Sunday, July 24, 2016

Project #5 - 240 mm D2 gyuto

With first relative success with grinding smaller kitchen knife (see Project #3) I decided to give a 'full size' gyuto a try. This project proved to be very labor intensive, but I learned a lot as well. Even though it is a long article - do check out 'Lessons learned' at the end.


I have taken part in a pass-around organized by Dan Prednergast (via and loved the profile and grind of the blade and decided to use it as starting point for this knife.

Basic numbers
  • Japanese style kitchen knife (gyuto) with 240 mm cutting edge
  • 50 mm tall blade
  • Continuous convex grind
  • D2 steel
  • WA style handle

One of the challenges apart from the size (and thus long grinding times) was to get the grind of the knife as close to final prior to heat treatment as possible. The reason for that is - when I started to work on this knife I did not have a belt grinder yet (I got a small 1x30" while the project was ongoing) and I have learned already, that changing the grind (thinning) after heat treatment can easily take 5 - 10 hours with an Atoma 140 diamond plate and I wanted to keep that to minimum. Still - I would not grind the edge to zero thickness to minimize possible warping during the quench.

Making the blank

(I somehow did not take photos during this part of the process, sorry for that)

Once I was happy with the design I traced in on the steel. Since the steel was only 50 mm wide, the knife could not quite get the same width - I managed to get about 49 mm.

I have used a hack saw to cut out the blank. With knife this long it proved very helpful to be able to set the blade under 45° angle relative to the plane of the saw - so that the frame would clear from the blank itself. Still - it took me quite a while to cut the blank out - about an hour.

Tip: Do not use D2 steel for you first large knife - it is rather abrasion resistive and will make all cutting, grinding and sanding steps take longer. Simple carbon steel is the best way to go with hand ground knives. If you have a belt grinder this will be less of an issue.

Here I made a first mistake - I have cut little too much just few centimetres from the heel and it took me a lot if time afterwards to remove this mistake with a coarse file, since I had to file the whole cutting edge to preserve the designed profile.

I have left the tang considerably wider than what it would be once finished - the reason was to have better mechanical stability while grinding the bevels. I would only cut the tang to its final shape once the bevels were ground and then finish the surface of the whole knife before heat treat.

Once the blank was finished I have scribed a center line on both the spine and the cutting edge so that it would be easier to keep en eye on the left-right symmetry during the grinding.

Grinding the bevels with a jig

Since I had some lessons learned from the Project #3, I realized that I need to be more careful with the grinding angles. My idea to produce a more-less continuous convex grind (i.e. not a full flat grind which is not a good choice for kitchen knives in general) was to approximate the convex shape with 3 planes and blend them in a later stage.

The idea is represented with the figure below.

  1. grind -  should be done under such angle, that once the edge has the desired thickness, the bevel should at the same time have the desired width.
  2. grind - would push the bevel further up, but would stop about 5 mm from the edge
  3. grind - would push the bevel even more further up and stop about 10 mm from the edge.
Grinding strategy with the filing jig. Yellow line is the intended final blade geometry.
Not to scale :)

In the photo above:

d1 - 1/2 of the thickness of the edge prior to heat treat ~ 0.15 - 0.2 mm
d2 - 1/2 of the thickness 5 mm (w2) from the cutting edge prior to heat treat ~ 0.35 - 0.4 mm
d3 - 1/2 of the thickness 10 mm (w3) from the cutting edge ~ 0.6 - 0.65 mm
a1 - first grinding angle ~ 2.4°
a2 - first grinding angle ~ 1.6°
a3 - first grinding angle ~ 0.8°

The above strategy would, before following hand filing would be done, yield a rough approximation of the convex bevel AND would lay the base for the distal taper, because after the 3rd grind the bevels would hit the spine somewhere 1/2 way between the handle and the tip.

One needs to realize here that while you can calculate the approximate angle under which you want to grind the first bevel, it may not be practically possible to grind under that angle because you have flex in the system - the holder is made out of wood, the blank is long and thin, the file is attached to a long steel bar which will flex slightly under pressure (and thus will give you variation of the effective grinding angle). This means that one should keep checking the width of the bevel as the grinding proceeds and check whether it develops as expected. Now should you find out that your grinding angle is small or larger than planned (meaning you are getting to the designed width of the bevel but not the edge thickness or vice versa), than just adjust it, re-paint the ground part with a permanent marker and keep grinding.

