90°
Spotting & Step Drills, Countersinks & Center Reamers Technical Information
Drill bits, countersinks, and reamers are used to create holes in materials like wood and metal. They vary in size and material composition. Hole-making typically starts with spotting and often ends with countersinking, depending on the application.
Spotting/Center Drills
Using a spot drill to start a hole ensures a true center for more accurate drilling. Always select a spot drill with an angle equal to or greater than that of the final drill.
Angles
• Used to create a chamfer for the hole, the countersink should always be larger than the drill used to make the hole.
120°
• Used for preparing a hole for a 118° or 120° drill bit.
140°
• Used to prepare holes for 130° or 140° high-performance drill bits.
Countersinks & Center Reamers
Countersinks are versatile tools typically used after drilling to chamfer, deburr, and create an angled cut at the top of a hole, forming a seat for fasteners. Center reamers are ideal for countersinking holes for centers, flathead screws, and rivets. They can also be used to clean or slightly enlarge existing holes.
Types of Countersinks & Center Reamers
Single Flute
• Provides the best centering of all countersinks and a smoother surface finish.
• Suitable for hand-held operations and production set-ups.
3 & 4 Flute
• Offer excellent chip clearance and are ideal for machining plastics and non-ferrous metals like aluminum, copper, brass, and bronze.
6 Flute
• Supports the highest feed rates among countersinks and offers longer tool life by distributing the cutting load across more edges.
Drill Point
• Enables spot drilling, countersinking, and edge chamfering with a single tool.
CNC
• Delivers the tightest tolerances.
Chatterless
• Reduces vibration and noise.
Jobber Length Step Drills
• Step drills create holes with multiple diameters in a single setup.
• The step drill is a modified standard drill with a point ground to a specific diameter, functioning as a combination tool using the same flute for multiple hole sizes.
• Jobber-length step drills, also called subland drills, are used for drilling and countersinking flat-head machine screws, creating chamfered holes before tapping, and drilling and counterboring cap screw clearance holes.
Combined Drills & Countersinks
As the name suggests, these tools boost productivity by combining drilling and countersinking in a single pass.
Types of Combined Drills and Countersinks
Plain
• Most common style with standard flute clearance.
Radius
• Featuring increased flute clearance, they offer superior productivity and more accurate holes than other countersinks.
Bell or Bugle
• Bevels the hole’s outer edge to prepare the workpiece for further machining.
Angles
Materials
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