Wednesday, December 7, 2016

Project #14 - Mounting Aiiwatani natural stone on a wooden board

This is another project not directly related to knifemaking. Friend of mine asked me whether I could help him to mount his new Aiiwatani sharpening stone from JNS on a wooden board. I

Materials:

  • Plum wood (flat and dry), cca 3cm thick
  • Shellack (flakes)
  • 95+% acohol
  • hair brush
  • Epoxy (G/flex)
  • 5 minute epoxy
  • Diamond flattening plate from JKI
  • brass (metal) brush
  • sanding paper (120, 240, 400, 1000)
  • steel wool (extra fine)
  • marble table top plate (used as flat surface to support the sanding paper)



 have not done that before and at the beginning got a real headache researching what materials to use to seal the stone and to finish the surface of the wood. Cashew lacquer is often recommended to seal sharpening stones, but I could not get my hands on any, then there is Urushi which is rather expensive plus different modern water resistant . For wood there are many different options. Finally - I have decided to go with shellack and it turned out to be a good solution.

So - I started finding a nice flat piece of plum wood. Why plum wood? It was not too expensive, it is a hard wood and it holds up well with water around (I have 2 plum wood spoons and they are great) and it looked lovely. And it had the proper width, so I did not have to do much cutting :)

I started with cutting the board to size. I was left with a piece of about 8 x 10 cm large and I have decided to use it to test the finish.

The wood - testing

I have first rounded all corners with a file and then sanded the wood with 120, 240, 400 and 1000 grit sanding paper. With the bottom I only went up to 240 so it would not be sliding on wet surface too easily.

Left: original surface of the wood
Right: Wooded sanded to #1000 and finished with steel wool

I have mixed the shellack with alcohol at a ration 1:5 (weight). I actually first did 1:3, but that has proved to be too thick. 1:5 ratio made it easier to get an even layer on the wood.

When I was lacquering the testing piece I sanded the wood with steel wool after each coat. That has proved not to be the best idea as the coat was so thin, than I nearly completely took it of. After this experience I first did 3 thin coats on the board before I would sand it with a steel wool. I would then apply 4th coat and sand it again (very lightly). Because I have used steel wool to finish the surface it was not polished, but slightly matted (but still very smooth to touch).

The stone - testing

To test the second step I have used small piece of stone that was a by product of making fingerstones. I have flatten it with the diamond plate before put tin on a few coats of shellack then glued it to the testing board using epoxy. Since the bond was very strong I have proceeded to the main board & stone.

Piece of stone glued to the testing board using epoxy.

Preparing the stone

This was a little challenging. The stone did not have a regular shape and the bottom of it was strongly uneven. While it was not necessary (and frankly also not possible) to flatten the whole bottom side of the stone, I wanted to achieve to have contact points over full length and width at least on some areas of the stone. Even though this stone was not particularly hard, I needed 2 hours of work to get the result I wanted. During this process a short-hair metal brush proved very helpful to remove stone dust from the diamond plate. When finishing the stone shaping I was particularly careful to make sure the flattened part is indeed flat.

After about 20 minutes of flattening with the diamond plate.

After 2 hours of flattening.


A lot of stone dust was produced in the process
Once the stone was flattened I have brushed the whole bottom side and the sides with the brass brush to remove all the dust and loose little pieces of stone. Subsequently I have covered the whole top (sharpening) surface with an orange Tesa plastering tape (this is my favourite for these purposes as it does not leave any residue) and started to apply coats of shellack. Over the course of a few days I have applied around 8 coats. This created smooth glossy surface on the stone.


The stone was very thin in one place. To minimize the risk of loosing this part too early I have applied a thick layer of 5 minute epoxy from underneath to support the thin stone. This worked rather well.

Applying a layer of epoxy to support thin part of the stone.

 Preparing the board

I have basically followed the steps as described in the testing. To speed up the sanding I have taped a sheet of sanding paper to a marble plate which gave me a perfectly flat surface to sand on.



Sanding the wood.

Once the wood was sanded I have applied 3 coats of shellack, then gently polished/sanded it with steel wool. One more coat and one more sanding and it was finished. The shellack really brought up the fine structure of the wood. I could not help but think that it would have made for a few lovely knife handles :)


Applying a coat of shellack to one side of the stone. 

