Reference

Glossary

Short, plain-English definitions. Each term links to the guides that cover it properly.

A

Accuracy · also stated accuracy, tolerance: How close a gauge's reading is to the true thickness, usually stated as a tolerance: a percentage of the reading plus a fixed amount. UNI-T, for example, states the UT343E's accuracy as ±(2%H + 2 µm). Accuracy is not the same as resolution. Read more: Paint gauge accuracy vs resolution, Paint thickness gauges: what each type can measure
Amazon Brand Store · also brand storefront: A free brand page on Amazon for sellers enrolled in Amazon Brand Registry. It shows brand enrollment, not who sells a given offer: Makita links its Brand Store, but each offer's 'sold by' still needs checking. Read more: Buying polishers and gauges on Amazon and AliExpress: what to check
Amp-hour (Ah) · also Ah, capacity: A measure of battery capacity. RUPES pairs its HLR15/HLR21 iBrid with an 18 V 5 Ah pack and its HLR75 mini with an 18 V 2.5 Ah pack; capacity does not make packs interchangeable. Read more: Cordless polisher battery compatibility
ANSI Z87.1 · also Z87: The US standard marking for safety eyewear. Milwaukee's polisher manual calls for eye protection marked to ANSI Z87.1. Read more: Car polisher safety checklist
ASTM D7091: An ASTM practice for measuring dry film thickness with magnetic gauges on ferrous metals and eddy-current gauges on non-ferrous metals. It describes calibration, verification and adjustment as three steps, and supplements the maker's instructions. Read more: How to calibrate, verify and zero a paint gauge, Paint thickness gauges: what each type can measure

B

Backing plate · also backing pad, backer: The disc on the polisher that the pad attaches to. Milwaukee's manual says the plate diameter should match the pad diameter on its 2684-20 and 2685-20, and to use only accessories it recommends. Read more: Pad and backing-plate compatibility, Polishing pads and backing plates: sizes and fit
Bare tool · also tool only: A cordless tool sold without battery or charger. Milwaukee's -20 suffix marks its bare tools, and Makita sells the XOP02Z tool only. Read more: Cordless polisher battery compatibility, Cordless polishers and battery platforms
Battery platform · also battery system: A maker's family of tools, batteries and chargers built to work together. Makita says its batteries fit only within each platform (CXT, LXT, XGT) and Milwaukee says its batteries are interchangeable within a system, not across systems. Read more: Cordless polisher battery compatibility, Cordless polishers and battery platforms
Bluetooth gauge · also app gauge: A paint gauge that sends readings to a phone app over Bluetooth, such as UNI-T's UT343E. A radio-equipped gauge's FCC or ISED status has to be checked for each model. Read more: Bluetooth and app paint gauges
Body filler · also plastic filler: A paste used to fill dents or rust repairs before painting. In a DeFelsko case study, filler over a rust repair read 270 µm and then 930 µm where the rest of the car read 105-115 µm. Read more: Can a paint gauge detect body filler?
Brushless motor · also brushless: An electric motor without carbon brushes. FLEX's XFE 15 and Makita's XOP02Z are brushless. Read more: Corded vs cordless polisher

