DM-42 Sharpening Head for Gun Drills up to
2 1/8” Diameter

DM-42 Sterling Gun Drills, Inc. announces a new sharpening head for single flute gun drills to increase the range of our Manual Regrind Fixtures to over 2 1/8" (54mm).

Part # DM-42 Large Manual Sharpening fixture has a range of .75" (19mm) to approx. 2 1/8" (54mm), and is offered complete with the base assembly.

Part # DM-42-A, Large Sharpening Head, is offered as an option* for the DM-41 Manual Regrind Fixture.

No additional collets or adapters are necessary to sharpen single flute gun drills of any manufacture with the popular “facet” nose grind to virtually any configuration required.

Changeover of the standard sharpening head DM-41-A to the DM-42–A large sharpening head on the base fixture involves just two screws to swap the vertical register from the standard fixture to the large fixture.

Due to variation in flute shape from size to size and from one manufacturer to another, a fine adjustment feature is built into the clamping wedge that allows leveling the cutting face on gun drills with flute angles from 105º - 120º. A 1/8” hex key is furnished for this purpose.

DM-42-I Inserts can be attached to the clamping wedge of the DM-42 using the 10-32 x 5/8" "fine adjustment" button head cap screw. A 1/8" hex key through the access slot removes the button head screw to attach the #1 Insert for sharpening gun drills from .156" (4mm) to 15/32" (12mm). The #2 Insert is used to sharpen gun drills from 15/32" (12mm) to 3/4" (19mm). No insert is used for 3/4" (19mm) and larger gun drills, but the button head cap screw is re-installed to make fine adjustments as detailed above.

Existing sharpening instruction is suitable for all diameters.

DM-42 System and Accessories
Part #DescriptionPart #Description
DM-42Manual Regrind Fixture (large)DM-41Manual Regring Fixture (std.)
DM-42-AHead Assy. (large)DM-41-AHead Assy. (std.)
DM-42-BBase Assy. DM-42-IInserts for DM-42
DM-42 + DM-41A Head assy. Includes the "large" fixture base assy., large head, and standard head allowing gun drill sharpening from .156 (4mm) to 2.125" (54mm).

Regrinding Instructions for Standard Nose Grinds:

Initial Setting

  1. Place the fixture on the table of the machine. The base of the fixture has two through slots that clamp the base to the table. Install two through bolts but do not tighten. Position the horizontal (base) register at zero. Indicate front face of the fixture zero to the table movement then tighten the through bolts.
  2. Select the appropriate clamping blade for the drill type. The angled blade is to "V" flute gun drills, ensuring the "F" mark on the blade is toward the front. The flat blade is for half round drills. Store the unused blade on the tapped hole provided on the base.
  3. Slide the gun drill or half round drill under the blade clamp and forward of the "V" base. Lock in position on the tube only with the carbide tip fully clear of the base and blade clamp. With both horizontal and vertical scales set at zero, the drill's flat cutting surface should be parallel to the table.
  4. Grind the drill by following the steps outlined for the most common grinds. Custom nose grinds can be ground to your requirements. It is recommended that a suitable dust collection system is used. A cold gun or spraymist is recommended for large diameters.

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