As a leader in the offering of Stainless Steel No. 4 polish/30 Ra Inch Maximum, we’ve been the premier source for quality stainless steel plate finishes in North America since 1976. We’ve pioneered many of the protocols and practices that have become today’s recognized industry standards. We provide uncompromising polish processing to fabricators, service centers, and mills, skillfully meeting the most exacting requirements. Our long-standing field expertise, coupled with an exceptionally high customer satisfaction rate, makes us best of brand stainless steel no. 4 polish finishers you can trust.


About Stainless Steel No. 4 polish / 30 Ra Micro Inch

Often referred to as the ‘workhorse finish,’ Stainless Steel No. 4 polish is one of the most common finishes suitable for architectural and processing vessels. Consistent satin grain appearance satisfies strict sanitary requirements and is easily blendable. This worry-free finish is universally acceptable for process equipment systems and tanking wet surfaces as well as meeting high visual aesthetic requirements. Available in many options and customizations, stainless steel No. 4 polish is a versatile and high-quality finish for multiple applications.

  • Suitable for architectural or process applications
  • Refined, consistent satin grain appearance
  • Universally accepted for process equipment systems and tanking wet surfaces
  • Available with many customization options for a variety of applications including pit-free BPE & Dairy
  • 30 Micro Inch Maximum


Even though a No. 4 finish is the most commonly requested of all polished finishes, there is nothing common about the importance of quality, precision, and exactitude. Not all No. 4 finishes, or those that provide them, are equal. Too often, the mediocrity of finish quality is what’s common, while perfectly met expectations by the polish provider are not. Stainless Steel Services’ 45 years of unceasing obsession with perfect, repeatable No. 4 finishes has been our hallmark. Great, predictable finishes meeting and exceeding customer specifications cost no more – you just have to partner with those who take your business as seriously as you do.


Stainless Steel No. 4 Polish Applications/ 30 Ra Micro Inch

Most commonly used for architectural and processing vessels and equipment, our Stainless Steel No. 4 polish also meets and exceeds 3-A Sanitary requirements.

The following is a sampling of industry applications of Stainless Steel No. 4 polish:

  • Aerospace
  • Interior and exterior architecture
  • Chemical
  • Cosmetics
  • Fossil and solar energy
  • Food/dairy/beverage
  • Microchip manufacturing
  • Nuclear energy
  • Water treatment
  • Vacuum Chambers

Are you looking for stainless steel no. 4 polish for a different application? As polishers for industry and architecture since 1976, we can help. Reach out to our finishing team to learn more.


Stainless Steel No. 4 Finishing Materials

Whether using stainless steel no. 4 or another polish, we have the expertise to finish a variety of stainless steel& stainless alloy materials. Whether you provide the material, or we provide it for you, the following is a sampling of the materials you can trust us to finish skillfully with excellence and integrity:

  • Stainless Steel; ie 304/L, 316/L ,309/L ; All 300 & 400 Series
  • Stainless Steel duplex alloys; i.e. C2726, 2205, AL6XNK, INVAR 35, LDX2101
  • Stainless Steel clad; carbon backer on any of the above cladding
  • Inconel
  • Hastelloy
  • All Nickel Alloys

If you need to finish a material not listed here, please contact us to learn more about the materials we can finish with stainless steel no. 4 or another polish.


Our Stainless Steel No. 4 polish capabilities

Our Stainless Steel no. 4 polish capabilities include the ability to polish any size plate or sheet and finish on one or both sides. It meets 3-A Dairy and Sanitary application requirements and is 30 RA maximum in any spot taken without averaging. As with all our finishes, our Stainless Steel no. 4 polish includes 100% removal of the HRAP surface scale revealing clean parent metal. If your job requires 100% pit-free, please let us know and we are happy to quote

  • Finish available using any size plate or sheet on one or both sides
  • Meets 3-A Dairy and Sanitary standards
  • #4/ 30 Ra max. in any spot, never averaged
  • Flat-rolled polishing capabilities available for thicknesses from 14 gauge up to 10”, dimensions up to 14’ wide and 46’ long, and finishing on one or both sides
  • Includes 100% removal of HRAP surface sale, but is not 100% pit-free unless specifically requested

Stainless Steel No. 4 finish custom options

Depending on your application, consider the following additional Stainless Steel No. 4 polish finishing options:

  • Guaranteed sanitary/pit and crevice-free polishing available in any size, thickness, or Ra to BPE or Dairy options.
  • Surface prep refinement for non-destructive testing
  • Customized ground-to-gauge processing
  • Surface prep clean-up using judicious stock removal method
  • Irregular and pre-machined shape capacity, including shapes, diameters, and half-diameters up to 14 feet
  • Fabrication “kit” with ready-to-build polished materials, including pre-beveled edges and pre-drilled and pre-perforated holes.
  • Shape and Part Master Plate Nesting Program maximizes material yield by effortlessly nesting parts into larger plates or sheets and includes finish application and protection for laser or water jet cutting after polishing

Do you have a stainless steel no. 4 polish application request not listed on this page? Reach out to our sales team and tell us about it. As highly-skilled stainless steel finishers with a deep fabrication history, we routinely develop breakthrough techniques and achieve new standards of excellence to satisfy the ever-changing polishing needs for architecture and industry. Whether your company is large or small, or your project is common or complex, our team goes above and beyond to meet even the most exacting polish requirements. Expect us to exceed your expectations every time.


