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Knife set - first test production run of handles (part 3)

Posted by Dave Bull on February 25, 2012 [Permalink]

Still working through the first sample run of handles ... It's going so slowly because I'm still building some of these jigs as I go along. It will be very interesting to run a test batch once I'm done, and see just how long it takes to make these things. And indeed, I'll have to get that information before I'll be able to set the final prices ...

Anyway, at the point we left off yesterday, the handles had been resawn and the parts needed to be sanded. Here's the setup (coffee cup optional ...):

I'll do the thicker of the two pieces flat on a sanding stick. No way will this go on the belt sander, as that would rip off way too much wood, and it would be very difficult to control for flatness. (Tape is for protection ...)

But I can't do the thin strip this way; it is too difficult to hold, and it would be very easy to lose the flatness - getting it 'dipped' at one corner, etc.

So it goes into this jig.

The base is nothing but a flat piece of wood with a strip of sandpaper glued on. The stock goes on top of the sandpaper. The other piece is a cover, to do the rubbing, which has a recess in the wood with a strip of sticky rubber glued into the bottom of it. The dimensions are arranged so that the wood to be sanded fits into that recess and is held in place by the rubber during the sanding motion ...

Flatness is guaranteed, as the two pieces of the jig mate perfectly, and slide back and forth with no wobbling or dipping. The little piece comes out perfectly flat, and presto - we have our two-part handles!

Now we get to a tough one ... cutting the grooves for the blades. I can't actually go through with that today, because (as I mentioned earlier) I don't have any of the 'hardware' here at present. But I can get the basic jigs ready, and them adjust them once I can measure the blades.

Here's what I plan to use - the same router jig we saw yesterday for cutting the string slots. Before reading on, can you guess what the skateboard ramp is for?

Putting the main body of the jig in place should give a pretty big hint!

Here it is, ready to go, with one of the handles in place, with the 'belly' exposed to the point of the router.

As I push the jig forward, the slot for a blade (in this case, a 3mm wide flat chisel) is cut. Just as the router gets to the place where the back end of the blade will be, the handle hits the ramp, begins to slide upward, and moves out of the way of the router blade ...

... leaving us with a smooth finish to the end of the slot.

Given that I don't actually have any of the hardware on hand now, I'm not going to spend more time getting a full set of 'ramps' ready at this point. I have the router bits prepared for 3 and 6mm 'U' grooves, as well as a 60 degree V-bit for that shape of blade. Once I have the actual blades on hand, I'll finalize this part of the process.

So ... moving right along, let's get these two parts fixed together. We haven't had any success yet in locating good hardwood dowel for this step. We are also considering using bamboo, as that would be very long-wearing we think. But I need something right now, so let's take a peek down at the foundation of the building, next to the stairs heading down to the river. There is a pile of stuff left behind by the previous owner of this house ...

... among which is the remains of a long-ago bashed-up baby crib. A mahogany baby crib.

This will do just fine. I grabbed a piece of it, and back up in the workshop ripped it to thin strips on the table saw, then roughly planed off the corners. (Coffee optional.) And now it's time to meet an old friend ...

... my bench motor. This has been quietly sleeping in a box for quite a few years. I need to figure out how long ... and as near as I can tell, the last time I used this would have been in about 1975 (give or take a year or so). I was working on flute design, and although I never got as far as building one, I did make a number of rough mockups of design concepts. A bench motor like this is the most basic tool that a musical instrument builder (and jewelry maker) needs, and I bought a good one.

After more than 36 years, I was a little hesitant to power it up, but there was no concern. She runs beautifully.

Bracing against some wood on the bench, I used a file to do a quick wood-turning job.

The mahogany cuts very smoothly, and we're down to size in a matter of seconds.

I don't want to jam a slightly oversize peg into the chisel handle, to avoid splitting it, so I polished the dowel with a block of cherry with the same size hole drilled in it, then cut it off and put the handle together.

I forgot to take a snapshot of sanding the dowel ends, but you can figure that one out, I'm sure.

Then, the bench motor comes into play again with a felt pad for buffing.

I don't have any polishing compound on the buff. I have no experience with polishing bare wood, and Sato-san and I have yet to decide how to finish these. We don't really want to varnish them, but are not sure which way to proceed: nothing, wax, oil, ?, ... Cherry will darken naturally, and actually it starts to do so within a few hours of a new surface being exposed; the samples I made last week are already deepening quite nicely. 'Doing nothing' is actually an option here ...

If you have any experience with this sort of wood finishing, and have ideas to share, please do so in the comments below.

So here we are. It's actually not finished, but that's as far as I can get it at present.

I still need to build a jig for tying the shamisen cord accurately and neatly, and there will be one other step inserted into this sequence at some point, and that will be a very important one ...

... I have to come up with an unobtrusive way to put our name on these. Many tools of this type have the brand 'burned' on, but at the small scale that the characters for 木版館 will appear, that would just be a brown mess, so that is off the table.

We actually have a solution worked out, but the outside workshop that we contacted for the job wants 140 yen each to do it, and we can't possibly justify that much, so we're still casting around ...

And now, in an extraordinary example of the famous Japanese 'Just In Time' production systems, a package was delivered to my front door this morning. A very heavy package. I have to get started on the production of the 'other' tool in this set of six - the one that will not use a rectangular handle, but a round one ...




