Chicago-Latrobe
Chicago-Latrobe 40478 135° NAS-Type Aircraft Extension Drill 5/16 in HSS Black Oxide
135-degree split-point HSS drill bit with black-oxide finish for aircraft extension work
- TypeDrill Bits
- MaterialHAWA
- 135° split point starts on contact for accurate holes
- High-speed steel with black oxide resists wear and corrosion
- 28° helix clears chips efficiently in deep drilling
- 4×D reach handles extended-depth aircraft work
- 1-1/4 in maximum drilling depth suits structural tasks
Chicago-Latrobe 40478 Aircraft Extension Drill
This 5/16 inch drill bit uses high speed steel with a black oxide finish for corrosion resistance. The 135 degree split point reduces walking and starts holes cleanly in tough alloys. A 28 degree helix angle clears chips efficiently during deep drilling operations.
Suited for aerospace maintenance
Mechanics drilling rivet holes in wing structures or fuselage panels will value the NAS-type geometry and extended reach. Builders needing a standard jobber length bit for general workshop tasks should look at a different tool because this design prioritises deep-hole access over rigidity.
Sustained drilling in hard materials
High speed steel maintains cutting edges through repeated passes in aluminium and titanium alloys when lubrication is adequate. The 1 1/4 inch maximum drilling depth at 4xD means heat builds quickly in deep holes so peck cycles and coolant are essential to prevent premature wear.
Highlights
- 135° split point starts on contact for accurate holes
- High-speed steel with black oxide resists wear and corrosion
- 28° helix clears chips efficiently in deep drilling
- 4×D reach handles extended-depth aircraft work
- 1-1/4 in maximum drilling depth suits structural tasks
Specifications
| Brand | CHICAGO-LATROBE |
|---|---|
| Type | Drill Bits |
| Material | HAWA |
Questions about this item
What size drill chuck does the 5/16 in shank on the 40478 need?
The 5/16 in shank fits any standard drill chuck that opens to at least 5/16 in, which covers most 3/8 in and 1/2 in capacity chucks.
Will the 135° split point on the 40478 start cleanly in the work-hardened spots left by my older cobalt bits?
Yes, the 135° split point is designed to self-centre and reduce walking, so it enters hard or work-hardened material without a centre punch.
How can I confirm the 40478 is cutting correctly once I start drilling?
Look for short, curled chips in a straw-to-blue colour and a smooth hole wall; those show the 135° point and black-oxide finish are evacuating heat properly.
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