Detailed of the finished surface

Gluing

This may sound trivial, but it proved a little tricky. One of the less ideal decisions was to chose a thin and long curing epoxy (G/flex). I really like this epoxy and have made very good experience with it so far, but being really on the thin side made the gluing a lesson in patience. The slow curing was the good part of it, as it actually takes quite a while to mix and apply this large amount of glue (and I had to mix up some more as I underestimated how much will be necessary), but being thin the glue had a tendency to run off long after I have expected it to. 

Using a clamp and machinist square as an 'anchor' to keep the stone in place
while the glue was curing.

Summary

Arguably this was a relatively simple project and since I (apparently) did not make any major mistake it turned out really nice. One possible update to the future would be to grind/sand the wood from the bottom part so that board would get a slightly 'bridge' like shape standing only on the ends of the board. All stones that were mounted in Japan were done this way - I suppose to allow the wood to dry after sharpening.

Also, since this project went rather well I will son be mounting a lovely Aka-Renge shiro suita from Ohira-yama in a similar manner.

Thank you for reading, please do not hesitate to ask questions :)

Tuesday, November 1, 2016

Project #10 - WA handles for two 165 mm single bevel funayuki knives

I have got two cheap-ish 165 mm traditional single bevel funayuki knives for me and my friend, so that each of us can learn how to sharpen single bevel knives and how to put kasumi finish on the bevel and also to have a knife to filet smaller fish (what none of us does often enough to justify a 'proper' 180 mm deba).

A few words about the knives. Funayuki are today less popular than deba knives. In their construction they are not quite as strong & thick as deba knives. The knives in question weight about 150g with their original handles while a 165 mm deba would weight 200 - 250g.

Two 165 mm funayuki knives.


Since the knives were on the cheap side (which is in general not a good idea with single bevel knives as these are harder to make than knives with symmetric grind) the handles ware not too nice, just simple Ho-wood (which would be fine) with plastic ferrules (which I can not stand). So I though it why not use the occasion to improve my handle making skills :)

I have decided to make handles with 5 mm thick brass bolster and one piece of wood, this had implications on how the handle was makde.

As I started to work on the knives I found some more things to change or tweak, so here is a full list of what was done:
  • Remove the old handles (easy, as these are not glued)
  • Square up the 'shoulders' so there would be a nice fit with the bolster
  • Grind the tang to remove the scale (the original handles were burned-on) and rust.
  • Round the spine and choil (the choils were realy nasty sharp
  • Make the bolster (nice and tight) and finish the front face
  • Drill the tang and make sure it fits nicely against the bolster
  • Rough shape the bolster before the handle will be glued (and watch for the heat!)
  • Glue up the handle
  • Shape the handle
  • Sand the handle and bolster
  • Apply a few coats of Tru-oil

Handle design

This time I have decided to go with different handle than what I did so far. I would make a bolster from 5 mm thick brass plate which would be made to fit tightly onto the tang and then the handle would be made from one piece of wood. The challenge was that the handle would be shaped AFTER it was already glued with epoxy onto the tang.


But let's get started ...

Materials

  • Mora wood (from dictum.com) in 25 x 25 x 150 mm
  • Purple heart wood (also from dictum.com) in 25 x 25 x 150 mm
  • 5 mm thick brass plate
  • 0.8 mm thick black fibre spacer
  • G/flex epoxy 

Tools (apart from the obvious)

  • Wooden block with opening large enough to fit onto the tang so when you hammer-in the spacer you do your imprint the edges of the pipe you use to clear the length of the tang for the hammer
  • Self adhesive sanding paper in about #240 and #400 (or even higher) grit. Double sided tape might do the job too.
  • #40 grit belt for rough shaping of the bolster and handle and #80 grit sanding disc for final shaping seemed to work just fine 

Blade No. 1


Removing the old handles was relatively simple as these are not glued on the tang. Usually handles on Japanese kitchen knives are first drilled to nearly fit the blade tang, then the tang is heated to red color and then the handle is 'burned in' to fit the knife. That was the case also here. To remove the handles I have just used a piece of wood longer than the blade, holding the blade against the wood so that the end of the wood would be pushing against the bolster and hitting the other side of the wood until the handle would come off.

Before I started - original handles and material for the new ones.

Removing the handle showed that the both tangs had a rather coarse (forged) finish with some surface rust, so I cleaned them a little with a belt grinder.

These tangs do not look too nice, Let's clean them a little.

