Testing sharpness - Paper test and....?

[YorkshireMartin]

The generally accepted method of testing for sharpness, as far as I know, is to cut the edge of a piece of copier paper with just the weight of the blade/chisel.

I've had situations where despite the blade doing this, it underperformed somewhat on wood, and required re-honing.

Is there any other method of testing that I could try that requires superior sharpness, that I can do at the sharpening station, other than the obvious of trying on the wood?

Cheers

 

[Sawdust=manglitter]

2 pieces of paper? :lol:

 

[novocaine]

I never bother with the paper test, it doesn't tell you anything on most wood working tools, great for a knife you are sliding through though.

shave your forearm, wet shave means it sharp enough for everyday work, dry shave means it's sharp enough for fine work but won't last long.

note: whilst I'm serious about shaving your arm, it should only be tried if you are feeling brave or have previous knowledge of what you are doing, I will not be held responsible for you sliding it across you wrist.

 

[MattRoberts]

Does it cut the wood?

Yes. No probs
No. Sharpen it.

 

[ED65]

Cutting paper is actually a really bad test of functional sharpness. A good sign of this is that sometimes you've had edges that passed the test but then they didn't do what you wanted on the wood. Cutting paper you can 'cheat' accidentally (as some YouTube videos do) by drawing the blade through the paper instead of doing a push-cut which is what we rely on so often in woodworking.

... other than the obvious of trying on the wood?

That is THE test really.

Like a lot of amateurs I often test for shaving sharpness on the back of a hand or my forearm which usually signals an edge is good enough, but when I need something as sharp as possible real-world performance is what I count on, so I check the edge on pine/spruce end grain. If it'll do that cleanly it's sharp enough for anything.

 

[Harbo]

Samurai sword makers used to cut through wide diam bamboo stalks to test their sharpness - it simulated cutting a persons head off!

Rod

 

[JohnPW]

Look for any light reflected off the edge, there shouldn't be any.

Rub your your thumb across (not along!) the edge, it should "catch".

 

[custard]

Blimey, I don't know about "accepted method of testing for sharpness", if you tried any of that paper or forearm hair stuff in a professional workshop you'd see a lot of craftsmen silently mouthing the words "silly twit" or something very similar!

There are some edge tools, like the tiny cutters you use for inlay work or heavily shaped moulding plane irons, where judging sharpness by the reflected light method that John mentioned might be a sensible step because with these tools you're often using slip stones or files and can easily end up achieving sharpness in some areas but not in others.

I don't think bench planes fall into this category though, the only arbiter of sharpness (and more importantly still, bluntness) is how the tool performs on the workpiece. If you raise a wire edge along the entire edge, and then fully remove it, then it's a banker's bet that you're good to go. After you've been doing it a while you can detect really minute wire edges, or even anticipate when one's just forming, but for the sake of a few extra strokes why take the gamble? If you start getting tear out or fuzziness, or you're sweating like a pig even with a waxed sole, then it's time to sharpen!

 

[YorkshireMartin]

Samurai sword makers used to cut through wide diam bamboo stalks to test their sharpness - it simulated cutting a persons head off!

Rod

Sounds just the job considering how I handle a chisel. :lol:

 

[YorkshireMartin]

Blimey, I don't know about "accepted method of testing for sharpness", if you tried any of that paper or forearm hair stuff in a professional workshop you'd see a lot of craftsmen silently mouthing the words "silly twit" or something very similar!

There are some edge tools, like the tiny cutters you use for inlay work or heavily shaped moulding plane irons, where judging sharpness by the reflected light method that John mentioned might be a sensible step because with these tools you're often using slip stones or files and can easily end up achieving sharpness in some areas but not in others.

I don't think bench planes fall into this category though, the only arbiter of sharpness (and more importantly still, bluntness) is how the tool performs on the workpiece. If you raise a wire edge along the entire edge, and then fully remove it, then it's a banker's bet that you're good to go. After you've been doing it a while you can detect really minute wire edges, or even anticipate when one's just forming, but for the sake of a few extra strokes why take the gamble? If you start getting tear out or fuzziness, or you're sweating like a pig even with a waxed sole, then it's time to sharpen!

Right, I'll keep an eye out for this, literally. Sometimes I think I blunt the edges I sharpen because the leather has too much give in it. But thats a topic for another thread I have no desire to start!

Cheers everyone.

 

[JohnPW]

There are some edge tools, like the tiny cutters you use for inlay work or heavily shaped moulding plane irons, where judging sharpness by the reflected light method that John mentioned might be a sensible step because with these tools you're often using slip stones or files and can easily end up achieving sharpness in some areas but not in others.

I don't think bench planes fall into this category though, the only arbiter of sharpness (and more importantly still, bluntness) is how the tool performs on the workpiece. If you raise a wire edge along the entire edge, and then fully remove it, then it's a banker's bet that you're good to go. After you've been doing it a while you can detect really minute wire edges, or even anticipate when one's just forming, but for the sake of a few extra strokes why take the gamble? If you start getting tear out or fuzziness, or you're sweating like a pig even with a waxed sole, then it's time to sharpen!

Good points.

I find the reflected light trick is very useful on gouges, where you don't have contact all the way along the edge on the stone because you have to roll the tool, esp with old tools that need a lot of work. And as you said, if you can feel the wire edge and then remove it, the edge should be sharp!

 

[lurker]

Maybe if you stop theorising and start doing, you will quickly learn to "know" when the edge is correctly sharp for the task in hand.

I have never used any test beyond feeling for a wire edge, as the sharpening task develops

 

[rosinante]

Using the tool to cut wood would be the best test, if it cuts its sharp and when it doesn't it's blunt, after all that's what you want isn't it, no Zen required
Chris

 

[MIGNAL]

I mount the blade in a vice, edge pointing towards the ceiling. I then throw a ribbon of silk into the air and when it lands on the blades edge it should cut it into two.
Works for me.

 

[ED65]

...I then throw a ribbon of silk into the air and when it lands on the blades edge it should cut it into two.

Despite the tales that doesn't even work with a Japanese sword

 

[MIGNAL]

. . . it was worth a try.

 

[Phil Pascoe]

Yeah ... :lol:

 

[Aggrajag]

It works with lightsabers though :roll: #-o

 

[YorkshireMartin]

Wire edge it is then. Cheers.