In my shop, travishers are an intermediate tool in the seat carving process between initial shaping with an inshave and fine-tuning the surface with a card scraper. Travishers remove the gross irregularities, and they do it in a hurry. They are the jack plane of seat carving. That said, the body mechanics involved in using a travisher are somewhat counter-intuitive and can take some getting used to.
Practice NOT cutting. This is the best way to learn to use a travisher correctly. Hold the travisher in two hands, thumbs resting on the flat pads on either side of the throat. The blade is facing away from you — travishers are usually pushed. Put the travisher onto the work, then roll your wrists up and away from you until the blade is no longer in contact. The sole of the travisher is all that contacts the work (see photo). Now push the tool, trying to keep the blade from cutting. This is where you should start each and every cut. Once you get the feel of not cutting, straighten your wrists slightly, and the blade will come in contact with the work. Straighten your wrists more for a heavy cut, less for a light cut. End the cut by rolling your wrists away from you to bring the blade out of the cut.
As I already mentioned, these travishers are meant to be used in a way that gives you control over the depth of cut as you are using the tool. However, if you need to increase the blade exposure, inserting pieces of paper between the blade and the body will raise the blade. Evenly scraping the sole will have a similar and more permanent effect. Carefully filing the shoulders which the blade seats on, will lower the blade. It doesn’t take much. A single thickness of paper will have a noticeable effect.
Sharpening most tools is the same basic process. You sharpen the bevel with a coarse enough stone to be expedient. Work up through the grits to polish the surface and make a longer lasting edge. Then remove any burr you’ve created by working the burr back and forth with your finest stone until it breaks off, leaving a crisp edge. There are many ways to do this, most of which work. Here are some thoughts:
The Bevel: A deburring wheel, called a Beartex wheel (from MSC or Highland Hardware), followed by a hard felt or leather buffing wheel, is a quick way to sharpen the bevel. The Beartex is like a very aggressive buffing wheel. The tool can quickly overheat or the edge can quickly round over, so it takes a little getting used to. Putting your wheel on a homemade threaded-rod mandrel, chucking it in a variable speed lathe, and reducing the speed could solve this problem.
A safer method would be to screw the blade — bevel up — to a wooden form, and use some kind of slip (diamond, Japanese waterstone…). An old Japanese bench stone, the face rounded with a rasp, gives plenty of room for the hands if you plan on a lot of sharpening. The bevel can then be polished on a felt or leather wheel. Skew the blade on the wheel to give maximum surface contact. Start with the heel of the bevel in contact with the wheel to give yourself a frame of reference. Then move the blade across the wheel towards the edge until you see a very slight feathering of the polishing compound curling up off the edge. This indicates that you are right on the edge. A heavy curl indicates you have tipped the blade too far, changing the shape of the bevel and blunting the edge.
The Back: The back of the blade must be kept flat. If the back is rounded over or made convex, however slightly, the tool will not cut. Only sharpening stones should come in contact with the back — no strops and definitely no buffing wheels. The back comes flattened and polished, so unless you run the tool into a nail, your finest grit stone should be enough to remove the burr after sharpening from the bevel.
If the Beartex wheel gets away from you and grinding the bevel is the only option, a small grinding burr chucked into an electric drill should do the trick.