Once the shoulders were squared-up I have used masking tape and some carpet tape to cover the blades. before I would proceed.

Shoulders squared up, tangs cleaned.

Since I was going to fit brass bolster onto the tang I have squared-up the shoulders so that the bolster could fit without gaps (this worked only partially). I have used a filing guide to help me to file the shoulders to the same plane.

Squaring up the shoulders on the tang.
I have of course forgotten to ease the choils so I have removed some of the tape and used a 120 ceramic followed by A100 Trizact Gator belt. The result was not optically perfect, but felt very nice in hand.


Choils rounded with a belt sander.
Then I realised that I should have also rounded the spine (it hat really sharp edges), so I have removed the tape and used the A100 belt to ease them. I did not completely round the spine as I want that it can offer more support should more pressure be needed later when this knife will be used.


I forgot to round the spine, so let's do that. Belt: 3M Trizact 'Gator' A100


Now I have moved ahead and finished the first bolster-fit.


Fitting the bolster.

Once the bolster was in place and its front facing surface finished to about 800 grit it was put back on the tang, painted with a permanent maker, marked and ground to shape with a #40 grit belt.


Bolster rough shaped to slight over-size

I then shaped to bolster to an approximate octagonal shape. This is still over-sized, but I wanted to minimise the amount of the brass to be removed before the handle will be glued as a lot of heat is created in the process and brass trasfers it very fast what could damage the epoxy joint.

Bolster roughly shaped

Once the bolster was ready the handle block was squared-up, marked and drilled (3 partially overlapping holes with 4 mm diameter). I have used needle files to get the tang to fit and it was a slow. process. I have since ordered needle rasps which make the process much faster. I actually had to burn-in the last few milimeters what was a slow process with this dense and hard wood.

Fitting the handle block onto the tang - not quite there yet.

Finally - the handle block fits tightly onto the tang.
Once the handle block could be fit onto the tang it was roughly sanded before being glued onto the tang. With the next knife I have first glued the handle before shaping it.


Handle rough shaped.
Before glunig up the handle I have filed notches onto the tang. I have not done this before and it probablny is not necessary (not on a kitchen knife anyhow), but I just wanted to be sure the handle will not get loose over time.

Filing the notches into the tang
I have used G/flex epoxy to glue the handle. I love this glue - it is thin enough so that it will flow down the tang opening without pre-heating or other tricks. And it gives you enough time (cca. 45 minutes) to get all done and cleaned where necessary.

After gluing - cleaning the joint before the handle will be sanded to shape.

Once the glue has cured I have cleaned up the joint with a belt sander and moved to disc sander with #80 grit to first flatten all sides. Once that was done I would measure the handle and draw the lines to first get the distal taper (vertically and horizontally) before moving to final shaping of the handle.

Sadly, I have found out that I did not do good enough job of fitting the handle onto the tang during gluing resulting the handle sitting under an angle against the bolster what resulted in an obvious gap on the upper side of the handle. Lesson earned - take more care next time.

Flattening the handle sides before moving to final shaping.

Once you start grinding the brass bolster in the proces - keep checking the temperature as the glue joint could be damaged or get loose.

I would stress that it is important to take the handle into you hand and check whether the shape and size is right. I needed several iterations to get the size that feeled 'right'. It is way to easy to make the handle too large.

In the middle in the final shaping - still not quite there yet.


And this is how a poor handle glue-up job looks like. See that gap on the top?


Once the handle was sanded to its final shape it was time for hand sanding. This was different to 'normal' WA handles as these can be finished before being mounted onto the tang. Here the sanding had to be done to a handle already glued onto the tang.

To get the job done I have used a small woodeb block of about 10 x 3 x 6 cm and self adhesive sanding paper from 3M (Gold Stikit) in #240 and #400 grit. I would attach a piece of about 10 x 3 cm to the block and sand each facet of the handle.

Important: Since you have thick bras bolster next to much softer wood, you may sand a 'dip' in just before the brass. To avoid that I would first sant just the wooden part and skipping last centimetre and the brass bolster. Then I would switch to much smaller piece of wood and use only about 2 x 4 cm large piece of sandpaper and sand only the bolster WITHOUT leaving it - so that I would not sand in that dip.

I also use the #240 grit to ease the edges on the brass bolster.

Once I was done with #240 grit I would do the same with #400. In the future I plan to use normal sanding paper together wit 2-sided tape as I would like to go higher than #400 grit - in particular because of the bolster. The wood does not really need it.

