Thursday, November 9, 2017

Project #19 - 210 mm Niolox gyuto for a local chef

There is a small Italian restaurant in Aalen called Buon Giorno. We have been their regular guests since they have opened a few years back and we must have eaten there well over 100 times. We love their food and became friends with the owners and it is a place I always look froward to when we head to town on Saturday to do some shopping on a local market.

Since I have started making knives I had this idea that one day I will make a knife for the chef. It took me a while to get to the point when I was able to make a decent looking knife with a western style handle, but I kept this idea and finally I have managed to make it happen.

One surprising fact about this project was that I did not produce any major screw-ups or mistakes, an exception to the rule :)

The design

I have watched the chef cooking, so I know that he uses about 21 cm German chef knife, so I have decided to make him a knife that would follow similar pattern to increase the chance that the knife will suit his cutting style.

The main design points were:
  • 21 cm blade with just a tad more belly towards the tip than I would normally do
  • Niolox stainless steel at 61 HRC
  • Western style, hidden tang handle (I have not made a full tang handle yet, so I stick with what I can do)
  • Handle materials: Buffalo horn, white G10 spacer, stabilized & dyed handle.
  • Some sort of blade protection for storage and transport - which became a simple leather sheath.

The blade

As usually it started with designing the blade, copying it on a piece of steel and cutting out with a hack saw.

The rough blank of the 210 Gyuto at the bottom of the photo
The blank was then brought to final profile with a belt sander, edges cleaned up to #220 grit. After that the edges were painted with a blue permanent marker and center lines were inscribed. Now the grinding could begin

After first few passes on a #40 belt
I usually start putting a relatively steep bevel on the blank (see the photo above) and leave the edge thickness at cca 1mm. The only practical reasons to that is, that having limited grinding experience and a bit wonky setup, little mistakes may happen in the next hour or two if grinding and having little more material on edge gives me a bit of a 'buffer' should my hand slip. Later during the pre-HT grinding the edge is brought to about 0.5mm thickness.

In further grinding steps I have pushed up the (at this stage slightly convex) bevel towards the spine and then started to grind the distal taper. I would go down to about 1mm thickness at the spine at the tip and around 2mm half way between the handle and the tip. Then it was time for a HT (done by J├╝rgen Schanz)

Blade right after HT.
After the HT I would first finish most of the grinding with the #40 belt. I usually leave the edge thickness at about 0.3 mm before moving to #60 and #120 belts. 

Setting the bevels with #1000 water stone

Once the rough grinding work was finished I would take the blade to my #1000 water stone (Watanabe AI#1000) to check for any low & high spots that I may have induced along the way. This stone is particularly suitable for this job as it not only cuts fast, it also does not wear much so after flattening it keeps flat without excessive flattening - something that is important to get the bevel setting done.

Note: This step with setting bevels with a water stone before I actually finish grinding with finer belts should not be necessary later down the road once I take my new 2x72" grinding into operation, as with the wider belt and more flexibility in setting up the grinder I should be able to get more even results. 

Scratch removal

Note: There are many ways to put an even finish on a blade. Different approaches have different pros and cons. At some point I may write an article on that topic, but I am far from having a decent grip on this topic at this point. With every knife I tend to try a slightly different approach and see what works best for me.

This is probably the least enjoyable part of the whole process, but it is necessary to be able to put any decent finish on the blade. Since the grinding was done with a #40 belt, one needs to go through some sort of progression of abrasives to get to at least #400 (or finer) finish. My progression with this knife was the following:
  • Most of the grinding is done with #40 belt - so that is the starting point
  • Finish the grind with #60 belt under slight angle to make sure all #40 scratches are removed. This IS important
  • Clean up with #120 belt - this time the scratch direction is as with #40 belt, so that I can make sure all #60 scratches are gone
  • Bester 220 stone - firstly to finish the grind and secondly to put a first more-less even finish on the blade
  • Watababe AI 1000 stone - full blade finish
  • Gesshin 4000 full blade finish, This one is NOT completely smooth as the stone is rather hard. I may skip this step in the future.
  • #600 sandpaper
  • #1000 sandpaper
  • #2000 sandpaper

Starting to grind with #60 belt after #40.