C

Calibration: A controlled, documented process of measuring traceable standards and checking that the gauge reads within its stated accuracy, typically done by the maker or a qualified lab, as DeFelsko defines it. Elcometer also uses the word for user adjustments, so check which sense a manual means. Read more: How to calibrate, verify and zero a paint gauge, Paint thickness gauges: what each type can measure
Calibration adjustment · also adjustment, user calibration: Aligning a gauge's readings to a known sample to improve accuracy on a specific surface or part of the range, as DeFelsko defines it. Elcometer calls its zero, smooth, rough and two-point methods 'calibration' for the same idea. Read more: How to calibrate, verify and zero a paint gauge
Calibration certificate · also certificate of calibration: A document recording that a gauge or standard was checked against traceable references. DeFelsko ships the PosiTector 6000 with a certificate traceable to NIST or PTB and puts no expiry date on it; owners set their own recalibration interval. Read more: How to calibrate, verify and zero a paint gauge
Calibration foil · also calibration film, foil set: A thin film of known thickness laid on bare metal to check or adjust a gauge. Elcometer states its 990 foils at ±1% accuracy, each with a unique serial number for traceability, in thicknesses from 12.5 µm to 20 mm. Read more: How to calibrate, verify and zero a paint gauge
Calibration interval · also recalibration interval: How often a gauge goes back for calibration. DeFelsko does not put an interval on its certificates and says customers should set their own, with one year as a typical starting point rather than a rule. Read more: How to calibrate, verify and zero a paint gauge
CE mark · also CE: A European conformity marking. UNI-T lists CE and UKCA for its UT343E; CE is not among the marks Health Canada names for plug-in products in Canada. Read more: UL, ETL, CSA and CE on power tools
Clear coat · also clearcoat: The transparent top layer over the base color. DeFelsko gives typical clear coat as 35-50 µm, its rough figure rather than an automaker spec. A magnetic or eddy-current gauge cannot measure it separately. Read more: Can a paint gauge measure clear coat?
Coating thickness · also paint thickness: The thickness of paint or another coating over a substrate, usually given in microns (µm) or mils. On a car, a magnetic or eddy-current gauge reports the total of all layers together. Read more: Paint thickness gauges: what each type can measure, Normal car paint thickness
Coating thickness standard · also thickness standard, reference standard: A reference sample of known coating thickness used to verify a gauge. DeFelsko's standards are smooth steel or aluminum with an epoxy coating of known thickness and come with a calibration certificate traceable to NIST. Read more: How to calibrate, verify and zero a paint gauge
Combination gauge (Fe/NFe) · also combo gauge, FN gauge, FNF gauge: A paint gauge that measures on both steel (Fe) and aluminum (NFe), switching automatically or by hand. Examples include DeFelsko's FN probes and PosiTest DFT-Combo and UNI-T's UT343E. Read more: Magnetic vs eddy-current paint gauges, How to check a used car's paint with a gauge, Paint thickness gauges: what each type can measure
Counterfeit battery · also knock-off battery, fake battery: A pack made to look like a brand's genuine battery. Makita USA warns that knock-off Makita batteries may burst and cause fires, and can defeat the battery-tool-charger communication system. Read more: Genuine vs aftermarket tool batteries
Couplant · also couplant gel: A gel spread between an ultrasonic probe and the surface so the sound pulse passes into the coating. DeFelsko says ultrasonic measurement needs it. Read more: Can a paint gauge measure plastic bumpers?
CSA mark · also CSA: A Canadian certification mark. Health Canada says plug-in electrical products must be certified and tells consumers to look for marks such as CSA, cUL or cETL. Read more: UL, ETL, CSA and CE on power tools
cULus mark · also cUL, UL Listed: UL's listing mark for Canada and the US. Milwaukee's 2684-20/2685-20 manual includes it in its symbology list, and Health Canada names cUL among the marks to look for. Read more: UL, ETL, CSA and CE on power tools
Curvature effect: The influence of a curved surface on a reading. DeFelsko names curvature among the factors that may need adjustment, and Linshang lists minimum curvature for the LS221 as 5 mm convex and 25 mm concave. Read more: Paint gauge readings that mislead

D

Data logging · also reading memory: Storing readings in the gauge or app to review later. UNI-T lists 3,300-reading storage for the UT343E; NexDiag says PDF reports are not supported on its NexPTG Standard and Standard Plus. Read more: Bluetooth and app paint gauges
Dry film thickness (DFT) · also DFT: The thickness of a coating after it has dried or cured. ASTM D7091 covers measuring it with magnetic gauges on ferrous metals and eddy-current gauges on non-ferrous metals. Read more: Paint thickness gauges: what each type can measure
Dual-action polisher (DA) · also DA polisher: A polisher whose plate orbits as well as rotates, either freely (random orbital) or through gearing (forced rotation). RUPES describes both kinds. Read more: Rotary vs dual-action polisher, Car polishers: dual-action, forced-rotation and rotary

