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Testing your edge

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Chris Knight

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I have finally started on carving practice - having finished chairs, a box for the carving tools and a carving super bench (where super = above, ie it sits on my regular bench! - to bring the carving surface to somewhere that does not kill my back) I have no more excuses and have started serious practice.

I have been quickly reminded of the lessons I learnt with Chris Pye on the sharpening of carving tools (for any carver, those lessons alone would be worth the price of the course!) and wondering what, if anything, could be applied to regular woodworking.

I offer the following observations:-

1. When sharpening a chisel, say, you should not be able to see the edge under a strong light and with magnification (I use an Anglepoise type lamp and an Optivisor magnifier ( http://xtronics.com/optivisor.htm ) to look at the edge. If you can see any, I repeat ANY light reflected from the edge it is not sharp.

2. If, running your finger or nail over the edge you can feel ANY roughness, it is not sharp.

3. Don't waste your arm hair, it is no test at all, you can cut that stuff with a lawnmower. Instead, cut a hard piece of wood a few times and repeat tests 1 and 2. This has the benefit of "consolidating" the edge and may well reveal weaknesses once tested as described above but will also strengthen the edge. Simply sharpen it again but taking off the minimum of metal.

4. When you think the edge is really sharp, cut a piece of wood like Lime (the carver's favourite) or Jelutong - a good second best, or Walnut at about 45 degrees across the grain and observe the result. If you see ANY scratching within the cut area, your blade is not sharp.

5. Do NOT rely on stropping to sharpen an edge that is revealed as less than perfect by the tests above - it won't work, you will simply round over the edge. Stropping- do this by hand- will make an edge that passes these tests into a gift from the gods.


I tested eight of my woodworking chisels with this method and whilst I could not see the edge of any of them( for 95% of the edge, slight slivers of light on the rest), only one passed the scratch test. I resharpened all so that they too passed and it made a world of difference to their paring ability.
 
G

Guest

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Thanks for the tips Chris, I'll try to achieve an edge when I sharpen my chisels. I have had a go at sharpening planer blades but I will try your test in future
Alan
 
A

Anonymous

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Thanks Chris

interesting and eye opening stuff :wink: I have never considered scraping the hair off of my arms to test a chisel edge but have also never had any idea how to really test them for sharpness. I usually sharpen until a burr appears and then break this off with no real idea of how good/bad the thing is

I think I may need to invest in a strop by the sound of it :D

Have fun with the carving and when you're ready show us some results :D
 

gidon

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Hi Chris

I only recently discovered the nail test - and find it works best for me. I have also read that the lower the angle you can ride your edge against your nail, the sharper tool. You can really check your progress this way. Works well for me - and I still have a little nail left!

I was also reading on the wreck the other day, that tools for carving shouldn't be too sharp?? Can that be true?

Cheers

Gidon
 

Chris Knight

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gidon":2saumyrf said:
I was also reading on the wreck the other day, that tools for carving shouldn't be too sharp?? Can that be true?
"Absolute pineapples" to coin a phrase! It is vital that they be sharp as possible and for me that is a lot sharper than I usually bother to get my woodworking chisels and far sharper than a razor blade - I kid you not!

Additionally carving chisels have to be carefully shaped with two bevels (an inner and outer in the case of gouges) this is a one time operation but very time consuming for me at the moment. Doing it all by hand except the initial grind on a dry (conventional) grindstone it takes me anything upto 2 hours depending on the size and shape of the tool. Thereafter, maintenance is basically a quick stropping on suitable shaped strops.
 

gidon

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Fair enough! Perhaps I read it wrong.

I think I'll stick to getting a decent edge on my flat blade tools!

Cheers

Gidon
 

tx2man

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Waterhead37 wrote
Absolute B*******
:shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock:
:shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock:
:shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock:
:shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock:
Chris, at least tell Gidon what you think :roll:

TX
 

tx2man

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I know Chris:wink:
It was just your eloquency of tongue that made me sit up :lol:

TX
 

gidon

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Too late for that now Chris, I've been sulking in the corner of my office since yesterday :wink:.
Cheers
Gidon
 
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