Sanders

Sanders take off paint and filler before you polish

What do sanders do on a car? They take material off: runs, dust nibs and orange peel in the clear coat, body filler and primer before painting. Random orbital sanders work with a round pad, orbital sanders with a rectangular plate. They can't polish; the polisher takes over after them.

Sanders are electrically driven hand tools that move an abrasive across the surface on a moving pad or plate and take material off in a controlled way. On a car they come before the polish: they level a defect, and the polisher then smooths out the sanding marks. At Detailing1 you'll find the different types in the tools section, split into random orbital sanders and orbital sanders.

• Two motions for two jobs. The random orbital sander spins a round 150 mm pad and swings it on a small orbit at the same time. The orbital sander moves a 70 × 198 mm plate with a 2 mm stroke and stays especially flat on filled areas.
• The orbit decides the scratch pattern. FLEX builds the same random orbital sander with a 3 mm and a 5 mm orbit, both running 8,000 to 20,000 orbits per minute. Three millimetres leave finer marks in the paint, five millimetres cut filler and primer down faster.
• Mains or 18 V battery, same speed on the random orbital. The FLEX cordless random orbital sander hits the same speed as the 230 V machine and weighs 1.23 kg without the battery. If you already run FLEX 18 V batteries on your polisher, the same battery powers this one.

Detailing1's tip from the shop: You burn through on edges, body lines and curves first, not on the flat. That's where the clear coat is thinner, and the pad only sits on part of its face, so there's more pressure per square centimetre. Tape off edges and body lines before sanding and only work the flat area next to them. Whatever is left on the edge you polish out later by hand or with a small pad.

A sander cuts, a polisher smooths

A sander uses a fixed abrasive grit to take material off until a defect is level; a polisher then uses a pad and polish to smooth out the marks that sanding left behind.

The difference is in the mechanics. The random orbital sanders in our range run a 3 or 5 mm orbit, the orbit being the diameter of the small circle the pad swings on. FLEX polishers use different figures: 15 mm free-floating on the FLEX "XFE 2 15 18-EC", 8 mm forced rotation on the XCE series. More throw, softer pads, liquid polish instead of sandpaper.

One question that keeps popping up in search suggestions is whether you can polish with a sander. The honest answer: it isn't built for it. Orbit, speed and pad are matched to fixed abrasives, and FLEX makes separate machines for polishing. If you want to remove swirls or holograms, meaning fine circular scratches and shimmering polishing marks, you'll find the right tool under polishers.

The term scratch pattern is where it all comes together. Every sanding step leaves a pattern of fine scratches whose depth depends on grit, orbit and pressure. Each finer step replaces that pattern with a shallower one, until the polish can smooth out the rest. Skip a step and you're polishing against scratches that are too deep for the polish, and you'll see them again in the sun.

The defect itself tells you whether you need to sand at all. If a scratch sits only in the clear coat and you can barely feel it with a fingernail, a cutting compound is usually enough. If a run stands proud of the surface or a dust nib is trapped in the paint, no polish will take it down in a reasonable time. Then sanding is the controlled route, because it only takes off the high spot.

FLEX itself puts the two machines in a fixed order: clean, sand, polish, finish. So the sander isn't a replacement for the polisher, it's the step before it.

The random orbital sands round, the orbital sander sands flat

A random orbital sander combines rotation and orbit on a round pad for panels and paint defects; an orbital sander moves a rectangular plate for flat, filled areas.

On a random orbital sander, two motions overlap. The pad spins and runs along its orbit at the same time. That way the grit never follows the same track twice, and the scratch pattern stays even, with no deep gouges. The 150 mm hook-and-loop pad takes round sanding discs, and with a soft backing pad it also follows gently curved panels.

The orbital sander works with a 70 × 198 mm plate and a 2 mm stroke. The long, straight edge makes it a levelling sander: it doesn't follow dips, it flattens them out. FLEX explicitly names the OSE series for filled car parts and block sanding before primer. Right where a round pad would dig into a filled spot, the plate stays level with the surrounding surface.

The choice depends on the area, not just the material. A single dust nib on the bonnet is a job for the round pad, because it only hits the defect. A filled spot on the wing that has to end up flush with its surroundings is a job for the plate, which bridges the edges, rests on the sound paint and sets the height that way. Its straight edge also gets it closer to transitions.

Both types come as 230 V and 18 V cordless machines. The cordless versions run on the same FLEX 18 V batteries as the 18 V polishers; which capacity suits which machine is explained on the battery systems page. A word on the search landscape: the guides that come up in search results for sanders are thinking about wood and DIY. On a car you're dealing with microns of clear coat, not millimetres of timber.

A 3 mm orbit for paint, 5 mm for filler

For single defects in the clear coat, a random orbital sander with a 3 mm orbit is the right fit; for filler, primer and larger areas, go for the 5 mm orbit, because it takes off more material per minute.

The smaller orbit means a shorter path per swing. The grit digs in less deeply, the scratch pattern comes out finer, and the polish has less work to do afterwards. The bigger orbit works faster but leaves coarser marks. On clear coat, which is only a thin film over the base coat, control matters more than speed.

Beyond the orbit, three features count. FLEX supplies the ORE pads in three hardnesses: soft pads follow curves, hard pads level better. A pad brake is meant to prevent sanding gouges, according to FLEX. And the self-extraction with micro filter has a 27 mm port for a vacuum that pulls the dust away right at the pad.

