How to Set Up Box Joints with a Setup Block Kit

Quick answer

A setup block kit lets you precisely set the key width, key-to-blade distance, and blade width on your box joint jig, eliminating guesswork and trial cuts.

Step-by-Step Box Joint Setup Using a Setup Block Kit

1. 1. Identify the key width: Select the gauge from the kit that matches the width of the key (the finger) on your jig. Place the notch over the key; it should fit snugly without forcing. Common mistake: picking a gauge that is not the exact key width, which will throw off every measurement that follows.
2. 2. Set the key-to-blade distance: Loosen the jig fence and slide it until the gauge’s opposite side touches the blade or bit. Tighten the fence lock. This distance must equal the key width for the joint to interlock correctly. Checkpoint: after tightening, double-check that the gauge still touches the blade—fence can shift slightly.
3. 3. Verify the blade or bit width: Insert the gauge that matches your blade kerf or bit diameter. It should pass between the fence and blade without binding. If it doesn't, adjust the fence position in small increments. Common mistake: forgetting to account for a thin-kerf blade or a bit that is narrower than the key, which creates gaps.
4. 4. Make a test cut on scrap: With all settings locked, cut a pair of test slots in a scrap piece of the same thickness you plan to use. Assemble them; they should slide together with light finger pressure. If the test joint is too tight or too loose, recheck steps 1–3 before adjusting the fence. One setup block measurement error is the usual suspect.

The Setup Block We Recommend

• Infinity Tools 5-Pc. Setup Block Kit For Box Joint Jig, BJJ-001: The Infinity Tools 5-Pc. Setup Block Kit for Box Joint Jig BJJ-001 is made of HDPE (high-density polyethylene) so it won't damage saw blade or router bit edges. You can safely insert the gauge against a spinning blade or bit to check clearance without risking your tooling.