Sharpening advice....

Kitchen Knife Forums

Help Support Kitchen Knife Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Zwiefel

Senior Member
Joined
Jul 22, 2012
Messages
3,294
Reaction score
6
got a couple of knives in from a friend to sharpen/repair.....they're in rough shape....here's a sample:

8484391028_1a7c9eddae.jpg


So I have a couple of questions...

1) last time I worked on a broken tip, everyone said to work from the spine down. How does one do that w/o creating a bevel on the spine? Grind the knife against the stone perpendicular to the stone? Would this be a good task for the steel flattening plate (#150)?

2) What's the best way to get those massive chips out? Something similar to the spine? (grind it perpendicularly on the flattening plate)

Any other thoughts? (I don't know the details of the abuse that led to this...)

I can't quite make out the brand....here's the best photo I could get of the maker's mark:

8483296481_55ae58ec16_z.jpg


TIA!
Z
 
It's a Shun, most likely vg-10. Just put tip of the spine down on a diamond plate and start pushing and pulling away and towards yourself until the spine reaches the edge or is about 1mm away. Then just start on a low grit stone and sharpen as usual until the chips are mostly gone. Move up to a 1k stone and just sharpen as regular up to 5k then strop.

You can even take a magic marker and draw on the knife the new curve down to the edge as a template to follow. You kind of have to start back a bit to keep the tip natural looking.
 
For both spine and edge I would use automotive sandpaper, grit P120, 90 degree with the spine. With the edge, I would suggest an edge trailing motion under some 80 degree.
 
the problem with fixing the tip by grinding down the spine is are you not going to completely change the look of the knife with a very triangular tip? Or is that just something you have to accept if you break off a tip?
 
the problem with fixing the tip by grinding down the spine is are you not going to completely change the look of the knife with a very triangular tip? Or is that just something you have to accept if you break off a tip?

You gotta blend it in, which means grinding quite far back from the tip as well
 
the problem with fixing the tip by grinding down the spine is are you not going to completely change the look of the knife with a very triangular tip? Or is that just something you have to accept if you break off a tip?

My knives don't look like that and I've broken many a tip. You just have to start back far enough to make it blend naturally. In this particular case I would start about halfway back in the first image shown.

fix tip 1.jpg
 
That's what I thought. I did it once on a cheap knife with a belt grinder before. It worked and fast but looked funny afterwards. As far as the chips though I also used my grinder before perpendicular then thinned the edge back out. Worked quite well and put actual edge on with stones. That was easy. Fixing a tip takes a lot more skill.
 
Here's a little bit better idea of what needs removal. Still this is by no means exact but a basic guideline.

fix tip 2.jpg

It is a good bit of removal still but keeps the profile basically the same.
 
Thanks guys...I'll think on it and give it a go next weekend....will be interesting to use the diamond plate in this way.
 
That line actually helps a lot. I know it's not my thread but thanks. That's helpful when I have to do this eventually
 
Here's a little bit better idea of what needs removal. Still this is by no means exact but a basic guideline.

View attachment 13383

It is a good bit of removal still but keeps the profile basically the same.

I didn't see these graphics before...very helpful, thanks Rick!

Any thoughts on the suggestion of a Kiritsuke tip?
 
I've done a few tips, but nothing nearly as bad as this. So, here is a question for you all. Would it be better to fix the bevel and take out the large chips before even trying to fix the tip by grinding the spine? It seems that it would make it easier, at least for me, to see what the final shape would end up as. Or would it be better to switch back and forth as you work, sort of making the 2 meet in the middle?

Thanks,
Chris
 
I didn't see these graphics before...very helpful, thanks Rick!

Any thoughts on the suggestion of a Kiritsuke tip?


My old shun is fairly thick toward the spine, affording it quite a small amount of tip flex and a large amount of toughness. Turning this into a kiritsuke tip would require you to take all the stability away from the new formed tip by grinding the spine down to meet the thin bevel. If this person already broke off the "thicker" tip, imagine what he would do to a kiritsuke tip.
Just my thought, but I will defer to those with more knowledge than myself.

Regards,
Chris
 
Z,

The 0701 pictured is shun's version of a petty, 150mm. I own one just like it - without the chips. The only thing mine does well is trim silverskin from beef and pork loins. Being stainless I also use it on citrus and tomatoes if I don't have a knife handy. A new one is 100 bucks from amazon.

That said I would pass on the repair unless you're looking for a project. It would require way too much time and stone wear for a knife that at best would have limited application.

Regards,

Dave
 
Turning this into a kiritsuke tip would require you to take all the stability away from the new formed tip by grinding the spine down to meet the thin bevel. If this person already broke off the "thicker" tip, imagine what he would do to a kiritsuke tip.
One of the advantages of a kiritsuke tip - beside simplicity and edge saving - is its strength. It's a easy way to at least double the angle between spine and edge. The old angle was probably some 20-30 degree, I would put a 60 degree kiritsuke tip on it.
 
Can you explain the logic/geometry to me? The only kiritsuke style gyuto I have is a Yoshikane. It has a much thinner tip than its "Standard" Shaped counterpart.

Thanks in advance

Chris
 
As always, it depends. You may have a kiritsuke tip of 30 degree, or one of 70 degree. A kiritsuke tip is not stronger or weaker than another one. I gave a few other reasons, but I can't agree, if one states a kiritsuke tip is weaker in se.
 
I want to know what the heck he used it for. Was he cutting rocks? I know the shun knives are fragile with regards to this but I've never seen such a mess
 
I've done a few tips, but nothing nearly as bad as this. So, here is a question for you all. Would it be better to fix the bevel and take out the large chips before even trying to fix the tip by grinding the spine? It seems that it would make it easier, at least for me, to see what the final shape would end up as. Or would it be better to switch back and forth as you work, sort of making the 2 meet in the middle?

Thanks,
Chris


Grind the spine down till it almost hits the edge that way when you start removing from the edge you can make the two meet. This way you lose less steel from the spine. Barely. But it's a bit easier since you don't have to take the thicker spine all the way down.
 
It would require way too much time and stone wear for a knife that at best would have limited application.

Not with a diamond plate or belt grinder. :biggrin:
 
i would use a dremel tool. cut it down to the desired shape. would only take 15 minutes to cut it down. then just sharpening it up and rounding down the edges on the new spine.
 
ive done this twice. once with dmt 325 and shapton pro 220 and 320, which took like 5 hours. once with a belt sander, took like 30 mins. shaptons were ruined 4-5 mm and needed serious lapping afterwards, which took at least another hour with 400 grit silicon carbid. even with dmt coarse its a pain in the ass. i wouldnt do it again, especially not if i wouldnt get paid for it...
 
even an angle grinder, a vice and water to cool the blade down would work faster.
 
I also this you should use sandpaper for fixing this knife. Maybe so much work will wear on your expensive diamond plate and also I agree about it is not the best knife to wear your equipment with. Tell us after how this goes!
 
That said I would pass on the repair unless you're looking for a project. It would require way too much time and stone wear for a knife that at best would have limited application.


Not with a diamond plate or belt grinder. :biggrin:


I know this anathema to some here but the best possible outcome of such a repair (on this knife) is a well polished turd. :biggrin:

Wrap it and round file it.

Regards,
 
Yeah, I'd have a hard time investing much sweat, time, or wear on my sharpening equipment on this one.
 
Back
Top