How to level tables to tools
Whether you're building the dual-function workstation or making your own base for a tool, such as a tablesaw, mitersaw, or thickness planer, you need to level the tables to the tool (bring them to the same plane). Coplanar tables provide a continuously even worksurface necessary for stable stock support, accurate cutting, and safe workpiece movement. You'll learn how to level tables in four simple steps.
You also can use this process to check and level accessories, such as infeed and outfeed support tables, to your tools. Because accessories have various types of leveling provisions, refer to the manufacturer's instructions on how to adjust them.
Step 1 Find two straightedges of sufficient length to span the tool and extension tables. You can use metal straightedges, or make wooden ones by jointing the edges of two boards. For example, to reach across the 51"-long router-cabinet top of the dual-function workstation and the 20"-wide cast-iron tablesaw top, we made straightedges by jointing two 1x6x72" boards.
Clamp the straightedges along the front and back of the extension table or top, as shown in the photo, top. (When leveling an accessory table to a tool, clamp the straightedges to the tool's table.)
Step 2 Determine the approximate shim thicknesses needed for leveling by measuring the offset between the tool's table and extension near the straightedges, as shown in the photo below. Then, measure the gaps between the straightedges and the tool table at the table's opposite edge.
Step 3 Insert shims to get a snug fit between the tool's table and straightedges, as shown in the photo, below. Suitable shims include metal flat washers; 1⁄8 " and 1⁄4 " hardboard; sheet metal (available at hobby stores and home centers); and metal shim stock, such as from an automotive feeler gauge. When you need just a smidgen more thickness for a perfect fit, add a piece or two of aluminum foil (it measures just .002" thick) to the stack.
As an alternative to combining shims, you can make custom shims by planing hardwood, such as oak or maple, to the exact thicknesses needed. Don't use any material that will compress at all under the weight of the machine.
Step 4 Finally, remove the shims, drill holes in them if necessary for your tool's mounting screws, and install the shims under the tool. Also, recheck the level periodically as tool movement, knocks, and changes in humidity can cause table misalignment.
Use an adjustable square or calipers to measure the tables' offset and gaps under the straightedges.
Find the right combination of shims to fill the gaps between the tool's table and straightedges at the locations over the mounting holes in the tool's base.