E

Eddy current · also eddy-current method: The measuring principle for non-conductive coatings on non-ferrous metals such as aluminum. DeFelsko says paint over aluminum is measured with eddy-current gauges. Read more: Magnetic vs eddy-current paint gauges, Paint thickness gauges: what each type can measure
Edge effect: A change in reading close to a panel edge. DeFelsko lists edge effects among the conditions that may need an adjustment and advises measuring near seams about one inch from edges. Read more: Paint gauge readings that mislead
ETL Listed Mark · also ETL, cETL: Intertek's certification mark. Intertek says it shows a product was independently tested and certified by Intertek, an OSHA-recognized NRTL, to applicable safety standards. Read more: UL, ETL, CSA and CE on power tools

F

Fe mode · also F mode, ferrous mode: The gauge setting for coatings on magnetic metals such as iron and steel. UNI-T says FE means magnetic substrates; DeFelsko says F means a magnetic principle on ferrous metal. Read more: Magnetic vs eddy-current paint gauges
Ferrous substrate · also ferrous metal, Fe substrate: A magnetic metal base such as iron or steel. Paint over it is measured in Fe mode with a magnetic gauge. Read more: Magnetic vs eddy-current paint gauges
Foam pad: A polishing pad made of foam. RUPES lists 130-150 mm BigFoot foam pads for its LHR15ES. Makers grade foam their own way, and we do not assign cut levels without a maker statement. Read more: Polishing pads and backing plates: sizes and fit
Forced rotation · also gear-driven: A dual-action motion where the plate both orbits and is forced to rotate through gearing. RUPES says it is more aggressive and generally vibrates more than random orbital motion. Read more: Forced rotation vs free-spinning DA polishers
Free-spinning · also free spin: A dual-action plate that is not geared to rotate, so its spin depends on friction, pressure and angle. RUPES and Auto Care HQ describe it as able to slow or stop rotating. Read more: Forced rotation vs free-spinning DA polishers, Why a DA polisher stops spinning

G

GFCI · also ground-fault circuit interrupter: A ground-fault circuit interrupter, which cuts power when current leaks to ground. Milwaukee's power-tool safety rules call for a GFCI-protected supply if a tool must be used in a damp location. Read more: Car polisher safety checklist, Corded vs cordless polisher

H

Hall effect · also Hall-effect sensor: A magnetic sensing principle some gauges use on ferrous metal. Linshang specifies its LS221 with Hall-effect sensing on ferrous substrates and eddy current on non-ferrous ones. Read more: Magnetic vs eddy-current paint gauges
Hook-and-loop · also H&L: The fastening that holds a pad to a backing plate: hooks on the plate face grip loops on the back of the pad. Read more: Pad and backing-plate compatibility

I

iBrid (RUPES): RUPES's name for polishers that can run on battery or from a power adapter. RUPES says its HLR15 and HLR21 iBrid run cordless or corded on an 18 V 5 Ah pack, and the HLR75 runs continuously with the iBrid Power Adapter. Read more: Corded vs cordless polisher, Mini polishers for tight areas

L

Lithium-ion · also Li-ion: The rechargeable battery chemistry in cordless tool packs. CPSC says high-energy lithium-ion batteries can overheat and cause fire and thermal burns, and recommends testing cells, batteries, chargers and products together as a system. Read more: Lithium-ion tool battery safety, Cordless polishers and battery platforms
Long throw · also long-throw polisher: A dual-action polisher with a large orbit, typically 15 mm or 21 mm, such as RUPES's LHR15ES or Milwaukee's 2685-20. Read more: 15 mm vs 21 mm polisher, Polisher throw explained

