Drill Bit Guide: Choose a Jig for Straight Holes

For occasional holes perpendicular to a flat woodworking surface, start with a metal-bushed guide block that matches your exact bit diameter. Choose a portable, rail-guided attachment when you need adjustable angles or a carriage depth stop. For repeated shelf-pin holes, use a jig that controls spacing as well as direction.

Here, “drill bit guide” means the accessory that guides the bit—not a guide to cutting-bit types. If you need to choose the cutter itself, see what to buy for each material.

The named products below illustrate different designs and their published specifications; they are not a hands-on ranking.

Choose what the guide needs to control

Guide block: direction at a fixed diameter

A guide block sits against the workpiece and guides the bit through a metal bushing. It is the simplest option when your hole diameter matches one of its openings.

For example, the Milescraft DrillBlock 1312 has six bushings: 1/8, 3/16, 1/4, 5/16, 3/8 and 1/2 inch. Milescraft specifies a heat-treated metal bushing block, alignment centerlines and a V-groove for cylindrical stock or corners. Those are useful features to compare, rather than treating every plastic-bodied block as equivalent. Milescraft specifications

The Kreg KDG-6000 covers the same six diameters and explicitly lists twist and brad-point bit compatibility. Its edge-centering feature is designed for 1/2- and 3/4-inch material—not arbitrary board thicknesses. Kreg specifications

Choose this design for: individual pilot holes, hardware holes and other straight holes in its supported sizes. Do not assume a six-hole block accepts every diameter between its smallest and largest openings.

Chuck-equipped portable guide: adjustable angle and depth

This design holds the cutting bit in its own chuck, with the chuck assembly moving along guide rails. Your drill drives the attachment’s spindle rather than holding the cutting bit directly. Kreg’s setup explanation

The Milescraft DrillMate 1318, for example, has a 3/8-inch keyed chuck, an adjustable stop collar and angle markings for 45, 60, 75 and 90 degrees. Its published drill compatibility is 3/8- and 1/2-inch power drills. That does not make its supplied bit chuck a 1/2-inch chuck. Milescraft specifications

Choose this design for: angled holes or repeated depths where the base and rails fit the work. Check the attachment’s chuck capacity, base opening and travel separately; none alone tells you which holes it can drill.

Task-specific jig: direction plus repeatable location

For a row of shelf-pin holes, keeping each hole perpendicular to the panel is only part of the task. You also need consistent spacing and distance from the panel edge.

The Kreg Shelf Pin Jig KMA3225 illustrates the difference: it has six drill guides, a positioning fence, an indexing pin and a supplied 1/4-inch bit with a stop collar. Its guides use 32 mm spacing. Choose this type when the hole diameter and pattern match your project, rather than laying out every hole again with a general-purpose block. Kreg shelf-pin jig specifications

Check fit before buying

• Exact diameter: A bushing guides the cutting body, not just the shank. Match its marked size to the bit; do not force a nearby metric or fractional size into it.
• Bit geometry: Follow the guide’s compatibility list. Kreg’s basic block lists twist and brad-point bits; that is not approval for spade bits, Forstner bits or hole saws.
• Usable reach: A block occupies some of the exposed bit length above the workpiece. Check that the bit can reach the required depth without the chuck or stop collar contacting the guide prematurely.
• Support and access: The guide must seat securely at the drilling location. Check nearby edges, clamps and obstructions—not only the hole center.
• Operating restrictions: Milescraft says the DrillMate 1318 is not intended for impact drivers or hammer drills; its manual also prohibits reverse operation. Restrictions differ by model, so read the specific manual. DrillMate product page and manual

Set up for the hole, not just the mark

1. Disconnect power before adjustments. Fit the bit, set the angle and adjust any depth stop. Wear eye protection and keep hands, hair and loose clothing away from rotating parts. Milescraft safety instructions
2. Secure the work and seat the guide. A 90-degree guide references the surface beneath it; it does not compensate for a tilted base. The DrillMate manual calls for holding its base flush during drilling. For round stock, it specifies securing the base to a workbench and firmly clamping the stock. DrillMate setup instructions
3. Align the actual bit tip with the hole mark. Use the guide’s alignment marks or fence, then check the position before starting.
4. Test on matching scrap. Check location, angle and depth with the same guide-and-bit setup, especially before drilling blind holes in finished panels.
5. Feed without levering the drill sideways. Pause to clear packed chips rather than adding force. If the guide shifts or the bit binds, stop and reassess the setup.