Packaging and protection options

Whether you choose Stainless Steel No. 4 polish or another finish, we offer several standard and optional packaging and protection options to protect the integrity of your finished materials that are always included in our pricing.

Standard packaging and protection options:

  • 5 mil laser PVC film
  • Fluted cardboard interleaving
  • Re-skidded with caution corner protection& multiple banding.

Optional packaging and protection options available upon request or as needed:

  • New skidding and or crating
  • Van/common carrier durable, high-impact “Bomb Proof” packaging

How Stainless Steel No. 4 polish works

The secret to Stainless Steel No. 4 polish starts with carefully chosen abrasive belts that feature refined grains of refractory material, such as silica, alumina, or zirconia. These refractory materials are embedded in an adhesive layer on a flexible cloth or paper backing.

Our expert stainless steel finishers begin the finishing process by applying the abrasive belts to the material as individual sheets. Then the abrasive belt is applied w/ consistent speed and pressure over the entire exposed surface. A predetermined and prescribed sequence of abrasive belt pressures and speeds is then executed resulting in a highly consistent final surface finish and appearance. Our time-proven expertise includes mid-process adjustments that take into account the high variation in raw stainless steel surfaces and result in a monolithic, consistent final finish from plate to plate. Finally, the stainless steel no. 4 polishing process is complete and inspected for quantitative and qualitative compliance to the highest standard.


Our guarantee

If you’re new to us, we’d like to introduce you to a refreshing customer-first philosophy that drives our day-to-day operations and defines the essence of our company culture.

We guarantee that:

“If our work is found to not meet the agreed-upon customer’s specifications, we promise to repolish, replace, or refund, including freight costs, to the customer’s satisfaction.”

As a long-standing stainless steel finishing company for industry and architecture, we believe in quality, value, trust, and integrity. We hold ourselves accountable and stand behind our work – guaranteed.


Our criteria for a properly polished plate

Whether applying a Stainless Steel No. 4 polish or another finish, we use the following criteria to ensure a properly polished plate:

  • Uniform surface roughness that doesn’t exceed the specified maximum Ra – When it comes to #4/30 Ra maximum, you may take multiple readings at any spot on the plate, and be confident that each reading will be under 30 Ra. We never average RA readings because it invites an unnecessary quality assurance debate. You can rest assured that under the protective film, our surface roughness will be uniform and will never exceed expectations upon final inspections
  • Judicious removal of stock – To retain as much of the original thickness as possible, we only remove enough material to attain a cleanly ground surface allowing us to transition from the grind phase to the final finish. We are keeping aware that excessive polish removal becomes problematic and possibly rejectable during fabrication if the plate thickness does not meet engineering structural integrity requirements.
  • Attention to aesthetics – Whether it’s stainless steel no. 4 polish or another finish, the final finish must look just as good as it functions. This means that both specifications such as Ra & final thickness are met equally with a finished appearance that is uniform, attractive & professional. Our attention to finish aesthetics help the end-user attain higher value and overall satisfaction in the final finished product, hence improving the products perceived value

10 Reasons to choose us for Stainless Steel no. 4 polish

As former fabricators, we bring our superior field expertise to every stainless steel no. 4 polish job. Unlike other companies without fabrication backgrounds, our history supports a deep understanding of how the stainless steel will be used, constructed, and deployed downstream. By not operating in a “polisher’s vacuum”, you can be confident that your Stainless Steel no. 4 polish job is in the caring hands of capable professionals.

The following are 10 more reasons to work with us:

  1. We guarantee not to exceed the agreed-upon maximum RA required in any polished spot
  2. We take full responsibility for what we do and support our customer in doing so
  3. We have deep field expertise and knowledge
  4. By reliable, dependable, and honest. Integrity is paramount and is exhibited in our performance
  5. We guarantee customer satisfaction as we assure a partnership in every job
  6. We are a family-owned company with four generations of steel industry expertise
  7. We’ve pioneered many of the stainless steel finishing industry standards, protocols, and techniques
  8. We never cut corners or sacrifice quality in the name of profitability
  9. We deliver on time and on budget with specific, predictable ship dates, that are openly communicated to the customer throughout the job
  10. We believe in transparency and genuinely open communication; by creating expectations and fulfilling them so you’ll always know what we promise and when we will deliver

How to order stainless steel no. 4 polish finishing

It’s easy to order material finished with stainless steel no. 4 polish from us

Simply let us know:

  1. If you will provide the material or if you’d like us to provide it for you
  2. The ultimate use or function of the finished plate or sheet
  3. The surface roughness, best expressed in Ra scale; however, we are able to interpret most specification requests regardless of how they are stated
  4. Item type, quantity, thickness, length, one or both sides polish

Contact us for stainless steel no. 4 polish today

Founded in 1976, we are Industry leading stainless steel finishers for industry and architecture you can trust to deliver quality and value with integrity – every time. Our mission is to be the premier source for stainless steel polishing throughout North America. We’re succeeding, in part, thanks to our extraordinary team of expert skilled craftsmen who continually go above and beyond to meet and exceed customer expectations, every time.

We invite you to begin experiencing stainless steel finishing in an entirely new way – one that places value on quality, value, trust, and integrity. Contact us to learn more about our stainless steel no. 4 polish and other finishing capabilities or download a Request for Quote form to get started.