Answering the common search for reliable 3/8″ flat washers, this article highlights five well-suited options covering stainless steel and alloy steel variants. These washers are best for DIY enthusiasts, homeowners handling permanent fixtures, automotive projects, and outdoor setups where corrosion resistance and load distribution matter. Each entry explains who it’s best for and why, plus practical cautions to consider.
Chosen products offer a mix of stainless steel (304) for corrosion resistance, and alloy steel with zinc plating for heavy-duty uses. Use this guide to compare inner/outer diameters, thickness, and material performance to select the best fit for your fastener needs. The quick-reference table below helps compare core specs at a glance.
| Product | Material | Inside Dia | Outside Dia | Thickness |
|---|---|---|---|---|
| 3/8″ Inch Stainless Flat Washers 100 Pack | 304 Stainless | 0.401–0.421 in | 0.805–0.827 in | 0.051–0.080 in |
| 3/8″ x 7/8″ Stainless Flat Washer, 50Pcs | 304 Stainless | 0.4 in | 0.866 in | 0.078 in |
| 100PCS 3/8” ID, 7/8″ OD, 304 Stainless | 304 Stainless | 0.75 in | 0.875 in | 0.051–0.080 in |
| 100 Pcs 3/8 Inch Grade 8 Alloy Steel | Alloy Steel, Yellow Zinc | ~0.375 in | ~0.831 in | Not specified |
| 3/8″ x 0.812″OD Stainless Flat Washer | 304 Stainless | Not specified | 0.812 in | Not specified |
3/8″ Inch Stainless Flat Washers 100 Pack
Material and size: 18-8 (304) stainless steel with inner diameter 0.401–0.421 inches, outer diameter 0.805–0.827 inches, thickness 0.051–0.080 inches. Best for: projects requiring excellent corrosion resistance and hygienic, durable washers. Why chosen: universal fit for standard 3/8 bolts with broad indoor/outdoor use. Caution: slight variation in inner/outer diameters within the tolerance range may affect fit in tight assemblies.
3/8″ x 7/8″ Stainless Flat Washer, 50Pcs
Material and size: 0.4 inch inner diameter, 0.866 inch outer diameter, 0.078 inch thick. Best for: outdoor and indoor uses where corrosion resistance and a larger bearing surface are needed. Why chosen: 304 stainless steel enhances corrosion resistance. Caution: fits 3/8 and M10 bolts; ensure compatibility with bolt shoulder dimensions.
100PCS 3/8” ID, 7/8″ OD, 304 Stainless
Material and size: Inside diameter 3/4″ (slightly smaller than 0.75″), outside diameter 7/8″, thickness 0.051″–0.080″. Best for: general electrical connections and various household, automotive, and industrial projects. Why chosen: 304 stainless steel provides improved corrosion resistance. Caution: note the inside diameter is specified as 3/4″ rather than exactly 0.75″ in all cases, so verify fit for precise bolt sizes.
100 Pcs 3/8 Inch Grade 8 Flat Washer
Material and size: 3/8 inch outer diameter with an inner diameter around 3/8 inch; yellow zinc plating provides extra rust and corrosion resistance. Best for: heavy-duty fastening in automotive and construction environments. Why chosen: suitable for indoor/outdoor applications requiring stable load distribution and enhanced durability. Caution: zinc plating may wear in extremely abrasive environments, and magnetic properties may be present for 304 stainless equivalents.
3/8″ x 0.812″OD Stainless Flat Washer
Material and size: 18-8 (304) stainless steel with 0.812″ OD. Best for: projects requiring precise outer diameter with a consistent flat washer profile. Why chosen: ASME B18.21.1 SAE Type A standard compliant. Caution: data shows limited specification for inner diameter; confirm compatibility with bolt size before purchase.
Buying Guide
What material should you choose?
- Stainless steel (304/18-8): Best for corrosion resistance, outdoor use, and environments with moisture or salts. Choose this for longevity and hygiene-sensitive applications.
- Alloy steel with yellow zinc plating: Best for heavy-duty, high-load applications where strength is critical and corrosion protection is needed in less harsh environments.
What inner and outer diameter matters most?
- Match the inner diameter to your bolt or screw size. A loose fit can fail under load, while a tight fit may prevent proper assembly.
- The outer diameter affects bearing surface area. A larger outer diameter distributes load more effectively but may not fit in tight enclosures.
When is thickness important?
- Thicker washers add stiffness and load distribution, reducing indentation. Thinner washers may be suitable for lightweight or delicate assemblies.
What about coating and aesthetics?
- Yellow zinc plating offers rust resistance and a distinct finish. Stainless washers provide consistent appearance and corrosion protection without plating.
Practical selection tips
- For outdoor projects and water exposure, prefer stainless steel 304 to minimize corrosion.
- For general hardware in dry indoor spaces, alloy steel with plating is often sufficient and cost-effective.
- Always confirm bolt compatibility (thread size, shoulder type) to prevent loosening or misfit.
Frequently Asked Questions
- What does 3/8″ refer to in washers?
Answer: It typically refers to the bolt size the washer is designed to fit, i.e., the inner diameter around 3/8 inch for many options. - Are stainless washers magnetic?
Answer: 304 stainless washers are generally non-magnetic or only weakly magnetic, depending on processing; magnetism varies by alloy and heat treatment. - Can I use washers for electrical applications?
Answer: Yes, many stainless washers are suitable for electrical connections, especially when corrosion resistance is needed. - Which washer is best for outdoor metal projects?
Answer: 304 stainless steel washers are preferred for outdoor use due to their corrosion resistance. - Do all washers fit standard 3/8 bolts?
Answer: Most do, but verify inner diameter tolerance and bolt dimensions for a precise fit. - Is thicker always better for washers?
Answer: Not necessarily; thickness should align with load demands and space constraints of the assembly.