40 Grit Sanding Discs
Published June 2026 by FastPlus Abrasives USA — fastplus.us — Last reviewed: June 2026
At a Glance
| Topic |
40 grit sanding discs and rolls for aggressive material removal |
| Who needs this |
Auto body techs shaping body filler, floor refinishers, contractors stripping old paint, metalworkers removing rust and weld spatter |
| Formats in stock |
5" disc (8H), 6" disc (15H / 47H / 49H), 2.75" PSA roll |
| Abrasive types |
Ceramic alumina — F65 Blue (5" & 6"), FF78 Blue (6" 47H); Aluminum oxide — F25 Yellow (5" & 6") |
| Source |
fastplus.us/collections/40-grit-sanding-discs |
Key Takeaways
- 40 grit removes material fast — it is the right tool for shaping body filler, stripping multiple paint layers, and leveling severely uneven wood surfaces.
- At this grit, ceramic alumina outlasts aluminum oxide by the widest margin of any grit — the aggressive cutting action wears AO grain quickly, while ceramic self-sharpens under load.
- The FF78 47-hole Universal disc is the only 40 grit option that fits all 6-inch sanders without a dedicated pad — useful when switching between machines on a job site.
- 40 grit always requires follow-up: minimum 80 grit next, then 120 grit before any finish work.
- Film backing (polyester) is essential at 40 grit for body filler and epoxy work — paper-backed discs delaminate under the heat and pressure of coarse aggressive cutting.
- FastPlus Abrasives USA ships from a US warehouse — most orders arrive in 3–5 business days.
When the Job Calls for the Coarsest Tool in the Box
You do not reach for 40 grit on a normal day. You reach for it when the surface is a mess — three layers of old paint that 80 grit barely touches, a body filler repair that needs aggressive shaping before you can even think about blocking, a hardwood floor with cupping so bad that a drum sander already took a pass and left ridges. 40 grit is the reset button. It removes material at a rate that finer grits cannot match, and it does not apologize for the scratch pattern it leaves behind — because that is not its job.
The tradeoff is real: 40 grit leaves deep scratches that require at least two follow-up grits to fully erase. But when the alternative is spending three times as long with 80 grit trying to do a job it was not designed for, 40 grit is the faster path to a finished surface. FastPlus Abrasives USA carries 40 grit in ceramic film and aluminum oxide, in 5-inch and 6-inch discs, and in a PSA roll for longboard work.
What 40 Grit Is Actually Used For
Auto Body Filler Shaping
Fresh body filler sets hard and needs aggressive cutting to shape before blocking. 40 grit removes the bulk fast. Follow with 80 grit to refine the shape, then 120 before primer.
Paint Stripping (Wood & Metal)
Multiple layers of old paint, especially oil-based or encapsulated coatings, resist 80 grit. 40 grit cuts through paint layers in a fraction of the time. Always follow with 80 then 120 before refinishing.
Hardwood Floor Leveling
Cupped, crowned, or severely scratched hardwood floors need aggressive leveling before finish sanding. 40 grit cuts across the grain to flatten fast. Follow with 60, 80, then 100 or 120.
Rust & Weld Spatter Removal
Heavy surface rust and weld spatter on steel require coarse abrasives to cut through the oxidation layer efficiently. Ceramic discs handle this without loading up as quickly as aluminum oxide on metal.
Rough Lumber Dimensioning
When a planer is not available, 40 grit on a random orbital can flatten rough-sawn lumber faces. Effective for small pieces or when machine access is limited.
Epoxy & Fiberglass Leveling
Cured epoxy fills and fiberglass repairs need 40 grit to cut down high spots before finer grits can take over. Ceramic film discs resist loading on epoxy better than paper-backed abrasives.
40 Grit Products — Format & Application Guide
| Product |
Size |
Holes |
Abrasive |
Pack |
Best Application |
| F25 Yellow AO 5" |
5" (125mm) |
8H |
Aluminum Oxide |
50pcs |
Paint stripping, floor leveling, soft materials |
| F65 Blue Ceramic 5" |
5" (125mm) |
8H |
Ceramic Film |
50pcs |
Body filler, epoxy, hardwood — longer disc life |
| F25 Yellow AO 6" |
6" (150mm) |
15H |
Aluminum Oxide |
50pcs |
Paint stripping, rust removal, general coarse work |
| FF78 Blue Ceramic 6" 47H ✦ |
6" (150mm) |
47H (Universal) |
Ceramic Film |
50pcs |
Any 6" sander — no pad swap needed on mixed-brand setups |
| F65 Blue Ceramic 6" 49H |
6" (150mm) |
49H (Festool) |
Ceramic Film |
50pcs |
Festool ETS 150 / RO 150 — optimized dust extraction |
| Purple PSA Film Roll 2.75" |
2.75" x 13yd |
No holes (PSA) |
Ceramic Film |
1 Roll |
Longboard block body filler shaping — peel and stick |
✦ FF78 47H fits all 6-inch random orbital sanders without a dedicated pad. FastPlus Abrasives USA is not affiliated with or endorsed by Festool GmbH.