Final finish would be done with steel wool and then the handle was off to the first coat with Tung Oil.



Applying first coat with Tung Oil

Blade No. 2


The second handle was made in a very similar way. Here are a few details I have missed to photograph with the first one.

Working on the bolster I went up to 2000 grit.

Bolster finished to about 1200 before final fit.
However during final fit it showed that the fit was too tight and hammering on the bolster caused the brass to raise a bit around the tang. So I have carefully removed the bolster to re-sand it.

Bolster after first fitting - you can see the raised area on the right side.

Bolster removed after inital fit - you can see how the tang shoulders
 pressed themselves into the brass.

Bolster re-finished to 2000 grit.

Then followed rough shaping of the bolster and drilling of the handle block.

Bolster ready for rough shaping.
I have decided to use clamps to assure a tight fit of the handle relative to the bolster.

Important: When dry-fitting the handle to the tang&bolster watch that the handle is in axis with the knife. If it is not you have several options to correct: sand the front face of the handle (where it will contact the bolster), file the tang opening, or bend the tang a little.


Reading for gluing of the handle.

The clamping solution worked even though it needs some improvements - ideally a small dedicated vise/clamp as it was a little clumsy this way. The point is - make sure that there is not gap between the bolster and the handle.

Using  2 clapms to make sure the fit is tight. Only little force was applied.

Once the glue was cured the handle could be rough and the final shaped.

Drawing the lines for rough handle shaping.
Subsequently the handle was tapered in vertical direction then then final shaped. Since I already had the first handle finished I knew what size I want it to be so it took fewer iterations.

Handle rough shaped and ready for final shaping.

Lessons learned

Quite a few this time, actually...

  • Make sure you have all the adjustments made to the blade necessary or intended (choil or spine rounding, straightening of the blade, re-finish of the blade) before you start working on a handle. I did not want to re-work the blade finish what made fitting the bolster harder as the tang did not have a well defined shaped.
  • When drilling the opening in the handle for the tang drill 1 cm deeper than you need and then keep adjusting the opening with files or rasps until you get a comfortable fit without too much wobble. If the fit is too tight you may have hard time gluing the handle tightly to the bolster (see above) without any gaps.
  • Be super careful when shaping the handle already glued to the knife - think how much work it would be to remove it if you make a mistake ;)
  • When hand sanding the the handle make sure that when you sand the bolster you do not run on and off it with sanding paper as you will tend to create a dip just behind bolster. Keep the sanding block over the bolster while sanding (or avoid the bolster all together while sanding back part of the handle
  • If you plan to finish the bolster to semi-mirror polish with a steel wool, than you want to go to about 1200 sanding paper before that.
  • Honestly - I am still figuring out how to finish the bolster evenly. The problem is - you finish the front side first, than you finish the sides during hand sanding, but you also need to round the edges of the bolster and ideally you would want to blend it all together. 
  • If you plan to use steel wool it may be good idea to put some tape on the front side of the bolster and on the transition from the bolster to the blade tang as the steel wool tends to get everywhere, it will stuck to whatever tiny bits of epoxy are left at that joint and it will be hard to clean afterwards.
  • Shorten the handle before you start to sand it to shape. I forgot that with the first one. Also - you can use the rest of the block to test different finishes. Just finish it the same way as you plan to finish the handle.
  • When power-sanding wood be careful not to burn the wood, Not only you may damage the wood (if you are close to final finishing), but even more importantly you will clog the belt or sanding disc in no time.
  • If you plan to make similar kind of handles where you fit the tang of the knife in relatively narrow opening - do get a few needle rasps  - the 160 mm long ones from Corradi are perfect for the job. I just got them and only briefly testing them and they will speed up the job considerably.


Please do not hesitate to ask questions - I love questions :)

Finished knives

In general - far from perfect, but they do look nice, feel nice in hand and will most certaily serve their purpose. I do have a lot to learn.




And here is that gap again. It is going to haunt me for quite a while I guess.



Tuesday, October 4, 2016

Project #11 - thinning & refinishing Hide 225 mm gyuto

OK, this is not a knifemaking project in the true sense of the word, as I did not make a knife (or even a handle) here, but since I did quite some work on the blade I though it could be interesting to share.

