The turning saw is the progenitor of the bandsaw, used to cut curves before the advent of machinery. I've also heard them referred to as bow saws. Very thin blade material can be used because tension is provided by the wooden frame and a "Spanish windlass". The handles and blade rotate to allow for cutting stock deeper than the frame, hence the name turning saw . In addition to cutting curves, they are quite good for cutting dovetails or other joints where a narrow kerf is required. They can be pushed or pulled for cutting depending on your preference. I'm making this one with London Pattern handles featured in my previous post.
I have made bowsaws in the past with metal pins inserted into the handle and a slot to hold the blade. This was unsatisfactory because the pin was epoxied into the handle and eventually worked loose. I've seen examples of older saws that have wooden pins, but that too seems a weak link for a joint in tension. A joint that I've seen on European saws is a metal pin with a flat end that keeps the blade with a bolt and wingnut. I used a hybrid approach, turning the handle and pin as one piece and attaching a flat metal keeper to the wooden pin with brass rivets. The saw blade is attached with a small stainless steel bolt and a wingnut.
The frame is made from cherry, and the cross member tenon has curved shoulders that correspond to the mortise in the sides. This allows these members to rotate slightly in response to tension or wear. Chop the mortises and cut the tenons while the members are still squared up.
Shape the frame elements with a spokeshave, rasp and finish up with sandpaper. Leave the frame full at the handles and joints, but the rest of the frame can be sculpted into graceful slender elements. The Spanish windlass toggle is also a turned element. A deep cove accepts the string and once tightened by rotation, the end is inserted into a small round mortise on the top of the cross member to keep it in place.
The blade is cut to length from a band saw blade. Several different blades can be made up for this saw depending on the intended operation. Band saw blades are easily cut with a cold chisel, just remember to use eye protection and leather gloves. I intend to use this one for dovetails and occasional curve cutting which are mostly rip cuts, so I used a general purpose, 15 tpi bandsaw blade and reduced the set of the teeth by running a sharpening stone down both sides. If desired, the teeth can be reshaped with saw files and a vise; more on that later. I use hemp twine for the windlass. This can usually be found in upholstery supply shops, used to tie springs in furniture. This is a great weekend project with a result you can use for a lifetime.
At left are some of the tools that I've made for myself. The tool in the top left is a travisher, which is a specialized spoke shave for hollowing and sculpting seats. One starts with the inshave or scorp in the top right and then refines or "fairs" the surfaces with the travisher. The tool in the foreground is the chair devil. I've seen manufactured travishers and inshaves but I think all the chair devils in existence are craftsman made, and that in itself contributes to the mystery of it's construction. Chair devils are scrapers, the blade cuts by means of a burr raised on the tool steel edge with a burnisher. You may be familiar with card scrapers or the venerable Stanley #80 cabinet scraper which is a most useful tool to tame tearout after hand planes have reached their limit. A chair devil is a scraper for parts that are round in cross section, although I have seen examples that are simply flat scrapers held in a handle. In the photo above you can see what it does. The stock is held in the shaving horse and when pulled like a spokeshave, this tool raises curly shavings and leaves the surface of the wood smooth and uniform.
I start with a squared piece of stock 1 1/4" square, 12" long and turn the handles on the lathe, leaving the center portion square. Then cut the bed into the square center section the depth of the cocobola cap, about 3/8". Note that it is important to make the bed dead flat, and the blade is recessed into the osage bed by the thickness of the blade, no more. A throat is cut into the the cocobola cap for shavings to escape, but the throat should be narrower than the blade width, only as wide as the curved area so the blade is captured between the flat areas of the osage bed and cocobola cap. If the blade isn't seated properly, or if there are any gaps between the cap and bed, shavings will clog the throat. Some fine tuning will be necessary to refine the throat so that shavings feed smoothly through the opening.
