How to Specify Custom-Made Washers: A Step-by-Step Engineering Guide

We have been manufacturing custom-made washers since 1919, and the single most common cause of quote delays, production errors, and cost overruns is an incomplete or incorrectly written specification. Engineers who need custom metal washers often submit drawings that over-specify non-critical dimensions, under-specify critical ones, or omit key information entirely, forcing back-and-forth communication that slows every step of the process.

Proper specification of custom-made washers requires balancing dimensional requirements, material properties, surface finish, and tolerance against manufacturing capabilities and budget realities. Too tight a tolerance on a non-critical dimension inflates cost without adding value to your assembly. Too loose a tolerance on a critical dimension causes assembly failures that cost far more to correct than the savings achieved by relaxing the specification.

At Brewster, our engineering team is available to assist with any step in the process, and we review every drawing before quoting to flag issues before they affect production. Readers will finish this guide equipped to write a clear, complete custom washer specification that generates accurate quotes and produces parts that work the first time.

Step 1: Define Your Geometry

Four geometry elements form the foundation of every custom-made washer specification:

1. Outer Diameter (OD): Specify the minimum OD required for adequate load distribution based on your bearing stress calculations, accounting for any space constraints in the assembly that limit the maximum diameter your design can accommodate
2. Inner Diameter (ID): Define the ID with appropriate clearance for your fastener shank, typically fastener nominal diameter plus .010″ to .030″ for a standard clearance fit that allows installation without binding
3. Thickness: Specify the exact decimal thickness required, not a gauge number, with an explicit tolerance such as .032″ plus or minus .001″, to ensure the washer functions correctly within your assembly stack-up
4. Special Features: Note any slots, multiple holes, non-circular profiles, or chamfers required, capturing these in the drawing rather than describing them verbally to prevent misinterpretation during manufacturing

Getting each of these four dimensions right before requesting a quote prevents costly revisions mid-production. We accept blueprints in any CAD format and in hand-drawn sketches with sufficient dimensional detail. Your custom precision parts inquiry starts the moment we receive your drawing.

Drawing Requirements for Custom Metal Washers

A complete custom metal washer drawing must include all critical dimensions with tolerances, a full material callout with grade designation, surface finish specification, and any special requirements such as heat treatment, plating, or passivation. Incomplete drawings are the single most common cause of quote delays and production errors in custom washer manufacturing. We ask clarifying questions rather than assuming, but a complete drawing eliminates that round-trip entirely and gets your quote back faster.

Geometric dimensioning and tolerancing (GD&T) adds value for complex custom metal washers by specifying flatness, parallelism, and concentricity requirements beyond standard dimensional tolerances. Standard plus or minus .005″ dimensional tolerances are adequate for simple flat washers in non-critical applications, but precision assemblies need explicit geometric controls to ensure proper function.

Customers on controlled programs should notify us of any ITAR restrictions on their technical data before submitting drawings, so we can apply appropriate data handling protocols from the first contact. Our quality and compliance systems are built to handle sensitive program data correctly.

Step 2: Select Your Material

Material selection for custom-made washers requires matching material properties to the operating environment, mechanical loads, and any regulatory or certification requirements that govern your application. The primary questions every engineer must answer before selecting a material are: What temperature range will the washer experience? Is corrosion a concern, and from what specific agents? Are there weight, conductivity, magnetic permeability, or biocompatibility requirements? The answers narrow the material choice quickly and prevent costly substitutions downstream.

The material landscape for custom metal washers covers most engineering needs across a small number of categories. Stainless steel covers most corrosion-resistant structural applications with grades from 304 through 316L, depending on chloride exposure. Aluminum handles weight-sensitive assemblies in aerospace and automotive applications. Brass and copper address conductivity and sealing needs. Titanium and Inconel are used in extreme-temperature or weight-critical aerospace applications where commodity metals fall short.

