel used, the wood type ... Just find a method when you want to make comparisons.

When woodworking, I never check for sharpness. Experience says it will be so.

Regards from Perth

Derek

[Mobyturns]

When testing blade steels, and documenting the results for all to read, the Radiata Pine method was always my preference. This offers a Real World test that anyone can replicate.

There is no such thing as "sharpest" It is always relative .... relative to cutting angle, the steel used, the wood type ... Just find a method when you want to make comparisons.

When woodworking, I never check for sharpness. Experience says it will be so.

Regards from Perth

Derek

... also relative to tool angle and presentation angle. Real world

I was taught to sharpen chisels & plane iron by my Dad (a wood machinist /carpenter/joiner) so the hair test was pretty much the arbiter on whether an edge was keen enough. We often would substitute the "hair test" by running an arris edge off the corner of a piece of scrap material to test the tool edge sharpness.

I like the paper test - just hold a sheet of standard 80 gsm paper vertically by a corner then run the sharpened tool edge down the sheet. A very keen edge should start to cut as soon as it comes into contact with the papers edge. Dull tool edges will fold the papers edge over & not cut.

[bunya pine]

Would cutting/slicing paper be a good test?

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[Mobyturns]

Would cutting/slicing paper be a good test?

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Not really as it only tells you that the edge is keen, same as shaving hair. keeps the hair on your arm or the back of your hand though. The longevity of the edge is the real world test.