My Friend bought this Hide gyuto in a, let's say 'well used' condition. The knife had some heavy patina on the blade. Also - the blade was apparently never thinned, only sharpened on the edge what left the knife thick behind the edge. At the same time, the knife was ground relatively thick - in particular near the tip (I have not seen such a thick tip on a gyuto before). Also the handle (otherwise a very nice one made from Ichii wood and water buffalo horn ferrule) needed to be touched-up. The knife has a nice Ichii saya, but that one did not require any servicing.

After discussing what should be done with the knife I have agreed to thinning and refinishing the blade. Please do note - this is the first time I have attempted such a work on a traditional Japanese kitchen knife. One may argue that learning on something cheaper than a 500€ gyuto would be a good idea. I would tend to agree.

The ToDo list was the following:
  • Thin the blade behind the edge and up to about 20 mm from the edge
  • Thin the tip (distal taper)
  • Sand the blade to 2500 grit
  • Make finger stones (from a soft natural sharpening stone)
  • Refinish the blade to a kasumi finish with the finger stones
  • Refinish the handle.

Before starting

It is important to check the blade up close and understand what grind it has, whether it needs thinning and decide how the thinning should be done. It is important to notice whether the blade has any sort of bend, what kind of grind the blade has. Failing to notice a bend to a blade would have considerable implications during thinning as because of the very shallow grinding angles even the slightest deviation from the plane the blade would be ground asymmetrically in the vicinity of the bend.

Last but not least - one should have as clear idea as possible what should be the outcome of the refinishing, as there is no way going back once you start to remove metal. This particular knife

This particular blade had an asymmetric grind. The left side was relatively flat with a shallow hollow grind higher up the blade face, while the right had a strong convex. For me it meant that if I did not want to disturb the grind too much, then most of the metal removal would happen on the right side.

Here are a few photos that show the knife before I started to work on it.


Choil shot of the knife before thinning. The asymmetry of the grind is well visible.

The tip of the knife - definitely needs thinning to give it some distal taper.

Some heavy patina, but no rust or pitting.



You can see here that the core steel is more revealed close the tip.
Patina can have such cool colors.


Thinning of the blade

I have used Atoma 140 as I needed to remove a lot of material - over large area the blade needed to 'loose' 0.2 - 0.5 mm in thickness. The price for the speed of Atoma is that it leaves deep scratches and in particular if small pieces of removed metal stick to the surface of the Atoma they may leave nasty deep scratches.

Note: When thinning on a coarse diamond plate make sure to stop before you reach the desired thickness as you will remove more material with coarse stones or coarse sanding paper to remove the scratches left by the diamond plate.

The main point when working with the Atoma was to avoid working too close to the edge as that could leave to unintended material removal directly at the edge what could mess up the profile of the knife.

To get the work done I have used similar technique like in the Project #3 - applying pressure at constant distance from the edge and moving the point where the pressure was applied step-by-step from the heel towards the tip. I was measuring the thickness of the blade regularly with a digital calliper.


About to start. Stone holder, Atoma 140 and digital calliper.

Removing steel up to about 20 mm from the edge.



Right side after some work.


Left side after some work.

Moving higher towards the tip and grinding the distal taper.

Left side after more work - the concave part of the blade can be seen.

Once I was 90% where I wanted to get with the blade thickness and distal taper, I have moved to JNS300 and started to remove the scratches left by the Atoma.

Once the worst scratches were removed I moved to #180 sanding paper. To be sure that I was going to remove all remaining scratches from Atoma and the JNS300 and, at the same time, to be able to proceed as fast as possible, I have sanded the knife parallel to the spine.

The thinning removed quite some amount of cladding close to the tip on the right side of the blade what also made that part of the blade hardest to get the scratches out.

After 180 grit sandpaper. Still a long way to go.

After 180 grit sandpaper. The tip shows that more of the
core steel was revealed during the thinning.

Once (after about an hour) I got all (well, nearly) the scratches removed I moved to #240 grit paper. Again - I have changed the direction so that I could be sure that once I am finished all #180 scratches are gone.

One point worth mentioning is - because of the concave grind on the left side of the blade I had to find a way to get inside that hollow part. I have used wine cork wrapped in sanding paper to do so. While it was awkward to hold, the curved surface of the paper did sand the steel rather fast.

Sanding with 240 grit. The cork serves as semi-stiff support tu get
 inside the concave part of the blade.

