Global knives.....going off the boil

[Rob]

Hi folks

Had a bit of a head scratcher today.  You may recall from a thread about Japanese knives quite a while back that I had some global knives and I'd sharpened the main cooks knife on the Tormek and got good enough results.  Then on a daily or at least regular basis I just use a kitchen steel to keep the edge.

Well today I was doing my usual 5 or 6 passes/swipes on the steel and I noticed the edge went all crumbly/serrated on me.  Looking closely at it its really become quite jagged and is obviously going to need another proper sharpening on the T7 again (about a year after getting away with just a steel).

Anyone got an clue as to what on earth is going on? I've avoided dishwashing them although it has slipped through the net a few times when other people have stacked it.

None of the other knives have had this happen although the chefs knife is my go to knife and has had considerably more use than the others.

Any help to throw light on this would be gratefully received.

[jeffs55]

Sounds like the edge through constant honing has thinned to the point of destruction. I have trouble imagining the Global steel doing that but the proof is in the pudding. I know, it does sound ridiculous but what else could it be? I look forward to a knife wizard explaining this.

[Rob]

Thanks Jeff but just one point I didn't mention, its not a global steel just an ordinary common or garden variety that I've had for yonks.

I remember when I bought the knives I read the blurb about their special steels and then when I actually tried my old one it worked so thought no more about it.

[grepper]

It's frustrating when a knife won't take an edge!

Does it crumble along the entire length of the blade or just in a spot(s)?

What angle are you sharpening to?

What model of Global knife?

How hard does the steel seem?  Is it hard to remove much steel from the edge?

If you magnify the edge where the it has "crumbled", do you see any abnormalities in the steel?  Discoloration or non uniform surface?

Are the crumbled areas sharp triangular chips or more like, say, a rusted area?

I take it that the other knives that don't suffer this are of the same set?

[Jeff Farris]

A couple of scenarios come to mind. Someone else in the house who doesn't appreciate the knives as much as you may have used a hacking motion while you were paying attention to your turning. Or, there could have been a flaw in the steel at that particular point. There are probably dozens more that I just haven't thought of yet.

I've had this happen while using a steel. The same crumbling appearance, however that was a ceramic knife, so it may have no correlation at all.

I wouldn't be too concerned unless it happens again.

Just as aside to this discussion, I have a Global steel, which isn't a steel at all, but a ceramic rod in the shape of a butcher's steel. Personally, I'm rubbish with a conventional steel, but with the Global ceramic steel I can maintain an edge for months before needing to use the Tormek.

[grepper]

Can you post a picture, including a closeup of the "Global" stamping on both sides of the blade, and another of the handle?

How long have you had them?

As per my first question above, it may just be abnormalities in small spots in the steel, and you might just get through them as Jeff is suggesting.

[Rob]

Thanks for the input guys.  I wont be able to do piccys this time round cos we're taking the kids to Turkey for an Easter hol and I just don't have time. I remember reading about those ceramic "steels".  In fact the only reason I've been using my traditional butchers one is cos I was being a skinflint and not wanting to fork out the dosh for the posh global ones.

I think I'll just give them a tickle on the Tormek when we get back from abroad and see if they hold up for another year.  I have a sneaking suspicion that when we had the wake for my Mother (we had 18 to stay for 4 days), that some kindly family member may have dish washed at 65 deg or hacked something with it. So thanks Jeff....thanks to that seed you've planted I'm now going to accuse my entire family of abusing my property :-)

[Herman Trivilino]

Rob, any time I've seen that crumble on the edge it was with steel that was just not capable of holding an edge.  The only solution known to me is to sharpen them at a more blunt angle and dedicate them to low-level tasks such as digging in the garden. 

But seriously, I would pay closer attention to this one because you didn't notice the crumble until the knife had been used a year.  Sharpen it at the same angle as before.  If the edge holds, take a steel to it and see if it crumbles.  If the edge holds put the knife back in the kitchen and see how it goes.

It may be that some types of steel don't like to be sharpened with a steel.  I don't know, but when it comes to the performance of different kinds of steel, I've come to expect all sorts of weird behavior. Remarkable, really, how iron can be fashioned into so many different types of steel.

Just think how strange it is that you can use a steel file to remove material from a steel bolt!

[Rob]

you nearly had me for a moment 

I had visions of cutting root balls of weeds with the glint of the sun off my lovely globals, sacrilege!

I will treat them to a proper tormekking when back from hols.  Then I might have a gander at those ceramic "steels" as that might be the long term day to day solution.

[Herman Trivilino]

Or it may be that it's best to not use a steel on that type of knife.  My local sushi chef sharpens his knife daily using a stone.  It never touches a steel.

[grepper]

On this page, http://www.globalknives.uk.com/sharpening, Global proclaims:

"NOTE: DON'T use traditional steels made from other materials as they are likely to damage your Global knives."

Why, you may ask?  I wondered that myself.  Just to sell more of their own ceramic and diamond steels?

On Global's web site here, http://www.global-knife.com/global/index.html, they say:

"GLOBAL knives are made from the finest stainless steel material. The blades utilize CROMOVA 18 stainless steel, Ice tempered and hardened to Rockwell C56°-58°which holds a razor sharp edge longer than any other steel and resists rust, stains and corrosion."

It sounds a little boastful to say, "...holds a razor sharp edge longer than any other steel", but, oh well.

At Rc 56-58 they aren't all that super hard, so I would not expect them to be all that "chippy".  Maybe they think a traditional steel is a little to agressive?  Anyway, they say a regular steel may damage their knives.  Huh.

[Herman Trivilino]

Anyway, they say a regular steel may damage their knives.  Huh.

I have a gut feeling that that's the case.  Maybe the coarseness sets up some kind of vibration that chips the edge away.

[jeffs55]

The man has called his knives "Global" for reasons known but to him. They are not "Global brand" knives and so are not the same steel. See his response to my reply above.

[Rob]

Slightly confused by your response Jeff?  The knives are Global brand Japanese jobs ie expensive with posh knife holder etc. what I said isn't Global is the steel I've been sharpening them with

I read that blurb (was shipped with them) when I bought them (circa $400 for 5 knives). I then subsequently ignored that advice and didn't buy their proprietary ceramic "steel". For a whole year my cheap butchers steel has worked keeping the edge. Perhaps finally it's poor quality has knackered the edge and it's time to bite the bullet and get the more pricey ceramic thingy

[jeffs55]

I see now what you mean. I would have said honing steel but that is just me.  I took you to mean steel blades as made by Global Knife Co.