How to Use the Kreg MortiseMate Loose Tenon Jig

By Welcome to Kreg Tool | Published: 2026-10-29

Category: How-to Guides

Learn step-by-step how to set up and use the Kreg MortiseMate Loose Tenon Jig to cut precise mortises with just a drill. Perfect your mortise and tenon joinery with expert tips.

Quick Answer

Set up the Kreg MortiseMate on your workpiece, adjust the micro screws for your desired tenon fit, and use a drill with the auto-indexing step-down mechanism to cut precise mortises in just a few passes.

Why the MortiseMate Simplifies Mortise Cutting

Traditional mortise cutting often requires a dedicated mortiser or a router with a fence—both bulky and time-consuming to set up. The Kreg MortiseMate changes that by letting you cut clean mortises using only a standard drill. Its auto-indexing step-down mechanism lowers the cutter by exactly 1.5 mm per pass, so you don't have to measure depth manually or risk uneven cuts.

One trade-off: because the jig relies on a drill rather than a router, you may need to take more passes for deeper mortises. However, the consistent depth control and micro adjustment screws make up for it by giving you a tight or loose tenon fit without guesswork.

Choosing the Right Tenon Fit

Before you start cutting, decide whether you want a snug or slightly loose fit for your tenons. The MortiseMate’s micro adjustment screws let you dial in the mortise width precisely. For a tight joint that requires glue and clamping, set the screws for a narrower mortise. For a slip-fit joint that allows easy assembly, widen the mortise slightly.

A common mistake is to skip this adjustment and assume the default setting works for all projects. Always test on scrap wood first to confirm the fit before cutting into your actual workpiece.

Step-by-Step Guide to Using the Kreg MortiseMate

1. Mount the Jig on Your Workpiece: Clamp the MortiseMate securely to the edge of your workpiece, aligning the guide bushing with your marked mortise location. Ensure the jig is level and won't shift during cutting. Double-check that the clamp is tight and the jig is perpendicular to the workpiece to avoid angled mortises.
2. Set the Mortise Depth and Width: Use the micro adjustment screws to set the mortise width for your tenon fit—tighten for a snug fit, loosen for a looser fit. Adjust the depth stop on your drill to match the tenon length. Always test the fit on scrap wood; a common mistake is assuming the depth stop is correct without checking.
3. Insert the Bit and Start Cutting: Insert a straight bit (sold separately) into your drill and place it into the guide bushing. With the drill running, lower the bit into the workpiece until it contacts the depth stop. The auto-indexing mechanism will advance the bit by 1.5 mm per pass. Keep the drill perpendicular and let the mechanism do the work—pushing too hard can cause the bit to bind or break.
4. Complete the Mortise: Continue making passes, moving the drill side to side within the guide bushing to clear the waste. After each pass, the jig automatically lowers the bit, so you don't need to adjust anything manually. Stop when you reach the desired depth. Clear chips frequently to prevent clogging and ensure smooth cutting. A vacuum attachment can help keep the area clean.
5. Remove the Workpiece and Test Fit: Unclamp the jig and remove the workpiece. Test the fit with your pre-cut tenon. If it's too tight, use the micro adjustment screws to widen the mortise slightly and make another pass. If too loose, adjust the screws narrower and recut. It's easier to widen a mortise than to make it narrower, so start with a tighter fit and adjust outward.

Product Used in This Guide

Kreg MortiseMate™ Loose Tenon Jig: The MortiseMate’s exclusive auto-indexing step-down mechanism enables precise mortise cutting with just a drill, eliminating the need for complex setups. This means you can cut accurate mortises without owning a dedicated mortiser or router table, saving space and setup time.
Kreg MortiseMate™ Loose Tenon Jig