240 grit finish.
As always - it was harder to remove the scratches from the core steel - on top of that I had to be careful not to 'slip over' the edge and damage it. After all the material removal and sanding the edge had basically zero thickness.

Hagane is hard and thus the scratches are harder to remove.


Some more Hagane scratches. Oh well.

After #240 grit I have proceeded with #320, #400, #600, #1200, #2500. After #600 I only sanded along the blade trying to get as smooth finish as possible. Also - with every step I tried to leave as smooth finish as possible to make it easier during the following (finer) grit to observe the progress. #2500 left semi-mirror finish.

#400 grit finish


#400 grit finish. Interestingly - the core steel seemed to oxidize faster]
than the cladding.

# working on the #600 grit finish

#1200 grit finish

#2500 grit finish

Once I had an acceptable (far from perfect) #2500 grit finish I have moved to finger stones as at this stage there was barely any contrast between the core steel and the cladding.  See my article on the fingerstones to find out more how these were made. Here I would only mention that these fingerstones were made out of soft natural sharpening stone and were thus easy to use, but each of them would last only a few minutes.



Setup for the finger stone finish.

Already after few strokes the fingerstones were creating mud.

The contrast between cladding and core steel starts to show as the cladding
turns cloudy, but the core steel gets polished.

After about 10 minutes with fingerstones.



Figures above: Just to show the difference:
left: blade with #2500grit finish on the left side
right: finger stone finish on the right side



Boosting the contrast in the blade in Lightroom to show its structure.

Boosting the contrast in the blade in Lightroom to show its structure.

After some work with the fingerstones a strange pattern showed on the cladding - like a set of parallel lines (see below). I could not figure it out where did it come from (maybe a pattern I have ground into the blade while sanding it?), but luckily these disappeared with some more work with fingerstones.

Strongly boosted contrast to show the pattern.
It took me about 10 hours of work of grinding and sanding until the blade was finished. Since I did not take much are about the handle - at this stage it was covered and soaked with fine steel mud and not looking pretty. To remedy that I have sanded the handle with 400, 600, 1200 and 2500 and then polished a bit with steel wool. A few coats with board butter and it came back to life :)

Photos below are courtesy to my friend as I was too short of time to take some.


Refinished handle. That Ichii wood is really lovely.


It really does cut now!

I need to get one of those cherry cutting boards.

Lessons learned

  • Complete re-finish of a knife is a LOT of work. You get faster with experience, but it still takes many hours. 
  • Atoma 140 (or any other diamond plate or stone) will tend to tear the cladding leaving deep grooves on some places. Not every cladding reacts that way - test before you go with full power as you could end up with blade thinner than intended (once you remove those deep scratches)
  • When you start thinning on a diamond plate or very coarse stone (like 150 or 220) - do NOT start at the edge, but higher up the blade. If you bring the edge to near zero thickness too early in the thinning process, you risking removing too much of material at the edge (because you just can not hold perfect angle by hand). Once you get the parts of the blade that are further away from the edge finished only then move closer to the edge. The very last 2-3 mm are best made on 300 - 500 grit harder stone with good feedback.
  • While thinning - measure (or otherwise check) the blade regularly and in particular if using corse diamond stone or very coarse sharpening stone - stop about 0.1 - 0.2 mm (thickness wise) from what your target is because you will remove more material during the scratch removal. Process. Once you get to about 240 grit sanding paper the material removal will become very little.
  • If you want to put a nice hand-sanded finish on the blade you need to have '0 scratch policy' before you move to higher grit. This is in particular important if you aim for near mirror or mirror finish - that will make every scratch that you left behind stand out and your only chance will be going back to much coarser grit and thus wasting hours of work.
  • Finger stone finish on san-mai knives needs at least 1000 sanding paper grit finish, but higher is better. Once the blade was sanded nicely, the work with fingerstones does not that long.
  • Thinning produces a lot of fine steel and stone mud and it will get everywhere. Wear surgical gloves if you do not want to have really dirty hands for several days.
  • The same goes for handle - if you want to keep it clean, either remove it (if possible), or oil it and cover it with some sort of easy to remove tape (or food foil) while working. However do not leave it wrapped for longer time as there will always be some water getting onto the handle what could cause problems if left wet for longer time.
Last but not least - a big thank you to my friend Jan who trusted me enough to let me work on this special knife. The biggest satisfaction for me was hearing that the knife cuts much better now - made the whole effort worth a while :)

And as always, your questions and comments are most welcome :)