Using an angle cube to set the angle for the first of the 3 grinding steps.

My calculation gave me angle of about 2.4° per side for the primary grind. Not that may sound very little, but one should not forget, that the edge will be left with thickness of some 0.3+ mm so there will be some more grinding happening after the heat treatment, so the angle will increase somewhat. For the second grind I have used angle of about 1.6° and about 0.8° for the third. Do not take these numbers as cast in stone - you may be after very different grind that what I am trying to do here. The grinding jig has also a finite stiffness, so these values really are just approximate.

About to start the grinding. I have marked the blade to see how the progress develops. Note the wide tang at this stage.
Tip: You will need a stop pin of some sort close to the tip of the blade, so the blade does not move during the grinding (you can not clamp the tip, obviously). I simply used a brass screw. Since brass is much softer than the steel, once the spine close to tip starts to get thinner during the grinding, the head of the screw will be ground too and not get in the way, while it will keep working as a stop pin.

While grinding I would recommend moving slowly from the heel to tip and then backwards. Observe the scratch pattern to see that you remove the material more-less evenly. This will become gradually harder as the ground surface gets wider. Keep switching hands as this is quite a work-out.

You will also experience the file 'skating' on the bevel. You can try to remedy that with changing where you apply the pressure with the hand that is not holding the handle of the file. Clean your file regularly from the steel pieces that get stuck to its surface as these will cause deep scratches.

Working on the first grind. The red area show the part that should be ground. The blue should stay.

Getting close to the final width of the primary grind.

Once you have finished the first grind on one side, flip the blade over and to the same on the other side. Do not grind one side completely (all 3 grinding steps in this case) as the blade changes shape and only small part of it will remain flat (unground), so once you flip it over you do not have the same contact with the board underneath and that may (and will) influence your grinding angles. So flipping the blade more often will give you little more reproducibility.

About to finish the first grind on the right side of the blade.

Working on the third grind. Part of it was ground when going from the heel towards the tip (upper left part of the photograph). Here I am grinding from tip to heel and grinding down to about 10 mm from the edge.

Once you get the first grind (on both sides) finished you can proceed with the second one. This will be actually much less work. Again, once finish with these on both sides you move to the third grind. 2nd and 3rd grind are from principal point of view very similar - they differ only in grinding angle and in how close to the edge you want to get.

Choil shot of the blade ground with the grinding jig.
Once you have finished all 3 grinds it is time to move to free hand grinding.

Hand grinding / finishing the bevels

At this stage you have the bevels in form of 3 separate planes, the distal taper is not quite there yet either. One could try to continue with the grinding jig, but I prefer to do the rest of the pre-heat treatment grinding by hand.

For this you need a file little less coarse than the bastard file (I have used file cut #2) with length of 250 mm (10"). This gives you enough room for both hands.

As a support I have used a piece of wood with 30x60 mm cross section which I roughly shaped (with a saw and a rasp) so that its profile somewhat follows the shape of the edge. The idea is - you do NOT want the edge to stick outside the support - on one hand you do not want to hurt yourself, on the other hand you do not want to accidentally bump against the edge with some tools, because since it is thin now (we left it at around 0.3 mm) it is very easy to dent.

Draw filing setup. Notice the 'tip protector'

After previous experience I also used a small clamp placed some 10 - 15 mm (about 1/2 the width of the file) in front of the blade to serve as a tip protector. It does not allow you to slip off the blade and with the motion towards the handle severely damage the tip.

Grinding technique

Option (1) - you hold the file with your both hands, set the file flat on the blade and move along the blade. You adjust the angle with your hands what seems to work pretty well. Still - check the progress regularly and swap the sides regularly. Also - best is to paint a 5 mm wide stripe along the edge with a marker - you do not want to grind that part.

Option (2) - is very similar to the first one, but you slightly tilt the file (rotate the file around its long axis), so that you only use the edge of the file. I call it 'edge-draw'. This speeds up the process considerably, but there is a price to pay. You will get VERY deep scratches. So deep, that you should calculate some 0.3 mm on the blade thickness that will take to remove them (first using the option (1) followed by a #60 grit wet sanding paper). I did not take this into consideration what meant that until I had all these scratches removed, the blade lost several millimeters of its height.