Also - normally before I would switch to the finer belts I would finish grinding the profile of the tip (as up to this point there was no point). But since here I have ground the blade up to #120 belt I had to watch for scratching of the side of the blade that will have contact with the work rest, so I would put some tape on it.


About to grind the profile of the tip

Putting some tape for protection on the right side of the blade.
In this case I did not final-shape the tang of the blade before HT (because I forgot), so I had to do that as well. It actually makes more sense to do that beforehand as it is much easier to shape the heal/choil area before HT as it can be done rather quickly with files and sandpaper.

Bevels cleaned up on the Bester 220
Whole blade finished on Bester 220.

Once I had the blade at #120 belt finish I moved to sharpening stones to finalize the grind (I still had some steel on edge at this stage) and to continue with refining the finish. I would start on the Bester 220, get the bevels even and edge thickness close to 0.1 mm and then work higher up the blade until the whole surface of the blade had a finish from #220 stone.

AI#1000

After the Bester I continued with the AI#1000 stone and removed all the scratches left by the Bester. The final stage was done with the Gesshin #4000 stone. The finish was very 'patchy', but the important part was that all the scratches from the 1000 stone were removed.

Finish after Gesshin #4000

I have yet to find a better tape than the orange Tess -
it hods well and does not leave any residue - even when
left on the blade for longer time (up 2-3 weeks)
Last step before switching to

Now I would switch to hand sanding. I always put a masking tape on the bottom side of the blade to protect it from scratching while the upper side is being sanded.

About to start sanding the left face of the blade

As usually I have used my very simple 'sanding station' - a blade-like shaped piece of a 3cm thick beech wood clamped to my workbench. Yes - there is a room for an improvement there.

I usually use WD40 as a lubricant for grits up to #240 (#400) and switch to Windex (less viscous than WD40) with finer papers. The advantage of the Windex is, that it keeps carbon steel blades from rusting. That is important as hand sanding take s long time.

Left face of the blade at #1000

With this particular blade the sanding of the left face went fine - I went through #600, #1200 and finally #2000 grit and the result was fine. But something wend wrong with the right side. Once I switched to #1200 paper I started to discover short (about 5-10 mm long) scratches parallel to the spine of the knife all over the blade.

Short scratches all over the blade ... oh well ...
I had no other choice that go all the way down to #400, remove all these little scratches (which proved to be quite deep) and then work my way back up to final grit.

Starting to remove the scratches with a #400 sandpaper ...
... and gone they are!

#2000 grit finish (semi mirror)

Note: I am yet to figure out how to put a finish on Niolox that I really like. Going for a mirror polish may be possible, but give how hard the steel is to abrade (it literally eats sandpaper) that would be a lot of work. At grits around #600 - #1000 one gets a mixture of scratches and reflecting surface that does not look too nice. What I am trying to achieve is a fine semi-matt finish, but I will need to experiment more to get there.

The only thing left to do on the blade was to etch the logo.

Stencil taped in place for the etching.

At this stage the blade was finished. I did work on the handle in parallel, but decided to separate this two parts here for simplicity.

The handle

The decision to go with a western style handle was based on the fact, that the chef has not used a Japanese style so I decided to make a handle that will in handling be closer to what he is used to.

I wanted to make the whole knife relatively lightweight and so to keep the balance point on around the pinch grip, I had to be careful with choice of materials and avoid heavy/dense woods or metals. The choice fell on a stabilized maple burl from Stabwood Lab. I do not know what kind of stabilization process they use, but the resulting wood is not as dense/heavy as from other makers and also feels more natural to touch. On the other hand, there seems to be a bigger chance for small voids and I also assume that the strength of the wood is not going to be quite as high as of the denser. But until today I did not have their product to fail on me so I plan to keep using it.

I need a band saw :)

Flattening & squaring up.
I wanted the handle to be a bit eye catching, so I have decided to use a blue-red dyed maple burl. Since the block was large I used only one half of it. Once the block was cut I flattened and squared up all sides by hand with #80 and #180 sandpaper.

Drilling the handle block.

Drilling the ferrule.

