Saturday, January 13, 2018

Project #25 - 150 mm tall petty from 1.2442

This was one of the fastest projects I have finished till today. A friend of mine who got a Moritaka AS 150 mm petty just a few months ago managed to bend it at work (while cutting !) and was in a need of a stronger & stiffer petty.

Since we have some experiments with 1.2442 steel in mind for the near future, I offered him that I could make him a petty from this steel as I have not used it yet (though I bought it about a year ago).

From the design point of view the idea was simple - ca 35 mm tall, 150 mm on edge, WA handle.

The blade

As usually, I have started with the blade design. Here I have decided to use the profile (of the cutting edge only) of a Yoshikane SLD 150 petty, which has proven to be very practical. I have then adjusted the height as the Yoshi is only about 30 mm tall. 

This was the first time I have worked with the 1.2442 steel (not in production since quite a while), which bears some similarities (composition wise) with Japanese blue #1 steel. When cutting the steel with a hack saw one would notice that there are alloying elements present, but it was still easier to work with than for example Niolox, though not as easy as O1.

All of the pre-HT steps were 'standard' ones, so here just shortly:
  • cut out the blank from 2.7 mm thick stock with a hack saw (yes, I leave the tip flat until after HT)
  • finish the profile with a #40 belt
  • clean up to #220 belt
  • paint the edges blue with a permanent marker
  • scribe the center line on both edge and spine (including tang)
  • grind the bevels and distal taper - I went down to about 1 mm on edge to minimize the risk of warping during the HT - I have not worked with this steel before.
  • Finish the profile of the heel (much harder to do after HT)
  • Sent the blade off to HT to Achim Wirtz to be hardened to HRC63

Blade after HT.

After HT I would first thin the the grind down to last 10% (leaving about 0.3 mm edge thickness) with the #40 belt.

Grinding after HT with #40 belt
Distal taper - the tang will be worked on a little later.


Close to final geometry

At this stage I would go briefly to 300 water stone from JNS to check and clean up the bevel grind to make sure that there are no defects like over-grinds and low spots. I was not trying to get the final bevel grind - really just checking the consistency. It all looked pretty good, just at usually the heel was a little thinner last 2-3 millimetres.  I was not trying to get 'perfect' bevels at this stage or even shinogi line.

After that I would proceed with shaping the tip and tang of the blade.


Shaping the profile of the tip (after working the bevel on 300 stone)


Once all the coarse grinding was done (blade geometry, tip shape, tang shape) the next step was scratch removal. During this step I would not worry too much about that bevel I did on stones as I was not trying to get as little as possible material removed. I would proceed with #60 and #120 ceramic belts and then proceeded to 3M Trizact 'gator' A100 belt. The A100 would be around #200 grit and frankly I would have been preferable to have the coarser A160, but it appears not available in 1x30" size. 

Grinding with #60 belt under different angle to remove all #40 scratches.
After the A100 I went  to A65 - always slightly changing directions. At this point I realized, that I forgot to round the choil and spine (ideal point to do that would have been after #120 belt), so I first coarsely rounded the spine with a belt and finished to #1000 grit by hand. The choil was rounded entirely by hand and then also polished to #1000. Once these parts were done I continued with #65 and #45 Trizact belts.

Rounding the choil with #240 grit. The light accentuated the scratches,
they were far less scary :)

At this stage of finish I would normally switch to hand sanding going to whatever grit would look nice (I am normally by semi-matte finish). But I was under a time pressure as I wanted to present the knife to my friend (who did not expect to see it anytime soon). So I took a shortcut. I decided to make  an experimental finish. I had a second session on the stones - this time a progression of 300, 1000 and 4000 and ground the bevel down to is final edge thickness (not more than 0.1 mm before sharpening).

I followed by finishing the blade with A30 belt making sure all scratches are gone. I tried to avoid the bevel as I did not intend to remove any larger amount of material there, just final finishing before sharpening once the knife was completed.

