The Delta ShopMaster Model GR250 is a 6" Variable Speed Grinder/Sharpener, designed for various grinding and sharpening tasks. This robust machine is equipped with a flexible lamp, adjustable tool rests, and two large eye shields, enhancing both its functionality and user safety.
Function Description:
The primary function of the GR250 is to grind and sharpen workpieces using its two aluminum oxide grinding wheels. It is suitable for a range of materials and applications, from rough shaping to fine sharpening. The variable speed control allows the user to adjust the grinding speed to match the specific task and material, providing greater precision and control. The flexible lamp illuminates the work area, improving visibility and accuracy during operation. The adjustable tool rests provide stable support for workpieces, ensuring consistent angles and reducing user fatigue. The eye shields offer crucial protection against sparks and debris, contributing to a safer working environment.
Important Technical Specifications:
- Model: GR250
- Type: 6" Variable Speed Grinder/Sharpener
- Power Connection: Requires a separate electrical circuit, not less than #12 wire, protected by a 20 Amp time lag fuse.
- Voltage: 120 volt, 60 Hz alternating current.
- Variable Speed Control:
- Minimum RPM (counter-clockwise): 2000 RPM
- Maximum RPM (clockwise): 3450 RPM
- Grinding Wheels:
- Diameter: 6 inches
- Arbor Hole: 1/2 inch
- Grit: One 36 grit and one 60 grit aluminum oxide grinding wheel supplied.
- Rating: Accessories and attachments should be rated for 3600 RPM or higher.
- Tool Rest Adjustment: Maintain a distance of 1/8" (3.8mm) or less between the grinding wheel and the inside edge of the tool rest.
- Lamp: Flexible lamp, requires a 40 watt or less, 120 volt, reflector track type light bulb (not supplied). Standard household light bulbs should not be used, and the bulb should not extend below the lamp shade.
- Grounding: The machine must be grounded while in use to protect the operator from electric shock. It is equipped with a 3-prong grounding type plug and requires a matching grounded outlet.
- Extension Cords: Use 3-wire extension cords with 3-prong grounding type plugs and matching 3-conductor receptacles. The gauge of the extension cord should be appropriate for the ampere rating and total length to prevent voltage drop and overheating. For example, for 0-6 Ampere Rating and up to 25 feet, 18 AWG is recommended; for 12-16 Ampere Rating and up to 25 feet, 14 AWG is recommended. Cords greater than 50 feet for 12-16 Ampere Rating are not recommended.
Usage Features:
- Variable Speed Control: A knob on the front of the grinder allows for easy adjustment of the grinding wheel speed from 2000 RPM to 3450 RPM, catering to different grinding needs.
- Flexible Lamp: The lamp operates independently of the grinder, controlled by a separate rotary switch, providing focused illumination on the workpiece.
- Adjustable Tool Rests: The tool rests can be positioned slightly below the centerline of the wheel and as close as possible to the grinding wheel, offering maximum support and stability for the workpiece. They should be adjusted to maintain a gap of 1/8" or less from the wheel.
- Adjustable Spark Guards: These guards can be adjusted close to the grinding wheel to prevent sparks from striking the operator's hand.
- Eye Shields: Two large eye shields are provided for operator protection against flying debris and sparks.
- Switch Lock-Out Feature: The "OFF" position of the switch can be locked by pulling out the switch toggle, preventing unauthorized use. The grinder cannot be restarted without inserting the switch toggle.
- Secure Mounting: The grinder base has two holes for securing the machine to a supporting surface with fasteners (not supplied), preventing tipping, sliding, or "walking" during operation.
- Wrench Storage: An open-end wrench and a wheel dresser wrench are provided and can be conveniently stored in a wrench holder at the rear of the grinder.
Maintenance Features:
- Grinding Wheel Dressing: Regular dressing of the grinding wheels is crucial for best grinding results and to maintain good balance. This can be done using a suitable silicone carbide stick type dresser or the provided wheel dresser. The dresser should be moved back and forth across the face of the wheel until it is clean and the corners are square.
- Grinding Wheel Replacement: To change grinding wheels, the side covers must be removed. A wedge is placed between the grinding wheel and the tool rest to prevent shaft rotation. The arbor nut is loosened (clockwise for the left side, counter-clockwise for the right side) to remove the old wheel and tightened (counter-clockwise for the left side, clockwise for the right side) to secure the new one. It is important not to overtighten the wheel nuts, but to tighten them enough to drive the wheel and prevent slippage.
- Cleaning: The machine should be unpacked and cleaned by removing the protective coating from unpainted surfaces with a soft cloth moistened with kerosene (avoid acetone, gasoline, or lacquer thinner). After cleaning, unpainted surfaces should be covered with a good quality household floor paste wax.
- Lubrication: Follow instructions for lubricating the machine to maintain top condition and performance.
- Inspection: Regularly inspect grinding wheels for cracks or chips and replace damaged wheels immediately. Check for alignment of moving parts, binding, breakage, and any other conditions that may affect operation.
- Cord Maintenance: Repair or replace damaged or worn power cords immediately to ensure safety.
Safety Guidelines:
The manual emphasizes numerous safety rules, including:
- Always wear eye protection (safety glasses conforming to ANSI Z87.1 requirements), and use a face or dust mask if the operation is dusty.
- Keep guards in place and in working order.
- Remove adjusting keys and wrenches before turning the tool on.
- Keep the work area clean and well-lighted, and prevent children and visitors from accessing the work area.
- Do not force the tool; use the right tool for the job.
- Wear proper apparel, avoiding loose clothing, jewelry, and long hair.
- Secure workpieces with clamps or a vise.
- Maintain proper footing and balance, and avoid overreaching.
- Disconnect tools from the power source before servicing or changing accessories.
- Use only Delta recommended accessories.
- Ensure the switch is in the "OFF" position before plugging in the power cord.
- Never stand on the tool.
- Feed work against the direction of rotation of the blade or cutter.
- Never leave the tool running unattended; turn power off and wait for it to stop completely.
- Stay alert and use common sense; do not operate while tired or under the influence of drugs, alcohol, or medication.
- Be aware of dust generated by certain woods and construction activities, which can be injurious to health. Operate in well-ventilated areas and use dust collection systems.
- Never grind near flammable gas or liquids due to spark hazards.
- Avoid awkward operations and hand positions that could lead to hands moving into the grinding wheel.
- Hold work firmly against the tool rests.
- Dress the grinding wheel on the face only; dressing the side can make it too thin for safe use.
- Never apply coolant directly to the grinding wheel; dip the workpiece in water to cool it.
- Do not touch the ground portion of a workpiece until it has cooled sufficiently.
The Delta ShopMaster Model GR250 is designed for safe and efficient grinding and sharpening, provided that all assembly, operating, and safety instructions are strictly followed.
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