Stainless steel polishing and grinding abrasive and tools

HOME > Stainless steel polishing

Abrasives for achieving finest stainless steel mirror finish

Stainless steel polishing process

Stainless steel polishing and grinding is known as one of the most difficult projects. This is because most stainless steel polishing requires a mirror-like finish devoid of even the slightest of scratches or pinholes. The polishing process usually consists of 3 to 7 (or more)process depending on where you start from.

However, each project for stainless steel polishing and grinding is similar in that just a single tiny scratch exceeding the aforementioned grit size cannot be endured. If you leave a scratch or are unable to grind the surface enough at that grit, those scratches remain in post-process and become irreversible. In order to remove them, you need to begin all over again. Therefore, people who engage in stainless steel polishing often suffer in a strait condition.

What makes stainless steel a difficult material to polish?

Stainless steel, also referred to as SUS, is basically an iron that contains Cr and Ni, which are resistant to rust, wear, and corrosion. The differences between these added materials and their ratio in relation to one another determines the grade and characteristics of the stainless steel. Generally speaking, Cr is responsible for the hardness and Ni or Mo enhance the anti-corrosion capacity. As you can easily imagine from these characteristics, stainless steel is difficult to process with any method.

Nevertheless, due to these characteristics, stainless steel has added value that can be applied to many kinds of industries, so stainless steel polishing methods and abrasives have been developed to accommodate these special circumstances.

What kind of abrasive suit to stainless steel polishing and grinding?

In terms of abrasives for stainless steel polishing and grinding, there are some grains that interact well with this material, including white alumina (WA) and Green carbonite (GC). There is some debate among experts about which is superior for stainless steel. We observe these differences during the polishing process. The shape and friability are different, but basically both grains are in practical use. We have applied WA due to its cutting power as compared with that of GC. The reason why cutting power is needed for stainless polishing will be explained below.

In terms of selecting an abrasive for stainless steel polishing, it is often pointed out that abrasive that are sticky and have a high viscosity are not appropriate for this usage. This is related to the relative hardness of the stainless steel, which is softer than glass or stone. Abrasives need to "cut" the surface in order to achieve the fine surface.

Two major characteristics that make stainless steel polishing and grinding difficult are as follows.

Work hardening
This phenomenon has been observed during the process in which a certain amount of stress has been placed on the metal surface. Placing stress on the metal, in any form, can cause the hardness of the metal to rise. This is why stainless polishing cannot take a long time. Once the surface becomes hardened, the polishing will be much more difficult. Therefore, before the hardening occurs, you need to move onto the next grit.
The term stainless steel is self-explanatory-steel that is resistant to rust and stain, mainly due to the oxide layer that coats its surface. Each time the oxide layer breaks, the stainless surface quickly restores it, thereby avoiding rust. So when polishing the stainless surface, you need to finish polishing before the oxide layer reverts because this layer is hard enough to be obstacle to polishing.

Due to above characteristics, abrasives that have high cutting power are the only choice for stainless steel polishing,

RWA: Abrasive for polishing stainless steel

We have developed an abrasive that is especially suited to stainless steel polishing. The abrasive consists of a resin-based bond and white alumina grain. It is called RWA, and can be applied to both a CNC machine and a hand polishing machine. Round or block, either type can easily cut or make a groove according to your polishing conditions.

Applicable materials Stainless steel(SUS), Titanium alloy, Aluminum alloy
Process mirror polishing process, non-ferrous metal
Product size φ150 mm(Outer diameter) × 25 mm(height) × φ64 mm(Inner diameter)

φ200 mm(Outer diameter) × 30 mm(height) × φ90 mm(Inner diameter)

Block type: 200 mm × 75 mm × 30 mm
We also offer hand polisher type which fit into electric hand polishing machine or air polisher.
Grit 80, 120, 180, 220, 320, 400, 600, 800, 1000, 1599, 3000

Alumina powder for finishing stainless

We also offer an Alumina powder abrasive for final finishing. Achieving a mirror-like finish, (also known as a No. 8 finish), usually requires a powder abrasive. When it follows the RWA process, Alumina finishing will make stainless surfaces shine. The RWA process is especially important because this powder cannot remove large scratches.

