A bigger bottom extends the versatility of your router.
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Sometimes a job calls for a task-specific router subbase—one more affordable to build than buy, like a circle-cutting trammel. Whatever the application, here's how to make and mount a router subbase successfully.

Choose subbase material based on your needs

Although your first thought may be to use any scrapwood on hand, the material you choose for your router base can dramatically affect accuracy and stability. We recommend sticking to these three materials:

Hardboard: So affordable (around $.65 per sq. ft.), a subbase made of hardboard can be considered disposable. It also resists humidity changes that lead to warpage.

Baltic-birch plywood: With thin, voidless plies, Baltic-birch plywood makes a sturdy and affordable subbase. (It costs around $2 per sq. ft.) Other 14 "-thick plywood warps easily—a big problem when building large subbases.

Acrylic: A transparent acrylic subbase improves bit visibility—especially important when routing stopped chamfers, round-overs, or grooves. However, at around three times the price of Baltic-birch plywood, and 10 times hardboard, you may find acrylic cost-prohibitive.

For best results when cutting acrylic on a tablesaw, use a thin-kerf blade with a high tooth count for less chipping; but reduce the tooth count if melting occurs. (More teeth also means more friction and heat.) When drilling or boring holes in acrylic, be sure to use a backer board, a sharp bit (twist or brad-point bits work well), and a slow bit speed to avoid melting and chipping. As bit size increases, bit speed should decrease.

Now make it and mount it

After selecting a subbase material, remove the factory-supplied subbase from the router. Transfer the subbase's mounting-hole pattern and bit opening to the new subbase material using one of the techniques shown below.

After removing the factory-supplied subbase, drill matching mounting holes in the new subbase. One simple method: Tape the factory subbase to the new one and use it as a drilling template.
To make several subbases, photocopy the factory-supplied subbase and drill the mounting-hole locations through the photocopied template after taping it to your blank.

Next, drill the holes for the mounting screws and bore the bit opening.

Quick Tip! For another way to locate and bore out the exact center of the bit hole, insert a straight bit into the router collet, mount your new subbase to the router, and plunge the bit through the subbase.

Finally, countersink or counterbore the new subbase's screw holes, as shown below. If necessary, replace the factory-supplied mounting screws with screws long enough to account for any additional thickness your replacement subbase adds.

Match the depth of the factory-supplied subbase's counterbore or countersink in the mounting holes of your new subbase to keep the screw heads flush with or below the surface.