|Handling with care and precision
||[Jun. 15th, 2004|01:06 pm]
Spent a bit of time last night putting a handle on one of the offset handle knives, a design that is attributed to the 12th century by some texts, but which I've seen executed in bronze dating back thousands of years (babylonian, if I remember correctly) in museums. Also used nowadays for kitchen knives so you don't bark your knuckles as you cut your bread. |
Here's a modern example of what I'm talking about: http://tinyurl.com/ytbku
I wasn't able to find a good example of what I'm making, though if you have the Knives and scabbards (Medieval Finds from Excavations in London) book, there are plenty of examples in there.
For this knife, I am using olive wood for the handle, just a simple slab type, full tang, pinned with four brass tube rivets. Tube rivets are just tubes used to hold the handle slabs to the tang, though the real adhesion comes from glue. Historically, hide or fish glue would be used, but I use a modern two-part epoxy (System 3 Marine grade, 24 hour cure.) I use the epoxy because it holds a lot better, doesn't degrade (System 3 marine grade has a 10 year warrantee), and gives me the set time to ensure everything is in the right location before it sets.
To start, then, I first anealed the tang of the knife by heating to a black heat, softening the metal enough to drill the holes. By clamping the knife in a metal, smooth-jawed vise, I was able to keep from ruining the temper of the blade -- the jaws acted like a heat sink. Next I laid out where I wanted the holes, and punched a dimple in using an automatic center punch. After cleaning out yet another mouse nest from the drill press workings, I drilled the holes in the tang. I used a cobalt-alloy HSS bit, with Anchor nuclear-grade cutting drilling and tapping lube. This stuff is great, and only costs about a dollar more than the non-nuclear grade for about a quart.
Using a scratch awl, because I couldn't find a pencil (note to self, buy another pack of pencils for the workshop. I swear, the mice must be stealing them or something), I laid out the outline of the tang on the handle material, a piece of stabilized olivewood 1/2" thick. Olive is a golden wood with dark streaks, so the scratch marks didn't show up very well. After trying a couple of different things, I found that soapstone would fill the grooves left by the awl and be fairly visible under the light available at the bandsaw, where I cut out the slab for the handle. I cut oversize by about an eighth of an inch to allow for positioning and oopses.
To ensure the holes in the handle lined up with the holes in the tang, I lined the tang up with the scratched-in outline on the slab, then marked and punched the wood for the first hole, then drilled it in. I then used one of the tube rivets (1/8" diameter brass tubing cut into 3/4" lengths, one end beveled to make insertion easier) to fix the tang to the slab. With that end secured, I drilled the hole in the far end, and pinned that as well, then drilled the other two holes. Next: turning the slab into scales.
Normally, I'd have measured and marked out the halfway point on the slab before cutting it in half for the two scales I wanted, but a) I didn't have a pencil, b) it was getting late, and c) I'd been watching some Japanese videos on how they do their sheathes and handles, and noticed that they did it by eye. So, I grabbed my japanese rip saw (Kataha Tatebiki), eyeballed the centerline, and did a decent job of bisecting the handle material.
I did a quick cleanup of the saw lines on the belt sander, then did an initial assembly. Everthing fit, so I cleaned up the surfaces and mixed up the epoxy.
Now, my father was a fanatic about mixing epoxy for the proper amount of time, and I've gotten into the habit of doing the same. Sure, you'll still get a polymer if you just mix it enough that the two parts are no longer discernable, but if you read the directions and mix vigorously for the duration therein listed, you'll get the predicted result every time -- a hard plastic with a tight bond to both surfaces that sets in the listed time period. Skimp on the time, and your bonds could be weakened, and the epoxy will certainly take longer to set.
Final assembly and clamping went as planned, and the piece is now curing in the workshop. I'll do the finish work on Wed. with any luck, and put up some photos.