How do you know when it's sharp enough?

[Nod]

It might sound like a daft question, but how can you tell when your knife is at the right level of "sharp".

I've always rubbed my thumb across the edge, but as I get older, the skins getting tougher and it's harder to tell.

I've seen people test by cutting paper, then oters have told me not to cut paper with my knife (why not? I cut wood with it?)

So, whats the best way you to tell that you've got a good edge on the blade?

 

[AntarcticFire]

Probably not the best way to check, but I tend to try and shave hair off of my arm.... if it shaves
nicely, then it's sharp enough.... :twisted:

 

[MartiniDave]

Looking at it is not a bad way.
Viewed from the cutting edge you should see 2 differently coloured surfaces with a crisp change of colours where the surfaces meet. You should not see a silver line between the 2, or the edge is dull.

Difficult to describe but I hope you catch my drift. Try using something like a brand new stanley blade or scalpel blade to give you a starting reference.

Dave

 

[Hoodoo]

If it does what you want it to do and holds an edge for an acceptable length of time, you've probably got it plenty sharp. If the knife is not working as well as you would like it to, either it's dull or needs reprofiling or both. For instance, when I'm using one of my whittlers, I can usually tell when the edge needs to be touched up by the way it's performing. The duller the knife, the harder I have to work. \:

 

[Stew]

... I tend to try and shave hair off of my arm.... :twisted:

Or your legs or someone else's head!

And occasionally he tries it with an axe too!
T:
:roll:

 

[faca]

For me is very easy.
Take a paper sheet and cut using all the knife edge from botton to the point and you can notice where the knife stop cutting clearly so this point must be sharped.
Enjoy

 

[Andy]

i use a light and check if there are any glints along the edge as martin then try a bit of shaving as well. the thing about not cutting paper it to do with the structer of paper i.e. it hasn't got a grain which wood of course does so has flesh things with a grain are much easier to cut and don't blunt your knife as much, having said that one piece of paper wont kill the edge

 

[Nod]

I tried shaving last night, all it did was push the hairs flat :-(

I've been at my waterstones for ages trying to get a proper flat grind on my WS Micarta. It feels sharp but I can still see a difference in the texture of the metal close to the edge, sort of what a secondary bevel looks like, but when I get the magnifying glass out, i can't see any difference in the shape, so I presume I must be getting close.

 

[Keith_Beef]

Find somebody who is alseep (hibernating, drunk, comatose, or otherwise drugged does not count).

If you can shave off his eyebrows without waking him up, you've got a sharp knife.


K.

 

[Shing]

Sharp is a complicated subject. It depends on the angle the edge was sharperned and the degree of finish on the knife.

An edge with a shallow angle like a Stanley knife blade will cut even when the edge is a little blunt. Compared to an edge with a more obtuse angle like an axe, even a little blunting will make it difficult to cut because there is more material to force through the cut.

The degree of finish will also determine how sharp a blade feels. A blade finished on a course grit will feel rougher and not as sharp but will easily cut meat, rope and veg because it have fine microscopic teeth but would find it difficult to shave hair. A blade finished on a fine grit then stroped will be as sharp as a razor and easily shave hair but could not cut rope as well or slice meat and veg as good.

I like a rougher edge on my kitchen knives because I use them to slice meat and veg but on my pocket and other knives I prefer a razor edge as I find they last longer and easy to maintain with a few strops.

A sharp knife with whatever the edge should be able to slice strips off a piece of paper held vertically.

 

[Shing]

I agree it is a strang knife that would not cut paper, perhaps the knights of old should have used paper rather than steel for armour.

 

[Hoodoo]

I tried shaving last night, all it did was push the hairs flat :-(

I've been at my waterstones for ages trying to get a proper flat grind on my WS Micarta. It feels sharp but I can still see a difference in the texture of the metal close to the edge, sort of what a secondary bevel looks like, but when I get the magnifying glass out, i can't see any difference in the shape, so I presume I must be getting close.

Sounds like you need to use a really coarse waterstone to get rid of that bevel. Like a 250. Otherwise, you will be at it for a long time. If you are sharpening the knife by laying the bevel flat on the stone, it will never get sharp until you get rid of that secondary bevel. That's a given. The alternative is to sharpen the seconday bevel. Five minutes or less on a sharpmaker will do that for ya, but you will decrease the knife's ability to carve wood, even if it will shave hair. It all depends on how you plan on using the knife. After you are done, be sure to strop the blade on some leather.

 

[Nod]

Ah.......I've been using an 800 as my rough stone, best get on the phone to Axminster Tools!!!

Are you sure 250 won't make my blade disappear before my very eyes?

 

[Doc]

Nod, you won't need the coarse grit very often, so why not use wet and dry paper for the serious metal removal - cheaper and works very well on a flat surface.

 

[Nod]

....so if I just tape the wet and dry onto something flat and level and pass the blade over in the same way I do on the stone, would that do it?

Can you get wet and dry paper from places like B&Q and Do It All etc?

 

[Hoodoo]

I agree with Doc that wet/dry sandpaper will work well. Save ya some money too. But I do enjoy using waterstones, especially because I have a Stone Pond which makes them easier to use and maintain.

http://www.leevalley.com/wood/page.asp?SID=&ccurrency=2&page=33027&category=1,43072,43071

But you can make a nice, flat "stone" for sharpening by using a block of wood with sandpaper.

The hone in the top left of the pic will do scandi grinds easily. I glued some leather on the backside for stropping. All you have to do is cut a piece of wood, put a slot in each end, mount the sandpaper with some wedges, and you are good to go. The bottom and top right hones are for sharpening convex edges. BTW, convexing the edge on a scandi grind ain't a bad way to go. I've done it often and it works well and might save ya some sharpening in the short term.

 

[gurushaun]

You'll probably find a bigger selection of grits at your local motor factors (used for rubbing down bodywork prior to painting), of your local car paint shop (look in Thompson/Yellow Pages).

Cheers

Shaun

 

[sargey]

you can get a pack of mixed grits from halfords for about four quid. you don't even need to tape it down, you can just soak the whole thing in water and it'll stick to pretty much anything flat, and peel off easier too.

a quick tip for holding sharpening / water stones still on the kitchen work top, is to put them on a sheet of folded over and soaked newspaper.

cheers, and.

 

[Andy]

or a piece of rubber say from a washing up glove, that makes less mess

 

[Adi007]

Don't try this at home ... especially if the misses is looking :-D :shock:

a quick tip for holding sharpening / water stones still on the kitchen work top, is to put them on a sheet of folded over and soaked newspaper.

cheers, and.