Quick Answer
To set up engraving cutters for deep CNC work, use a long reach bit with a 1/4 inch shank, set the cutter depth using the brass knob, and make multiple shallow passes rather than one deep cut.
Why Long Reach Bits Matter for Deep Engraving
When you engrave deeper than the cutter's length of cut, you risk the shank rubbing against the workpiece, which can cause heat buildup and poor finish. A long reach engraving bit, like the 1/8 inch single flute with a 1/4 inch shank, provides the extra length needed to reach deep cavities without sacrificing stability.
The tradeoff is that longer bits are more prone to deflection. This means you need to reduce feed rates and take lighter passes to maintain accuracy.
Understanding Cutter Depth and the Brass Knob
Engraving cutters from this category come with a brass cutter knob that sets the cutter depth. This knob is essential for consistent depth control, especially when you need to repeat the same engraving job multiple times.
The brass knob works by providing a physical stop that limits how far the cutter extends from the collet. Setting it correctly ensures that you don't accidentally plunge too deep and break the cutter.
Step-by-Step Setup Process
- Select the Right Cutter: Choose a long reach engraving bit with a 1/4 inch shank that matches your required depth. For most deep engraving, a single flute cutter with a length of cut of at least 0.200″ is recommended. Check that the length of cut exceeds your maximum engraving depth.
- Insert the Cutter into the Collet: Insert the cutter into the collet, leaving enough shank exposed for a secure grip. Do not fully insert the cutter; leave at least 1/8″ of shank visible above the collet to prevent the collet from clamping onto the flutes. Never let the collet grip the flutes—this can break the cutter.
- Set the Cutter Depth with the Brass Knob: Use the brass knob to set the cutter depth. Loosen the knob, adjust the cutter to the desired depth, then tighten the knob securely. The knob acts as a stop to prevent the cutter from being pushed deeper during operation. Test the depth on a scrap piece before running your job.
- Calculate Step-Down and Feed Rate: For deep engraving, use multiple shallow passes. A good rule of thumb is to step down no more than 50% of the cutter's diameter per pass. For a 1/8″ cutter, that's 0.0625″ per pass. Reduce feed rate by 20-30% compared to shallow engraving to compensate for the longer reach. If you hear squealing or see excessive deflection, reduce the step-down further.
- Secure the Workpiece and Run a Test: Make sure the workpiece is firmly clamped. Run a test pass at a slow feed rate to verify the depth and finish. Check for any signs of rubbing or burning, which indicate that the depth is too aggressive. Always wear safety glasses and keep hands clear of the spindle.
Engraving Cutters for Deep Work
-
1/8″ (.125″) Single Flute Engraving Cutter – 1/4″ Shank x 6-1/2″ w/ Knob: 1/8″ (.125″) Single Flute Engraving Cutter – 1/4″ Shank x 6-1/2″ w/ Knob. Solid carbide, length of cut 0.375″, includes brass cutter knob. The longer length of cut (0.375″) makes this bit suitable for deeper engraving tasks, and the brass knob helps you set consistent depth.
1/8″ (.125″) Single Flute Engraving Cutter – 1/4″ Shank x 6-1/2″ w/ Knob
-
.060″ (1/16″) Single Flute Engraving Cutter – 1/4″ Shank x 6-1/2″ w/ Knob: .060″ (1/16″) Single Flute Engraving Cutter – 1/4″ Shank x 6-1/2″ w/ Knob. Solid carbide, length of cut 0.200″, includes brass cutter knob. This finer tip is ideal for detailed deep engraving where you need a smaller cutting edge but still require the reach of a 1/4 inch shank.
.060″ (1/16″) Single Flute Engraving Cutter – 1/4″ Shank x 6-1/2″ w/ Knob
-
.060 (1/16″) 2 Flute End Mill – 1/4″ Shank x 6-1/2″ w/ Knob: .060 (1/16″) 2 Flute End Mill – 1/4″ Shank x 6-1/2″ w/ Knob. Solid carbide, length of cut 0.200″, includes brass cutter knob. The two-flute design provides a better finish on some materials, and the 1/4 inch shank offers rigidity for deep passes.
