Chicago-Latrobe
Chicago-Latrobe 40590 135-degree NAS aircraft extension drill bit
Aircraft extension drill bit with a 135-degree split point, high-speed steel construction and black oxide finish for precision drilling
- TypeDrill Bits
- MaterialHAWA
- 135-degree split point starts holes on contact
- High-speed steel with black oxide resists wear
- 28-degree helix clears chips from deep holes
- NAS-type geometry meets aircraft extension standards
- 4×D reach drills up to 2 in deep
Chicago-Latrobe 40590 NAS extension drill
This Chicago-Latrobe 40590 is a 135-degree NAS-type aircraft extension drill bit made from HAWA-grade high-speed steel with a black oxide finish. It features a split point design for accurate starts and reduced walking on tough materials. The tool is built for precision drilling in aerospace and machining applications where performance matters.
Upgrade from standard bits for deep holes
Standard jobber drills lack the reach and specialised geometry needed for deep-hole work in aircraft structures. This extension bit provides a 4xD drilling ratio and a 28-degree helix angle suited for chip evacuation at depth. The jump is worth it when drilling 1/2 inch holes up to 2 inches deep in high-performance alloys where rigidity and accuracy are critical.
Straightforward chuck fit with depth care
The fractional inch shank fits standard drill chucks and collets without adapters. Install by securing the shank fully and running at appropriate speeds for high-speed steel in the target material. What usually goes wrong is insufficient chip clearing at maximum depth or excessive feed pressure causing the split point to chip or the extension to deflect.
Highlights
- 135-degree split point starts holes on contact
- High-speed steel with black oxide resists wear
- 28-degree helix clears chips from deep holes
- NAS-type geometry meets aircraft extension standards
- 4×D reach drills up to 2 in deep
Specifications
| Brand | CHICAGO-LATROBE |
|---|---|
| Type | Drill Bits |
| Material | HAWA |
Questions about this item
What chuck size fits the 1/2 in shank of the 40590 drill bit?
Use a drill chuck that accepts a 1/2 in shank; the bit has a split point for self-centring in standard three-jaw chucks.
How do I start the hole correctly with the 135-degree split point?
Apply light pressure and let the split point bite at 135 degrees; do not force the bit or the point can wander in hard material.
When should I replace this high-speed steel bit?
Replace it when the cutting edges dull, the black oxide coating wears off, or the split point no longer centres cleanly.
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