Speed is a tool too. The ORE machines can be set between 4,000 and 10,000 rpm, the cordless one in four steps. On clear coat a lower setting helps, because it builds up less heat and lets you follow the cut more closely. On filler you can go faster. If you're sanding for the first time, start low and only step up once you've got a feel for the pad.

On paint, extraction is more than a comfort feature. The self-extraction catches some of the dust in the filter on the machine. For paint, filler and primer dust, hook a vacuum up to the port, because that dust is fine and otherwise settles on freshly cleaned surfaces, in gaps and in the interior. That saves you a clean-up before painting or polishing.

An honest picture includes user criticism. Users call the FLEX "ORE 5-150 EC 230/CEE" heavier and louder than comparable machines and say dust still escapes despite the extraction. One hands-on test criticises the single grip position, which tires your hand out on long sanding sessions. The mains machine weighs 1.4 kg. For single paint defects that hardly matters; for block sanding the filler on a whole door, it does.

A run gets sanded flat, not sanded away

A paint defect is sanded with fine grit only until it's level; after that come finer steps and the polish that brings the scratch pattern back to a high gloss.

Grit sequences come from the abrasive manufacturer, not from gut feeling. For runs, 3M names P1000 or P1200, then P2000 and finally P3000. For orange peel, the dimpled surface of fresh paint, Kovax describes the sequence P1200, P1500, P2000 and a 3000 step. In the filler and primer zone, 3M works much coarser, with 320 grit before primer.

Clear coat reacts to heat. 3M advises against sanding too soon after painting, while the paint hasn't cured yet. Paint dust doesn't belong in the air: for dry sanding paint, the DGUV (German Social Accident Insurance) calls for extraction at the workplace and P2 or P3 respiratory protection, and advises against blowing off with compressed air.

Wet sanding with a machine needs the manufacturer's approval. We don't have one for the FLEX sanders. So if you want to wet sand single defects, do it by hand, with the Koch-Chemie Schleifblüten "P2500" on the Koch-Chemie Handstempel für Schleifblüten. The small discs only work the defect, not the area around it.

A quick stop between steps pays off. Wipe off the sanding slurry or dust, dry the spot and look at it in low-angle light. If a small shiny dot is still showing in the middle, the defect sits deeper than your sanding, and you stay on the current grit. If the area is evenly matt, move on to the next finer step. That way you never sand further than the defect demands.

Straight after sanding the spot looks worse than before: matt, grey, clearly visible. That's part of the process, not a mistake. Only the cutting compound on the polisher brings the gloss back. The first time, allow a lot more time than you expect, and check after every step instead of skipping one.

The FLEX sanders form a matrix of orbit and drive

The range covers two types in two drive options: random orbital sanders with a 3 or 5 mm orbit and orbital sanders with a rectangular plate, each corded or with an 18 V battery.

On the random orbital side there's the FLEX "ORE 3-150 EC 230/CEE" with a 3 mm orbit for fine paint work and the FLEX "ORE 5-150 EC 230/CEE" with a 5 mm orbit for more cut. Both draw 400 W, run at 4,000 to 10,000 rpm and use a brushless EC motor. The FLEX "ORE 5-150 18-EC C" rounds off the line as the cordless version, with four speed settings and no battery included.

On the orbital sander side there's the FLEX "OSE 2-70x198-EC" with 260 W, 10,000 to 20,000 strokes per minute and 1.3 kg, plus the FLEX "OSE 2-70x198 18-EC" as the cordless version with 12,000 to 20,000 strokes and 1.12 kg without the battery. The mains machine has restart protection, which stops it from starting up again on its own after a power cut.

The cordless machines are listed in the shop without battery and charger. That's not a shortcoming but the logic of a platform: if you already own FLEX 18 V batteries for your polisher, you only buy the tool. If you're new to it, you'll need a battery and charger on top, and you should check beforehand what capacity a sander needs for continuous use.

The abrasive is part of the system. For hand sanding single defects, you'll find sanding discs and hand blocks under abrasives. Sanding discs for the machine have to match the pad diameter and, with extraction, the hole pattern too. For the step after that there are the dual action polishers, which make the scratch pattern disappear. That keeps sanding, polishing and finishing on one platform.

If you only maintain your paint, you don't need a sander

For maintenance, swirls and holograms, a polisher is the right tool; a sander only pays off once paint defects, filler or primer have to be levelled mechanically.

If your paint is just dull, marred from washing or full of holograms, a polish will do. Leaving the sander out then saves clear coat, because a polish takes off much less than sanding, and every layer you remove never grows back. If a single run or dust nib bothers you, a sanding disc by hand or a random orbital sander with a 3 mm orbit is enough.

If you're shaping filler, block sanding primer or prepping plastic parts for paint, your route leads to the 5 mm random orbital or the orbital sander. For large, flat areas with filler the rectangular plate is the better choice, for curved areas the round pad. If you already own FLEX 18 V batteries, the cordless version saves you the cable and uses the charging kit you've already got.

Timing plays a part too. A sander is a tool for projects, not for your Sunday detail: paint repair, smart repair after a scratch down to the base coat, or prepping a body part for paint. If projects like that are rare, sanding by hand is often enough for the odd job. If they come up regularly, the machine saves effort and gives you a more even scratch pattern than your hand.

In the end it comes down to one insight that no data sheet mentions. The sander takes the most clear coat off your car. The polish afterwards only takes off the scratch pattern and brings back the gloss. That's why on a car the DIY logic flips: as fine as possible, as short as necessary, and one check too many rather than one too few.