Product Description
CMT Hinge Boring Bit 30 x 70mm Left-Hand Rotation is a long-series, carbide-tipped boring bit engineered for drilling precise flat-bottom hinge cup holes required in European-style concealed hinge installation. Built on a super-strength steel body with a tungsten carbide (HW) cutting head, this 30mm diameter bit delivers clean, accurate bores in cabinet doors and panel components where standard-length bits cannot reach adequate depth. The 70mm overall length makes it the right tool for thicker cabinet parts, and the left-hand (LH) rotation is designed to match the spindle direction of multi-spindle boring machines and CNC boring centers configured for counter-clockwise tooling positions. Whether you are fitting 35mm cup hinges on solid hardwood doors or boring into MDF and chipboard panels, this CMT bit provides the dimensional accuracy and cutting-edge durability that professional cabinet and furniture production demands.
Key Features
- Tungsten Carbide (HW) Cutting Head - the carbide tip maintains a sharp cutting edge far longer than high-speed steel alternatives, reducing downtime for tool changes on high-volume boring runs.
- Super-Strength Steel Body - the steel shank and body resist flex and deflection under load, keeping the bore straight and on-center even when drilling deep into thicker panel stock.
- PTFE-Coated Spiral Flutes - the orange or black P.T.F.E. coating on the spiral portion prevents pitch and glue buildup, so chips evacuate freely and the bit stays clean without interrupting production.
- Precision-Balanced Centre Point - the HW head includes a precision balanced centre point that seats accurately at the marked bore location, preventing bit walk and producing repeatable hole placement across every workpiece.
- 2 Precision-Ground Cutting Edges with Negatively Ground Spurs (Z2) - two negatively set spurs score the perimeter of the hole cleanly before the main cutters remove material, delivering flat-bottom holes with smooth walls and no tear-out on face veneers or laminates.
- 2 Spiral Flutes - dual flutes balance chip load between the two cutting edges and improve chip evacuation, contributing to cooler cutting temperatures and longer carbide life.
- Parallel Shank (10 x 26mm) with Driving Flat and Length Adjusting Screw - the driving flat locks the bit against rotation in the machine collet, and the length adjusting screw lets the operator dial in the exact boring depth without resetting the machine stop for each tool change.
- Left-Hand (LH) Rotation - matched to LH spindle positions on multi-spindle boring machines and CNC boring centers, ensuring correct cutting geometry and preventing back-threading in LH-configured tool holders.
- 30mm Diameter x 70mm Total Length - the long-series 70mm length reaches the cup depth needed in thicker cabinet components that a standard-length bit cannot accommodate, while the 30mm diameter matches the most common European concealed hinge cup specification.
Why This Product
- The 70mm long-series body is purpose-built for thicker cabinet door and panel stock where standard boring bits fall short of the required hinge cup depth - providing a direct solution without improvised tooling setups.
- Left-hand rotation is a specific machine requirement, not a preference - using a correctly oriented LH bit in an LH spindle position ensures the cutting edges engage the material properly and the shank seats securely in the tool holder.
- The combination of a carbide cutting head, PTFE-coated spiral flutes, and negatively ground spurs addresses three common production problems at once: edge quality, chip clearance, and tool longevity - in a single bit.
- The parallel shank with a driving flat and length adjusting screw reduces setup time between tool changes, keeping boring cell throughput high when producing large batches of cabinet components.
Specifications
- Manufacturer Part Number: 369.300.12
- Brand: CMT Orange Tools
- Diameter: 30mm
- Total Length: 70mm
- Shank: 10 x 26mm
- Rotation: Left-Hand (LH)
- Number of Spurs: 2
- Number of Teeth: 2
- Tooth Geometry: Negatively ground spurs
- Blade Material: HW (Tungsten Carbide)
- Product Type: Hinge Boring Bit
- Series: Hinge Boring Bit (70mm)
Approved Applications
- Drilling flat-bottom hinge cup holes for European concealed hinge installation
- Cabinet door hinge mounting in production and custom cabinet environments
- Boring hinge cups in thicker cabinet components requiring long-series bit reach
- Panel processing on multi-spindle CNC boring machines and CNC boring centers
- Boring operations on drill presses and boring machines equipped with an adapter or chuck
- Use in boring cells configured with left-hand spindle positions
Frequently Asked Questions
What is the difference between this 70mm long-series bit and a standard-length hinge boring bit?
The 70mm total length is classified as a long-series hinge boring bit. It is designed for drilling hinge cup holes in thicker cabinet components where a shorter bit would not reach the full required bore depth. The cutting geometry - 30mm diameter, 2 negatively ground spurs, and a carbide head - is otherwise the same as shorter-series equivalents, but the extended body provides the additional reach needed for heavier panel stock.
Why does rotation direction matter, and how do I know if I need a left-hand bit?
On multi-spindle boring machines and CNC boring centers, individual spindle positions are assigned either right-hand or left-hand rotation depending on their location in the machine's spindle block. Using a bit with the wrong rotation direction in a given spindle position means the cutting edges will be dragging rather than cutting, producing poor hole quality and risking damage to the bit and workpiece. Check your machine's spindle configuration chart to confirm which positions require LH tooling before specifying this bit.
What does the PTFE coating on the spiral flutes actually do during use?
The P.T.F.E. coating on the spiral portion of the bit is a low-friction, non-stick surface treatment. As the bit bores into materials such as MDF, chipboard, or resin-bonded plywood, the PTFE layer prevents pitch and adhesive residue from bonding to the flute surfaces. This keeps the chip evacuation path clear, reduces heat buildup from friction, and extends the service life of the bit between sharpenings. The feature is noted explicitly in the product specifications by CMT.
What does the length adjusting screw on the shank do, and is it needed for every application?
The parallel shank includes both a driving flat and a length adjusting screw. The driving flat locks the shank against rotation within the collet or chuck so the bit cannot spin independently under load. The length adjusting screw allows the operator to set and lock the exact protrusion depth of the bit in the tool holder, which controls boring depth without having to adjust the machine's depth stop independently for each tool change. This is particularly useful in production boring cells where multiple bits are being swapped and consistent cup depth across all holes is critical.
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