Scratches left by 'edge-draw' grinding technique.

During the 'edge-draw' grinding these kind of fine turnings are produced.

Detailed view of the tip and the tip protector.

Choil shot after hand grinding. The scratches are not yet removed.

Since quite some time passed until I got to the point of removing those deep scratches which would have taken a very long time to remove by hand, I decided to my new 1x30" belt grinder a try. I have used the 3M Trizact 'gator' belt with grit A100 (100 micro-meters sized particles - should be comparable to 'standard' grit rating of about 200). Even this proved to be a slow process - mainly because I had zero experience with the grinder.

Most of the scratches removed, a few more to go.

I have to admit I did not anticipate how much material had to be removed to get all the scratches out. The choil shot below shows the blade becoming considerably thinner in the process.

Choil shot of the blade ready for heat treat.

Tang shaped, heel and spine sanded. The blade is ready for heat treat.

Once the blade came back from the heat treat (done by J├╝rgen Schanz) it was time to finish the bevels and make a handle. What also needed to be done was some straightening of the blade. I only use the edge of the work bench and my hands to do that, but there are better ways to do it (I got some very good advice from Jon Broida of Japanese Knife Imports) and I may post it with some future projects.

In the process of the blade straightening I managed to break off the tip of the knife (was not the first time in the process). It was minor though and easy to repair with the grinder.

Broken tip - result of the straightening process.

Blade finishing

Even though the blade was ground thinner than I wanted prior the heat treat (because of the scratch removal process) I still needed to finish the bevels close to the edge (up to about 5-10 mm from the edge) and also refinish the blade further up the blade face. I used 80 grit Sait 7S belt and and ground the blade VERY carefully as I was trying to avoid not to overheat the edge - in particular since the cutting edge was already very thin. However it turned out to be better idea to do the job with a 40 grit belt as it produced less heat.

The inevitable result of the grinding was putting a load of scratches basically over the whole blade. I have tried, but apparently failed to remove these with a progression of finer belts (#80, #120, #240). Part of the reason was that the platen of the grinder is just a thin piece of "L" shaped steel with a relative large amount of flex to it what made it hard to apply pressure to certain area of the blade (which at this stage was relatively flat). Also the limited amount of usable space on the belt did not allow me to change grinding angles and thus observe the progress of the scratch removal.

Realizing that I am not going to get any usable scratch removal on the grinder I have moved to hand sanding. Given the experience from project #3 I have covered the side facing the support with a tape (Tesa plastering tape). Since I had rather coarse scratches on the blade I had to start as low as grit #80 and it took me 30 minutes (per side).

One side of the blade completely covered with a tape to protect the
blade from being scratched while the other side is being sanded.

I have switched the sanding setup to lower the working height to where I was able to use my body weight to push down on the blade. Also - since I needed around 3 hours of sanding per side (something I was not able to do in one go) I would write a short note on the blade as to where I should continue.

Original hand sanding setup - rather flexible but too high to work comfortably.

Modified hand sanding setup to allow a more user friendly working height.

Self explanatory note :)

The scratches from the grinder were perpendicular to the edge and normally I would start hand sanding under ca 45 deg. relative to the edge. But since the scratches I needed to remove were deep (and D2 is not easy to grind or sand) I have decided to sand the blade parallel to the edge with the #80 grit to be able to sand with more pressure and less chance of slipping on the edge or spine.

Starting with the #80 grit parallel to the edge/spine.
The scratches from the belt are clearly visible.

After about 15 minutes of sanding with grit 80 sand paper.
Some more work to be done.

Once the scratches from the belt sander were removed with grit 80 sand paper I have moved up to 120, 180, 240, 320, 400 and 600 sand paper always alternating the angle of the sanding such that the subsequent scratches would be perpendicular to the once made with the previous grit. Once I got to grit 400 I would sand parallel to the knife spine, get as smooth finish as I could - including the long pull movements from the tang towards the tip without changing the direction - and then I would repeat the same with grit 600.

