How to Use Brass Setup Gauges for Router Bit Depth

By Premium CNC & Router Bits for Precision Cutting | Published: 2026-10-31

Category: How-to Guides

Learn a reliable method for setting router bit depth with brass setup gauges. Get repeatable cuts, avoid test-cut guesswork, and keep your setups consistent.

Quick answer

Use a brass setup gauge as a physical stop to set router bit height: lower the bit, slide the gauge under it, and raise the bit until it just touches the gauge. This gives you a repeatable reference for depth without guessing.

Why brass gauges beat test cuts for repeatability

Test cuts work, but they rely on memory and eyeballing. A brass setup gauge gives you a solid reference you can return to for every piece in a batch. Because the gauge is a fixed thickness, you can set the bit to that exact height and repeat it without measuring again.

The main trade-off is that you need a gauge that matches your target depth. If your depth is not covered by a single gauge, you can stack them, but stacking introduces small cumulative errors. Keep stacks to two blocks when possible.

When to use a gauge instead of a depth stop

A router table depth stop or a bit-depth ring is faster for on-the-fly changes, but a gauge is more reliable when you need to reproduce a setup after changing bits. Use a gauge when you are batching parts, when you need to match a previous cut, or when you are setting up a new bit and want a known starting point.

For very shallow cuts, a feeler gauge or a single thin block is more precise than stacking. For deep cuts, check that the bit shank is fully seated before you raise it to the gauge.

Step-by-step: setting router bit depth with brass gauges

Unplug the router and lower the bit: With the router unplugged, lower the bit below the table surface or base. This gives you room to place the gauge without interference. Always unplug before reaching near the bit.
Choose the gauge or stack that matches your target depth: Select a single gauge that matches your desired depth. If your depth is not a single size, stack two gauges and add their thicknesses. For example, a 1/4” plus 1/8” gives 3/8”. Avoid stacking more than two blocks; cumulative error grows with each block.
Place the gauge on the router table or base: Set the gauge flat on the table surface next to the bit opening, with the long edge parallel to the fence. Make sure it sits fully on the table, not on the insert ring. A gauge resting on the insert ring will give a false height.
Raise the bit until it just touches the gauge: Slowly raise the bit until its lowest cutting edge just contacts the top of the gauge. Use the fine adjustment on your router lift or base. Then lock the depth. A light drag is better than a gap; you should feel the bit touch the gauge but not lift it.
Remove the gauge and make a test cut: Slide the gauge out, then make a test cut on scrap. Measure the cut depth with calipers. If it is off, adjust the bit and re-check with the gauge. Test cuts confirm the setup; do not skip this step for critical joinery.
Record the setup for repeatability: Note the gauge size or stack and the bit model. Store the gauges together so you can reproduce the setup later. For repeatable router cuts, keep a log of bit height and gauge combinations. A written log turns a one-time setup into a repeatable process.

Product facts

Whiteside 9810 Brass Set-Up Gauges – 5PC, 4″ Long: Includes 1/8”, 3/16”, 1/4”, 3/8”, and 1/2” solid brass blocks, each 4” long. The five sizes cover common router bit depths, and the 4-inch length gives you a stable reference across the bit opening.
Whiteside 9810 Brass Set-Up Gauges – 5PC, 4″ Long