STI Prep/Master Jr. Floor Grinding Machine (Electric)


SKU: 823752201 Categories: ,


Ideal for Polishing Projects up to 1,000 SF (100 M2)

Our customers’ favorite little grinder! The Prep/Master® Jr. 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.

This grinder is very aggressive, yet extremely easy to operate due to the smooth operation of the STI rotary gear system. In addition, the low price of the Prep/Master Jr. is very affordable and fits any project budget.

  • Working width: 23 in. (58cm)
  • 7.5 HP (5.6kW)
  • 220-240V Single Phase, 40A
  • 450 lbs. (204 kg) including pocket weights
  • 2 tool plates (included)
  • Uses 6 tools

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

Watch the Prep Master Junior in action


Additional information

Weight 455 lbs
Dimensions 50 × 23 × 48 in

Spec Sheets

STI PMJr Spec Sheet

STI Brochure PM Grinders