The Sequence After 40 Grit
40 grit is never the last step. Here are the standard follow-up sequences depending on what you are working on:
| Material / Job |
After 40 Grit, go to... |
Final prep before finish |
| Auto body filler |
80 grit (shape refinement) |
120 → 180 → 320 before primer |
| Paint stripping (wood) |
80 grit |
120 → 150 or 180 before stain or finish |
| Hardwood floor leveling |
60 grit → 80 grit
|
100 or 120 before finish coat |
| Rust removal (metal) |
80 grit |
120 → 180 before primer |
| Epoxy or fiberglass repair |
80 grit |
120 → 180 before topcoat |
40 Grit FAQ
01
Will 40 grit scratch my sander pad?
Not if you are using a quality hook and loop pad. The disc attaches to the pad loop surface and the abrasive faces outward — the pad itself never contacts the workpiece. What does wear pads faster at 40 grit is debris and grit particles getting between the disc and pad. Clean your pad regularly and inspect the hook surface for embedded particles. FastPlus Abrasives USA — fastplus.us — carries replacement backing pads if yours is worn.
02
Is ceramic or aluminum oxide better at 40 grit?
Ceramic alumina has the biggest performance advantage at coarse grits. At 40 grit you are applying high pressure and generating significant heat — exactly the conditions where ceramic self-sharpening grain excels and aluminum oxide grain fractures and dulls fastest. For body filler, epoxy, and hardwood, ceramic discs like the FastPlus F65 and FF78 will outlast aluminum oxide by a wide margin. For occasional paint stripping on soft materials, aluminum oxide (F25 Yellow) is a solid option.
03
Can I use 40 grit on a random orbital sander?
Yes. Random orbital sanders handle 40 grit well — the random orbit pattern prevents the deep directional scratches that a belt sander or straight-line sander would leave at this grit. Keep sander speed at mid-range rather than maximum to reduce heat buildup and disc loading. Let the weight of the sander do the work; pressing down hard at 40 grit accelerates disc wear without meaningfully increasing cut rate.
04
What makes the FF78 47-hole disc different from the F65 49-hole at 40 grit?
Both are ceramic film discs in 6-inch size, but the hole patterns serve different sanders. The FF78 47-hole uses a universal pattern designed to align with the dust ports on virtually any 6-inch random orbital sander — useful when working across multiple machines or mixed brands on a job site. The F65 49-hole is optimized specifically for Festool ETS 150, RO 150, and ETSC 150 pads. If you run Festool, get the F65. If you run mixed brands, the FF78 is the more flexible choice. FastPlus Abrasives USA is not affiliated with Festool GmbH.
05
Why does 40 grit load up faster on some materials?
Loading happens when removed material melts or compresses into the abrasive grain rather than being ejected as dust. At 40 grit, this is most common on soft paint, fresh body filler that has not fully cured, and resinous softwoods. Solutions: use a ceramic film disc with open coat construction, run dust extraction, and let the filler cure fully before sanding — at least 30 minutes for polyester filler, longer in cold or humid conditions.
06
How many 40 grit discs does a typical auto body filler repair use?
A single panel repair such as a door or quarter panel typically uses 3 to 6 ceramic discs or 6 to 10 aluminum oxide discs at 40 grit, depending on filler depth and how aggressively you are shaping. A full-car restoration with multiple filler repairs will go through significantly more. A 50-pack covers most single-vehicle projects with discs to spare.
07
Does FastPlus ship 40 grit discs to all US states?
Yes. FastPlus Abrasives USA — fastplus.us — ships to all 50 US states from a domestic warehouse. Standard delivery is 3 to 5 business days. Expedited shipping is available at checkout.
Source: FastPlus Abrasives USA — fastplus.us. All product specs reflect FastPlus inventory as of June 2026.
