Diagram: Details for the electric chain saw sharpener tool.
MOTHER EARTH NEWS STAFF
If you're not too keen on manually sharpening your chain saw, build a chain saw electric sharpener tool and dress your chain saw for success. (See the chain saw sharpener diagram in the image gallery.)
While there are people who enjoy hand-filing their chain-saw chains, for most of us, keeping the cutters sharp can be a tedious, time-consuming, and often frustrating chore. And although such regular maintenance is a necessity, there's nothing that says you can't take steps to get it over with as quickly as possible!
Some can wield a mean freehand file, and others rely on jigs to keep the teeth set, but thanks to some workshop wizardry, MOTHER's staffers can now simply clamp the chain saw electric sharpener tool shown here to a truck bumper or a workbench and dress a saw chain clean as a whistle in a matter of minutes . . . and with a little bit of work, you can duplicate this time-saving tool!
It's built from dimensional steel stock and uses a 12-volt blower motor and commercially available abrasive wheels to do the dirty work. But it also has a couple of features that make it downright convenient to use. For one, the DC motor can be run directly off your vehicle's battery, so you can sharpen your saw right in the field. Second, once you've drilled two 5/16 inch holes in your chain bar, the saw can be clamped and sharpened without disassembly. Likewise, because the mount is designed to pivot, both the right-and left-hand cutters can be dressed without dismounting the tool. Finally, because the grinding wheel is set at a predetermined angle, the cutters are always filed at the correct pitch.
All the parts are dimensioned and described in the accompanying illustration, and they're commonly available as hardware or steel scrap items. The 12-volt motor (Part No. J-19991) was ordered at a cost of $11.50, including shipping, from Jerryco Inc., Evanston, IL, and the 1/8 inch abrasive wheel (Part No. 3700588) is available from the Foley-Belsaw Co., Kansas City, MO (other wheels are available to fit larger saws).
We won't walk you through the tool's assembly step-by-step, because the illustrations should provide all the instruction you'll need. But we will offer some suggestions that'll make things easier as you go along. To start, you'll need to cut a 1-5/8 inch strip of metal from one leg of the angle iron section that'll be used as the bar mount. This piece of scrap can later be employed to make the switch mount and the leveler tongue. Also, rather than welding the swivel stops to the base, simply cut 45 degree angles into the end of each one and drill slots in their centers; they can then be adjusted to suit the pitch of your chain's teeth and fastened with 3/16 inch machine bolts.
Another point of concern is the angle of the wheel itself. This is determined by the degree of bend you put into the flat bar post which supports the rocker assembly, and this angle must match the contour made by the top and side plate of each cutter. A 65 degree angle is adequate, and you can bend the metal easily once it's heated to a dull glow with a torch.
Important, too, is the hinge-pin arrangement of the rocker assembly, which is detailed with the illustration. First, a 1/8 inch hole should be drilled through the side of the support post, parallel to the upper end. Then two 1/4 inch sockets, 1/4 inch deep, must be bored at the ends of this hole. The pins are 1/4 inch machine screws with the heads removed, with 1/8 inch tapers or needles cut into the shanks, and with slots added at the threaded ends. Nuts welded to the rocker arm and ear hold the pins in place.
Another "custom fit" operation involves mating the 5/16 inch motor shaft to the arbor shaft and installing that assembly in a bushed housing. The 1/2 inch by 3-1/2 inch cold-rolled rod gets a 1/2-13 thread at one end, and a 5/16 inch by 1-1/2 inch socket at the other. A 3/32 inch hole drilled into the socket and tapped for 1/8-32 thread accepts an alien-head set screw. The 1 inch by 1-3/4 inch rod should be center-bored to 23/32 inches, and a 1/2 inch by 3/4 inch oil-impregnated bushing must be driven into the opening once the housing is installed on its support. The motor must be aligned perfectly with the bearing housing, so don't weld the motor mounts to the rocker face or drill the mounting holes until the housing is installed.
Finally, there's no room for roughshod workmanship in the construction of the tooth stop assembly. The lever and the arm must be perpendicular to each other, and the tooth stop and collar squarely fastened to the lever. The unit pivots on a No. 12-32 machine screw that's threaded and surface-welded into a hole centered 3/8 inches from the bar mount's upper edge and 3-1/4 inches from its right end.
To use the sharpener the first time, clamp it to a bench and place your saw's cutting bar alongside the bar mount to determine the best place to drill the 5/16 inch holes that will hold the saw in place. To play it safe, you might even want to hold off on actually welding the 5/16 inch bolts until you've established their ideal location with reference to the saw's bar. Once you've bored the two holes through the bar, swing the swivel right and left to assure that the chain doesn't shift when you make the transition. If the 1/2 inch pivot bolt isn't perfectly plumb with the grinding point of the abrasive wheel when it's in the working position—or if the swivel or bar mount is somehow warped or cocked out of line—the chain will shift and will ultimately be sharpened improperly. Minor irregularities can be alleviated by adjusting the leveler and placing shim washers behind the chain bar as necessary.
The swivel stops should be adjusted to suit your chain's cutter pitch; 30 degree and 35 degree angles are common, but you can set them at any angle you wish up to 45 degrees. Likewise, the depth of the grind can be adjusted with the T handle at the top of the rocker post. The tooth stop, of course, assures that the cutters are fixed at the right location as you pull the chain along the bar during the dressing process. Its alien-head screw can be locked so the stop's position doesn't change. (To simplify things, sharpen every other cutter as you go so you won't have to be changing the swivel position more than once.)
With the sharpener properly set up, it'll whip through a ragged chain in a few minutes . . . leaving you with more time to do the things you enjoy this winter.