Equipment Care & Repair

Walk-Behind Scraper Maintenance

The daily checks, blade care and adjustments that keep a walk-behind floor scraper cutting, based on National's 550 manual.

Updated · 2 min read

Walk-behind scrapers are simple machines, which is why they get neglected. Most performance problems are a dull blade, a loose fastener or the wrong angle. This checklist follows the National 550 manual[1] and carries over to most walk-behinds; check the manual for your model.

Every day

Walk the machine before each job; a quick look catches most problems.

  • Inspect guards, switches and cords for damage. Replace damaged cords; don't tape them.
  • Check for loose screws, misalignment, binding of moving parts and broken parts. Retighten fasteners that have worked loose.[1]
  • Check the blade edge before you start. A dull edge shows up first as a machine riding over material.

Blades

The blade is the part that wears fastest and matters most.

  • Keep blades sharp. A dull blade hurts performance and causes unnecessary wear on the machine.[1]
  • Sharpen with a 4" disk grinder at 120 grit or finer. A bench or belt grinder in the shop gives a better edge.[1]
  • Keep the wings on self-scoring blades sharp.
  • Carbide-tipped blades need a green (silicon carbide) wheel.

Adjustments

Match blade angle, handle height and weight to the subfloor before you start cutting.

  • Blade angle: on the 550, rotate the handle clockwise to raise the wheels (steeper angle) and counterclockwise to lower them.[1]
  • Use a steep angle for hard tear-outs such as tile over concrete. Use a low angle for vinyl, VCT or carpet over plywood and other soft subfloors.
  • Handle height: set it at the operator's belt line, whatever the wheel angle.
  • Weight: removing the counterweight helps on wood subfloors.

Safety while running

A few rules keep the operator and everyone nearby safe.

  • Keep hands and feet out from under the machine, and stay 3 ft from it while it runs.[1]
  • Wear a respirator approved for the material when grinding or cutting creates dust.
  • Unplug before changing blades.

Signs something's wrong

When the machine isn't cutting well, start with these checks.

Symptom Check first
Machine rides over material Blade dull or too wide; blade angle too low
Gouging the subfloor Blade angle too steep; blade installed with bevel wrong for wood
Excess vibration Loose fasteners, bent blade holder, worn parts
Motor stalls Blade too wide for the adhesive bond; extension cord too long or undersized

Parts

Replace worn blades, cords and fasteners with parts for your model.

References

  1. National 550 operating and service manual

Linked PDF documents are archived copies saved by PreFloor Tools so they stay available if the publisher moves or removes them. Check the publisher's website for the latest revision.

Tools for this job

Shop by category

More Equipment Care & Repair guides

Parts for these machines

OEM replacement parts, organized by assembly, with the manual for each machine.