Features for RWA stainless polishing abrasive stone

High cutting power

We have applied grains that have comparatively high friability and bonds that can be self-sharpened. Due to the reasons elaborated above (on the polishing of stainless steel), cutting within a certain time frame is the key factor for efficient processing.

High elasticity

Due to its porous structure and resin composition, RWA has high elasticity and softness. When considering protrusion (the length of the grain that sticks out from the abrasive surface), soft and elastic bond make this figure low. Stainless is a sensitive material so if you have too much protrusion, it can easily become a scratch. To avoid this and to maintain the cutting power, we have adjusted our abrasive bond for stainless use.

Easily dressed

No matter what kind of abrasive you use, at some point, you need to dress the surface of the abrasive because of the loading. Tiny chips that have been cut from the surface will go inside between the grains, and eventually, abrasive stone will begin to slip from the stainless surface. By laying down the grinding wheel with larger grit (grains consisting of GC or A are preferable) you can easily dress the surface by hand.

Tips about SUS grade


This is one of the most basic grades that contains Cr18, Ni8. Among the various stainless grades, this one said to be the easiest for polishing.


This grade contains, Cr18, Ni12, Mo2.5, which has more anti-corrosion properties as compared with the SUS304. Generally, if there is more added value, the difficulty of the polishing will increase.


This grade is known as a hard oxide layer. One of the most difficult stainless surfaces to polish.

Comparision for standardized stainless steels

Steel no. k.h.s DIN
Steel name
SAE grade UNS
440A S44002
1.4112 440B S44003
1.4125 440C S44004
440F S44020
1.4016 X6Cr17 430 S43000
1.4408 G-X 6 CrNiMo 18-10 316
1.4512 X6CrTi12 409 S40900
410 S41000
1.4310 X10CrNi18-8 301 S30100
1.4318 X2CrNiN18-7 301LN N/A
1.4307 X2CrNi18-9 304L S30403
1.4306 X2CrNi19-11 304L S30403
1.4311 X2CrNiN18-10 304LN S30453
1.4301 X5CrNi18-10 304 S30400
1.4948 X6CrNi18-11 304H S30409
1.4303 X5CrNi18-12 305 S30500
X5CrNi30-9 312
1.4541 X6CrNiTi18-10 321 S32100
1.4878 X12CrNiTi18-9 321H S32109
1.4404 X2CrNiMo17-12-2 316L S31603
1.4401 X5CrNiMo17-12-2 316 S31600
1.4406 X2CrNiMoN17-12-2 316LN S31653
1.4432 X2CrNiMo17-12-3 316L S31603
1.4435 X2CrNiMo18-14-3 316L S31603
1.4436 X3CrNiMo17-13-3 316 S31600
1.4571 X6CrNiMoTi17-12-2 316Ti S31635
1.4429 X2CrNiMoN17-13-3 316LN S31653
1.4438 X2CrNiMo18-15-4 317L S31703
1.4539 X1NiCrMoCu25-20-5 904L N08904
1.4547 X1CrNiMoCuN20-18-7 N/A S31254

Stainless steel finishing category

No. 0 Hot rolled, annealed, thicker plates
No. 1 Hot rolled, annealed and passivated
No. 2D Cold rolled, annealed, pickled and passivated
No. 2B Same as above with additional pass-through highly polished rollers
No. 2BA Bright annealed (BA or 2R) same as above then bright annealed under oxygen-free atmospheric conditions
No. 3 Coarse abrasive finish applied mechanically
No. 4 Brushed finish
No. 5 Satin finish
No. 6 Matte finish
No. 7 Reflective finish
No. 8 Mirror finish
No. 9 Bead blast finish
No. 10 heat colored finish-wide range of electropolished and heat colored surfaces