3/4" x 20-1/2" Surface Conditioning Belts (Non-Woven), 16 PACK
3/4" x 20-1/2" Surface Conditioning Belts (Non-Woven), 16 PACK
Available in stock (49998)
Fabrication and automotive shops that run an Astro Pneumatic 3035 air belt sander use this belt for the second half of the job: after a coated belt has cut the weld down or removed the rust, a 3/4" x 20-1/2" non-woven belt blends the scratch, cleans the heat tint and leaves a finish that is ready for paint, powder coat or a brushed look. It fits the Astro 3035, and the JET JSM-620 and Dynabrade 40326 named on our original listing.
The nylon web carries aluminum oxide grain in resin, so it conforms to tube, flange and corner work instead of flattening it. We convert these belts in Anaheim, California and pack 16 of one grade per box in Coarse (brown), Medium (maroon), Very Fine (blue) or Ultra Fine (grey).
- Fits the Astro Pneumatic 3035 and other 3/4" x 20-1/2" air belt sanders
- Non-woven web blends, deburrs and cleans without removing measurable stock
- Four colour-coded grades: Coarse, Medium, Very Fine, Ultra Fine
- Runs cooler than a coated belt and sheds swarf instead of loading
- Reinforced scrim backing handles the small wheels on a file-sander arm
- 16 belts per pack; free shipping on orders over $200
Which grade should you put on an Astro 3035?
Every grade is the same web; the grain size sets the finish. Buy the grade that matches the surface you need to hand off, then work up to it.
- Coarse (brown, 40-60 grit equivalent): light rust and scale on steel chassis parts, weld spatter, old paint on a bracket. It is the only grade with real bite, so keep the tool moving and the pressure light on thin exhaust or body sheet.
- Medium (maroon, 80-120 grit equivalent): the everyday grade. It takes the discolouration off a TIG weld on stainless exhaust tubing, blends the 80-120 grit scratch from a coated belt, and gives a uniform surface for primer or powder coat.
- Very Fine (blue, 180-240 grit equivalent): a #4-style brushed finish on stainless and a soft satin on aluminum. This is the grade to match an existing brushed panel or rail.
- Ultra Fine (grey, 320-400 grit equivalent): the finest blend before buffing, and a low-sheen satin on aluminum and titanium that hides fingerprints. Not many converters make this grade in belt form.
Typical progression on a welded steel bracket headed for powder coat: coated 80 grit to level, Coarse to clean scale from the heat-affected zone, Medium to unify the surface. Stop there; powder needs a keyed surface, not a polished one.
Grit guide: what the colours mean
| Grade / colour | Use it for | Notes |
|---|---|---|
| Coarse / brown | Rust, scale, spatter, paint | Roughly 40-60 grit; light hand on sheet |
| Medium / maroon | Blending, heat tint, coating prep | Roughly 80-120 grit |
| Very Fine / blue | #4-style brush, satin match | Roughly 180-240 grit |
| Ultra Fine / grey | Fine satin, pre-buff | Roughly 320-400 grit |
Treat these as finish equivalents. A brown belt leaves a scratch that looks like 40-60 grit but removes only a fraction of the material a 60 grit coated belt would. That is what makes it safe on thin-wall tube and finished castings.
Which machines take a 3/4" x 20-1/2" belt?
- Astro Pneumatic 3035 air belt sander, the most common tool in this size and the one most of these belts go on.
- JET JSM-620 and Dynabrade 40326, both named on our original listing for this belt.
- Other 3/4" x 20-1/2" pneumatic belt sanders sold under various tool-truck and import brands. If the tool takes a 20-1/2" coated belt, it takes this one.
Do not confuse this with the 3/4" x 18" Dynafile II size, which we sell separately; the 2-1/2" difference is enough that neither will tension on the other's arm. To mount, pull the arm in, slide the belt on with the seam running in the same direction as the belt you removed, release, and jog the trigger to confirm the belt tracks centred on the contact wheel. The web is thicker than a coated belt, so a small tracking adjustment is normal.
How to get the most out of it
- Turn the air down. Non-woven belts want less speed than coated belts. On a variable-trigger tool, feather it; on a fixed-speed tool, drop the line regulator.
- Light to moderate pressure. The web works by contact, not force. Bearing down folds the fibres, heats the part and tears the belt. Coarse in particular will remove material if leaned on.
