– Angled: Treat entry and exit of angled surfaces the same. If the surface doesn’t meet these requirements, mill a flat before attempting to drill. You can drill the wall of a concave surface. – Concave: Don’t attempt a concave surface unless the radius is more than 15x the drill diameter and the drill is centered on the concavity and not the wall. If this is not the case, mill a flat spot for the drill to get started on before attempting to drill. – Convex: Convex surfaces are hard to do unless the radius of the convex surface is greater than 4 times the drill diameter and you’re entering perpendicular to the convex radius. – Irregular or Rough Surface: Cut the feed back to as low as 1/4 the normal feedrate to avoid chipping the twist drill. Entry Conditionsĭepending on the condition of the surface, feedrate should be varied to accomodate the surface. Also, take a look at whether nice curled chips are coming out or there are bent chips. If the sound starts and stops, you’re getting some chip jamming. Listen to your twist drill for a steady sound. The ideal chips are short curled chips because they evacuate the most easily. The deeper the hole, the more likely chips can jam. The number one factor affecting twist drill performance is chip formation and evacuation.

If you want the scoop on how to maximize twist drill performance, you’re in the right place. As such, it’s worth getting to know them a little better.įor general information about twist drills, check out our Guide to CNC Twist Drills and Holemaking. By all accounts, it also has some of the highest material removal rates of any of the tooling available. The lowly twist drill is one of the most commonly used tools in the machinist’s arsenal. Introduction to Twist Drills and Chip Formation For specific information on Carbide Drill Feeds and Speeds see the linked article.

It contains information applicable to all twist drills. Note: This article is Lesson 9 from our Free Feeds and Speeds Master Class.

Cobalt t slot cutter speeds and feeds