Super-Strong Mitered Corners with the Insert-Pro Lock Miter Shaper Cutter

The lock miter joint is very popular. And for good reason. It makes a strong and accurate 90° joint with excellent glue surface for added strength. Both sides of the interlocking joint are made with the same cutter using a single setup — run one piece flat against the table and the other vertically against the fence.

By design, the lock miter is ideal for production applications such as box beams, columns, hollow table legs or any number of other projects that require strong and perfect-fitting 90° miter joints. While the lock miter profile has it roots in production work, options for the shaper are limited.

Here at Infinity, we're excited to introduce out new Insert-Pro™ Lock Miter shaper cutter. This shaper cutter is designed for the serious hobbyist all the way up to production cabinet shops running shapers and CNC machines. The Infinity Insert-Pro Lock Miter shaper cutter has some very unique features that make it ideal for the professional. Let's take a closer look. The first thing you'll notice about the Infinity Insert-Pro Lock Miter shaper cutter is that it's an aluminum cutter head that accepts insert-style carbide knives. This allows for easy replacement of damaged cutters and re-use of newly sharpened cutters.

A unique feature of this system is that the knives are adjustable. This means that the overall fit of the joint can be fine-tuned to make a tighter-fitting or looser joint to suit the craftsman's preference and the requirements of the project at hand. Because the knives can be adjusted they can also be sharpened without affecting the resulting fit of the joint.

Adjusting the knives to produce your desired fit is easy and requires only a set of feeler gauges, a flat-blade screwdriver, a 1.5mm Allen wrench, and the included 4mm Allen wrench. NOTE: The Allen wrenches are included with the shaper cutterhead.

First, loosen the stop on the bottom of the cutterhead that has been marked at the factory and then loosen the internal set screw.

Remove the corresponding knife. Insert a feeler gauge between the cutter body and the stop. The stock spacing is .020”. For a tighter-fitting joint reduce the spacing. For a looser joint, increase the spacing. We recommend making changes in no more than .002” increments until the desired fit is achieved.

Tighten the stop screw against the feeler gauge by hand then tighten the internal set screw in the stop. Reinstall the knife and make a test cut to confirm the fit of the lock miter joint.

The profile created by the Insert Pro Lock Miter shaper cutter is a little different than that created by the lock miter router bit. With the Insert-Pro knives, the tongue and groove portion of the joint is rounded. This makes for a more durable knife that is less prone to chipping or premature wear. It also creates a small relief at the tip of the tongue to allow room for excess glue.

All Infinity Tools Insert-Pro shaper cutters come standard in 1-1/4"-dia. bore for use on shapers with 1-1/4" machine spindles. Infinity offers a line of T-bushings to adapt these cutters to 30mm, 1" or 3/4" spindles.

The knives used in the Infinity Insert-Pro tooling are special in their own right. All are made of C4 sub micro-grain carbide. This is the hardest and most durable carbide available for woodworking applications. These knives come with a mirror polish and the sharpest edge possible meaning the knives are sharper right out of the box and will hold their edge longer then any other carbide available.

We don't mean to brag but we are pretty confident that if you give our lock miter shaper cutter a try, you'll be pleasantly surprised with its quality manufacturing, perfect cuts, and long life.