Precision Airframe Hole Making
Double Margin Drills
Engineered for tight hole tolerances, superior burnishing finish, and structural fastener alignment across global aerospace MRO and manufacturing operations.
High-Precision Double Margin Tooling for Aircraft Assembly & Repair
Pan American Tool Corporation’s Double Margin Drills are specifically engineered to solve hole quality and size control challenges in critical structural applications. Built with a secondary margin ground directly behind the main cutting edge, these high-performance cutters burnish the hole wall as they advance. This dual-margin action dramatically enhances stability in non-ferrous alloys, titanium, and cast irons.
By eliminating tool wander, belly, and hole ovality, double margin designs produce exceptionally round, straight holes with fine surface finishes. In many high-volume airframe assembly and MRO workflows—including Hi-Lok® fastener preparation—our NAS 937 compliant drills achieve final tolerances in a single step, effectively eliminating separate reaming passes and saving significant labor costs.
Product Selection
Explore Double Margin Aircraft Drill Families
Select from jobber lengths, NAS 937 piloted styles, threaded shank configurations, and 6-inch extension series designed for high-density airframe repair and production lines.
Double Margin Jobber Length Drills
Piloted Double Margin Drills (NAS 937)
Cobalt Threaded Shank Double Margin Drills - NAS 937
Cobalt Threaded Shank Double Margin Drills with Pilot
Double Margin - 6" Extension Drills (NAS 937)
Piloted Double Margin - 6" Extension Drills
Hi-Lok® Sizes Piloted Double Margin Drills
Cobalt Aircraft Stove Burner Drills
Cobalt Stove Burner Drills - 6" Extension
Technical Capabilities
Engineering Advantages of Double Margin Cutting Geometry
Designed to meet strict aerospace standards, double margin cutters solve critical hole accuracy challenges across aluminum skins, titanium ribs, and composite airframe structures.
Dual Margin Wall Burnishing
The primary margin performs the cutting operation, while the secondary trailing margin contacts the hole wall immediately behind. This secondary margin stabilizes the bit, dampens chatter, and burnishes the interior wall, yielding finish quality comparable to chucking reamers.
Hole Diameter Tolerance & Straightness
Standard jobber drills are susceptible to flexing, resulting in bell-mothing and oversized hole entries. Double margin drills remain concentric and true, maintaining strict class-fit tolerances required for modern aerospace interference-fit fasteners.
NAS 937 Specification Compliance
Manufactured to aerospace NAS 937 standards, our cobalt and carbide-tipped double margin tools ensure exact compliance for military, defense, commercial airline MRO, and OEM aerostructure production lines.
Optimized for Hi-Lok® Installation
Designed specifically for precision fastener preparation, these tools achieve structural hole alignment in stacked materials (aluminum/titanium/composite), eliminating burrs between structural layers.
Machining Guidelines
Double Margin Drilling Parameters by Material
Recommended starting values for handheld pneumatic drills and automated CNC machining setups in aerospace manufacturing.
| Workpiece Material | Recommended Tool Type | Point Angle | Performance & Process Advantage |
|---|---|---|---|
| 2024-T3 / 7075-T6 Aluminum Skin | Jobber or Threaded Double Margin | 135° Split Point | Prevents hole ovality; eliminates secondary reaming step in sheet metal assemblies. |
| Ti-6Al-4V Titanium Alloys | Cobalt M42 NAS 937 Double Margin | 135° Heavy-Duty Split | Dual margin stabilizes cutter under high thrust load; prevents work hardening of hole walls. |
| CFRP / Aluminum Stacks | Piloted Carbide Double Margin | 118° / 135° Custom Point | Prevents inter-laminar burring and delamination during multi-material hole penetration. |
| Hi-Lok® Fastener Structural Holes | Hi-Lok® Specific Piloted Double Margin | Precision Step / Split Point | Ensures tight diametral tolerance required for fatigue-rated interference fasteners. |
Technical Support
Frequently Asked Questions About Double Margin Drills
How does a double margin drill eliminate the need for reaming?
A standard drill bit has only one margin per land to clear clearance space. A double margin drill carries a second margin ground behind the main margin. This trailing margin burnishes the hole wall as the tool advances, correcting minor alignment variances and producing a rounder, straighter hole with a fine surface finish—often eliminating a separate reaming pass.
What is NAS 937 and why is it important for aerospace buyers?
NAS 937 is the National Aerospace Standard covering piloted and non-piloted double margin extension drills. Adherence to NAS 937 guarantees precise flute geometry, overall lengths, shank configurations, and concentricity standards required by commercial airlines and defense defense depots worldwide.
Can double margin drills be used in handheld pneumatic air motors?
Yes. Double margin drills excel in portable pneumatic motor applications (such as Nova® air drills) because the dual margins self-stabilize the tool inside the hole, counteracting the hand wobble typical of manual airframe repairs.
Do you offer international shipping and export support for MRO buyers?
Pan American Tool Corporation ships directly to global procurement managers, MRO stations, and defense contractors worldwide from our Fort Lauderdale, Florida logistics facility under CAGE Code 0PFP1.
Need Bulk Aerospace Tooling Pricing or Technical Support?
Speak directly with our technical tooling specialists to match exact drill sizes, NAS specifications, and custom tooling packages for your airframe program.