4" x 24" Glass Fabrication Sanding Belt, 12 PACK

The heavy 4 x 24 portable sander, the Makita 9403 and 9404 above all, is what fabricators reach for when the edge is long, the glass is thick, or the job is a big flat face rather than a narrow seam. These are the silicon carbide belts for that class of machine: a full four inches of grain for edge sanding and bevel grinding on glass, stone, solid surface and fiberglass, in twelve grits from 50 through 800.

The wider belt spreads the cut over more grain, so a 4 x 24 runs cooler and flatter than a 3 x 21 on the same edge and leaves a straighter bevel line. We convert these in Anaheim, California on a wet-capable cloth backing and pack them 12 belts of one grit to a box.

• Silicon carbide grain cuts glass, stone, tile, fiberglass and plastics without dulling
• Four inch width keeps long edges flat and bevel lines straight
• Twelve grits, 50 through 800, including 150 for a full step-by-step progression
• Fits Makita 9403/9404, Milwaukee 4 x 24 sanders and the Ridgid EB4424 edge sander
• Wet-capable cloth backing; run dry with extraction or wet on a rated machine
• 12 belts of one grit per pack; converted in Anaheim, California

Which grit should you choose for a 4 x 24 belt on glass or stone?

The material is silicon carbide throughout, so the decision is grit, and on a 4 inch sander the coarse end gets used more than on smaller machines because this is the tool for heavy edge and bevel work.

• 50 and 60 grit: bevel grinding on thick glass, taking down a rough score-break on 1/2 inch or thicker lites, shaping stone and solid-surface edges, fairing fiberglass.
• 80 and 100 grit: the standard seaming and edge-truing grit; clears the coarse scratch on a bevel.
• 120 and 150 grit: refining an exposed edge or a flat face. This size includes 150, so you can step 120, 150, 180 on polished work where a fine, even scratch matters.
• 180 and 220 grit: satin edge and surface finish on table tops, shelves and etched panels.
• 320 and 400 grit: smooth matte; the minimum before a cork belt or polishing pad.
• 600 and 800 grit: pre-polish, the fastest route to a clear cerium polish.

On fiberglass and gelcoat, where the 4 x 24 is a common repair sander, 50 to 80 to knock down and 120 to 220 to finish. On acrylic, 120, 220, 400 then flame or buff.

Grit guide for edge sanding and bevel grinding on a 4 x 24 belt

Which machines take a 4 x 24 belt?

• Makita 9403 and Makita 9404 4 x 24 belt sanders, the machines most glass and stone shops run this size on.
• Milwaukee corded 4 x 24 belt sander.
• Ridgid EB4424 oscillating edge belt and spindle sander, a bench machine useful for small parts, stone samples, tile and plastics with dust extraction fitted.
• Wet-capable glass belt sanders and other 4 inch by 24 inch machines. Confirm the length in the manual; a 4 x 36 bench sander will not tension this belt.

Mounting on a portable sander: release the tension lever, slide the belt on, check the inside of the belt for a direction arrow and run it that way, re-tension, start the sander clear of the work and set tracking so the belt runs centred on the front roller. A 4 inch belt shows tracking errors faster than a narrow one, so check it again after the first minute.

How to get the most out of it

1. Water on the glass where the machine allows. Wet sanding keeps the edge cool, stops micro-chipping and holds silica dust down. A standard corded 4 x 24 sander is not built for water, so on those machines run dry with dust extraction and a fitted respirator; save wet work for a sander rated for it.
2. Set the sander down moving and lift it off moving. A 4 inch belt started at rest on glass will chip the edge.
3. Use the machine's weight, not yours. Pressure chips glass and glazes silicon carbide. The 4 x 24 is heavy enough on its own.
4. Hold the bevel angle constant the full length of the stroke. The wide platen makes a straight bevel easy, but any rocking shows as a wavy line.
5. Overlap strokes along the edge or face, never across it, and do not dwell at the ends.
6. Step one grit at a time, rinse the work between grits, and store spare belts hanging or loosely coiled, away from sunlight and damp.

Use it for / don't use it for

Use it for

• Bevel grinding and edge sanding on thick float glass, mirror and table tops
• Long straight edges on shower door panels and shelves
• Flat face finishing on etched or sandblasted glass
• Granite, marble, quartz, tile and solid-surface edges
• Fiberglass, gelcoat and composite fairing and repair
• Acrylic, polycarbonate and cast plastics

Don't use it for

• Steel or weld grinding; silicon carbide wears fast on ferrous metal
• Dry glass or stone work without extraction and a respirator
• Wet use on a tool not rated for it
• 4 x 36 or other belt lengths; 24 inches must match the machine

Finishing the edge with the 4 x 24 cork belt

Silicon carbide leaves a fine matte, not a clear polish. For a polished edge, finish at 400 or 800 grit, rinse the glass, then mount the 4 x 24 cork belt, charge it with cerium oxide slurry and run it wet at moderate speed with light pressure, re-charging as the cut slows. Cork has no grain of its own and will not clear a scratch coarser than about 400 grit. Never run it dry against glass with compound caking on the face.

Specifications

Frequently asked questions

Related products and guides

• 4" x 24" Cork Sanding Belt, 6 pack, for cerium polishing
• All glass fabrication abrasives (belts, cork belts and discs)
• 3" x 24" Glass Fabrication Sanding Belts, 12 pack
• 4" x 54" Glass Fabrication Sanding Belts for wet belt sanders
• Custom sanding belts made to order in about 3 days