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Prevention of Sanding Marks

The last thing you want with a floor you’ve sanded and finished is to have sanding marks pop like neon signs in the night. If you can spot sanding marks
while standing at full height on the floor and looking only with ambient light, then something went wrong.

This final blog post that comes from Lägler’s “Sanding of Wooden Floors” manual (free download) lays out the reminders of how to avoid sanding marks ruining
your success on the job.

Tips to Prevent Sanding Marks

The wood flooring and expansion gaps or the staircases always should be thoroughly vacuumed immediately before each work step (every sanding step, gap
filling or surface treatment).

Here are some general tips to keep in mind:

  • The abrasive must be suitable for the respective machine and should not be damaged.
  • The abrasive must be correctly attached and fastened.
  • The wheels should not be soiled or damaged.
  • The V-belts should not be soiled, damaged or worn out.
  • The pulleys should not be soiled, damaged or worn out.
  • The machine operation must be uniform and adapted to the corresponding process.
  • The grit sequence must be followed.
Drum and Belt Sanding Machines
  • The sanding pressure setting must match the abrasive grit to be used.
  • The side wheels must be set so the sanding drum sands in the center.
  • The lowering rod must move freely and not jam.
  • The sanding drum should not be soiled or damaged.
  • The tension roller of the assembly should not be soiled or damaged.
  • The sanding drum must always be lifted from the floor before the machine is turned on or off.
  • The sanding path displacement always should proceed from left to right.
  • The displacement from one sanding path to the next should not be too far out.
  • The sanding direction must be selected to match the laying pattern of the wood flooring.
  • Excessive pressure should not be exerted on the sanding drum during sanding.
    • No additional weight should be placed on the machine.
    • The rear portion of the machine should not be lifted by the handle during sanding.
    • The lowering lever should not be pressed down during sanding.
    • As soon as it is determined that the subfloor or wood flooring tends to vibrate, the sanding steps must be executed as early as possible, using
      the three-disc sanding machine instead of a drum or belt sanding machine.
Edge Sanding Machines
  • The wheel setting must be adjusted to the respective attachment.
  • The two wheels must be set to an equal height.
  • The sanding plate should not be set too steep. Otherwise, digs can result.
  • The sanding plates overlay must not be damaged.
  • The abrasive must be firmly positioned in the center of the sanding plate.
  • The machine always must be tipped slightly back so that the abrasive is lifted off the floor before it is switched on or off.
  • The machine must always be guided with circular movements during sanding.
  • Excessive pressure should not be applied to the attachment during sanding.
  • To increase the abrasion of the machine, change the angle by adjusting the wheels.
Three-Disc Sanding Machine
  • The abrasives must be firmly positioned in the center of each sanding plate.
  • The three sanding plates must be identically equipped.
  • The sanding plates must be correctly installed and attached.
  • The flexible Velcro rings should not be damaged.
  • The flexible Velcro rings must be used with abrasives coarser than 60 grit.

Visible Sanding Marks After Surface Treatment

Brightness differences:

The finish coat was accidentally sanded through at certain spots during the intermediate finishing sanding, which later leads to differences in the brightness
on the completed finished surface.

An abrasive with a different grit and cutting material was used for the edge sanding as for the previous field sanding.

Cloud formation:

Glossy spots can be seen on the surface (cloud formation). The same abrasive was used for too long in the last sanding step that it became too blunt. Excessively
blunt abrasives burnish the wood surface.

The wood absorbs less finish on burnished spots. This causes differences in the brightness.

The abrasive must be changed frequently enough to prevent burnished spots.

Visible sanding marks:

The final sanding step was performed with an excessively coarse grit. Oiling requires finer sanding than finishing.

For the full rundown of how to get the most out of your sanding machines, especially if they are Lägler machines, read each post on this blog.

Or, better yet, download Lägler’s free PDF, print it out, carry it on your phone,
whatever will help you and your crew be the best you can be.

Hands-on training and instruction are available through Lägler’s one-day Premium Sanding Technology (PST®) certification course, too. Call 800-848-6635 to schedule your session in Denver.

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