Bosch Hole Saw Kit HDG138QA 1-3/8 Inch Diamond Grit AutoStart Mandrel (1-1/2 Deep Cut Wet Drilling Vacuum Brazed Masonry Alignment Countertop Securement)

Professional 1-3/8-Inch Vacuum-Brazed Diamond Grit Hole Saw Kit with AutoStart Retractable Pilot and Quick Change Mandrel for Stone Fabrication

The Bosch HDG138QA 1-3/8 Inch Diamond Grit Hole Saw Kit AutoStart Pilot Bit Mandrel for Granite Stone Tile Countertops delivers specialized abrasive substrate boring utility and exceptional material clearing efficiency across demanding trade layout arrays, commercial stone countertop fabrications, and professional tiling retrofits. Engineered with high-density vacuum-brazed diamond grit bonded natively onto a rigid steel support shell, this high-performance layout tool accessory withstands the extreme thermal heat accumulation typical when surfacing through hard porcelain, slate, and granite without cracking or chipping fragile finish horizons. This professional contractor solution resolves frequent material shattering defects encountered when using standard carbide bits, slow boring progress rates, and drill-bit walking errors on smooth polished stone surfaces by combining a patented spring-loaded AutoStart retractable pilot bit with a rapid-ejection side slot architecture and a versatile Quick Change system compatibility. Outfitted with an exact 1-3/8 inch circular boring track diameter, a robust 1-1/2 inch deep clearing cup capacity profile, and structural optimization for wet-cutting mandates, this refined stone processing hardware optimizes subcontractor project turnaround timelines during kitchen sink faucet installations, custom stone surfacing modifications, and architectural cladding adjustments.

Best Used For:

• Faucet and Air-Switch Installations: Coring precise 1-3/8 inch circular channels natively through high-density granite or quartz kitchen countertops single-handedly without surface fracture errors.
• Commercial Stone Fabrication: Boring accurate fixture openings directly into natural stone surfaces and heavy-duty slabs cleanly under constant wet-cooling lubrication.
• Professional Masonry Retrofits: Establishing smooth circular alignment entry tracks into brittle slate, glass-fused tiles, and natural marble slabs for high-end interior finish work.

Key Performance & Safety Features

• AutoStart Retractable Pilot: Spring-loaded pilot shaft eliminates bit walking across polished surfaces, ensuring exact centering alignment before the primary diamond ring engages.
• Vacuum-Brazed Diamond Matrix: Advanced thermal-fusion bonding of diamond grit to the cup shell maximizes structural cutting velocity while checking premature grit shedding failures.
• Quick Change System Integration: Precision-threaded hub mounts natively onto professional rapid-swap mandrels, allowing for near-instant sizing changes during complex stone installation sequences.
• Segmented Debris Clearing Slots: Wide side-wall ejection windows dissipate cooling water flow through the cutting face, forcing slurry away from the boring path to prevent binding.
• Hardened Steel Cup Chassis: Power-tempered internal cup walls resist deformation under rotational torque loads, maintaining perfectly circular bore geometry in high-pressure drilling environments.

What's Included

• (1) 1-3/8 Inch Diamond Grit Hole Saw Cup
• (1) Quick Change Mandrel Assembly
• (1) AutoStart™ Retractable Pilot Bit

Technical Specifications

Pro-Tip: Always initiate your hole placement by tilting the saw slightly to score a shallow starter notch, then gradually level the tool flat as the diamond grit bites into the surface. This controlled start prevents dangerous bit walking across polished granite or slick glass tile surfaces, keeping your finish perfectly clean and secure.