Odd thing about my penknife.

[KIMBOKO]

When I moved into our present hopse I found a folding knife. It is marked 1147 Solingen at the base of the blade and c. lutters &cie with a lying lion on the other. As its below 3 inch in blade length and not a lock knife I believe it should be alright for an every day carry.
So I had ago at sharpening it and it seems to have to be excellent. I used various grades of abrasives with mousemat to sharpen and slightly convex the edge. I have since stropped it on a leather belt to keep it finely honed. It will cut the hairs off my arm, and I have no proplem in finely shaving green wood into Gypsey flowers so all in all I think it a fine tool.
Except when I took it to some tomatoes. Instead of deftly cutting through the tomatoes, it tends to press down on the skins without pieceing. A sawing action doesn't dramatically help either.
I'm not saying that it doesn't cut, just that I need to apply more pressure than I would have expected, considering how well its can cut my arm hair and wood.
I don't have a problem with my steel sharpened kitchen knife. So why is that?.
Any answers appreciated.

 

[bikething]

That's tomatoes for you

somethings like tomatoes / bread / juicy fruits cut better with a serated edge whilst others like meat, some woods, etc work better with a smooth straight edge.

One trick with tomatoes is to use the point of your knnife to puncture the skin first to provide a start to your cut

Cheers

Steve

 

[Bardster]

I am sure there will be a more expert statement along soon but i will have a go
You have discovered the great thing about knives - takes a different edge to do a different job
Because you have honed/stropped the edge you have created a polished edge, which as you have found creates a hair popping sharp edge - but - to cut things that are also smooth.polished, like tomato skin or modern ropes you need a serrated edge. It doesnt have to be grossly serated like you see on the half and half knives. if you had left the edge after say 400grit then you would probably find it fine for tomatoes. if at that point you look at it under magnification you would see a very finely serated edge. if you then strop and look you will see a polished edge with even finer or no serations (depend upon mag level)
Your steel sharpened kitchen knife woill not have a polished edge - therefore cuts tomatoes fine.

hope that helps

 

[mark a.]

It's probably very simple - your knife isn't sharp enough. Knife shops use ripe tomatoes for testing, as they're notoriously tricky to cut unless you have a really sharp knife.

Hairs on your arms are actually relatively easy to cut (as they're so thin and soft).

 

[jdlenton]

Bikething and Bardster beet me too it but I typed this so I’ll post it



From what you say you have a super sharp smooth blade which will shave your arm hair and carve wood well but bounces of a tomato. I’ve seen this before with very good sharp kitchen knives and the explanation I got was, to cut a tomato what you need are serrations on the blade either a serrated knife or micro serrations on your blade edge from a course sharpening medium to start to cut at the tomato skin once your through the initial cut of the skin any blade will do the job to prove this I’ve poked a slit in the skin with point of the knife and carried on cutting it works.



But what are we like talking about the technicalities of cutting tomatoes what next "what sort of edge does my melon baller need”

James

 

[Hoodoo]

I'm with Bardster on this one. Tomatoes are very elastic and trying to slice them with a highly pollished edge is often ineffective. That's why thin-bladed kitchen knives that have been sharpened by a steel are so effective. You have an edge with microserrations that easily tear into the skin and flesh of the elastic tomato.

Highly polished edges are great for pushcutting and chopping, but not all that good for slicing soft, elastic types of things.

 

[bikething]

I am sure there will be a more expert statement along soon

That's me told then

 

[leon-1]

The others have seemed to have covered it, the knife is sharp, but when it comes to tomatoes use the tip to get into them first.

If a knife is sharpened on a butchers steel you will find that the edge has micro serrations on it (have a look at a knife sharpened on a steel under a magnifying glass).

I have a knife at home here (D2 Gene Ingram model #30) that I can shave the hair on my face with and this is not baby fluff as people who know me can vouch for, but even this does not like cutting tomatoes.

Grind also comes into it, a lot of my kitchen knives are full flat grind and they will happily slice through tomatoes if sharpened using a steel and although they can take the hair off my arm, they are in no way capable of taking the hair off my chin.

Edit:

Doh, Hoodoo beat me to it

 

[KIMBOKO]

Thanks for those replies, its kind of what I thought, but hadn't seen it expressed before.

A second comment that I should have made is that I have cut Tomatoes and Apples and greenwood with this knife and I probably havn't completely cleaned it afterwards. I now seem to have minute grey/black spots on the polished edge. I assume its some acidic reaction from the fruit or wood. So I think I may need a lot more stropping or return to the abrasives to clean it up.
C'est la Vie!

 

[mark a.]

Perhaps you could test out the theories, then. Run the blade edge lightly along a sharpening steel to roughen up the edge a bit (or do it Ray Mears style and use a car window) and see if it makes a difference to your tomato chopping.

And perhaps I should try to see if my straight razor (well honed and stropped) is any good at chopping tomatoes!

 

[KIMBOKO]

It is just a thought but would the slight convexing of the edge give a greater surface area and hence reduce the pressure on the Tomatoe skin.
With the grey/black marks on the polished edge I feel I might have to resharpen so I might as well try out the experiment. Though I am certain that you are correct. Please don't go ruining a razor for the sake of this experiment.
I have a couple of old cut throats that I can try it out with.
Nick P

 

[Bardster]

That's me told then

hehe youo must have posted as i was typing - no refelection was meant on you - was self referencing

 

[Hoodoo]

Perhaps you could test out the theories, then. Run the blade edge lightly along a sharpening steel to roughen up the edge a bit (or do it Ray Mears style and use a car window) and see if it makes a difference to your tomato chopping.

And perhaps I should try to see if my straight razor (well honed and stropped) is any good at chopping tomatoes!

I don't think you will have any trouble slicing tomatoes with a razor, even if the edge is polished. Razors are so thin that they should penetrate the skin easily. As someone mentioned earlier, geometry plays a role as well.