What makes a FFG so difficult?

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Nov 15, 2014
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Hello, Bladesmiths:

I am soon going to make a few kitchen knives and plan on doing full flat grinds. I've read a lot of comments on forums about FFGs being difficult, but haven't seen anyone say why they are so difficult. I'd love to know before I get started, and would also appreciate any tips. Thanks!
 
It is mostly a situation of needing lots of practice. Once you get it down pat, you can pull a blade across the platen in one smooth stroke with no variations.

If you grind horizontally with a plunge you can have problems with dips and high/low spots. I grind the blade bevels rough horizontally, and finish vertically. I don't use a plunge line on most kitchen blades.
 
It is mostly a situation of needing lots of practice. Once you get it down pat, you can pull a blade across the platen in one smooth stroke with no variations.

If you grind horizontally with a plunge you can have problems with dips and high/low spots. I grind the blade bevels rough horizontally, and finish vertically. I don't use a plunge line on most kitchen blades.

That actually answers my next question. I'd rather not have a plunge line, so if I'm understanding you correctly, I can eliminate it by grinding vertically after the FFG is in place.
 
That actually answers my next question. I'd rather not have a plunge line, so if I'm understanding you correctly, I can eliminate it by grinding vertically after the FFG is in place.
What I do on plungeless kitchen knives is get the bevels where I want them diagonally on the flat platen. I don't do a FFG really, rather the plunge runs at about a 30° angle to the spine. The picture below shows what I mean. P_20170602_232321_vHDR_Auto.jpg

Once this is set up to 220, I switch to a 12" wheel and trizacts and blend the plunge in grinding vertical. I used to do this on the flat platen vertically, but I much prefer the wheel. Remember, I'm not removing a lot of metal, just blending the plunge and refining the finish/ scratch pattern. P_20170609_113421_vHDR_Auto.jpg
 
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What I do on plungeless kitchen knives is get the bevels where I want them diagonally on the flat platen. I don't do a FFG really, rather the plunge runs at about a 30° angle to the spine. The picture below shows what I mean. View attachment 763323

Once this is set up to 220, I switch to a 12" wheel and trizacts and blend the plunge in grinding vertical. I used to do this on the flat platen vertically, but I much prefer the wheel. Remember, I'm not removing a lot of metal, just blending the plunge and refining the finish/ scratch pattern. View attachment 763324
Thank you for the response and for showing me your blades. Nice grinds. I have a low-budget shop and grind my blades on a 2x42 Craftsman, so the grinding wheel is not an option. Still, I think I can make it work. At what angle do you grind the blades?
 
The stock is .91" thick, the edge is a hair shy of zero. I don't know the angle, and since it's flat to the spine, it's immaterial anyway.
 
The stock is .91" thick, the edge is a hair shy of zero. I don't know the angle, and since it's flat to the spine, it's immaterial anyway.
When you switch to grinding vertically, I assume you have to be careful not to get into the area where the scales will go? In order to keep it flat there?
 
When you switch to grinding vertically, I assume you have to be careful not to get into the area where the scales will go? In order to keep it flat there?
That is correct. This is one reason I grind the bevels in at an angle. You can see in the picture, that the grind on the edge side of the blade, near the scales does not go into the scale area. After I have blended the plunge and gotten the finish to where I want (the progression i most use at this stage is- Trizact Gator A100, A160, A45, A30, fine scotchbrite), I then do a final grind on the flats of the tang (using a welding magnet on the flat platen, held vertical) to ENSURE that the tang area where the scales will go is dead flat. Then I will do a light vertical grind on the wheel with a fine scotchbrite belt to blend in the pattern, but not change the flatness of the tang. I have found that this leaves a nearly undetectable plunge (to the eye anyway, I can feel it with my hands, but I most likely wouldn't even be able to do that, unless I knew what I was looking for), while the scales fit with no gaps. I really prefer a plungeless kitchen knife. I know it adds nothing to the function, I just think it looks "right". Of course you can skip all of this if you go with a "Japanese" mindset and grind the whole bevel horizontal, and just don't take it higher than the tang. Of course, that's not an FFG, but I hear the Japanese are no slouch at cutlery.
 
