4" x 106" Cork Sanding Belt, 6 PACK | For Premium Glass Fabrication Finishing

The last belt on a CRL-type 4 x 106 wet belt sander is not an abrasive at all. It is a plain, ungritted cork belt that carries cerium oxide or pumice slurry against the glass and turns the fine matte left by a 400 to 800 grit silicon carbide belt into a clear, polished edge. Nothing coarser than that will polish out; the cork stage only works when the grinding stages before it were done properly.

We convert these belts in Anaheim, California from natural cork bonded to a cloth backing, in the 4 x 106 size that the CRL 2300, 2300RP and H82 wet belt sanders and the DBS106 twin belt seamers run. Six belts per pack. Glass shops polishing shower doors, mirrors, table tops and shelves buy them; so do stone and plastics fabricators who run the same machines.

• Ungritted natural cork on cloth: a polishing carrier for cerium oxide or pumice, not an abrasive
• 4 x 106 size for CRL 2300, 2300RP, H82 and DBS106-class wet belt sanders and seamers
• Follows the 400–800 grit silicon carbide belt in the same size on the same machine
• Takes a matte seamed edge to a clear polish on float, mirror and low-iron glass
• Six belts per pack; a charged cork belt is left mounted and lasts many shifts
• Converted in Anaheim, California; free shipping on orders over $200

What does a cork belt do that a silicon carbide belt cannot?

Silicon carbide grinds. Every grit from 50 to 800 leaves a scratch pattern, and even the 800 grit pattern reads as a fine grey matte on glass. Cork does not scratch. The ungritted cork face is soft enough to hold loose polishing compound in its pores and firm enough to press that compound against the glass, which is exactly the combination a polishing stage needs.

Loaded with cerium oxide, the cork belt removes the 400 to 800 grit matte by a combination of very fine abrasion and a chemical-mechanical action between cerium and the glass surface, leaving an edge you can see through. Loaded with pumice, it produces a bright pre-polish, cheaper per pound, that is either left as the finished surface on utility glass or followed by cerium for a full polish. Run dry against glass with no compound, the cork only heats the edge and glazes; it does not cut.

The same belt polishes stone, solid surface and acrylic after a 400 grit pass, and knife makers charge cork with a green stainless compound to pre-polish bevels after 600 to 800 grit.

Which compound should you charge a 4 x 106 cork belt with?

• Cerium oxide: the standard for a clear, optical-quality polish on float glass, mirror and low-iron edges. Mix with water to a thin cream. Use it after 600 or 800 grit for the fastest result, or after 400 if you accept a longer polish time.
• Pumice: a coarser, cheaper polishing powder. Use it after 400 grit to take out the matte quickly and give a bright pre-polish, then switch to a second cork belt with cerium if the job calls for a full polish. Keep one belt for pumice and one for cerium; never mix them on the same belt.
• Fine polishing paste or green stainless compound: for stone, plastics and steel work on the same machine. Apply sparingly and run at low to medium speed.

Compound is sold separately. Dedicate each belt to one compound for its whole life, because a grain of pumice trapped in a cerium belt will put a scratch in every edge you polish afterwards.

Grit guide: what has to happen before the cork belt goes on

Cork removes the previous scratch pattern, not the ones underneath it. The silicon carbide sequence on the same 4 x 106 machine sets up the polish.

If a polished edge shows haze or fine lines, the answer is almost never more time on the cork. Go back one silicon carbide grit, remove the lines, and polish again.

Which machines take a 4 x 106 cork belt?

• CRL 2300 and 2300RP upright wet belt sanders: one 4 x 106 belt at a time. Most shops keep the silicon carbide belts on the 2300 and dedicate a second machine, or a scheduled changeover, to the cork.
• CRL H82 horizontal wet belt sander: one belt, glass laid flat, a good arrangement for polishing long straight edges and table tops.
• CRL DBS106W and DBS106 twin belt seamers: two belts at once. Cork on both sides polishes both edges of a lite in one pass after the seaming belts have been through.
• Other wet belt sanders built for a 4 inch by 106 inch belt, including CRL-type machines from other makers. Confirm the length in the manual; a 4 x 84 or 4 x 132 machine will not tension this belt.

These are the same machines our 4 x 106 silicon carbide glass belt is made for. Mount the cork belt the same way: release tension fully, seat the belt centred on both drums, check the inside of the belt for a direction arrow, re-tension, jog the machine and set tracking before charging the belt. Cork is thicker than a coated belt, so expect to back the tension off slightly compared with a silicon carbide belt on the same machine.

How to charge and run a cork belt

1. Finish the grinding sequence first. Take the edge to 400 grit at minimum, 600 or 800 for the fastest cerium polish. Rinse the glass and wipe it so no silicon carbide swarf reaches the cork.
2. Mix the slurry. Cerium oxide and water to the consistency of thin cream. Too thin and it runs off the belt; too thick and it cakes.
3. Charge the running belt. Start the machine at low to moderate speed and apply slurry to the moving cork face with a brush or a squeeze bottle until the whole face is evenly coated and damp.
4. Present the edge lightly. Keep the lite moving along the belt with light pressure, the same motion you used on the silicon carbide belt. Pressure heats the glass and does not speed the polish.
5. Keep it damp, not flooded. A cork belt is not run under the full water flow you use on the silicon carbide belt; the water would wash the compound straight off. Add a little water or fresh slurry as the face starts to dry and the cut slows. Never let the belt run dry with compound caked on it.
6. Re-charge and inspect. When the edge stops improving, re-charge. Check the edge against a light; any remaining grey means a return to the last grit, not more cork time.
7. At shift end, back off the tension and leave the belt on the machine or hang it. Do not fold a cork belt.

Use it for / don't use it for

Use it for

• Clear polishing of flat, pencil and bevelled edges on shower doors, mirrors, table tops, shelves and architectural glass
• Polishing low-iron and annealed glass edges before tempering, once the seamed edge has been refined to 400 grit or finer
• Bright pre-polish with pumice on utility glass that will be framed or channelled
• Final polish on granite, quartz, solid-surface and acrylic edges after 400 grit
• Satin to mirror pre-polish on steel and knife bevels with a green compound

Don't use it for

• Removing chips, score marks or anything coarser than a 400 grit scratch; that is the silicon carbide belt's job
• Running dry against glass, or flooded under full water flow, or without any compound
• Mixing pumice and cerium on the same belt
• Machines built for a length other than 4 x 106

Specifications

Frequently asked questions

Related products and guides

• 4" x 106" Silicon Carbide Glass Fabrication Belts, 12 pack (the grinding stages before cork)
• All glass fabrication abrasives (silicon carbide belts, cork belts and discs)
• 4" x 132" Cork Sanding Belt, 6 pack, for the CRL BM132RP
• 5" PSA Glass Fabrication Discs with cork, 50 pack
• Custom belt sizes, including cork, made to order in about 3 days