11-7/8" x 31-1/2" Floor Sanding Belts, 10 PACK

Twelve-inch belt floor sanders come in two belt lengths, and this is the longer one: 11-7/8" x 31-1/2". If your machine's manual or the plate inside the belt guard calls for a 31-1/2" belt, the 29-1/2" version will not tension on the drum and nothing else will substitute. We convert this size in zirconia alumina on a heavy poly-cotton cloth backing, sold in packs of 10, in eight grits from 24 through 120.

Zirconia is the right grain for a big floor machine because the drum pressure keeps it fracturing into fresh cutting points, so it strips finish and levels boards fast without glazing or heating the wood. Buyers are commercial flooring crews, school and facilities maintenance departments, and refinishers running larger 12-inch machines on gyms, halls and whole-house jobs.

• Correct 31-1/2" length for 12-inch belt floor sanders with the longer drum
• Zirconia alumina self-sharpens under drum pressure: fast, cool cut through old finish
• Heavy poly-cotton cloth backing holds tension and resists tearing at the joint
• Eight grits from 24 to 120, including 50, for a tight progression with no skipped steps
• 10 belts of one grit per pack; case pricing for crews and facilities
• Converted in Anaheim, California; free shipping on orders over $200

Which grit should you choose?

This size is stocked in Zirconia only. Unlike the 29-1/2" belt, the 31-1/2" length includes a 50 grit, so you can run a tighter sequence on floors that need it. Pick by floor condition.

• 24 grit: the aggressive first cut for floors with layers of old finish, game-line paint, adhesive or heavy cupping. It takes off a lot of wood, so reserve it for floors that need it.
• 36 grit: the everyday first cut on a previously finished oak or maple floor in fair shape, or the second cut after 24.
• 40 grit: a slightly gentler start on softwood, thin-finish or previously sanded floors.
• 50 grit: the intermediate step between 36–40 and 60 when the floor was opened at 24 or when the species scratches easily. Having it in this size lets every step stay within about 20 grit numbers.
• 60 grit: second or third cut, where the floor comes flat and the coarse scratch disappears.
• 80 grit: third cut; by now the surface should be uniform with no visible coarse marks.
• 100 grit: final drum pass before stain, leaving enough tooth for even colour.
• 120 grit: final drum pass before clear coat, or on maple, birch and other close-grained floors where 100 grit scratches can telegraph.

Typical sequences: 36 → 60 → 80 → 100 on a stained oak floor; 24 → 40 → 60 → 80 → 120 on a painted or badly cupped floor; 36 → 50 → 80 → 120 on a maple floor going to clear finish.

Grit guide for 12-inch belt floor sanders

How do you know your machine takes a 31-1/2" belt?

• Check the manual or the belt-size plate inside the belt guard. 12-inch belt floor sanders are built for either a 29-1/2" or a 31-1/2" belt, and the two are not interchangeable.
• Measure an old belt if the plate is gone: cut it and measure end to end, or lay a tape around the inside. A belt that measures about 31-1/2" around is this one.
• Check the width: 11-7/8" belts fit 12-inch machines only. 10-inch machines take 9-7/8" belts and 8-inch machines take 7-7/8" or 8" belts, all stocked separately.
• Not for portable or bench sanders of any kind.

Mount with the tension lever released, slide the belt on square, tension it, and rotate the drum by hand to confirm the belt runs centred and clear of the flanges. Check the inside of the belt for a direction arrow first; if there is one, run it that way so the joint trails. If your machine takes a length or width we do not list, we make custom belt sizes to order in about 3 days.

How to get the most out of them

1. Lower and raise the drum on the move. Start walking, ease the drum down, and lift it before you stop at the wall. A stationary 12-inch drum leaves a wide dish in one second.
2. Hold a steady walking pace for the full lane; the drum sets depth and your speed sets the finish. Hesitation at the ends burns and dishes.
3. First coarse cut on a slight diagonal if the floor is cupped, crowned or painted; every later grit runs with the grain.
4. Overlap lanes by about a third of the belt width, and sand the second half of the room from the opposite direction so the lanes blend.
5. Do not skip steps. Use the 50 grit when you have opened at 24; a 36-to-80 jump leaves scratches under the finish.
6. Replace belts before they glaze. A dull zirconia belt rides on the finish and burnishes the wood. Shine on the boards behind the drum or a change in motor note means change it.
7. Vacuum after every grit so stray coarse grain does not get dragged under the finer belt.
8. Be ready for loading on floors that have been maintained with silicone-based polish; keep extra coarse belts on the truck.
9. Store belts flat or hanging and dry, and let cold belts reach room temperature before mounting; a belt with a set in it thumps and leaves chatter marks.

Use it for / don't use it for

Use it for

• Stripping old polyurethane, varnish, sealer and game-line paint from hardwood floors
• Levelling cupped or crowned boards and blending repairs on large floors
• Removing adhesive and underlayment residue ahead of refinishing
• Flattening new solid oak, maple, hickory and softwood floors before finish
• Gymnasiums, auditoriums, halls, showrooms and whole-house refinishing on 12-inch machines

Don't use it for

• 12-inch machines that call for a 29-1/2" belt; use that length instead
• Engineered or thin-veneer flooring at coarse grits
• Finish sanding finer than 120; that is the buffer's job
• Metal, concrete or tile

Specifications

Frequently asked questions

Related products and guides

• All floor sanding belts (8, 10 and 12-inch machines)
• 11-7/8" x 29-1/2" Floor Sanding Belts for shorter 12-inch drums
• 9-7/8" x 29-1/2" Floor Sanding Belts for 10-inch machines
• 8" x 19" Floor Sanding Belts for the Clarke EZ-8
• Custom sanding belts made to order in about 3 days