M

Magnetic induction · also magnetic method: A magnetic measuring principle used by Fe gauges to read non-magnetic coatings on steel. DeFelsko says paint over steel is measured with magnetic gauges. Read more: Magnetic vs eddy-current paint gauges
Measurement range · also range: The span of thicknesses a gauge is specified to read, such as 0-2000 µm for UNI-T's UT343E or 0-500 µm for the Elcometer 311. AUTO BILD's 2021 test found one budget gauge showing more than 2000 µm although rated only to 1000 µm, so treat readings beyond the range with suspicion. Read more: Paint gauge accuracy vs resolution, Paint thickness gauges: what each type can measure
Microfiber pad: A polishing pad faced with microfiber instead of foam or wool. Read more: Polishing pads and backing plates: sizes and fit
Micron (µm) · also micrometer, µm, um: One thousandth of a millimeter, the usual unit for paint thickness. DeFelsko gives 1 mil as 25.4 µm. Read more: Normal car paint thickness
Mil · also thou: One thousandth of an inch, equal to 25.4 µm, as DeFelsko gives it. US gauges and specs often quote paint thickness in mils. Read more: Normal car paint thickness
Mini polisher · also nano polisher: A small polisher for curves, contours and compact areas. RUPES's HLR75 uses a 75 mm (3-inch) plate and a 12 mm orbit. Read more: Mini polishers for tight areas

N

NFe mode · also N mode, non-ferrous mode: The gauge setting for non-conductive coatings on non-magnetic metals such as aluminum and copper, measured by eddy current. AUTO BILD notes that NFe capability is also what finds tin-filled repairs on steel. Read more: Magnetic vs eddy-current paint gauges, Can a paint gauge detect body filler?
Nominal voltage: A battery's rated working voltage, as opposed to its peak. DEWALT says its 20V MAX packs are 20 V at maximum initial voltage without load and 18 V nominal. Read more: 20V MAX vs 18V batteries
Non-ferrous substrate · also non-ferrous metal, NFe substrate: A non-magnetic metal base such as aluminum or copper. Paint over it is measured in NFe mode with an eddy-current gauge. Read more: Magnetic vs eddy-current paint gauges
NRTL · also Nationally Recognized Testing Laboratory: A lab OSHA recognizes to test and certify products to US safety standards. Intertek (ETL) and UL are both NRTLs; Intertek says ETL-marked products meet the same requirements as those bearing other NRTL marks. Read more: UL, ETL, CSA and CE on power tools, Buying detailing tools safely

O

OEM finish · also factory paint, original finish: The paint applied when the car was built. Published typical thicknesses differ: DeFelsko gives 100-180 µm and PPG Refinish (Australia/New Zealand) about 90-120 µm. Neither is a pass/fail line. Read more: Normal car paint thickness
Official store: A marketplace store whose name claims to be a brand's own. AliExpress says it cannot confirm each member's claimed identity, so the name alone is not proof; check whether the brand's own site links to the store. Read more: Buying polishers and gauges on Amazon and AliExpress: what to check, Buying detailing tools safely
OPM · also orbits per minute: Orbits per minute: how many times the plate completes its orbit each minute. Makita lists the XOP02Z at 0-6,800 OPM alongside 0-780 RPM. Read more: Polisher throw explained
Orbit throw · also throw, stroke, orbit diameter: The size of a dual-action plate's orbit, given in millimeters: for example 15 mm on RUPES's LHR15ES, 21 mm on Milwaukee's 2685-20 and 7/32 in on Makita's XOP02Z. Read more: Polisher throw explained, 15 mm vs 21 mm polisher

