National Flooring Equipment

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The 8274-4 is the only grinder on the market offering 3 HP at 115 volts while operating at a 230-volt level. With variable speed and a soft start to control its amperage draw, the 8274-4 adjusts to the needs of small or large jobs. This machine is well suited for removal of thin-set, coatings, adhesive, prepping concrete for overlays or coatings, and polishing.

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  • Dual rear vacuum ports
  • Removable handle and weights for easy transport


  • Three-part adjustable angle handle


  • Choose from 15A or 20A circuit-breaker settings with a convenient switch on the side of the controller; the 15A selection limits motor draw to 15 amps; the 20A selection pulls up to 20 amps
  • Forward and reverse directional controls increase tooling productivity with cleaner consumables and more even wear
  • Variable speed control
  • Flip-style weights for added or decreased head pressure
  • 18-inch grinding path; uses National’s patented self-tensioning, single-belt design to prepare concrete surfaces to a 3000-resin shine
  • Adjustable velcro dust guard lets the machine operate within an eighth of an inch of walls and promotes nearly dustless operation
  • Grinder head rotates 90 degrees for easy tooling change access; Morflex couplers, polishing undulating concrete surfaces or creating a uniform scratch pattern for coating applications; operates a complete dry grind and polish system to eliminate messy and hazardous slurry
Width20"51 cm
Disk Size18.5"47 cm
Max. Height52"132 cm
Min. Height27.5"70 cm
Max. Length75"191 cm
Min. Length38.5"98 cm
Weight388 lb176 kg
Drum RPM133.8
Motor RPM1740
Motor PhaseSingle*
HP32.24 kW
Amps15 or 20-controller can switch between both settings
Frequency60 Hz
*Conversion from three-phase to single-phase power
  • 401882: Morflex couplers
  • 9241 Quick-change magnetic-mount assembly: Three assemblies and three 73250 tooling holder mounting screws are required
  • 73135: 5/32" Hex key
  • 9245 Velcro adapter: Mounts onto the 9241 quick-change magnetic assembly for using polishing pads and brazed disks. Three adapters are required.
  • 6280-401B: 7/32 t-handle wrench
  • Instruction manual

National recommends adding these accessories to your order, so you can stay in the work longer.

DL2000 Dust Collector
9507-16: 16 Grit Half Bar Metal Bond Diamond Insert (6 min. suggested)
9507-30: 30 Grit Half Bar Metal BondDiamond Insert (6 min. suggested)
9521: Carbide Tooling Holder (6 min. suggested)
9554: 1Up PCD- 1/2 Round (6 min. suggested)