Tuesday, January 31, 2017

Project #12 - 180 mm gyuto in Niolox steel

The time has come for the to try a steel that is not all that well known outside Europe  - the Niolox also known as SB1. It was brought to the attention of knifemaking community by J├╝rgen Schanz who also himself is a knifemaker and experienced metallugist. He also sells knife supplies and offer heat treatment services. In other words - I have the chance to have my stainless blades heat treated by someone who has very detailed knowledge of the steel and lot of experience how to get the most out of it.

The Nilox is supposed to be similarly to AEB-L a very fine grained steel. The Niobium forms very small and very hard carbides what allows the steel to be fine grained and resist abrasion well. In other words a very interesting steel (not only) for kitchen knives.

At some point in the future I would like to compare it to AEB-L and D2 (which has usually much larger grain structure) - actually - that is what Project #13 will be all about :)

The design

For the testing purposes I have decided to make a smaller knife. At the moment I plan a simple WA handle, but may even give a hidden tang western handle a try.

The design of the blade was simply done by hand on paper on my bus commute. I am actually really starting to enjoy designing blades by hand.

The knife will be made of 2.2 mm thick (thin!) steel. The blade will have a continuous convex grind and I plan to make it nice and thin behind the edge.

The blade

I took a fresh blade for the hack saw and had the coarsely cut-out blank it under 10 minutes. Part of that was of course that the steel was only 2.2 mm thick. Still - this would have taken longer with a steel like D2.

20 minutes later the blank was shaped, edges ground up to #120 grit (I used cheap #40 ceramic belt to shape the blank) and thus basically ready for grinding the bevels.

You may notice that the bump where the tip of the blade is supposed to be. I have seen Don Nuygen doing this and realised how a great idea that was. This makes the tip more robust while grinding, heat treating and final shaping after HT. The bump also serves as heat dump when final shaping after HT. I will see how that will work for me.

The design and the blade blank. Notice the hump ner the tip.
The grinding was fairly fast - this is partially because of the thin stock and it would also seem that the steel is relatively easy to grind, even though it seems that it dulls belts quickly. The grind is a relatively flat convex with a little more curve close to the edge. I hope to get usable food release with this knife. We shall see how that will work. As usually I ground the bevel, then ground the distal taper and blended these two together. But I have to admit that I do not yet have a better defined procedure yet and I was jumping between the two until I felt the blade was about right.

As always - I was checking the thickness at the edge and at 5, 10 and 20 mm behind the edge and tried to keep it as consistent as possible with slight taper towards the tip.

Pre-HT grind.

Blade ground (pre HT) and cleaned up to #240 belt
Once the blade was ground I moved to the tang. Since this was going to be a fairly thin and lightweight knife I opted for the tang height of 10 mm (I use 12 mm on larger knives). I have used a filing guide and reshaped the tang with a belt grinder. The shoulders do not need to be quite as perfect as I planned a conventional WA-type handle and no metal bolster.

Sanding the tang to shape.

Tang finished.
 Before the blade was sent to HT I have it a quick finish with #240 and #400 sand paper. Not quite perfect yet - this is the area I need to improve my speed/efficiency as well as the final result.

Sanding the blade to #400. I write down the note if I do not manage
to finish in one session.
Once back from HT it was time for final grind. There was not all that much left to grind apart from close to the cutting edge. and once the grind was finished to profile the tip.

Blade after HT after first few passes on #120 Norton Blaze belt.

Detail of the grinding on the cutting edge.
Once the blade was ground and the tip profiled, I continued with 3M Trizact 'gator' Belts (A100, A65 A30) to refine the finish and with the flexible 3M Trizact (A30) for the last clean-up on spine and choil.

Note: Here I would like to mention that my blade grinding procedure is far from fine tuned and I am still learning what belt progression works the best for me, so take the above just as an example.

In Parallel I have started to work on the handle. I chose Mora for the bolster and Bocote body of the handle with yellow and black fibre spacers. The main reason to choose these materials (other than design) was that they are relatively lightweight. The blade is very thin and I did not want the knife to be butt-heavy.
Blade before finishing and handle materials.
The making of the handle was relatively straight forward. I would cut a piece of Mora for the bolster and squared it up, cleaned and squared up the Bocote, cut out the fiber spacers and glue it all together with a G/flex epoxy.

