How do you know when your knife needs attention?

[Windscale]

Hi all,

Looking for some knife care advice. There's lots of advice around about sharpening a knife, but for someone with little experience, can anyone explain how you can tell when your knife needs attention and what sort of attention is the right thing to do? I'm currently getting to grips with a Mora Companion Heavy Duty (didn't see any point in ruining something expensive I know you wouldn't want to do the full regrind everyday - you'd quickly run out of knife, but are there any "indicators" of various levels of current sharpeness and the best thing to do at that point?

I currently have a leather strop + honing compound and a combination aluminium oxide stone. I have waterstones but saving those for something worthwhile + when I have some sort of clue .

Regards,
Windscale.

 

[Robson Valley]

Same as for wood carving gouges and the like.

You need a small, very bright light and for old eyes like mine, a 10X loupe magnifier is good, too.

Consider that a very sharp edge is sort of zero wide, there's really nothing at a sharp edge to reflect light.
However, if your edge has hit something very hard, the edge will crush/fold to make a wee flat spot.
This is plenty big enough to reflect a spot of light. I call these things "sparks" of light.

So, hold the knife edge up to the light, rotate the blade a little as you examine the edge.
See any sparks? Big? Little? Just a few? Lots of them? These are the crushed bits of edge that make you sense that the edge is "dull."
Worse than that, experience now becomes your judge to decide what grit to select for a starter.

If I have a blade or chisel with lots of sparks, I'll begin with a dozen passes on 600 grit (sand paper stuck to a flat surface with masking tape.)
Holding my arms against my sides, I'll sharpen with pull strokes, moving from my knees, NOT my arms = I am the jig. Pull, lift straight up, back to start, down, again.
Make, say, 10 passes and examine with the light again. More or move on to 800? Then I do 1000 then 1500 then hone on box card with CrOx/AlOx.

Trick: paint the bevel with black felt marker. Makes it really easy to see if you're doing the whole edge, etc.

 

[Nice65]

Tomato test? Peppers, toms, and chillis have tough skins. If your knife slides through, then it's sharp.

Is your leather strop glued to a block of hardwood? And are you sharpening a Scandi ground blade? As a Mora I assume it is.

 

[santaman2000]

If it's cutting poorly, it's dull. If it's cutting well, it's sharp.

 

[Robson Valley]

One rarely mentioned fact is the actual bevel angle. Yes, my bone cleaver is sharp at 40 degrees, total included bevel. Yes, my serrated Henkel tomato knife is sharp at 12 degrees.
My other three cleavers are each about 15 degrees. Most top quality wood carving gouges are 20 degrees (Pfeil, Ashley Iles, Hernry Taylor, Hans Karlsson, etc).
Wood working skews (#2/12 in the London Pattern Book) are great at 25 degrees but for a push by hand, scrub them back to 20.
Stanley Bailey plane irons are 30, spokeshaves are 28, and the list goes on. Those edges are all "sharp" and they can cut you quite badly.

I have a 3" Kershaw folder so old it was made in the US. For campsite activities of all kinds, I like 25 degrees.
The value is to have enough steel behind the edge for the expected service. That's the point to consider.

 

[Leshy]

A blunt or dull edge is a dangerous edge.
I would prioritise having it razor sharp.

A good examination of your edge will reveal , if there are bright spots or "dings" that need to be sharpened.


Other than that, strop your knife regularly ....


If you are having to use quite a bit of force when using your knife on any wood ... then it's time to sharpen .
Don't be tempted to just push harder on the blade , as it will slip and hurt.
Take a pause, sharpen up and strop.

Plenty of videos on YouTube about that ...


The paper test also helps establish if some parts of your edge are duller than others ..
I hold my knife so that the handle end of the edge is on the paper's edge , and pull the knife back thus cutting the papers edge continuosly with the whole length of the blade.

When the blade hesitates or stops cutting , then that spot on the blade needs attention..


If you're not an OCD honing freak like me, Then just use the damn thing and sharpen it best as you can after each outing...