If you make many kitchen knives for sale, you'll hear folks grumble about food release with FFG. It cuts well and can be made laser thin, but food will stay on the blade. The next step in chef knives is modifying your geometry, while keeping it suitably thin, to promote food release. This can be a mild convexity near the edge, or other ways such as S grind bevels or centerline grinds. I personally don't much mind how FFG performs, after all it's what a person generally finds on knives when learning to cook. Just thought I'd throw that out there.
FFG is not too hard though. The key is to rough it in with sharp belts. That makes it WAY easier. So does using a push stick with a notch to hold the blade. I make a push stick for chef knives wide enough to support most or all of the width of the bevel, i.e. two inches tall.
No ricasso is, I believe, a preferable way to go- especially since a properly thin blade will have very little steel in it at the point of the plunge, to afford a defined line without significant effort. And then, the only reason to go to the trouble is if one likes a plunge cut visually, which I often find to be a holdover from non-kitchen fixed blades, when a maker first transitions to food knives. I find blending the area at what would be the plunge to be almost an afterthought on many blades, since the difference in thickness is pretty minimal there anyway.
My suggestion would be, to FFG down to an edge of .040" or so, and then heat treat... then, given a 2" wide chef, lightly convex the lower 5/8" or so of the bevel near the edge, down to .005" before sharpening. This should cut very well but promote food release by causing slices to flex just a bit when riding up the bevel from being cut.
 
Kevin, would you mind showing a photo after you blend the grind with vertical on 12" wheel? How far back toward bolster area you go for instance.

Salem, I like the idea of blending the last 5/8" in a convex grind - I think I'll try that on the next knife.

This is a GREAT thread - thanks to all for ideas and suggestions.

Ken H>
 
the knife in my signature is done this way. except for scales, that's what it looks like after it's blended. No plunge.
 
Kevin, would you mind showing a photo after you blend the grind with vertical on 12" wheel? How far back toward bolster area you go for instance.

Salem, I like the idea of blending the last 5/8" in a convex grind - I think I'll try that on the next knife.

This is a GREAT thread - thanks to all for ideas and suggestions.

Ken H>
so pretty much this.

P_20170609_143158_vHDR_Auto (1).jpg
 
Well, you don't even see where the vertical grind marks meet the bolster - they just blend in it looks like. Looks good - I will be trying that on the petty chef I'm working on now. Thanks..

Ken H>
 
Well, you don't even see where the vertical grind marks meet the bolster - they just blend in it looks like. Looks good - I will be trying that on the petty chef I'm working on now. Thanks..

Ken H>
let me know how it works out. The trick is not trying to remove a lot of material when blending. You are just blending and getting the scratch pattern uniform. All the surfaces up to this point should be flat on their own planes. since, as Salem pointed out, the low amount of thickness removed, spread over the relatively large surface means there shouldn't be a ton of transition to begin with.
 
oh, forgot to mention, if you use a wheel, as I do, take care not to stop when you are grinding. I make light even passes from the butt of the blade to tip, keeping consistent speed and pressure. Otherwise, you can create perceptible divots in the flats. If you've ever refinished a hard wood floor with a drum sander, you know exactly what I'm talking about.
 
You are so right Kevin about not stopping at ANY point when vertical grinding on a wheel! Lift before stopping for sure. Your method does work good, I just finished a blade today. It's a 5" petty chef ready for handles, then final sharpening. I think this method works very good. The final test will be with completed knife tested with slicing.

Ken H>
 
Salem thanks for the insight. I've been on the convexing wagon for a while now. I've been taking mine to maybe .12 before convexing. I'll try some a little thicker to see how that affects food release. Darn taters!
 
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