Make your grinder greater
Most bench grinders, whether outfitted with 6" or 8" wheels, come ill-equipped from the factory for use in a woodworking shop, thanks to stone wheels that prove too coarse for sharpening fine-cutting tools, clumsy tool rests, and accessories that are inadequate or just not helpful. Follow these simple steps to turn a ho-hum grinder into a smooth operator in no time.
Start with these tips for better sharpening
- Plug the grinder directly into an outlet. Many grinders require high amperage at start-up and typically run hot anyway, and an extension cord could magnify this problem.
- If your grinder has a variable-speed motor, run it at the slowest speed when shaping or sharpening a tool to reduce heat buildup. Save the high speeds for cleaning rust and gunk from tools with a wire wheel or polishing or stropping with a buffing wheel.
- Keep a "quench cup" nearby filled with fresh water to cool tools as they heat up.
Performance comes down to the wheels
Most grinders come with 36- and 60-grit silicon carbide wheels, identifiable by the gray, coarse texture. Those work great for lawn mower blades, but not for woodworking tools. So replace the 36-grit wheel with a 100- or 120-grit aluminum oxide wheel (usually sold in white or blue colors). Although the softer aluminum oxide wears more quickly than the silicon carbide, it also grinds cooler, saving the temper of your tools' steel. (See Sources below.) Keep the aggressive 60-grit wheel for quickly reshaping chipped or damaged tool edges. Then go to the finer wheel for final sharpening.
Most grinders come with 3⁄4 "-wide wheels, but 1"- or 11⁄4 "-wide wheels sharpen wider tools without sliding the tool side-to-side. To install wide wheels on many grinders you'll have to replace the bell-shaped flanges—which eat up 1⁄2 " or more of the arbor shaft on each side of the wheel—with thinner supports. We recommend tablesaw blade stiffeners [Sources], typically about 1⁄4 " thick, that measure at least 3" in diameter, as shown in photo below.
Find balance in your wheels
If you notice vibration, install balancers [Sources] on your grinder wheels, as shown in photo below. Start by mounting your wheel on the balancing flange —which requires a 1" arbor bore in the wheel—and securing the three balance bolts in the "4-8-12" clock positions. Next, mount the flange and wheel on the included stand. Starting with the same bolt at the top each time, rotate the wheel gently and let it coast to a stop. If the top bolt consistently returns to the 12 position, adjust the other two bolts toward it slightly to compensate for the out-of-balance weight. Repeat until the wheel stops in random positions.
Grinder wheels need dressing
Next, use a dressing tool, such as the diamond-tipped one [Sources] shown in photo below, to flatten the wheel edge. The dressing tool also removes metal filings that embed in the wheel's pores as you sharpen. Left embedded, these filings increase heat buildup and reduce sharpening effectiveness.
Give your tools a good rest
The key to creating crisp, sharp cutting edges: Hold tools at a consistent angle, matching the tool edge's bevel angle. If your grinder lacks an adjustable tool rest, make angled wood blocks to replicate the angle, build a tool-holding jig from our plans [see More Resources, below], or replace the factory-supplied tool rest with an aftermarket model.
Veritas' tool rest, top photo, mounts on your grinder support in front of the wheel. Use it alone or with an optional grinding jig that rides in the shelf slot. A handy angle gauge comes with the tool rest. Oneway's Wolverine grinding jig [middle and bottom photo, Sources] accepts a variety of rests to easily sharpen chisels, plane irons, or woodturning tools.
Get on solid ground
To keep your bench grinder from scooting away while sharpening, anchor it down. Build a dedicated stand, if you have floor space for it. Bolt the grinder to the stand, and if possible, bolt the stand to the floor. If you're squeezed for space, then bolt your grinder to a piece of 3⁄4 "-thick plywood, and clamp it to your workbench.
Aluminum oxide wheels: available at Lee Valley, 800-871-8158, leevalley.com; Rockler Woodworking and Hardware, 800-279-4441, rockler.com; Woodcraft Supply, 800-225-1153, woodcraft.com.
Blade stiffeners: 3 1/2" diameter, #16T01.01, 5" diameter, #16T01.02, $24.50 per pair; Lee Valley.
Wheel balancers: Wolverine Precision Balancing System, #2272 (for 5/8" grinder arbors), Oneway Manufacturing, 800-565-7288, oneway.ca.
Dressing tool: #124670, $15, Woodcraft.
Veritas tool rest system: Tool rest, #05M23.01; Grinding jig, #05M06.01, $24.50; Lee Valley.
Wolverine grinding jig: #2291 (with two toolrests); woodturning accessories sold separately; Oneway Manufacturing.