Plywood is sold predominantly in metric sizes that are slightly thinner than their indicated imperial thickness. Router bits with 1/4", 1/2", and 3/4" cutter diameter will leave a groove that is too wide when making common dado joinery. And we all know that a tight-fitting joint is stronger and looks better than a loose one. This is why we offer a 3-Pc Downcut Spiral Router Bit Set (00-856) specifically for "undersized ply" applications.
The Infinity Tools 3-Pc. Downcut Spiral Set For Plywood Dado Cuts (00-856) includes a 6mm (15/64") cutting diameter router bit with a 1/4" shank and a 12mm (31/64") and 18mm (23/32") router bit with 1/2" shank, perfect for making dadoes and grooves in undersized 1/4", 1/2", and 3/4" plywood.
Infinity Tools spiral router bits are made of a premium solid carbide round and the cutting edge is ground into the carbide to create a specific geometry to tackle a specific task or work in a specific material. You'll find spiral router bits in two main types; upcut, and downcut. To visualize the spiral direction, picture the bits working overhead like in a handheld router or CNC machine, and from underneath, like in a router table. There is an easy way to remember which is which. An upcut router bit acts like a drill bit and pulls sawdust out of the hole making it ideal for cutting deep mortises. A downcut router bit pushes sawdust down into the hole and is perfect for making shallow dadoes and grooves. While downcut bits feed slower they leave a superior quality finish on the top of your workpiece. Think "pushing" down on the wood fibers, there's less tearing going on.
Why do you want a downcut router bit for plywood? Because downcut router bits produce a really clean surface with a scissor-like shearing action. Most of the time dadoes and grooves in plywood are not very deep so the router bit does not need to pull a bunch of sawdust up and out of the cut. In delicate veneered plywood that tends to chip and tear, a down-cut router bit will simply produce the best possible cut without risk of lifting those veneers toward the surface and causing tearout.
Infinity Tools spiral router bits also have the advantage of being made from extremely hard and durable C4 sub-micro grain carbide. This carbide is harder and takes a sharper edge than the carbide traditional braised router bits are made from. This means that they start out sharper and stay sharp longer than traditional router bits. This makes them a great choice for materials like plywood that tend to dull router bits quickly.
Most spiral router bits are made from a solid piece of carbide. This limits the cutting diameter because the cutter can be no larger than the shank. The Infinity 18mm Downcut Spiral router bit (85-918) is a unique hybrid that combines an 18mm solid carbide cutting head with a 1/2" steel shank. This revolutionary design gives you all of the benefits of a true solid carbide bit with none of the drawbacks.
The Infinity Tools 3-Pc. Downcut Spiral Set For Plywood Dado Cuts (00-856) is perfect for any woodworker who uses plywood and wants to the best fit and cleanest cuts at a price that can't be beaten.
