Intro
FEIN is not a household name like Bosch or Makita, but among metalworkers, fabricators, and industrial tradespeople, the orange tools from this 150-year-old German company command near-legendary respect. FEIN invented the electric hand drill in 1895 and the oscillating multi-tool decades before anyone else, and their tools are built to survive in factories, shipyards, and demanding production environments. A reciprocating saw from FEIN carries those same expectations: precise, durable, and engineered for the kind of work that kills lesser tools within a year. Most cordless recip saws are designed for timber demolition and rough construction. A FEIN recip saw is aimed at a different user — someone cutting metal profiles, composite panels, and mixed materials in tight, awkward locations where precision matters as much as speed. This review examines FEIN's 18-volt cordless sabre saw, looking at what sets it apart and whether the premium price is justified.
Generalities
FEIN occupies a distinct position in the power tool market: smaller than the major conglomerates, but with a reputation for precision and longevity that rivals Festool. Their tools are typically more expensive than equivalents from Bosch or DeWalt, and the ASAS 18-21K AS reciprocating saw follows that pattern — it is a bare tool priced where competitors offer a kit with battery and charger. The trade-off is build quality, refinement, and access to FEIN's specialised blade ecosystem. A key practical advantage is battery compatibility: the ASAS 18-21K AS works with the AMPShare battery platform, which means it accepts Bosch Professional 18-volt batteries. If you already run Bosch blue tools, you can add this FEIN saw without buying into a new battery system — a significant cost and convenience benefit.
This review examines the FEIN ASAS 18-21K AS, an 18-volt cordless reciprocating saw with a 3,050 RPM stroke rate, fast blade change, LED work light, and ergonomic design optimised for work in confined spaces. We cover cutting performance, handling and build quality, the AMPShare battery compatibility, and who this tool is really for — because at this price, it is not for everyone.
Description
The FEIN ASAS 18-21K AS runs on an 18-volt motor that delivers up to 3,050 strokes per minute — a stroke rate that prioritises control and blade longevity over outright speed. FEIN designs its recip saws with metal cutting as a primary use case, and 3,050 RPM is well matched to the requirements of cutting steel, aluminium, and stainless steel profiles without overheating the blade or the workpiece. The saw accepts standard reciprocating saw blades with a maximum length of 200 millimetres, covering everything from short metal-cutting blades for conduit to long pruning and demolition blades for timber. The blade clamp is designed for fast, tool-free changes — essential when moving between cutting stainless brackets and timber studs on the same job.
FEIN's engineering focus is evident in the saw's ergonomics. The body is shaped for a secure two-handed grip with a slim profile that lets you see the blade and cut line clearly — a detail that matters when cutting to a marked line on expensive material. At approximately 2 kilograms without a battery, it is not the lightest recip saw available, but the weight is balanced to reduce the feeling of the tool pulling forward during horizontal cuts. The handle geometry and trigger position allow for comfortable use in multiple orientations — cutting vertically up a wall stud, horizontally through a pipe at waist height, or overhead through a ceiling joist. An integrated LED work light illuminates the cutting area, which is particularly valuable when working inside machinery housings, under vehicle chassis, or in dimly lit industrial environments.
The standout practical feature of the ASAS 18-21K AS is its AMPShare battery compatibility. AMPShare is a cross-brand battery alliance that allows tools from different manufacturers to use the same batteries — the FEIN ASAS 18-21K AS accepts Bosch Professional 18-volt batteries, which means you can use the same batteries that power your Bosch drill, impact driver, and circular saw. This is a significant advantage over proprietary battery systems: it reduces the number of chargers and battery types you need to manage, and it means you can buy the FEIN saw as a bare tool with confidence that you already have compatible power. For workshops already standardised on Bosch Professional 18V, adding a FEIN recip saw is seamless. The tool is also compatible with other AMPShare batteries from participating brands.
As a bare tool, the ASAS 18-21K AS ships without batteries or a charger — the box contains the saw body and essential documentation. This is standard for FEIN, whose target audience of professional users typically already owns compatible batteries and chargers. The tool includes FEIN's limited warranty, and spare parts availability is guaranteed for at least one year from the date of manufacture. CE certification confirms compliance with European safety and electromagnetic compatibility standards. The tool is manufactured in Germany, which carries weight for buyers who value domestic production quality — FEIN has been building tools in Germany since 1867 and the company's manufacturing standards are among the most rigorous in the industry.
