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Chicago-Latrobe 11155 #31 135° aircraft extension drill bit, black oxide finish

Chicago-Latrobe

Chicago-Latrobe 11155 #31 135° NAS Aircraft Extension Drill

SKU CH-BK5S-XW3QH

A #31 high-speed steel drill with a 135-degree split point, black oxide finish and 1-5/8 inch maximum drilling depth

  • 135° split point starts on contact for precise holes
  • #31 wire-gauge size matches NAS aircraft specifications
  • High-speed steel with black oxide resists wear in tough alloys
  • 1-5/8 in drilling depth handles extended reach jobs
  • 28° helix angle clears chips efficiently during deep drilling

NAS Aircraft Extension Drill

The Chicago-Latrobe 11155 is a #31 size drill bit built to NAS aircraft specifications. It targets aviation maintenance technicians and precision metalworkers who need accurate hole placement in thin sheet materials. The 135-degree split point reduces walking and ensures clean entry on hard surfaces.

High-Speed Steel Limits

High-speed steel construction with black oxide finish handles general machining at a 28-degree helix angle. The material suits wire and similar alloys but wears faster than cobalt or carbide in abrasive or high-temperature drilling. Maximum drilling depth reaches 1 5/8 inches, restricting use to shallow-hole applications.

Straightforward Chuck Fit

The straight shank fits standard drill chucks without adapters, so setup is quick on portable or bench machines. The split point self-centres, yet the long extension can deflect if side pressure is applied or if the workpiece is not rigidly clamped. Clear chips frequently to avoid binding at depth.

How it compares

Measured against everything we stock in Power Drills, Drivers & Cutting Bits, at today’s prices. Recalculated every night.

Price $8.99
Cheaper than about 94% of the 2,412 comparable items (median $81.99).

Specifications

Product
Brand nameCHICAGO-LATROBE

Questions about this item

Which drill bit size should I choose for my application?

The #31 size is a specific wire-gauge diameter; select it when your engineering drawing or fastener chart calls for a #31 hole.

What does the 135-degree point angle do once the bit is in the machine?

A 135-degree split point centres faster and reduces thrust on hard materials compared with shallower angles.

What does the 28-degree helix angle cap in practice?

The 28-degree helix controls chip evacuation rate and limits how aggressively the bit pulls into the workpiece.

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