- Keep it moving and keep it straight. For a linear satin on tube or rail, draw the sander along the length in overlapping passes. Dwelling in one spot leaves a bright patch.
- Come in from 120-220 grit. Use a coated belt for anything coarser than 60 grit scratches; the web will not remove them.
- Use the slack for contours. The unsupported run between the wheels follows fillets, tube saddles and inside corners.
- Lubricate aluminum lightly. A little oil or wax stops soft alloys smearing. Run steel and stainless dry.
- Store spares in the box, flat and away from solvent, sunlight and damp air.
Use it for / don't use it for
Use it for
- Cleaning heat tint and scale from stainless and steel welds on tube, brackets and frames
- Blending coated-belt scratches into an even finish before paint, primer or powder coat
- Deburring sheared, sawn and laser-cut edges on stainless, steel, aluminum and titanium
- Removing light rust and oxidation from small areas of chassis and body components
- Brushed or satin finishing on stainless, aluminum, plastics and fiberglass
Don't use it for
- Grinding welds flush or removing heavy stock; use a zirconia coated belt first
- Removing coarse 36-60 grit scratches; non-woven blends, it does not re-cut
- Achieving a mirror; after Ultra Fine, switch to buffing wheels and compound
- Running at full pressure and full speed, which wastes belts and heats parts
Specifications
| Size | 3/4" x 20-1/2" |
|---|---|
| Type | Non-woven surface conditioning belt |
| Abrasive grain | Aluminum oxide in resin-bonded nylon web |
| Backing | Reinforced scrim |
| Grades offered | Coarse (40-60), Medium (80-120), Very Fine (180-240), Ultra Fine (320-400) grit equivalents |
| Colour code | Brown, maroon, blue, grey |
| Pack quantity | 16 belts of one grade |
| Wet or dry | Dry; light lubricant acceptable on aluminum |
| Verified fit | Astro Pneumatic 3035; JET JSM-620 and Dynabrade 40326 per original listing |
| Converted in | Anaheim, California |
| Custom sizes | Made to order in about 3 days |
Frequently asked questions
Does a 3/4" x 20-1/2" surface conditioning belt fit the Astro Pneumatic 3035?
Yes. The Astro 3035 is built for 3/4" x 20-1/2" belts, and this non-woven belt is cut to that size. It mounts like any coated belt for the tool: retract the arm, slide it on, release and check tracking. Our original listing also named the JET JSM-620 and Dynabrade 40326 for this size.
Can I clean rust off steel with these before painting?
Yes, for light surface rust and scale on small areas. Use Coarse (brown) to remove the oxide, then Medium (maroon) to even out the surface so primer wets uniformly. Heavy pitting or thick scale needs a coated belt first; a 3/4" x 20-1/2" non-woven belt cleans and blends but does not remove much metal.
Which grade should I use before powder coating?
Medium (maroon) is the usual stopping point. It leaves a clean, evenly textured surface around 80-120 grit that powder adheres to well. Going finer with Very Fine or Ultra Fine is unnecessary for powder and can reduce mechanical keying. Use Coarse first only if there is scale or spatter to remove.
How do I get rid of the blue heat tint on stainless exhaust welds?
Run Medium (maroon) along the weld with light pressure until the coloured band disappears, then follow with Very Fine (blue) in straight strokes along the tube to blend into the mill finish. The tint is a thin oxide, so it comes off quickly; the skill is in not dwelling and leaving a bright spot.
Is 3/4" x 20-1/2" the same as 3/4" x 18"?
No. Both are 3/4" wide file-sander belts, but 20-1/2" is the Astro 3035 length and 18" is the Dynabrade Dynafile II length. A belt of the wrong length either will not fit over the arm or will not tension. Check the length printed on your old belt or in the tool manual before ordering.
Why does the belt shred if I press hard?
The web is nylon fibre bonded with resin, not cloth. Heavy pressure folds the fibres over on the contact wheel, generates heat and pulls grain and fibre out of the belt. Light to moderate pressure at reduced speed lets the web do the work and gives the long belt life these are known for.
What are the pack size, shipping and return terms?
Each pack has 16 belts of one grade. Orders over $200 ship free, and unused belts in original packaging can be returned within 30 days. Bulk and case pricing is available for shops running several sanders; call 714-646-3299 or email sales@maverickabrasives.com. Other lengths can be made to order in about three days.
Related products and guides
Couldn't load pickup availability
Get $20 off when you spend $1,000 or more! Learn more
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