The FEIN ASAS 18-21K AS holds a 4.6 out of 5 stars rating from 14 customer reviews on Amazon France, with a modest ranking of #237 in Reciprocating Saws. The review count is small — typical for a niche premium tool — but the high average suggests owners are satisfied. At approximately €149 for the bare tool, it is positioned at the premium end of the cordless recip saw market, especially when you factor in the cost of batteries and a charger if you do not already have them. The question for potential buyers is whether FEIN's build quality, refined ergonomics, and AMPShare compatibility justify the premium over a Bosch, Makita, or DeWalt recip saw that may offer higher stroke rates at a lower price. For metalworkers, industrial maintenance technicians, and professionals who value precision over brute force, the answer is likely yes.
Pros and cons
Pros
- AMPShare compatibility means it accepts Bosch Professional 18V batteries — a rare cross-brand feature that lets you use existing batteries from your Bosch toolkit and avoid adding another charger to the workshop.
- FEIN build quality with German manufacturing — the company's 150-year engineering heritage and rigorous production standards translate to a tool built for daily industrial use rather than occasional DIY.
- 3,050 RPM stroke rate is optimised for controlled metal cutting — the speed is well matched to steel, aluminium, and stainless profiles where excessive RPM generates heat and shortens blade life.
- Ergonomic slim-body design with good cut-line visibility — you can see exactly where the blade is entering the material, which matters when cutting expensive metal stock or following a precise marked line.
- Fast tool-free blade change — switch from a metal-cutting blade to a wood demolition blade in seconds without tools, keeping workflow moving on jobs that involve mixed materials.
- Integrated LED work light positioned to illuminate the cut zone — genuinely useful when working inside machinery, under vehicles, or in poorly lit industrial environments.
- 4.6 out of 5 stars from owners — a strong satisfaction score that, while based on a small sample, suggests the saw meets the high expectations that come with the FEIN name and price.
Cons
- At €149 for the bare tool alone, the total ownership cost is high — adding a compatible battery and charger pushes the investment well past €200, making it one of the most expensive recip saws in its class.
- 3,050 RPM is slower than many competitors that reach 3,200–3,500 RPM — tradespeople who prioritise raw cutting speed in timber may find the FEIN feels underpowered for demolition-focused work.
- Only 14 reviews and a #237 ranking — the extremely limited user base makes it difficult to evaluate long-term reliability patterns or compare against more popular alternatives with thousands of reviews.
- FEIN's dealer and service network is sparse compared to Bosch, Makita, or DeWalt — if the tool needs warranty service or spare parts, you may need to ship it rather than drop it at a local service centre.
- AMPShare compatibility, while innovative, is still a niche ecosystem — if your existing batteries are Makita, Milwaukee, or DeWalt, the cross-brand benefit does not apply and you face the full cost of new batteries.
Use cases
The FEIN ASAS 18-21K AS is a premium German cordless reciprocating saw built for metalworkers, industrial maintenance technicians, and professionals who already use Bosch Professional 18V batteries and value precision, durability, and refined ergonomics over maximum cutting speed or budget pricing.
Metal Fabrication and On-Site Installation
Cutting steel and aluminium profiles, threaded rod, conduit, and metal framing on installation sites is the ASAS 18-21K AS's core strength. The controlled 3,050 RPM stroke rate paired with FEIN's metal-cutting blades produces clean, burr-free cuts that need minimal filing before welding or assembly.
Industrial Maintenance and Repair
Maintenance technicians working on production machinery, conveyor systems, and processing equipment often need to cut damaged components out of tight spaces. The ASAS 18-21K AS's slim body, LED light, and precise trigger control make it the right tool for cutting a seized bolt shank or a damaged bracket inside a machine housing without collateral damage.
Automotive and Commercial Vehicle Repair
Cutting exhaust pipes, rusted bolts, body panels, and chassis components is standard recip saw territory in a workshop. The FEIN's AMPShare compatibility is a major plus in shops already running Bosch Professional 18V — the same batteries power the impact wrench, the recip saw, and the work light.
Plumbing and HVAC Pipe and Duct Work
Cutting copper, steel, and plastic pipe in tight joist bays, above suspended ceilings, or inside mechanical rooms is easier with a saw that fits into confined spaces and gives you a clear view of the cut. The fast blade change lets you switch between a fine metal blade for copper and a coarse blade for plastic waste pipe without breaking stride.
Precision Demolition in Occupied Buildings
When renovating in occupied homes or offices, controlled, accurate cutting matters — you need to remove a section of stud wall or a damaged joist without vibrating the entire structure or damaging adjacent finishes. The FEIN's balanced weight and refined motor control make it a better neighbour than aggressive high-speed recip saws that shake everything within a two-metre radius.