P

Pad capacity · also pad size: The pad diameter a maker rates a polisher for. Milwaukee gives the 2684-20 a 5-inch pad capacity (6-inch optional) and the 2685-20 a 6-inch capacity (5-inch optional). Read more: 5-inch vs 6-inch polisher pads, Polishing pads and backing plates: sizes and fit
Pad overhang: A pad larger than its backing plate. RUPES deliberately pairs its 125 mm LHR15ES plate with 130-150 mm foam pads, while Milwaukee says plate and pad diameters should match on its polishers. Read more: Pad and backing-plate compatibility, 5-inch vs 6-inch polisher pads
Paint burn · also burn-through, burning: Damage from polishing through or overheating the paint. Milwaukee warns that even its random orbital polishers may cause burning with too much pressure, the wrong angle or improper motion. Read more: Car polisher safety checklist, Rotary vs dual-action polisher
Paint protection film (PPF) · also clear bra: A clear film applied over paint to protect it from chips and scratches. Read more: Used-car paint inspection with a gauge
Panel map · also readings map: A sketch of the car with readings written on each panel, so you can compare panels and sides at a glance. Read more: How to check a used car's paint with a gauge
Plastic shim · also shim, check shim: A plastic sheet of nominal thickness bundled with many paint gauges. DeFelsko says a shim is less accurate than a coating thickness standard, so its tolerance adds to the gauge's when used for adjustment; a bundled shim is not automatically a traceable standard. Read more: How to calibrate, verify and zero a paint gauge, Paint gauge readings that mislead
Primer: The first paint layer on the bare panel, under the color and clear coat. A magnetic or eddy-current gauge includes it in the total reading. Read more: Normal car paint thickness
Probe · also sensor: The part of a gauge that touches the surface and senses thickness. DeFelsko's PosiTector 6000 probe families show capability: F for ferrous, N for non-ferrous and FN for both. Linshang's LS221 uses a separate split probe. Read more: Paint thickness gauges: what each type can measure

R

Random orbital · also RO: A dual-action motion where the backing plate orbits and is free to rotate. RUPES says that if friction stops rotation the motion simply becomes orbital, with rotation speed independent of the orbit count. Read more: Forced rotation vs free-spinning DA polishers, Why a DA polisher stops spinning
Refinish · also refinishing: Paint applied after the factory finish, usually in a body shop. PPG Refinish (Australia/New Zealand) recommends that refinish films of 300 µm or more be removed or sanded back before repainting. Read more: How to spot a repainted panel
Repaint · also respray: A panel painted again after it was built, by a shop or at the factory. A gauge can show a thicker reading but not the cause; AUTO BILD and DeFelsko both note that factories sometimes repaint. Read more: How to spot a repainted panel, Used-car paint inspection with a gauge
Repeatability: How closely a gauge gives the same reading when you measure the same spot several times under the same conditions. It describes consistency, not whether the reading is correct. Read more: Paint gauge accuracy vs resolution, Paint gauge readings that mislead
Resolution · also display resolution: The smallest step a gauge's display shows. UNI-T lists the UT343E at 0.1 µm resolution below 100 µm but states its accuracy as ±(2%H + 2 µm), so at 100 µm the tolerance is forty times the display step. Read more: Paint gauge accuracy vs resolution
Rotary polisher · also rotary: A polisher that spins its pad on a single axis, with no orbit. Auto Care HQ says it builds heat and friction faster and is mostly used by experienced users. Read more: Rotary vs dual-action polisher
RPM · also revolutions per minute: Revolutions per minute. Polisher makers quote rpm ranges, such as 2,000-5,000 rpm for RUPES's LHR15ES; on a random orbital, RUPES says rotation speed is independent of the orbit count. Read more: Polisher throw explained