Future-to-be bolster.

Once the glue cured I used first belt and disc sander to clean and square up the block. The challenge here was to remove as little material as possible before the next steps, as both woods were on the thin side and there was very little room for error.

Squared up handle ready for drilling.
The handle was subsequently drilled (10 mm) a dowel was made out of beech. I always make it a few mm longer so I can minimise the damage to the front of the dowel while final fitting. I cut the slot in the dowel with a hacksaw and then used belt sander to widen it until the tang fits. It pays to be careful here - the better fit the easier putting the knife and handle together. I also sand the dowel lightly from outside, so that it can be fit in the drilled opening (with the tang in the slot) with only very little resistance. Once covered in epoxy, the fit will be tighter and the epoxy will also tend to push the two halves of the dowel together.

Ready to glue the dowel.
I mixed the glue (G/flex has 45 minutes pot time, so no hurry is needed) cover the dowel with a thin layer of glue. I insert the blade - that makes it easier to get the angle right. I use a thin piece of steel (and off-cut from a blank) and sue it to make sure that there will be no gaps between the bolster and the dowel.


Once the glue cures I would do some light rasping with a needle rasp to get the tang fit cleanly - some glue usually leaks in the slot and needs to be removed.

... and if you hurry you will brake your brand new needle rasp ...
The handle will soon proceed to final shaping, but let's do some blade finishing first. Since I managed to get acceptable finish on the belt sander, I could start with a #400 grit sandpaper. The side of the blade facing down is completely covered with an orange Tesa tape (the best I found so far - leaves practically no residue)

It turned out that Niolox reacts quite differently to sanding than the D2 (the only other stainless steel I have used so far). When I went up to #600 grit I started to get a quasi-mirror finish, but at the same time I was seeing quite some #400 scratches I could not quite get out. So I went back to #400 and finished the blade with this grit.

Working with a #400 sanpaper - there are still grinding marks to be removed.
Back to the handle. I cleaned all sides on disc sander, and then squared up on #160 sandpaper.

Finishing the shaping before chamfering.


Flattening all sides.
The most critical part of the process for me (because I do it on the disc grinder) is to chamfer the handle to octagonal shape - I find it very important not to try to hurry as it is very easy to slip or grind too much away.
Chamfering to octagonal shape.

Testfitting the blade. Good!
Once the final shaping of the handle is finished it is time to finish the surface. I go through progression of #240, #400, #600 and #1000 sandpaper. The step with #240 is done on flat support - all scratches left by the disc grinder needs to be removed.

Note: One needs to be careful and watch where the pressure is applied as one may unwillingly 're-shape' the handle. Ask me how I know.

Sanding with the higher grits is done with a small sanding block (about 10 x 2 x 4 cm) - the long narrow sides have a double-sided scotch tape so that I can swap the paper. I do the sanding 'free hand'.

Hand sanding - finishing the handle.



Hand sanding finished.


Hand sanding finished.
Hand sanding finished.
Once the sanding was finished all that the handle needed was a few coats with a board butter and it was finished.

Oiled with board butter.
Once the handle was finished I glued it onto the knife with G/flex epoxy. That is a slow procedure in particular when it is colder in the shop and the glue does not want to flow quite as fast as I would like, plus it takes patience once the knife was fully inserted to take out all bubbles that may appear many minutes later.

As the photos of the finished knife show - I have one obvious need for an improvement. namely when putting the edge on the blade for the first time I inevitably scratch the blade 5mm or even more from the cutting edge meaning that the blade should actually be re-finished again. Hmmmm, I need to give it some thought.

Finished knife

Since I was in a hurry and the finished knife was already with my friend for testing, I did not manage to take some photographs, so here are a few taken by my friend.

Looking at the photos below I can not help but admit that the finish of the blade does look a bit ... particular (the photos do make it look a bit more scratchy than in person though). I really need to work on it in the future.