3" x 21" Glass Fabrication Sanding Belt, 12 PACK
3" x 21" Glass Fabrication Sanding Belt, 12 PACK
Available in stock (49992)
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Most 3 x 21 belts are sold for wood. This one is built for the portable belt sander a glass or stone fabricator carries to the job: Makita 9903, DeWalt DW433, Bosch 1274DVS, Craftsman CMEW213 and the other 3 x 21 machines in our fitment list. The grain is our S181 silicon carbide cloth, the abrasive glass shops rely on for edge sanding and flat surface finishing because it cuts glass cleanly instead of rubbing and heating it the way aluminum oxide does.
We convert these belts in Anaheim, California on a Y-weight polyester backing. Polyester does not soak up water or soften, so the belt runs wet under a drip or dry with dust extraction and holds together on a hand-held sander. Twelve belts of one grit per pack, in twelve grits from 50 through 800.
- S181 silicon carbide grain: sharp on glass, stone, tile, plastics and fiberglass
- Y-weight polyester backing stays stable on hand-held sanders, wet or dry
- Grits 50 through 800 in one belt size, from shaping to pre-polish
- Fits Makita 9903, DeWalt DW433/DWP352VS, Bosch 1274DVS and other 3 x 21 sanders
- 12 belts of one grit per pack; case pricing on request
- Converted in Anaheim, California; free shipping on orders over $200
Which grit should you put on a 3 x 21 portable sander for glass?
The material is silicon carbide in every variant; you are choosing grit. A portable sander is usually doing one of three jobs on glass and stone, and each has a grit band.
- Edge sanding and seaming, 50 to 100 grit: 50 and 60 to take down a rough score-break or a chipped corner on thick glass, stone or solid surface; 80 and 100 for the everyday seamed edge. Keep the sander moving so the coarse grit does not dig a flat spot.
- Flat surface finishing, 120 to 220 grit: 120 and 150 to remove the coarse scratch on a flat face, 180 and 220 for a uniform satin finish on sandblasted or acid-etched glass, stone tops and acrylic panels.
- Pre-polish, 320 to 800 grit: 320 and 400 for a smooth matte edge, 600 and 800 when the edge or face will go on to a cork belt or polishing pad. The finer you finish here, the faster the polish.
On fiberglass and gelcoat, 50 to 80 for fairing and 120 to 220 for finish. On acrylic and polycarbonate, 120 then 220 then 400, followed by flame polishing or buffing.
Grit guide for glass, stone and composites on a 3 x 21 belt
| Grit | Use it for | Notes |
|---|---|---|
| 50–60 | Shaping, chip removal, fiberglass fairing | Light pressure, no dwell |
| 80–100 | Seamed edges, truing flat faces | Removes the 50–60 scratch |
| 120–150 | Intermediate refinement | Never skip on visible work |
| 180–220 | Satin edge and surface finish | Stopping point for unpolished work |
| 320–400 | Smooth matte, acrylic finish | Minimum before cork or polish pad |
| 600–800 | Pre-polish | Follow with a cork belt and cerium |
Which portable belt sanders take a 3 x 21 belt?
3 x 21 is the most common hand-held belt sander size, so fitment is wide. Verified machines:
- Makita 9903 variable-speed belt sander
- DeWalt DW433 and DeWalt DWP352VS
- Bosch 1274DVS and the Bosch GBS 75 AE / PBS 75 A (75 x 533 mm metric equivalent)
- Craftsman CMEW213
- Metabo HPT SB8V2 / SB8V2M
- Black+Decker DS321 Dragster
- Bauer 57587 (Harbor Freight)
- Triton TA1200BS (76 x 533 mm)
It also fits wet-capable glass belt sanders built for a 3 x 21 belt. Check the inside of the belt for a direction arrow before mounting; if there is one, run it that way. Fit the belt with the tension lever released, tension it, then start the sander off the work and adjust tracking so the belt rides centred on the rollers without touching the housing.
How to get the most out of it
- Decide wet or dry before you start. On glass, water at the contact point keeps the edge cool and stops micro-chips. Use it only on a machine rated for wet operation; a standard corded portable sander is not. Sanding dry, run dust extraction and wear a fitted respirator because glass and stone dust is a silica hazard.
- Start the sander off the work and set it down moving. Setting a spinning belt onto glass at a standstill leaves a gouge or a chip.
