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A 12 inch cobalt drill bit with a 29/64 inch diameter and split point tip

Drill America

Drill America 29/64 in 12 in Cobalt Aircraft Extension Drill Bit

SKU CH-36V9-9D23B

12-inch cobalt aircraft extension drill bit with 29/64-inch diameter and split point for heavy-duty drilling

  • Product typeDrill Accessories
  • 29/64 inch diameter drills precise holes
  • 12 inch overall length reaches deep cavities
  • Cobalt steel construction resists heat and wear
  • Split point tip starts accurately without wandering

Cobalt Aircraft Extension Bit

This Drill America cobalt steel drill bit measures 29/64 inch in diameter with a 12 inch overall length. The heavy duty split point design promotes accurate starting on metal surfaces. Its aircraft extension length reaches deep or awkward holes in automotive and industrial work.

Replaces shorter standard bits

Standard jobber length bits cannot reach the depths this 12 inch extension accesses. The cobalt steel construction withstands higher heat than high speed steel when drilling tough alloys. The jump is worth it for maintenance tasks where extra reach and heat resistance matter most.

How it compares

Measured against everything we stock in Bits, Hole Saws & Accessory Kits, at today’s prices. Recalculated every night.

Price $21.99
Cheaper than about 60% of the 5,493 comparable items (median $27.99).

Specifications

Product
Brand nameDrill America
Product typeDrill Accessories

Questions about this item

What chuck size is needed for the 29/64 in shank?

A 1/2 in or larger chuck is required because the 29/64 in shank equals .4531 in and exceeds the capacity of a standard 3/8 in chuck.

How do you avoid breaking the bit when drilling deep with the 12 in overall length?

Drill in short increments, clearing chips every 1 in to 2 in of depth; the 4-3/16 in flute length cannot evacuate chips from the full 12 in hole in one pass.

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