Product Description
CMT Hinge Boring Bit 40 x 70mm Left-Hand is a long-series, carbide-tipped boring bit engineered for drilling precise flat-bottom hinge cup holes in cabinet doors and panels. Built by CMT on a super-strength steel body with a hardened carbide (HW) cutting head, this 40mm diameter bit is sized specifically for European-style concealed hinge installation - delivering clean, flat-bottomed cup recesses in a single plunge. The left-hand (LH) rotation makes it the correct choice for dedicated hinge boring machines and CNC boring centers that require counter-clockwise tooling. With a 10x26mm parallel shank fitted with a driving flat and length adjusting screw, it seats securely in boring machine chucks for repeatable, production-quality results on cabinet components of greater thickness.
Key Features
- Hardened carbide (HW) cutting head with precision balanced centre point - the centre point stabilizes entry and prevents the bit from wandering, producing accurately positioned hinge cup holes with no tear-out at the bore centre.
- 2 precision ground cutting edges (Z2) with negatively ground spurs - the negative spur geometry shears the perimeter of the bore cleanly before the main cutters remove material, leaving flat-bottomed holes with crisp, splinter-free walls suited to finished cabinet faces.
- 2 spiral flutes with PTFE-coated spiral portion - the orange or black PTFE coating prevents pitch, glue, and resin from adhering to the flutes, reducing buildup that would otherwise slow cutting speed and shorten tool life in production environments.
- Super-strength steel body - resists deflection and flex during deep-boring operations, maintaining dimensional accuracy across repeated cycles on chipboard, MDF, plywood, and solid wood cabinet components.
- 10x26mm parallel shank with driving flat and length adjusting screw - the driving flat transmits torque efficiently without slippage, while the adjusting screw allows fine depth calibration so every hinge cup is bored to a consistent depth without re-measuring between setups.
- Left-hand (LH) rotation - designed specifically for left-hand spindle positions on multi-spindle boring machines and CNC boring centers, ensuring correct chip evacuation direction and cutting engagement for those configurations.
- 40mm diameter, 70mm total length - the 40mm cutting diameter matches the standard European hinge cup spec, and the extended 70mm length accommodates thicker cabinet door stock where shorter series bits cannot reach full bore depth.
Why This Product
- The 70mm long-series length solves a common production problem - boring European hinge cup holes in thicker cabinet components where standard-length bits fall short of the required depth, eliminating the need for extensions or workarounds.
- The PTFE-coated spiral flutes directly reduce downtime in high-volume cabinet shops by shedding pitch and adhesive buildup that would otherwise require frequent cleaning stops, keeping the bit cutting cleanly through long production runs.
- Negatively ground spurs produce flat-bottomed hinge cups with clean perimeter walls - critical for proper concealed hinge seating and consistent door alignment across an entire run of cabinet doors.
- The parallel shank with driving flat and length adjusting screw simplifies changeover and depth repeatability on boring machines, supporting fast, accurate setup without elaborate fixturing between batches.
Specifications
- Manufacturer Part Number: 369.400.12
- Brand: CMT Orange Tools
- Diameter: 40mm
- Total Length: 70mm
- Shank: 10x26mm
- Rotation: Left-hand (LH)
- Number of Cutting Edges: 2
- Number of Spurs: 2
- Tooth Geometry: Negatively ground spurs
- Blade Material: HW (Carbide-Tipped)
- Product Type: Hinge Boring Bit
- Series: Hinge Boring Bit 70mm
Approved Applications
- Drilling flat-bottom hinge cup holes for European-style concealed hinge installation
- Cabinet door hinge mounting on thicker door stock
- Production boring on multi-spindle CNC boring machines and boring centers
- Panel processing on CNC boring centers and panel processing centers
- Hinge cup boring in solid hardwood, softwood, chipboard, MDF, and plywood cabinet components
Frequently Asked Questions
Why is left-hand (LH) rotation specified for this bit, and how do I know if my machine needs it?
Left-hand rotation means the bit cuts while spinning counter-clockwise. Multi-spindle hinge boring machines and CNC boring centers assign specific spindle positions as left-hand or right-hand. If your machine's spindle for a given boring position runs counter-clockwise, you need an LH bit like this one. Using an RH bit in an LH spindle would cause the bit to eject or refuse to cut rather than bore correctly. Check your machine's spindle rotation chart for each position before ordering.
What makes the 70mm long series necessary - when would a shorter hinge boring bit not work?
Standard-series hinge boring bits are shorter and designed for typical door thickness ranges. When cabinet door components are thicker - such as solid hardwood doors, overlay doors with added material, or frameless panels built to greater depth - a short-series bit may not achieve the full cup depth required for the concealed hinge to seat flush. The 70mm total length of this bit provides the additional reach needed for those thicker workpieces.
What is the purpose of the PTFE coating on the spiral flutes?
The PTFE (polytetrafluoroethylene) coating applied to the spiral portion of the bit creates a low-friction, non-stick surface. In cabinet production, chipboard and MDF binders, wood resins, and glue residue tend to accumulate on uncoated flutes over time, increasing cutting resistance and generating heat. The PTFE coating resists this buildup, helping the bit evacuate chips more freely and maintain consistent cutting performance across extended production runs.
Can this bit be used in a handheld drill or drill press instead of a dedicated boring machine?
This bit is primarily designed for use in multi-spindle boring machines and CNC boring centers where the parallel shank with driving flat locks into a dedicated collet or chuck. A boring machine with an adapter or chuck can also accept this shank. While a drill press with an appropriate chuck may physically hold the 10x26mm parallel shank, the left-hand rotation requirement means the drill press spindle must be capable of running in reverse. Handheld drills are generally not recommended for production hinge cup boring due to the precision and repeatability requirements of concealed hinge installation.
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