The handle block, the horn ferrule and the spacer were all drilled to accommodate a 12mm (diameter) dowel. Since this is a western style handle the ferrule was not drill through completely, so that the dowel would not show from the front. I call this a 'hidden dowel design'. 

Important: Since the drilling of the block is rather deep - even a small deviation from the intended direction could lead to problems later - I always check (with a straight longer piece of the dowel stock material) whether the drilled hole aligns. with what was planned. If not, than now is the time to make adjustments - either re-square the block, or just re-draw the center-lines so that later the dowel will be aligned with the handle.

Filing the tang opening.

The ferrule would be first drilled-through with a 3mm drill and then the 12mm drill would be used to drill through most of the length, leaving about 5mm of of material in the front. After that 2 more 3mm holes would be drilled in the front face and using a set of needle files a rectangular opening for the tang was made.

Testing the fit of the blade & handle components before gluing.

The dowel was made from a 12mm thick bar of beech wood. First a narrow slot was cut with a hand saw and this was later sanded with a #120 belt until the blade tang would fit. The fit was tested with all handle components before the gluing. Here some fiddling may be necessary to make sure, that there will be no gap between the bolster and the rest of the handle.

Gluing the whole handle.

To make sure the dowel will remain 'opened' first it was glued inside the handle block with a 5 minute epoxy. After that the spacer and the ferrule would be glued (G/flex epoxy) with the rest of the handle and allowed to cure for 24 hours.

Clearing the tang opening with a needle rasp.

It is advisable to use only as little glue as necessary, because otherwise it will leak inside the dowel-slot. Even though I was careful, I did need to do some minor filing/rasping after gluing to make sure the blade can be inserted inside the handle again. Here needle rasp is the best tool for the job. To make sure it will fit inside the narrow tang slot, it was flat-sanded on one side.

Cleaning & squaring up the handle block after gluing.

The handle block was quickly sanded to remove excess glue and to flatten the sides (the horn was a bit wider than the block). 


Now the handle design could be transferred onto the block. Care needs to be taken to get the alignment right. In some places there will not be much material left between the dowel and the surface of the handle.

Grinding the handle profile from the side ...

... and from the top/bottom

In subsequent steps a #40 belt would be used to roughly grind the profile of the handle - first from the side and the from the top. It helps to inscribe some guide-lines (symmetric relative to the axis of the handle) to make it easier to grind symmetrically from the left and the right side.

Coarse shaping the handle with #40 belt

Than the coarse shaping would start. I remove most of the material with #40 belt. Here one really needs to be careful, as the belt is very aggressive and it is easy to create dents with the edge of the belt. Once I had the approximate shape of the handle (though it would still feel too large in hand) I would switch to #80 or #120 belt to get closer to the final shape.

Filling the voids with glue.

Detail of the gluing.

I have mentioned voids in the wood - this particular block had one. So before I would move to hand sanding, I have decided to fill it with glue. For some reason I did not want to use epoxy and decided to give the 'Titebond Instant Bond' a try. This is basically a CA glue for wood. It turned out that while it works great on finer cracks, filling a larger void did not work so great (in retrospective - not a surprise) and I had to repeat the process several times. Eventually I managed to get the voids filled.

Finishing the surface with steel wool.

The handle was subsequently sanded with #180, #320, #600 and #1000 sandpaper. I have used either a rectangular piece of wood (in particular when sending over the spacer area) and piece of a round wood stock that I use for dowels, to finish the sanding (final shape little details, even out the surfaces, etc). Final sanding was done with #0000 steel wool.

Finished handle before Tung oil was applied.

Even though this handle is made of horn and a stabilized wood, I have used a few very thin layers of Tung oil (wiping away / polishing with a paper towel immediately after application) to seal a bit the not-so-dense handle bar.

The sheath

Since I did not know whether exactly the knife will be used I have decided that it should come with some kind of protection for the transport or storage. I have not made a saya or sheath before. I considered making a saya, but found out too late that the wood pieces I had for the purpose were too small. So I finally wend with a leather.