I have also switched from WD-40 to Windex with grit 400 and higher. I can not help but my impression was that the scratch pattern got considerably finer than what I would have expected with the change from grit 320 to 400.

Even though I have used the tape to protect the blade - some of the dirt produced during sanding would still leak-in around the edge of the blade. It turned out to be a good idea to finish both sides to the one before last grit step (400) and do the finishing strokes with 400 and 600 with just a piece of paper towel between the blade and the wooden support.

Sorry for not taking more photos from the hand sanding process, but it really is not fun work and I was lacking the motivation :)

Handle making

Since the design of the handle from the project #3 worked optically rather well, I have decided to make handle with the same design (ferrule from stabilized wood, fibre spacers and curly birch handle), the only relevant difference being that this time I went with a drill-through ferrule.  However I did manage to make some new mistakes :)

The size of the handle was based on octagonal Japanese-made burned chestnut handle on 240 Kato Workhorse (heavy duty knife with 280 g weight) which is 26 mm tall and 22 mm wide at the ferrule and a little larger at the far end. I went with a size by about 1 mm less in each direction as this knife was not going to be quite as heavy.

I have started with a nice, squared-up  block what proved to be a huge help. I will certainly try to square up the wood before starting to work on the handle next time (I do not quite have the proper tools as of today). After taking some measurements (length of the tang among other things) I have started with drilling the handle for the dowel.  Here I managed not to clamp the block properly in the vise and the resulting opening had a 'bump' mid-length. This may happen as the drill body is thinner than the head. I managed to correct it with the drill though.

Checking the alignment before drilling the handle.
The dowel was made with the same technique as in the project #3 - cutting with a wood saw and widen with the sander. I would then check the fit with the tang and the handle block to make sure they all fit together. After that I drilled the opening for the dowel in the ferule and checked together with the dowel and the handle.

Checking the fit of the tang inside the dowel.

Once all components were ready for gluing I have first glued the dowel inside the handle with a 5 minute epoxy and once the glued settled after about 30 minutes I have glued the fibres and the ferule. As it turned out I managed to get a small void on one side between the ferrule and the dowel - something to improve upon next time.

Important note - since the whole handle was clamped I had to make sure that the dowel would not stick out of the ferule as that would not allow to clamp the handle.

Gluing the dowel inside the handle. I have used a piece of scrap steel
to make sure the dowel was 'opened' while the glue was setting.

The handle was allowed to cure for 24 hours. After that I have drawn guide lines so that I could roughly shape the handle with the belt sander. I have also marked the center of the handle on the back end before I would start to grind the wood, as the lines would be removed in the process.

Handle after gluing.

Handle ready for rough shaping with the belt sander.

To rough shape the handle I would first remove excess wood on the narrow sides of the handle with 40 grit belt (that did not want to cut steel anymore, but was plenty good for wood) and flatten them on the disc sander with 80 grit. Then I would do the same for the wide sides of the handle. At this stage the handle already has the taper (the handle is lightly wider/taller at the end relative to the ferrule), but is about 1-2 mm wider & taller than the final size - to leave a margin for error, so that I could still correct some mild de-centering. I would measure the handle with a caliper and check whether the opening in the ferrule is on-center. The handle would be carefully ground to final size with the disc sander. 

Note: care needs to be taken with a disc grinder this small, as the grinding speed depends on the distance from the center. The solution is to use little pressure and move the handle back and forth and keep checking for the flatness.

Handle ground to final size and ready for final shaping.
Now the tricky part was to be done - put an octagonal shape on the handle. I still do not have any fixture for this and only use the work rest as support. I would hold the handle on both ends and very carefully and with little pressure I would start grinding the corners. I was more successful than the last time - only once did the disc grinder send the handle flying across my workshop :) The issue here is that because of the small diameter of the sander I have to use the full width, meaning that on one end of the handle there is downward force, but on the other upward - what makes it hard to make even grinds.

I would also recommend to first establish the octagonal shape, check for the symmetry and angles, and only then proceed grinding to the final shape. Most probably you will not get the angles as intended with this free-hand method and you want to have the possibility to correct.

First 3 corners ground, but only as much as to have a starting point.
Corrections are still possible as there is more material to be removed.
Once the grind of the octagonal shape was finished, the front side and back side of the ferrule would be ground to final length of the handle. Here I went with 145 mm.

