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Summary / What You'll Learn Who this article is for: Stone fabricators, countertop shops, and installers trying to understand when to use a stone polisher vs. a stone grinder — and whether they need both. Key takeaways:
What's inside:
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From the outside, a stone polisher and a stone grinder look almost identical. Both are handheld power tools with a 5/8-11 arbor, both accept disc attachments, and both get used on granite, marble, and other stone. So what is actually different?
The answer comes down to speed, attachment type, and the job you are doing. Grinding and polishing are not the same operation, and using the wrong tool for the wrong task either damages the stone, destroys expensive tooling, or both.
What Does a Stone Grinder Do
A stone grinder runs at high RPM, typically 8,000 to 12,000 RPM, and is designed for aggressive material removal. In a fabrication shop, you reach for the grinder when you need to:
Tasks for a Stone Grinder
- Cut profiles and shapes on slab edges
- Remove saw marks and rough cuts
- Grind down lippage or level surfaces
- Work with hard cutting discs and aggressive tooling
The Samurai ST-358, for example, runs at 10,000 RPM with a 570W motor. It is a heavy-duty rear exhaust grinder built for the demands of active stone cutting. High RPM means fast material removal, exactly what you want when shaping stone, not finishing it.
The tradeoff is that running high RPM with polishing pads, especially at finishing grits, generates heat and can damage both the pad and the stone surface. That is why grinders are not the right tool for finish polishing.
What Does a Stone Polisher Do
A stone polisher runs at lower, variable RPM. The Samurai ST-235 runs up to 5,000 RPM and is designed to work with diamond polishing pads through a sequence of grits from rough to finish. The lower speed gives more control over the polishing process and prevents heat buildup that can haze or discolor the stone.
Variable speed is a key feature. At 50 grit, you run slower for control. At 3000 grit finishing, you increase speed for a higher gloss. A fixed-speed tool, especially a high-speed grinder, cannot make those adjustments. That is why dedicated polishers exist.
Polishers are also built for extended use with water. The ST-235 includes a built-in oil port for lubrication and is designed for hours of continuous wet operation, which is a requirement in any shop doing high-volume polishing work.
Key Differences Between Stone Grinder and Polisher
Speed (RPM)
- Grinders: 8,000 to 12,000 RPM
- Polishers: 0 to 5,000 RPM variable
The speed difference defines what each tool is designed to do. Cutting and shaping benefit from high RPM and torque. Polishing requires control and lower speed to prevent heat.
Arbor and Attachments
Both the ST-235 and ST-358 use a 5/8-11 arbor, which is standard for stone fabrication tooling. This means both tools can physically accept the same accessories, but that does not mean you should use them interchangeably. Running polishing pads on a grinder at 10,000 RPM will destroy the pads and risk burning the stone.
Applications
- Grinder: profiling, edge shaping, rough grinding, heavy material removal
- Polisher: surface finishing, diamond pad polishing sequences, honing, buffing
The applications do not overlap much in practice. You use one for cutting and the other for finishing.
Pneumatic vs Electric
Both the ST-235 and ST-358 are pneumatic tools powered by compressed air. Pneumatic tools are lighter than equivalent electric tools, do not generate heat internally the way electric motors do, and are more durable in wet environments. The tradeoff is needing a sufficient air compressor, as both tools require 16 CFM at 90 to 100 PSI.
Do You Need Both a Grinder and Polisher
In most professional stone shops, the answer is yes. A grinder handles the cutting and shaping stages of fabrication, and a polisher handles the finishing stages. They are sequential in the workflow, not interchangeable.
Some shops run both tools off the same air supply and move between them as the job progresses. Others dedicate specific benches or operators to each tool. Either way, having both a reliable grinder and a quality variable-speed polisher is the baseline for a well-equipped fabrication operation.
Samurai Air Tools makes both: the ST-358 wet grinder and the ST-235 wet polisher, designed and built in Japan for professional shop use. Shop the full lineup at SamuraiAirTools.com.
ST-235 Polisher and ST-358 Grinder
Designed in Japan. Made for professional shop use. The industry standard wet polisher and grinder for stone fabrication.
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Shop at SamuraiAirTools.com
FAQ: Stone Polisher vs Stone Grinder
Can I use a grinder for polishing if I run it slow
Most grinders do not have variable speed and run at a fixed high RPM. Even if you could slow it down, the design is not optimized for sustained light-pressure polishing. Use a dedicated polisher for polishing.
What is the difference between the Samurai ST-235 and ST-358
The ST-235 is a variable-speed wet polisher running up to 5,000 RPM designed for diamond pad polishing sequences. The ST-358 is a high-RPM wet grinder running at 10,000 RPM designed for cutting, profiling, and aggressive material removal. Both are pneumatic, made in Japan, and use 5/8-11 arbor.
Do I need a specific air compressor for these tools
Both the ST-235 and ST-358 require 16 CFM at 90 to 100 PSI. Make sure your compressor can sustain that output before purchasing pneumatic tools. Most shop compressors rated for industrial use can handle it.
Why choose pneumatic over electric for stone tools
Pneumatic tools are lighter, run cooler in wet environments, and typically last longer in a stone shop setting. The main requirement is a sufficient air supply.
How long does a pneumatic stone polisher last
With proper maintenance, including regular oiling through the built-in oil port, keeping moisture out of the air line, and not running the tool without water, a quality pneumatic polisher should provide years of reliable shop use. The Samurai ST-235 includes a built-in brass oil port specifically for this.