The 8274-4 is National's 18.5" planetary grinder. National builds it to run 3 HP on 115 volts, with variable speed, a soft start and a 15 A / 20 A switch to control amperage draw. National lists it for thin-set, coating and adhesive removal, prepping concrete for overlays or coatings, and polishing.
Specifications
Specs from National's 8274-4 product page and the operating manual (402902 Rev D).
| Spec | Value |
|---|---|
| Grinding disk | 18.5" (47 cm) |
| Width | 20" (51 cm) |
| Length / height | Length 38.5"-75" (98-191 cm); height 27.5"-52" (70-132 cm) |
| Weight | 388 lb (176 kg) |
| Motor | 3 HP (2.24 kW) |
| Power supply | 120 V/60 Hz single-phase input, 3-phase operation (manual); 115 V, 60 Hz, single phase (product page) |
| Amperage | 15 A or 20 A switchable; normally runs on 20 A, 15 A setting for limited power |
| Drum RPM | 133.8 |
| Motor RPM | 400-2,000 (variable) |
| Dust collection | Dual rear vacuum ports; National's DL3000 page lists the 8274-4 as compatible, and the 2026 catalog recommends the DL2000 with the DLS2000 pre-separator |
Maintenance schedule
From National's 8274-4 operating manual (402902 Rev D). The manual gives no hour-based intervals; it covers belt, idler bearing, pulley, satellite shaft and satellite bearing replacement and leaves inspection to a service center.
| Interval | What to do |
|---|---|
| Before each use | Examine the general condition of the machine; stop if you hear abnormal noise or feel vibration |
| After use / as needed | Clean dust and debris from wheels and housing with mild soap and a damp cloth; do not pressure-wash |
| Service center | Inspect pulleys, belts, bearings, nuts, bolts, housing and labels; electrical inspection; testing |
Videos from National
National's 8274-4 videos, plus its planetary grinder comparison and tooling guide.
- 8274-4 Demo
- National's 8274-4 Planetary Floor Preparation System
- Meet the 8274-4
- What's the Difference Between the Helix and 8274-4?
- Planetary Grinder Tooling Application Guide
Sources
Everything on this page comes from National Flooring Equipment's own published material.
