Chicago-Latrobe
Chicago-Latrobe 40570 135 Degree NAS Aircraft Extension Drill 3/16 in HSS Black Oxide
135-degree split-point HSS drill bit with black-oxide finish drills 3/4 in deep in aircraft-grade material
- TypeDrill Bits
- MaterialHAWA
- 135-degree split point starts holes cleanly on hard alloys
- 3/16 inch high-speed steel handles tough aircraft materials
- Black oxide finish resists corrosion during extended use
- 28-degree helix clears chips efficiently at depth
- 4×D length reaches deep cavities without wandering
Chicago-Latrobe 40570 Aircraft Extension Drill
The Chicago-Latrobe 40570 is a 135-degree NAS-type aircraft extension drill made from high-speed steel with a black oxide finish. It features a 3/16 inch fractional drill bit size and a split point design for accurate starts. This accessory targets mechanics and technicians performing deep-hole drilling in aviation or structural maintenance tasks.
Split point geometry and depth constraint
The 135-degree split point reduces walking and improves centring on hard materials without a centre punch. Maximum drilling depth is limited to 3/4 inch, reflecting the 4xD design ratio for this diameter. The 28-degree helix angle supports chip evacuation in confined spaces but does not suit deep-hole applications beyond the stated limit.
Verify shank fit and material compatibility
Confirm that your drill chuck or collet accepts the straight shank of this extension bit before ordering. The high-speed steel construction with black oxide coating is intended for general-purpose machining in ferrous alloys; it is not rated for hardened steels or exotic alloys requiring cobalt or carbide substrates. Ensure the 3/16 inch size matches the hole specification for your fastener or rivet pattern.
Highlights
- 135-degree split point starts holes cleanly on hard alloys
- 3/16 inch high-speed steel handles tough aircraft materials
- Black oxide finish resists corrosion during extended use
- 28-degree helix clears chips efficiently at depth
- 4×D length reaches deep cavities without wandering
Specifications
| Brand | CHICAGO-LATROBE |
|---|---|
| Type | Drill Bits |
| Material | HAWA |
Questions about this item
Which drill bit size should I select for a 3/16 inch hole?
The 40570 is a 3/16 inch fractional drill bit, so it matches that exact hole diameter.
What does the 135 degree point angle do in a hand drill?
The 135 degree split point centres itself quickly and reduces wandering on hard materials.
What shank standard fits this extension drill?
It has a straight round shank that fits standard drill chucks and collets.
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