S

SAPL (NexPTG): NexDiag's system in its NexPTG app that interprets readings and color-codes panels as factory, repaired or touched up, or repainted or filled. It is the maker's interpretation, not proof of a repair. Read more: Bluetooth and app paint gauges, How to spot a repainted panel
Short throw · also short-throw polisher: A dual-action polisher with a small orbit, such as RUPES's 5 mm LK900E or Makita's 7/32-inch (about 5.6 mm) XOP02Z. Read more: Polisher throw explained
Side-to-side comparison · also mirrored-spot comparison: Measuring the same spot on both sides of the car. AUTO BILD advises that a much higher reading on one side than the mirrored spot indicates a repair, and DeFelsko says a significant difference between adjacent panels strongly indicates repainting. Read more: How to spot a repainted panel, How to check a used car's paint with a gauge
Single-stage paint · also single stage: A finish where color and gloss come from one paint layer, with no separate clear coat on top. Read more: Can a paint gauge measure clear coat?
Sold by · also ships from, fulfilled by: The marketplace label naming who actually sells an offer. Canada's Office of Consumer Affairs tells shoppers to check 'sold by', 'shipped by' or 'fulfilled by' to see whether they are buying from the retailer or a third party. Read more: Buying polishers and gauges on Amazon and AliExpress: what to check, Buying detailing tools safely
Stall · also stalling: When a free-spinning dual-action plate stops rotating under friction. RUPES says the motion then simply becomes orbital; it is how the design works, not a fault. Read more: Why a DA polisher stops spinning
Substrate · also base material: The material under the coating: steel, aluminum, plastic or fiberglass on a car. The substrate decides which gauge type can measure the paint, and DeFelsko notes one car can mix several. Read more: Magnetic vs eddy-current paint gauges, Paint gauge surface finder
Surface roughness · also roughness: How textured a surface is at a small scale. DeFelsko lists roughness among the conditions that may require a gauge to be adjusted, and Elcometer offers a rough-surface calibration method on its 456. Read more: Paint gauge readings that mislead
Swirl marks · also swirls, buffer trails: Fine circular scratches in paint, visible in strong light. Milwaukee's polisher manual warns that too much pressure, the wrong angle or improper motion may cause swirl marks or burning. Read more: Car polisher safety checklist, Rotary vs dual-action polisher

T

Tin filler · also tin-filled repair: Metal (tin) used to fill a repair in a steel body. AUTO BILD notes that tin-filled repairs on steel can only be found with a gauge that also has NFe capability. Read more: Can a paint gauge detect body filler?, Magnetic vs eddy-current paint gauges
Traceability · also NIST traceable: The ability to follow a measurement through an unbroken chain of comparisons back to an accepted national or international standard, as DeFelsko defines it. A 'traceable' label is only as good as the documentation behind it. Read more: How to calibrate, verify and zero a paint gauge

U

UL 62841: The UL standard family for hand-held electric tools. OSHA lists UL 62841-2-3 (disc-type polishers) and UL 62841-2-4 (polishers other than disc type) in UL's recognized scope; that shows the standard, not that a product is certified. Read more: UL, ETL, CSA and CE on power tools
Ultrasonic gauge · also ultrasonic thickness gauge: A gauge that uses sound pulses to measure coatings on non-metals such as plastic bumpers and fiberglass. DeFelsko's PosiTector 200 B3 can report total thickness and up to three layers; DeFelsko does not recommend its affordable models as do-all instruments. Read more: Can a paint gauge measure plastic bumpers?, Can a paint gauge measure clear coat?
UN 38.3: The UN transport test for lithium batteries. UL Solutions states that all lithium-ion batteries must be tested to UN 38.3 before shipping. Read more: Lithium-ion tool battery safety
Universal charger: A charger sold as fitting many battery types. In 2024 CPSC warned consumers to stop using SafPow and AMPOWSURE chargers sold as universal that could ignite incompatible 36 V lithium batteries; those were micromobility chargers. Read more: Genuine vs aftermarket tool batteries, Lithium-ion tool battery safety

V

Verification · also accuracy check: A user check of a gauge on known reference standards covering the expected thickness range, to confirm it still works as expected. DeFelsko says it does not replace regular calibration, and that if readings disagree, all measurements since the last check are suspect. Read more: How to calibrate, verify and zero a paint gauge

W

Wool pad: A polishing pad faced with wool fibers. RUPES lists 130 mm wool pads for its LHR15ES. Read more: Polishing pads and backing plates: sizes and fit

Z

Zeroing · also zero check, zero adjustment: Setting or checking a gauge's zero on an uncoated sample of the same metal. DeFelsko calls it the simplest form of adjustment, not a lab calibration, and its detailing guide suggests a zero check on an uncoated part before measuring. Read more: How to calibrate, verify and zero a paint gauge, Paint gauge readings that mislead