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Prep/Master Jr Electric Concrete Floor Grinder

High-Performance Concrete Floor Grinder for Residential-Sized Projects

Electric concrete floor grinder.

Our customers’ favorite little grinder! The Prep/Master^® Jr. concrete floor grinding machine by STI works extremely well in small, hard-to-reach areas that requires a more compact design – perfect for residential garage floors and basements.

The Prep/Master Jr concrete floor grinder is designed for professional surface preparation and polishing. It features a 23-inch grinding width and a powerful 7.5HP motor for consistent performance on commercial and residential flooring projects.

The moveable pocket weight system adjusts head pressure depending upon application and the standard water tank makes it easy to switch from dry to wet work. Uses four tool plates (included). Recommended for project sizes up to 1,000 SF (100m²).

✅ Key Features of This Electric Concrete Floor Grinder

• 23″ Grinding Width – Efficient coverage for faster production
• 7.5HP Electric Motor – High torque for demanding applications
• Variable Speed Drive – Adjust for grinding or polishing conditions
• 2 Tool Plates / 6 Tools – Consistent multi-head grinding performance
• Adjustable Weight System – Customize head pressure based on application
• Wet or Dry Operation – Built-in water tank for versatility

This electric concrete floor grinder is designed to combine production capacity with maneuverability, making it ideal for contractors handling mid-size jobs

🛠️ Special Features

• Heavy head pressure for a better grind and polish – 60% of its weight is on the head!
• Magnetic LED Light to illuminate front of machine or behind machine on the cutting path
• Easy disassembly of machine into two sections for easier transportation
  (Grinding head = 260 lbs. / Handle = 130 lbs. / Two Pocket Weights = 30 lbs. each)
• Screw-in Carrying Poles for two-three person lifting
• 8-gallon (30 liters) water tank
• On-board USB Charger & Phone Carrier

⚙️ Electric Concrete Floor Grinder Specifications

• Working Width: 23 inches (58 cm)
• Engine: WEG 7.5 HP (5.5 kW) 1 phase
• Voltage: 230V available
• Weight: Approx. 455 lbs (206 kg)
• Dimensions: 50″ L x 23″ W x 48″ H
• Tool Plates: 2
• Total Tooling: 6 tools
• Recommended Project Size: Up to 1,000 sq ft

🏗️ Applications for Concrete Floor Grinding & Polishing

Best Uses for an Electric Concrete Floor Grinder in Commercial Projects

The PM Jr is engineered for a wide range of surface prep and polishing applications:

• Concrete grinding and polishing
• Epoxy and coating removal
• Terrazzo surface finishing
• Warehouse and commercial floor prep
• Adhesive and mastic removal
• Stone and marble polishing

This electric concrete floor grinder is ideal for commercial and industrial concrete flooring applications.

🔥 Why Choose an Electric Floor Grinder?

This floor grinder offers key advantages:

• Consistent power output
• Lower emissions (ideal for indoor use)
• Reduced fuel handling vs propane
• Reliable performance for controlled environments

The Prep/Master PM Jr is ideal when power access is available and indoor air quality matters.

🧠 Why Choose the Prep/Master PM Jr?

• Designed for residential commercial projects
• Combines power of large machines with compact design
• Easy to transport and maneuver on job sites
• Compatible with STI tooling systems
• This concrete floor grinder is a reliable solution for contractors focused on productivity and finishing quality.

Whether you’re polishing concrete floors or removing coatings, this machine delivers reliable performance across multiple surfaces.

Item #
823752250

❓ Frequently Asked Questions

What size jobs is the PM Jr best for?

It is recommended for projects up to 1,000 square feet, making it ideal for mid-size flooring jobs.

Can this concrete floor grinder polish concrete?

Yes. With proper tooling, it can be used for both grinding and polishing applications.

What power does it require?

This machine is available in 230V only

What surfaces can it handle?

Concrete, terrazzo, marble, and stone surfaces.

How many tools does it use?

It runs 6 tools across 2 tool plates for even grinding coverage. Click HERE to see our selection of tooling!

🔗 Related Resources

• Prep/Master 3003AR dust collector for use with electric concrete floor grinders
• OSHA silica dust safety guidelines for concrete grinding