Sterling Gun Drills Media Releases

Gun Drilling on a CNC or Manual Lathe or Mill

For hole depths greater than 40 diameters deep, we suggest a shorter drill / longer drill combination that will allow the drilled hole of the shorter drill support the flute of the longer drill.

On a lathe or milling machine, a gun drill bushing to start a single flute gun drill is generally not practical. Drill supports, chip box, etc., are also unnecessary.

Start a gun drill with a pilot hole drilled, reamed, or bored to the gun drill diameter +.0005" (+.001" max.), -0 x ½ to 1 diameter deep. The shape at the bottom of a pilot hole is of no consequence.

Use oil, or oil based, high "EP" water soluble coolant at 10-12% concentration, NEVER use a synthetic as these have no lubricating action. General guidelines:


We offer our DM2000 / DM3000 Spraymist Kits as alternative to high pressure coolant. Operate with 100-125 psi of shop air pressure. Spindle speed will be same as Min psi above. Refer to our Speed & Feeds chart or our helpful Gundrilling Guidelines.

  • Enter the drill tip into the pilot hole dead spindle just off the bottom.
  • Start the oil, coolant or our Spraymist System.
  • Start the spindle.
  • Drilling will be continuous to depth.
  • When to depth, back off the bottom slightly if a blind hole, stop everything and remove the drill.
  • NEVER rotate the drill outside of the hole.

Note of drill wear on the outer edge to establish a re-grind interval. Tool life will depend upon a combination of material type, hardness, coolant type and pressure.

Special nose grind / Contour combinations are available for very deep holes, cross holes, interrupted cuts, special shapes, steps.

Learn about our Deep Hole Drilling Systems.

Doug Holley, General Manager

Sterling Gun Drills, Inc. North Bennington, VT.
Toll Free: (888) 338-1049 • Phone: (802) 442-3525 • Fax: (802) 442-6225
Company Website: