Turning Archive 2004

Making a Better Coping/Dovetail Saw

Bob Smalser, Seabeck, WA
>As the lads I'm writing for have made good progress in the last year, the next article I write for them is gonna be on something a bit more complicated than basic tools and joinery:

Store-bought coping saws never work to their potential because those flimsy steel frames donít hold the blade sufficiently taut. Their frames can be bent outwards for more tension, but with hard use they quickly bend back to their original mediocre performance. I want one I can speed up dovetail work with, cutting dovetails that require minimal paring in two cuts of the saw. Making that tight, 90-degree turn neatly at the bottom of the dovetail requires a taut blade, and Iíve made a number of frame saws over the decades to achieve that goal. This model is the just the latest refinement of time-tested designs made by my family for generations.

Iím using some very special wood for theseÖa 240-year-old Pacific Madrona growing at the high tide line of Hood Canal. Termite-ridden, it had to be taken down. While itís the largest and straightest-grained Madrone Iíve ever seen, the salt water seems to have had a stunting effect in spite of full sun, and the diffuse-porous growth rings are so tight I need magnification to count them in places. Truly exceptional, it is so dense it cuts like tough butter without the splintering normally common in the faster-grown examples of this wood. Normally a twisted understory tree and both harder and heavier than American Beech and Sugar Maple, we use the straighter trees for flooring and stair treads here in its Pacific Northwest native range. Like beech, it shrinks severely in drying, but also like beech, is sufficiently stable once dry for making tools. You can use mahogany, cherry, walnut, maple, ash or any number of hardwoods successfully for your saw. Because of the orientation of the holes in the design and the stresses on them, I recommend you use quarter or rift-sawn stock for the handles.

Iím making a run of 8 saws for economy of scale and full use of the rift sawn, 5/4 board I selected from the drying stack. When making saws, handles, hand screws or other tools, I always use up all the stock I devote to the project, saving any finished pieces leftover for completion later when the right offcut becomes available or for use as spare parts. In the picture above Iím laying out the mortises and holes in the handles, using the jointer fence as an index for efficiency and speed. I build furniture and boats the same way; gang cutting stock for multiple parts and cutting joints in sequence so I can both feel and see the perfect match Iím trying to achieve between each part.

As there are only 16 mortises to make, I chop them with the half-inch mortising chisel. Predrilling and paring arenít necessary once you get the hang of this simple, basic tool, and it takes 45 minutesÖ. less time that I would have spent making a jig and using the router.

I bore the holes for the quarter-inch drill rod Iíll use for blade mounts and tensioning rod, counter boring for the handleís ferrule and evaluate hardware fit after each task. I use brad point and Forstner bits for accuracy and ream the .25-inch holes to .27 using a wire gage jobber bit for clearance. I also like to use a 45-degree countersink where the drill rod emerges from the handlesÖjust for neat. If your bit wanders and you have a hole slightly off center, that 45-degree countersink can also be offset a bit to fool the eye, hiding your mistake.

If you donít have a drill press, this can also be done just as well using a hand drill. Simply use a long, bell hangerís bit thatís easy to keep plumb, and have a helper sight plumb from the end of the piece while you sight the face side as you are drilling.

Before turning the handles, I square up the ends of the rough stock and bore a small pilot hole for the drill rod blade mount, to be bored full size later. If I drilled the full-size hole before turning the handle, the hole would be too large for the latheís live center. A faster alternative is to fabricate and epoxy mount the drill rod before turning, using the drill rod stub to mount the turning square in the latheís 3-jaw or Jacobís ChuckÖbut most woodworkers donít own a chuck for their lathes, so Iíll do it without using a chuck.

I turn the handles on the lathe using a sizing gage on the parting tool matched to the ferrules Iím using. Any brass or copper pipe the correct size will do, but these are ready-made brass ferrules used by larger hydraulic repair shops to fabricate hosesÖthey are readily available in an amazing array of 50 sizes for 5 dollars a dozen. Acquire your hardware firstÖI rarely begin a project before all the hardware is on hand, as I prefer to pick my own challenges.

If you donít have access to a lathe, simpler, 8-sided handles can also be made, fitting the ferrules using rasps and files. Using thickened epoxy demonstrated below to mount the ferrules; the fit doesnít have to be perfect, as the epoxy will fill those gaps perfectly.

With the handles turned and ferrules mounted with epoxy, I drill the final .25-inch holes with a jobber bit that will follow the pilot hole neatly in preparation for installing the blade mounts, also using epoxy.


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