Since I had zero experience with working with leather I have decided to go with a very simple construction - two pieces with a spacer along the spine. I have used about 2.5mm thick, half tanned leather that was very stiff. The stiffness make it suitable for the job as the final sheath would be very strong, it was also a pain to cut and punch holes.




I have marked the profile of the blade on an A4 piece of leather and added ca 12mm for the seams. Then I have cut a piece of leather in with the same profile as the spine of the knife for the spacer.


Thinning the spacer
Since the blade has a pronounced distal taper I have decided to taper the spacer as well, so that the sheath would sit well when the knife was fully inserted. I first tried to use the curved beveler tool, but I was not very successful with it, so I used my belt grinder with #120 belt instead and in a few minutes I had a perfect distal taper on the spacer.

Gluing the spacer.
In the next step I have glued the spacer to one side of the sheath.



You can never have too many clamps in your shop.

Once the glue cured I have glued the tho halves of the sheath together.


Since it turned out that one can use the belt & disc grinder to work with leather I have used it to clean up all edges.

Punching holes made easy :)
After marking the position of the future seam with a groover I took the standard puncher and ... even with all the force I was able to produce I did not manage to punch a usable hole through the thick and hard leather. OK, a different approach was needed. Luckily, it did not take me long to realize, than I already have the optimal tool for the job - the drill press. I took a wooden board (some 20 mm thick) to have a smooth clean surface, drilled a small (about 3-4 mm) hole into it, so the needle would have enough space after going through the leather - and started punching. I still had a problem with the needle getting stuck in the leather, but once I got the idea to turn the drill press on - even this problem disappeared.

All holes punched (and re-punched from the other side)

I hurried a bit too much what resulted in holes not being quite as perfectly aligned as one could wish, but I got this part of the job done. 

Note: I must have made several things suboptimally, as for example - the groove I did for the stitch disappeared nearly completely during hole punching.

Yep, there is room for improvement.

The punched holes seemed to have fit the sewing needle and the thread quite well, so even though it was not a fast job to do, it went rather fine. Once I was done with stitching I have used a small amount of the wood CD glue to secure the seams.

Applying dark brown leather dye (in 2 separate steps) did help to make the imperfect stitching to stand out less. Even though not a work of art, I am happy to say that the sheath fits the knife very well. I will try to make it more elegant next time :)

Assembly

The handle, the blade and the sheath.

At this stage the main work left to do was the glue the handle on the tang of the knife. This was the first time I did it in 2 stages. This was also the first time I have used a heat gut (from Proxxon as I wanted a smaller one with not as much power) to make the glue less viscous and thus easy to pour inside the tang slot - that worked great.


So the first day I glued the tang inside the blade, and only made sure that I wipe all the excess glue with acetone. This would leave the narrow gaps between the handle and the tang not filled completely.

Filling the gaps with epoxy.

So the next day I would mix a faster curing (15 minutes) epoxy, heat it up, fill in the gaps and wait until the glue starts to get sticky. The reason for waiting at this stage is to avoid the glue being 'pulled out' of the gaps while wiping out the excess and cleaning the handle and the ferrule.

Once the knife was all done the last step was to give it its first sharpening. Since the edge had basically zero thickness after all the sanding, it was a very quick job done with Gesshin #2000 and #4000 stones.

Finished knife

I took me well more than 20 hours of work spread over several months to finish this project. It was a very rewarding moment to gift it to the chef at Buon Giorno, who did not expect anything of this kind. 

The position of the center of mass is about 1 cm in front of the heel - pretty much exactly where I wanted it to be. The knife weights 160g without the sheath.  Thickness of the blade 10 mm from the edge it about 1.2 at the heel and tapers to ca 1.0 mm close to the tip.


So - this is how it looks finished:












Lessons learned

  • Always change directions when removing scratches. It can save you hours of work. I needed about 2 hours of hand sanding to get the right face of the blade to #2000, but for the left side (because I had to go back to #400 grit) I needed nearly 5 hours.
  • Hot air gun is a great help to get glue to flow into tight places
  • Before starting a brand new thing (sheath making in my case), do some reading and watch few YouTube videos to avoid unnecessarily suboptimal results
  • Drill press is a great tool to punch hole is hard/thick leather