3. Boring the Pin Hole
The next step is to bore the pin hole. In doing this it is best to use a drill press, and a clamp or jig to hold the block in place, a misalignment of the bore hole for the pin can create some difficulties. In the absence of a drill press this can all be done with a hand drill, but take care to ensure that the pin hole is absolutely square to the block. Any major misalignment of the pin will result in a block inclined to jam its sheave.
Finally, you will want to score the block to help hold the strop in place. The scoring can be done with a round file, and you may want to round the edges and sand down the outside of the block to a smooth finish.
If you cut a tenion, you can place the mortise of the block over the tenion, and use it to hold your block while you file away at the excess wood. The tenion can be clamped in a vise or held in your hand.
A simple "block holder" to make filing and rounding easier
Filing, scoring and sanding the block to shape
4. Finishing the Block Shell
A microplane rasp is a great tool for helping to finish your block. In some cases it has been suggested to use a round over cove bit to help round the edges. You can also achieve similar results by using a sanding disk. In any event, you will definitely want some kind of pocket rasp. All of a sudden coffee and lunch breaks become "boat building" time as you can rasp away at your wooden block!
The original Microplane© Shaping Rasp is a great
tool for working on wooden blocks
Once you have finalized the shape, and sanded it smooth, it is time to finish the block to prevent cracking and splitting. There are various methods of finishing the block, it can be covered in epoxy resin, soaking in oil, or varnished. The traditional method of soaking in linseed or tung oil is very effective, offering a nice patena and good protection.
People have known about the unique properties of linseed oil for several thousand years. Linseed oil penetrates into wood, protecting it from moisture and rot.
Use boiled or double boiled linseed oil for best results. The raw linseed oil is purified and refined through the addition of oxygen to produce boiled or "cooked" linseed oil. This process eliminates protein and improves aspects such as the drying time, shine and purity. Even though linseed oil that has actually been boiled is still available -- it's called heat-treated or polymerized oil -- most of the boiled linseed oil sold these days that you find in the "big box" stores such as Home Depot, Canadian Tire, Home Hardware, or Lowes is raw oil that has been mixed with chemical additives to speed up the drying time. For wood finishing, you should use only boiled linseed oil. Thus, boiled linseed oil, though, is not boiled. The actual boiling of some varnish oils changes their drying characteristics. With linseed oil, though, it is the addition of certain solvents that causes linseed oil to dry more quickly, acting as if it were boiled. This makes it a better product for preserving tool handles, decks, and furniture.
Double boiled linseed oil contains a blend of driers (no lead) and inhibitors to get a high quality product that will dry to the touch in 8 to 10 hours. Also, with the inhibitors added, they ensure the final product will not be attacked by mold or mildew.
If you do plan to use raw linseed oil you will need to put it through a "boiling process" first. In this procedure, fill a can with raw linseed oil, submerge the shell and heat it gently until it starts to boil, cooking it for a minimum of a half an hour. The longer you "cook" the oil the better, it is suggested that you "cook" the oil for about three hours. In performing this process be careful not to overheat the oil, which could cause it to combust, or burn since it is cold pressed - it is not necessary to use a high heat.
To avoid having to heat the oil, a simpler method is to fill a container with purified double-boiled linseed oil. The quality of linseed oil you use is very important, take care to use only boiled or double boiled linseed oil in this process.
You can get boiled linseed oil from a variety of mail order sources, or in your local hardware store, some are mail order suppliers listed here:
Once you have submerged the shell in linseed oil, let it soak in the oil for about a week, once you are finished soaking the oil, wipe off the excess, and let it dry for another week. By soaking the shell for a long time, the wood pores are more completely filled and checking and cracking is prevented. The linseed oil will provide an excellent weatherproof finish that will not mar or crack.
Alternatively, you could also use tung oil. This oil, which is pressed from the nuts of a tung tree, was introduced to the West from China about 1900. It was useful for making superior, water-resistant varnishes, especially for outdoor use.
You apply tung oil just like linseed oil by sumerging the shell in a can. Tung oil comes from China, however, so it has a certain mystique. Because few people really knew what tung oil was anyway, many manufacturers began packaging varnish thinned about half with paint thinner and labeling it “tung oil,” “tung oil finish,” or “tung oil varnish.” Others further muddied the waters by calling their thinned varnish Val-Oil, Waterlox, Seal-a-Cell or ProFin. Tung oil doesn’t contain driers. It takes two or three days to dry adequately in a warm room when all the excess is wiped off. Real tung oil has a distinct smell that clearly separates it from wiping varnish and oil/varnish blends, both of which have a varnish-like smell.
5. Making the Pin
A pin can be made from a variety of materials. Traditional pins in the 18th century were made of of lignum-vitae, or cocus; When made of wood, the diameter of the pin is the thickness of the sheave. When made from metal, the pin can usually be about 1/16" larger than one-half the thickness of the sheave.
The strongest and best quality pin is made from silicon bronze. You can order a silicone bronze rod or find a silicone bronze bolt and cut it down to size and grind the head.
That being said, silicone bronze can be very expensive, and being a very hard metal it can be difficult to cut. A source for silicone bronze rods can be found here:Duckworks BBS
Alternatively, stainless steel or naval brass rod could be used. Naval brass is soft and is easy to work with, and in small sheaves is more than strong enough to handle the job. For large sheaves, and depending on the quality of the sheave silicon bronze or steel will work better over time.
For our pin, we found a marine hardware store locally that still sold brass bolts, we found a bolt long enough to fit through the shell, and cut off the threads, leaving just the head and the smooth part of the bolt.
Once the bolt was cut to size, we ground down the head of the bolt, so it was similar to a brass "lynch pin" - flat and thin.
The finished pin with the head ground round and flat.
Our "homemade" brass pin.
We then fit everything together and made sure that the sheave spun freely in our shell. We then "countersunk" the head of the pin, so it fit flush in the bore, so that the strop would fit nicely in the groove.
we fit it all together and checked for fit and finish and then
countersunk the head of the pin so if fit flush with the groove