Hand sanding a convex grind on a kitchen knife

[Sean Jones]

I have a 8 inch chef knife that I've done my first convex grind on. And it appears to have turned out OK before hand sanding. However I don't know how to hand sand a convex shape.

So how does one put a nice hand sand finish on a convex blade?

 

[Bruce McLeish]

S-L-O-W-L-Y

 

[J. Doyle]

Do your final finish on your last grit with straight pulls with a flexible backed sanding stick.

Use a hard stick but backed with something a little bit spongy/flexible like leather, hard felt or rubber. I personally like the synthetic rubberized cork gasket material you can get at an auto parts store.

 

[Sean Jones]

Do your final finish on your last grit with straight pulls with a flexible backed sanding stick.

Use a hard stick but backed with something a little bit spongy/flexible like leather, hard felt or rubber. I personally like the synthetic rubberized cork gasket material you can get at an auto parts store.

Thanks John

 

[fitzo]

I use pink rubber erasers to conform to hollow grinds. Fits 1" shop roll great. Same idea should work on a convex, though you might want a larger substrate. Perhaps something like a piece of crepe sole.

 

[Edwardshandmadeknives]

I really like using a rubber sanding block. It kind of depends how much of a convex you have. If I’m doing one that is nearly flat, I use leather backing on a piece of wood.

 

[Taz575]

Like others have said, do leather, rubber or really hard felt or cork. You can use something hard like micarta to get the first hand rub down at a lower grit to remove all of the belt sander scratches and then move to the material with a little give to it once the deep scratches are gone. I found a firm camo eva foam fishing rod grip worked well to smooth out a S grind with a hollow from a 36" radius platen and a convexed blade road.

 

[Sean Jones]

Thanks guys. I need to do a little more clean up on the grinder and then I'll most likely go to leather. I'll post some pics when I've made some more progress.

 

[Taz575]

Get some F3 firmness felt onto a platen. Gives a great convex and helps blend scratches and preps for a hand rub. You can go to leather as well. Hermes green flexible ceramics in 120 and 220, then Norax A45 and A30 works pretty well to prep for a hand rub. I did a 245mm S grind gyuto to a nice 800 hand rub in under 2 hours off the belt sander.

 

[mike miller]

I follow Fritzo's method of sanding.

 

[Smallshop]

I use a hard back with used skotchbrite between the paper and backer. Clean the slotchbrite with the air hose...

 

[jmforge]

I am old and crotchety, but I took the advice of Dr. Jim Lucie at the 2007 pr 2008 Batson's hammer in IIRC and bought one of those 3M rubber sanding blocks for hand sanding. Remember also that if you have trouble hand sanding that convex grind, it may be TOO convex. Many that I have seen over the years are. You see some where the spine is thinner that the blade bevel a bit below it. Slack belt is generally too slack for the entire width of the blade.

 

[Sean Jones]

I am old and crotchety, but I took the advice of Dr. Jim Lucie at the 2007 pr 2008 Batson's hammer in IIRC and bought one of those 3M rubber sanding blocks for hand sanding. Remember also that if you have trouble hand sanding that convex grind, it may be TOO convex. Many that I have seen over the years are. You see some where the spine is thinner that the blade bevel a bit below it. Slack belt is generally too slack for the entire width of the blade.

Yep. I think mine is a little more convex than I'd like. I'm being careful not to sand the spine too much. So far so good. I'll post some pictures when I'm further along.

 

[Taz575]

Try firm felt like F3 on a metal platen. It lets you push into it to get a convex, but not thin out the spine too much.

 

[Sean Jones]

Try firm felt like F3 on a metal platen. It lets you push into it to get a convex, but not thin out the spine too much.

Thanks Taz. Right now I have leather available so that's what I'm using currently. But I intend to try your method in the near future.

 

[Taz575]

Felt gives a nicer convex than leather. I got the F3 on amazon, 1/4" thick. Or do scotchbrite under the leather.

 

[jmforge]

Yep. I think mine is a little more convex than I'd like. I'm being careful not to sand the spine too much. So far so good. I'll post some pictures when I'm further along.

Sean, I had the opportunity to talk with Bill Moran a couple of times in 2005 right before he passed including a nice talk at the Little Washington Hammer In where I showed him an early attempt as a rough ground blade in his style. He was very kind in critiquing it and said that I got slightly more intially right than wrong. LOL. He is the one who told we that slack belt it too slack. He told me that he did convex grinds like the Japanese sword makers in that he would grind a series of small flats and then blend them. Of course, he rough ground vertically on a big emery wheel to save money on belts. LOL A rotary plaen is better tna a slack belt IMO even if you are just doing a convexed edge.

 

[Sean Jones]

Sean, I had the opportunity to talk with Bill Moran a couple of times in 2005 right before he passed including a nice talk at the Little Washington Hammer In where I showed him an early attempt as a rough ground blade in his style. He was very kind in critiquing it and said that I got slightly more intially right than wrong. LOL. He is the one who told we that slack belt it too slack. He told me that he did convex grinds like the Japanese sword makers in that he would grind a series of small flats and then blend them. Of course, he rough ground vertically on a big emery wheel to save money on belts. LOL A rotary plaen is better tna a slack belt IMO even if you are just doing a convexed edge.

Thanks for the reply. I actually started with a flat grind at 5 degrees and then one at 3 degrees and then blended on a somewhat slack belt. By that I mean I used the top area close to the wheel on my flat platen. It appears to have worked, but it's left me with a lot of hand sanding doing it this way. In the future if I use a flat grind initially, I plan on doing more. As in 5, then 4, then 3 and so on. Or as close as I can approximate it.

I should add that I use a Bubble Jig to establish my grinds initially.

 

[jmforge]

Thanks for the reply. I actually started with a flat grind at 5 degrees and then one at 3 degrees and then blended on a somewhat slack belt. By that I mean I used the top area close to the wheel on my flat platen. It appears to have worked, but it's left me with a lot of hand sanding doing it this way. In the future if I use a flat grind initially, I plan on doing more. As in 5, then 4, then 3 and so on. Or as close as I can approximate it.

I should add that I use a Bubble Jig to establish my grinds initially.

You always have to do a lot of hand sanding. I do those multiple grinds when doing an S grind. Shallow flat, deeper flat, shallow hollow. convex then blend it all together by hand until bone is showing.I will say that with the S grind, I am even more firm in my belief that if you don't have to use a business card laid on edge acorss the blade to really see it, it is too extreme. LOL Want to see an S grind? Can't really tell even from that angle, can you? And yes, that is a hand rubbed finish on through hardened DH III W2, not a buffer mirror polish.

Corrected: This knife has an S grind, not a convex grind.

 

[Taz575]

Not the best pic, but 800 grit hand rub on a 245mm S grind gyuto. Took about an hour each side working 220 up to 800. I went to a A30 micron belt on my belt sander before hand rubbing. My radius platen has leather facing on it and the convex portion was on F3 felt. It was pretty easy hand sanding, maybe 15-20 min per side at 220? I used a piece of home made micarta cut the match the radius platen for the 220 grit step on yhw hollow portion and hard micarta and a hard cork block for the convex portion to blend the convex. 600 and 800 grits were using a foam fishing rod grip and it was able to get into the hollow and convex at the same time. I was shocked at how quickly it went!