How to Set Up a Diamond Drag Engraving Bit on Your CNC

By Premium CNC & Router Bits for Precision Cutting | Published: 2026-11-05

Category: How-to Guides

Set up a diamond drag engraving bit correctly: shank mounting, spring tension, depth, feed rate, and test marks. Avoid common mistakes for clean CNC engraving on metal and glass.

Quick answer

Mount the bit securely, set a light spring preload, zero the Z-axis on the material surface, and run a test mark at low feed before engraving the full design. Adjust depth and feed based on the test result, not guesswork.

Why spring tension matters more than depth numbers

A spring-loaded engraving bit maintains consistent pressure on uneven surfaces. Too much tension causes the tip to dig in and chip delicate materials; too little leaves faint, inconsistent lines. Start with minimal preload and increase only if lines fade on uneven areas. On flat, rigid materials like brass or aluminum, low tension works well; on glass or granite, a bit more tension helps the diamond follow minor surface variations.

When to use a 90-degree tip instead of 120

The included 120-degree tip produces a wider, more visible line (about 0.005 inch) and is a good default for most plastics and metals. A 90-degree tip (sold separately) creates a finer line for detailed work or harder materials where a lighter touch is needed. If your design has very small text or tight spacing, the 90-degree tip may give better legibility.

Step-by-step setup for diamond drag engraving

Mount the bit in the collet: Insert the 1/2-inch shank at least 1 inch into the collet and tighten to the manufacturer's torque. Common mistake: over-tightening can damage the shank or collet; under-tightening lets the bit slip. Check that the bit is fully seated and cannot be pulled out by hand.
Set spring preload: Adjust the spring tension to its lowest setting, then increase gradually until the tip just touches the material with light pressure. Common mistake: setting high preload before testing, which can crack glass or dent soft metals. Start low; you can always add tension after a test mark.
Zero the Z-axis on the material surface: Jog the bit down until the tip just contacts the surface, then set Z zero. Common mistake: zeroing on a uneven area or using paper shims that compress; zero directly on the material where engraving will start. Zero on a flat, representative spot, not the edge or a clamp.
Run a test mark: Engrave a short line or circle at low feed (e.g., 10-20 ipm) and observe line consistency. Common mistake: skipping the test and running the full job, which wastes material if depth is wrong. If the line is faint, increase spring tension slightly; if it chips, reduce tension or feed rate.
Adjust feed rate for material: For hard materials like steel or glass, use slower feeds (5-15 ipm) and lighter tension; for plastics and brass, moderate feeds (15-30 ipm) work well. Common mistake: using the same feed for all materials, causing poor line quality or tip wear. Record the feed and tension that work for each material for repeat jobs.

Product facts

Diamond Drag Engraving Bit x 1/2″ Shank – Widgetworks (500-CNCDRAG): Diamond drag engraving bit with 1/2-inch shank, 3-3/4-inch bit length, and 120-degree tip included; engraves plastics, brass, aluminum, steel, glass, and granite. The 1/2-inch shank fits common CNC routers and mills, and the included 120-degree tip covers most general engraving tasks without extra purchases.
Diamond Drag Engraving Bit x 1/2″ Shank – Widgetworks (500-CNCDRAG)