The next step was hand sanding. I have used sanding paper with grits 120, 240 and 400 followed with a steel wool. To minimize the risk of grinding away the facets (edges) of the handle I have placed the sanding paper of a flat surface (piece of stone for counter top) and have used sanding strokes in just one direction. I have used small metal brush to clean the sanding paper in the process.

Sanding setup.

Once all sides of the handle were sanded to 400 I have carefully sander the front edges of the ferrule with slow motions during which I would continuously change the angle, so the final edge would be rounded. On the back side of the handle I have sanded the edges under 45 degrees. The handle was then sanded with steel wool what have a nice semi-glossy polish to the surface.

The last step was to oil the handle. As it turned out with the project #3 that just board butter did not give the surface finish I wanted, I decided to use Tru-oil here. I have used 2 coats and steel wool. I have always allowed the coat to cure for 24 hours before polishing and applying another one.

The handle was glued with a slow curing epoxy onto the tang. It was again a very slow process to get the viscous epoxy in. I am in search for a low viscosity epoxy for this purpose.

Here I managed to make one more mistake (though at this stage too late to correct) - apparently the dowel was not positioned as it should have been inside the handle - the blade is rotate a little bit relative to the handle (can be seen in the comparative choil shot below). My handle making process needs improvements.

Total time ~ 25+ hours
  • 1h - blade design 
  • 1h - cutting out the blank
  • 1h - finishing the blank with a file (removing mistakes from previous step)
  • 6h - grinding the blade with bevelling jig & free hand draw filing
  • 2h - hand & belt grinding the blade (scratch removal) prior to heat treat.
  • 6h - finishing the blade after heat treat
  • 2h - handle making
  • 1h - putting the knife together
  • 5h - all the little bits and pieces, fixtures, correcting errors, etc.

Lessons learned

There are quite some of them with this project:
  • If you are a starting knifemaker with only rudimentary tools and little skills, than do not hurry to start with a tool steel like D2 - it is very abrasion resistant what makes both grinding and sanding a lesson in patience. Simpler carbon steels will be easier to work with, but if you want use stainless than take something like AEB-L or 440C
  • When planning to work on a certain grind to achieve certain thickness of the blade (geometry) grind the blade some 0.1 - 0.2 mm thicker than the design value with the bevelling jig - and 0.3 - 0.4 mm if you plan to use draw-filing technique as you will not only remove some more material during the draw filing, but also afterwards when removing the rather deep scratches.
  • Try your best not to grind the edge too thin prior the heat treat. Yes - grinding afterwards will only be possible with diamond plate and coarse sharpening stones or a belt grinder. If you do not have a belt grinder than you are looking at several hours of work, but if you grind the edge too thin you risk damage during the heat treat. The same is true for the tip of the knife.
  • When grinding the blade after HT (thinning, etc) be careful not to overheat the edge. Use fresh, coarse (~ 40 grit) belts. Only use finer belts for scratch removal.
  • The better you manage to remove scratches with a belt grinder, the less time it will take to hand sand the blade to its final finish.
  • When hand sanding the blade - make sure that you remove all previous scratches before moving to finer grit, otherwise you will end up with otherwise nicely finished blade with a few scratches that will be screaming at you and wake you in the middle of the night :)
  • During any stage when doing hand grinding or sanding - mind the edge - do not let it stick outside the contours of the support you are using - you decrease the chance of accidentally cutting yourself or damaging the edge should your hand slip.

Finished knife

OK, it was not sharpened yet, but there is very little work to be done since all the sanding left the edge with basically zero thickness, meaning that I will have to remove very little material during the first sharpening.

The dimensions:

  • Weight 190g
  • 230 mm on edge
  • 47 mm at the heel

The Tru-Oil finish looks really nice and feels very good to touch.

600 grit hand finished blade

The blade is really thin behind the edge - between 1.0 and 1.1 mm 10 mm from the edge.

Left: Carter funayuki, Right: D2 gyuto.


  1. looks awesome... glad you're having fun with this :)

    Told you D2 was going to suck to grind though :P

  2. Thanks Jon, you were right indeed :)