That'll do...
😊

 

[Robson Valley]

We've explained how to find dull spots = sparks under a bright light.
There are at least 5 or 6 different techniques for sharpening fine knives and carving tools.
They all work just fine. You have to pick one and learn how to do it.
I don't carve fingers, paper or chest hair, I carve wood. I test edges in the woods that I carve.
I see that many BCUK members do the same.
Blades alone, some of my carving tools are $100+ and the hafting is up to me.

It's a lot of fun, there's some craftsmanship and a boat-load of frustration to get it right.
Don't ever feel discouraged if you don't get a good edge the first time out.
a) it's only a chunk of steel
b) tomorrow is another day.

 

[Muskett]

Depending on what you are cutting and the intended use for the blade design style and grind dictates the cutting angles. The keener the less metal behind the edge, the higher angle and the more. More metal means the edge will handle more forces behind it without sustaining damage. The trick is to match it all so the edge holds up to a good amount of use before needing attention, whilst still giving the cut demanded.

An edge that keeps picking up damage is probably too keen for what its taking on. Certainly a very keen edge doesn't like hitting stone.

Most of us like a smooth edge with no folds or nicks in it. Some users take any damage straight to the the honing stone to remove. Others put up with some for a while and then sort it all out with a full sharpen. Depends how much time you have.
Best if you do a little often. For every full sharpen then ten realignments, gentle strop, or wipes over a ceramic, should be done. Let big damage build up then the job is a full sharpen right back into the grind which means taking off a lot of material all at once. Damage encourages deeper damage.
Reprofiling into the grind to get the desired edge has to be done at some stage. After a lot of wear, a ;pt of sharpening, the blade loses material and the edge moves higher into the grind. The higher into the grind the thicker it is behind the edge. Therefpr o get the original profile means grinding back into the grind to get something like the original. Unlikely to happen or be required for a good few years unless a used day in day out.

There is quite a lot to it.
I do maintenance when my edges don't slice paper keenly and I can find a flaw with my thumb nail. I probably over sharpen. I like my edges to slice tomatos, and my axe can do that.
But a blade only needs to be sharp enough so sharpen when its not doing what you want it to. Most is maintenance to keep it in tip top condition.
Here is a ding in my Skrama, it hit an iron bar so not a fault with the knife. Now I will stabalise the damage but for this tool I won't take it all out immediately. I could but its not a huge issue for this type tool. Might take ten full sharpens to go, which might be in a few years work as this blade can take the punishment and only occasionally need a touch up.
On a different knife then I wouldn't tolerate such damage and would take if out straight away.

 

[Janne]

I think that a small ding or two does not matter for a knife that is used on wood.
I have a handful of knives that are used on preparing fish and those I like to have a perfect edge.

 

[Windscale]

Thanks for the feedback folks. I'll have a critical look at the edge this weekend and see what works.

 

[Amy Turner]

Look for spots, take the tomato test ….don’t over sharpen it

 

[Janne]

Look for spots, take the tomato test ….don’t over sharpen it

If you use the blade for whittling or cutting wood you do need it is sharp as that.

 

[Robson Valley]

"Carving Sharp" is a concept which is particularly valuable when working in soft woods.
Hand work with gouges, you will gain the experience to actually feel the edge "going away" in about 30-45 minutes steady work.
You will experience the sudden change after no more than half a dozen honing strokes on the strop. That's all it takes.

For tomatoes, some measure of fine serration is valuable for cutting the heavy cuticle and underlying multiple layers of epidermal cells.
My kitchen knives range from flint flakes through $8.00 asian cleavers to $100+ Porsche (gifts).
None are carving sharp as that's not their service. All the same, I still inspect them with a bright light.

 

[GGTBod]

Only way i can explain how i know a knife needs some attention is i sense it, nothing magic, when you use the same knives a lot you get a feel for how they move through materials and when this flow through the materials changes you feel it through your hands as you make cuts, my pleasure in the fluidity of the cuts diminishes and to bring it back i need to give my edge some attention