Added by: Michael Kohne on February 25, 2012, 12:22 am

For the name - can you find someone with a laser engraver? They can burn very tight lines very quickly. I don't know what they'd charge, but it's the first thing I can think of that would be able to imprint the way you want on the handles.

The other thing I can think of is a metal character punch, but I suspect that the characters are too intricate to read well in the wood if done that way.

Added by: Dave on February 25, 2012, 12:29 am

Laser engraving is indeed the method I was hinting at in the post. What I'm thinking is to have the characters engraved very shallowly - around 0.5mm at most, and then fill the cut area with a dark compound of some type - perhaps epoxy mixed with fine dark sawdust. After polishing, the lettering should be dark against the fairly light wood, and it would burnish nicely over time.

But the first company I asked wants (as I mentioned in the post) 140 yen per piece for the job, way more than we can budget for just putting on the name!

Added by: Marc Kahn on February 25, 2012, 11:51 am

Is the dowel glued to one of the sides of the handle, and free to swivel on the other side?

Added by: Dave on February 25, 2012, 1:56 pm

The dowel gluing is still in play ...

I'll probably glue it into the base section, and leave the top free to swivel, I guess. The downside of that is that if people play with it too much (it rarely needs to be opened, actually) and the top thus becomes loose, the back end will tend to 'float' upwards after the two parts are tied together at the front end.

If I were to glue the dowel into the top piece, there would be less chance of this happening, but the thing would then be more difficult to open, as the long portion in the lower section would of course not rotate easily (unless it were overly loose).

Added by: Simon on February 26, 2012, 8:19 am

Have you thought about threading the dowel? Glue the thin side, and screw it into the thicker side, so that it lines up when it's tight.

Added by: Dave on February 26, 2012, 8:23 am

Threading? At the level of 'engineering' we have available to us here, I'm not sure that we would be able to get the threads lined up so that the gap was closed exactly at the point where the two pieces lined up. I can't see getting that to work properly.

We could insert the dowel, and then glue the top piece precisely in place, but would it stay in such alignment ...

Added by: Peter J Dylag on February 26, 2012, 11:01 am

Where can we pre-order!! I'd love a blade and a little front money wouldn't hurt.

cant wait to hear back.



Added by: Dave on February 26, 2012, 11:53 am

Where can we pre-order ...

We really can't take orders yet, because without having even one sample set completed, it just wouldn't be right! And until the production process is more firmly settled, the price is still kind of unknown ...

Thanks for your patience, and it won't be much longer!

Added by: Lana Lambert on February 26, 2012, 11:38 pm

I really enjoy watching this beautiful process. I'm excited to see the blades. I also like how some of your wood is salvaged from an old baby crib. That mahogany tree is seeing a lot of stories being milled into a baby crib, languishing under the house for years, and then being revived into a working tool.

Added by: Kalle Pihlajasaari on February 28, 2012, 5:14 am

Now if you want the best of both worlds with the dowel you can take a page out of the camera filter container guide book. They used a cam action to lock the round jewel cases for polarizers and UV filters and such.

The lid and the bottom had a portion that was not round and as you rotated the boxes it would bind tighter and tighter, perhaps 3, 4 or 5 sides.

So if you had a 3 lobed pin and hole it could be made to bind when the two handle halves were aligned and then release when it was rotated open in the correct direction. A tricky bit of making but a nice bit of using, no play when in place and loose to fiddle with blades if required.

Added by: Julio Rodriguez on February 29, 2012, 7:36 am

Have you thought about purchasing hardwood dowels? here they are available in many lengths and thicknesses (1/8, 3/16, 1/4") and you would avoid the labor. Then again if you have a whole crib full of mahogany for stock that should be enough wood for mores knive sets that you could ever build.

Added by: Kalle Pihlajasaari on March 5, 2012, 4:49 pm

They sell small laser markers and rubber seal engravers in China these days for US$1000 or there about, the build quality is often poor and one may need some technical skill to align all the optics etc. However it is tempting when comparing to the same units for sale in USA and South Africa for about US$5000. Buying a couple would leave a lot of spare parts.

The software with these cheap units is also often pretty sad and one needs to have a small measure of trust in a Chinese supplier, some of them are on the popular auction site.

I have been tempted a few times and with a simple alignment jig one can mark and A4 sheets worth without any user intervention and even serialise or personalise them if you choose.

Added by: Dave on March 5, 2012, 7:47 pm

They sell small laser markers and rubber seal engravers in China these days ...

Well, after my experience with these - very simple - power tools, I'm not really sold on the idea of sourcing this kind of complex tool from a Chinese supplier, especially as there is no chance of after service ...

But I think that we've found the solution. I got an email from an acquaintance the other day, a man who had read a posting I made on the GDIY (gaijin do-it-yourself) internet forum mailing list about this situation.

He recommended a friend of his living in Nagasaki Prefecture, who owns a laser machine, and who does all kinds of work for hire with it. I got in touch, and it does indeed look as though he may well be the man to do it for me. I've sent him a small package of sample handles to work with, and he'll make a bunch of trial engravings of differing depths, etc for me later this week.

I'll of course post about the results as soon as I have any ...

Added by: scott robertson on March 13, 2012, 2:16 pm

Hey Dave,

Your quite a woodworker! I'm impressed. I'd like to chime in on the finish for your tools. I would use pure tung oil. It's also really cost effective you could finish thousands of tool handles with a 32 oz. bottle of high qulity tung oil. just my two cents.


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