In the process of last scratch removal with A30 belt.

The last step on the belt grinder was made with a fine (blue) Scotchbrite belt. There I just wanted to get the finish a little smoother (the belt is nearly too sharp for that). I knowingly also toughed the the bevels so that I had an even finish on the 'shinogi' line.

Finish after fine Scotchbrite belt. Again - the direct light makes the scratches
to stand out more than they would appear under softer light.
The same Scotchbrite belt finish under different angle

The blade would not be finished without a logo ;) On this blade I only did deep etching with DC without using AC afterward to blacken the logo - as was wished by my friend. I have to admit I like this less obtrusive and will probably stick to it with most of my future knives.

About to etch the logo.
As always until now I have used the Electrolyte 94 as electrolyte, 12V setting on the etcher and etched for 6x3 seconds (e.i. lifting the etching head every 3 seconds so that the gas that is produced in the process can escape and does not cause uneven etching

The handle

While waiting for the blade to come back from the HT, I would start to work on the handle. The design was again a 'standard' one using buffalo horn for the ferrule and stabilized & dyed Australian wood (curly spalted Boxelder) with a beech dowel inside. Since this handle was a rather subtle one, I decided that apart from cutting the ferrule and handle block to rough shape with a band saw, I will do all the shaping & sanding by hand on a stone sanding block.

Handle materials

The basic process of the handle making:
  • cut the & square up a piece of buffalo horn and handle block
  • drill the ferrule and handle block
  • check that the handle block axis (defined by the drilled hole)aligns with the ferrule & glue them (using my own gluing press that allows using a piece of dowel material for initial alignment)
  • Once the glue cured clean & square up the future handle

Handle components cuts and squared-up

Gluing the handle using a jig. The dowel is
removed once the handle is clamped down.

Normally I would glue in the devel before I would glue the handle parts together, but this time it took longer to get the blade back from the HT and I did not want to loose too much time, so I glued-in the dowel at a later stage (when the blade was back and I could test the fit).

Handle squared-up after gluing and ready for shaping


Normally I do the rough shaping (= final height and width including distal taper) with a coarse belt, but I decided to do this completely by hand. I would do this on a #80 grind sandpaper taped flat on a stone (old table-top)

Handle after coarse shaping
Once the desired height and width (with about 1 mm in every direction left for further sanding) was achieved, I continued through 180, 320 and 600 grits.


Coarse shaped handle refined to about #600 grit.

In the next step I have sanded the handle to octagonal shape. Again - this is something I usually do with the little disc sander that is part of my belt sander, but I simply wanted to do it by hand. This is an interesting experience and allows to get the feel of how important is even pressure distribution.

Once the handle was shaped and finished to #600 grit the blade finally arrived from the HT and so I could make the fitting dowel for it.

Handle shaped and finished up to about #600

I have to admit that since I got the little Record Power BS250 band saw, the cutting of dowels got so much easier. Once the slit was cut it gets widened on a belt sander (#80 or #120 belt seems to work the best) until I get a nice, easy with with the tang and the handle


Dowel cut, now the slit will be widened with a belt sander.
As you may see in the photo below - I tend to make the dowel some 5 mm longer that the drilled opening in the handle - the reason is, that the front side of the dowel might have suffered uneven grinding with the belt sander, or it might get sanded by a rasp after gluing. So I rather make it a little longer and then sand to length after gluing.

Checking the fir.

Once the dowel fits nicely I glue it inside the handle with epoxy. I tend to create small 'pockets' (dips) on the side of the dowel with a round file so that if there is a bit too much epoxy it can go there instead inside the slit itself. You really only want to use just a little epoxy at this stage, because if too much of it leaks inside the handle you will spend a lot of time with needle files and rasps trying to get it out.

As always I use a piece of scrap steel shaped like a very thin edge to push the dowel open while the glue cures, so there will be no gaps between the dowel and the ferrule.

