Knives 16 and 17

This next knife creation project will eventually be a set of 3 knives, all the same design, but one large and two smaller.  I cut the steel for all 3 blades at the same time, but then put the large one on the back burner while I worked on the pair of small ones in parallel.  They are almost identical except for the handle scales which are different woods.

I decided from the outset that these two smaller knives would be gifts for two of my special, but unrelated friends in America.  That meant I was working to a deadline because my next trip to the USA was scheduled for October.

The basic shape differs from all the others I have made before in that the cutting edge is perfectly straight.  The back of the spine curves gently like a dolphin’s back.  The spine is decorated with symmetrical bevels, but not sharpened, and there are a series of transverse grooves to the back end of the spine, just in front of the handle.  These grooves are partly decorative, but they also provide a comfortable thumb rest.  Because the knives are smaller, the length of the handle is such that it is only long enough for the first 3 fingers of the hand to wrap around it and the little finger will be positioned behind the back end of the handle.  That is of course, in an average size man’s hand.  The overall proportions have been chosen to give a good, balanced visual effect to the design.

My friend Craig from Mulberry, Indiana, sent me some blocks of old Teak, salvaged from the deck of the USS New Jersey during its recent restoration.  I had hoped to use some of this Teak for the scales on one of the knives, but unfortunately time and years at sea have weakened the structural integrity of the wood, making it unsuitable for knife scales.  Instead I have used Zebra wood for the one knife (the darker wood with the pronounced, striped grain), and I have used Maple for the other (the lighter colour wood).  The scales are secured with epoxy and brass pins.  The blades are made of O1 Tool Steel, hardened, polished to a mirror finish, and sharpened.  After final construction the scales were polished with a few coats of beeswax to protect the wood and give it a healthy lustre.

Knife dimensions
Overall length: 200mm (7.9”)
Blade: 115mm (4.5”) long, 25mm (1.0”) tall at its maximum, 4mm (0.2”) thick
Handle: 85mm (3.4”) long, 25mm (1.0”) tall in the middle, 17mm (0.7”) thick

For these two knives I also made matching leather sheaths.  The sheath design is quite simple, with just a pair of slots cut in for the belt, and the leather has been moulded to hug the shape of the blade and forward section of the handle.  This shaping has stiffened the leather so that the knives almost “click” into place when inserted and they will not slip out unintentionally.  The leather is stitched using Saddle Stitch and the cut edges were smoothed with fine sandpaper before being treated with “Edge Kote” to give the darker, professional looking finish.

Enjoy the photos.

Blades shaped and bevelled before heat treatment.

Blades after heat treatment.

Blades cleaned up, and scales cut and drilled.

Scales glued and pinned.

Scales roughly shaped.

Scales fully shaped and sanded.

Sheath leather cut.

Sheaths folded and glued.

Holes punched ready for stitching.

In the “Stitching Pony”.

Sheaths stitched and ready for moulding.

Moistened leather moulded to fit the knives and left to dry.

Cut edges finished with “Edge Kote”.

All finished.  Sheaths dry.  Blades polished.  Scales waxed.

Knives in their respective sheaths.

Mike with his new knife.

Craig with his new knife.

Sand Tumbler

I’m sorry the blog has been quiet for a while – blame it on other priorities getting in the way, such as vacations and preparing to put the house on the market.  However that does not mean the Kayfa workshop has been totally idle!  In this post I will tell you about another little machine I have designed and built, which I call a “Sand Tumbler”.

The principle is that, sometimes I may want to put a satin finish on a blade rather than a shiny polish, and for that I need a way of giving the blade a gentle allover sanding that will not leave any scratch marks from traditional hand sanding.  This Sand Tumbler should do exactly that.  It is basically a plastic tube, closed at both ends, but into which I can put a quantity of sand and small stones together with the blade to be buffed.  The tube then rotates slowly for several hours, possibly overnight, and the gentle tumbling of the blade in the sand will produce the satin finish.

The main components of the device are:

1. The tube, which is cut from a length of waste water pipe about 100mm in diameter and 400mm long.  The one end is permanently closed with an end cap, but the other end can be opened because the end cap has a screw thread.
2. The roller wheels for the tube to run on.  These were repurposed from a small skateboard.
3. The drive motor and gearbox to reduce the speed but increase the torque.
4. A power supply to convert the mains power to 24V DC.
5. A speed controller for fine adjustment of the drum’s rotational speed.  Experimentation will confirm, but I anticipate a speed of around 50-60 rpm will be good.
6. A toothed drive belt and pulleys to connect the gearbox to the main tube.
7. An on/off switch.
8. The frame that everything is mounted on or in.

My first attempt repurposed the motor from an old overlocker, but I could not slow the speed enough without overloading the motor and it burned out very quickly.  I then purchased a 24V DC motor with fitted gearbox that was theoretically powerful enough for this application, and it does work as expected, but I think the power rating is still insufficient because the motor runs very hot after about 10-15 minutes.  I will soon replace this with a more powerful motor that will be “man enough” for the job.  Until such time I am nervous about putting it to work too strenuously, so a full demonstration of its capability must wait for another day.

Until then, enjoy the photos.

The full Sand Tumbler device.  The power supply, speed controller and drive motor are housed within the wooden box.  The toothed drive belt is on the left side of this view.  The digital display gives the percentage rotation of full speed and the knob to its left is for adjusting the speed.

View from the right showing the power supply unit that converts mains AC to 24V DC.  The green button is a secondary isolation switch for safety purposes, if required.

View from the left showing the drive end with motor, gearbox and toothed drive belt.

Video showing the unit in operation.  (Turn down the volume before running the video!)