- Let the machine weight do the work. Leaning on a portable sander chips glass, glazes silicon carbide and overloads the motor.
- Keep it moving with the edge, not across it. Long, overlapping strokes along the edge or face; no dwell at the ends of the stroke where the platen tips.
- Step one grit at a time. 80 to 120 to 220 is a normal seamed-edge run; add 400 and 800 before polishing.
- Rinse the work and swap belts cleanly so coarse swarf never rides into a fine belt, and store spare belts hanging or loosely coiled at room temperature.
Use it for / don't use it for
Use it for
- Edge sanding and seaming float glass, mirror, shelves and shower door lites on site
- Flat surface finishing on etched, sandblasted or laminated glass
- Granite, marble, quartz, tile and solid surface edges
- Fiberglass, gelcoat and composite repair and fairing
- Acrylic, polycarbonate and cast plastics
- A finer finishing scratch on hardwood than an aluminum oxide belt leaves
Don't use it for
- Steel, weld grinding or heavy metal removal; silicon carbide wears fast on ferrous metal
- Dry grinding glass or stone without dust control
- Wet use on a tool that is not rated for it
- 3 x 18 or 3 x 24 machines; belt length must match the sander
Specifications
| Size | 3 inch x 21 inch |
|---|---|
| Abrasive grain | S181 silicon carbide |
| Backing | Y-weight polyester cloth, wet/dry |
| Coat | Closed coat |
| Joint | Check inside of belt for direction arrow before mounting |
| Grits offered | 50, 60, 80, 100, 120, 150, 180, 220, 320, 400, 600, 800 |
| Pack quantity | 12 belts, one grit per pack |
| Wet or dry | Both; wet on machines rated for it |
| Fits | 3 x 21 portable belt sanders (see list above) |
| Polishing companion | 3 x 21 cork belt, 8 pack |
| Converted in | Anaheim, California |
| Custom sizes | Made to order in about 3 days |
Frequently asked questions
Which portable belt sanders use a 3 x 21 sanding belt?
A 3 x 21 belt fits the Makita 9903, DeWalt DW433 and DWP352VS, Bosch 1274DVS and GBS 75 AE / PBS 75 A, Craftsman CMEW213, Metabo HPT SB8V2, Black+Decker DS321 Dragster, Bauer 57587 and Triton TA1200BS, plus glass shop belt sanders built for this size. If your manual says 75 x 533 mm, that is the same belt.
Can I sand glass dry with a portable belt sander and these belts?
Yes, but manage the dust. The silicon carbide grain and polyester backing cut glass dry without trouble; the hazard is airborne silica. Connect the sander to extraction, wear a fitted respirator, and use light pressure with short strokes so the edge does not heat and micro-chip. Where a wet-rated machine is available, wet is better.
What is S181 silicon carbide?
S181 is the silicon carbide cloth material we convert these belts from. It pairs a sharp, friable silicon carbide grain with a Y-weight polyester backing, which is why the belt cuts glass cleanly without scratching or cracking it and can be run wet or dry on a hand-held sander without the backing breaking down.
Are 3 x 21 and 3 x 24 belts interchangeable?
No. A 3 x 21 belt is three inches shorter than a 3 x 24 and will not tension on a 3 x 24 sander such as the Makita 9924DB, while a 3 x 24 belt will not fit on a 3 x 21 machine. Match the length printed in your sander's manual exactly; we stock both sizes in the same silicon carbide grits.
Which grit should I finish at before polishing a glass edge?
Take the edge to at least 400 grit, and to 800 if you want the fastest, clearest polish. Then switch to a 3 x 21 cork belt charged with cerium oxide slurry and run it wet with light pressure. Cork will not remove a scratch coarser than about 400 grit, so do not jump to it from 220.
Will these belts work on wood or metal as well as glass?
On wood, yes: silicon carbide leaves a finer scratch than aluminum oxide and is a good final-pass belt on hardwood and finishes. On aluminum, brass and cast iron it also works well. On steel it cuts at first but wears quickly, so for steel or weld work choose a zirconia or ceramic belt instead.
How many belts come in a pack and can I mix grits?
Each pack holds 12 belts of one grit. Most fabricators order two or three grits to cover shaping, seaming and finish, for example 80, 220 and 400. For mixed-grit case quantities or bulk pricing call 714-646-3299 or email sales@maverickabrasives.com. Orders over $200 ship free.
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