Gluing the dowel

Once the handle was finished this far I tested a little more to see how it feels in hand (with the blade inserted) and got the impression that while I like the overall size and shape, it would feel more nimble if it were a little narrower in the front. I have have covered most of the handle with tape (remember, it was already sanded to #600) and used #180 sandpaper to give a bit of horizontal distal taper to the ferrule.

About to start sanding the distal taper.
Thanks to the fact that the handle already had a #600 finish, it was very easy to observe where the material was being removed. I started by tilting the end of the handle upwards very slightly and applying pressure only on the very front of the handle. I would stop after every few passes and check the progress. Once I have established a new bevel I would continue until it reached the end of the ferrule. I would constantly check and if necessary compensate any unwanted tilts.

After first few passes - looking good so far.

The horizontal distal taper sanded in.

Once the taper was sanded the whole handle was finished up to #1000 grit and the front and rear edges were chamfered. I also used steel wool when finishing the handle, but it was not a particularly good idea with this wood which has a somewhat coarse and not homogeneous structure and the steel wool would tear little pieces out. 

Front side of the handle sanded to #1000 and the opening lightly filed
so that the shoulders of the blade would fit nicely.

Because of the slight tear-out I have the handle once coat of Birchwood Sealer & Filler, sanded it lightly afterward and followed with 2 or 3 coats of Tru-Oil for a good measure. As always, I would apply the Tru-Oil and while & polish the handle with a paper towel immediately after the application.

Tru-Oil curing after application.

At this stage both the handle and the blade were finished (the blade will still get slight refinishing of the bevels on stones) and thus ready for gluing.


Well, let's do the last step.
As with the last few handles I would heat up the G/flex epoxy to make it easier to get it inside the narrow tang slot, then heat up the tang of the blade and insert it carefully. Once the epoxy started to come out I wold let the blade to sink in the handle slowly while wiping the excess epoxy. Since I use G/flex which has 45 minutes pot time I did not have to hurry and even had time to take some photos :) Once the blade was in place I would heat the top of handle gently with the hot air gun to allow most of the bubbles to escape.

I have used small pieces of paper towel wound round ice stick and dipped in Toluene to clean up the blade and ferrule from epoxy rests.

The handle is in place, the last bit of epoxy is still to be cleaned off.
Gluing the handle this way also means, than more often then not the epoxy will shrink a little while cooling down (some air bubbles always remain trapped inside) and thus a shallow void between the dowel and the blade would appear. This is is filled with epoxy (Blade Bond Ultra that has pot time 15 minutes) the next day in a similar manner - the mixed epoxy is heated up and just very little of it is applied to the contact area between the blade and the dowel. Heating the applied epoxy with the hot air gut would allow it to fill the narrow void and the bubbles to escape. This time however I would wait until the glue starts to set it (get thicker) and only then I would use clean the rests off (paper towel, ice stick and Toluene). If I were to do it too soon, I would risk 'sucking' out the epoxy from the freshly filled void. The reason to use different epoxy is that I do not want to wait for an hour for the epoxy to start to set it :)

Gap filled with the epoxy, the excess was already removed.
After last clean-up of the bevels on the stones the knife was officially finished.

Finished knife












Lessons learned

Not so much went (thankfully) wrong this time
  • 1.2442 steel was nice to work with (in comparison to Niolox every steel feels nice to work with though) 
  • The "narrow wide bevel" grind appears to work very well (feedback from my friend)
  • The gentle horizontal distal taper improved the feel in hand considerably
  • I am very happy how the belt finish turned out, but I have a lot of room for improvement (the finish and the efficiency) there. I will need to experiment with different belts to get the most out of it. I plan to make this simpler but very functional finish in the future more often (not only on Niolox)
  • I may be doing more knives like this one in the future. In general I will probably start to make small batches of knives once I get a knife that I (and in particular my test users) like.
  • Again - I was in a hurry to finish this knife and so I did not make proper photos or a video. I need to improve on that.

No comments:

Post a Comment