Always specify the full material designation rather than a generic category. Calling out “304 stainless” rather than “stainless steel,” “6061-T6 aluminum” rather than “aluminum,” and “Grade 5 titanium” rather than “titanium” ensures the correct mechanical properties and enables material traceability from mill to finished part. Vague material callouts lead to substitutions that may not meet your performance requirements, and our material listing covers all common and exotic options available for custom metal washer production.

Step 3: Specify Tolerances Correctly

Tolerance over-specification is one of the most expensive mistakes in custom-made washer procurement, adding 20 to 40 percent to unit cost for every tolerance tightened by half without improving function. Specify only what your assembly genuinely requires:

• Thickness Tolerance: For precision custom-made washers, specify plus or minus .0005″ to .001″; for non-critical applications, plus or minus .005″ is acceptable and reduces cost significantly by allowing standard material thickness variation from the mill
• Diameter Tolerances: Inner diameter typically requires plus or minus .001″ to .002″ for proper fastener fit without binding; outer diameter plus or minus .005″ is standard, tightening to plus or minus .002″ only when the bearing area calculation is critical to your stress analysis
• Flatness: Specify flatness of .001″ to .002″ total indicator reading for precision shim or alignment applications where bow affects system performance; omit the flatness callout entirely for structural washers where slight bow is acceptable
• Surface Finish: 32 RMS or better for most aerospace and precision applications; 63 RMS is acceptable for general structural use; always specify if a particular finish is required for sealing surfaces or friction-dependent clamping applications

Our engineering team reviews tolerance callouts during quoting and will flag any that appear unnecessarily tight for the stated application.

Drawing Checklist for Custom Metal Washers

Before submitting any custom-made washer drawing for a quote, confirm the following are present and complete on your document:

• All critical dimensions are specified in decimal inches, not gauge numbers, with explicit bilateral tolerances on every feature that affects form, fit, or function in the assembly
• The material callout includes the full alloy designation with AMS or ASTM specification number, temper condition, and any special requirements such as DFARS compliance or country of origin restriction
• Surface finish is specified numerically in RMS or Ra units for all surfaces that affect sealing, friction, or fatigue life, with a general note covering non-critical surfaces
• Any special processing requirements, including heat treatment, passivation, anodizing, plating, or dry film lubrication, are called out with applicable specification numbers rather than described in general terms

Step 4: Determine Quantity and Lead Time Needs

Quantity affects pricing, lead time, and minimum order feasibility for custom-made washers in ways that differ significantly from standard catalog products. Brewster accepts orders of any quantity, from a single prototype to large production runs, with no minimum or maximum order requirements. Prototype quantities allow you to validate your design before committing to production volumes, and tooling created for your first order is stored at no charge for future repeat orders.

Lead time planning for custom metal washers requires accounting for material procurement, tooling creation or retrieval, production scheduling, inspection, and documentation preparation. First-time orders depend on material availability and production schedule.

Rush orders are available for critical situations where production lines are down or program milestones are at risk. Communicating your true hard deadline during the quoting phase, not just a preferred delivery date, allows us to schedule your custom-made washer order correctly from the start.

Step 5: Define Documentation Requirements

Every custom metal washer order should specify the complete documentation package required upon delivery, listed explicitly on the purchase order rather than communicated after the fact. Standard documentation from us includes a Certificate of Conformance, material test reports, and dimensional inspection reports covering all critical features. Aerospace and defense customers often require first-article inspection reports per AS9102, DFARS compliance statements, specific quality plan references, and heat- or lot-traceability linking the finished part to the original mill material.

Listing required documents explicitly on your purchase order eliminates ambiguity at receiving inspection and prevents delays when your quality team reviews incoming material. A purchase order note reading “Required: CofC, MTR, FAI per AS9102, DFARS compliance” takes thirty seconds to write and saves days of back-and-forth after delivery. Our quality team prepares all standard documentation as part of normal production; nothing in our standard package requires a special request or additional lead time.

Get Expert Help Specifying Your Custom-Made Washers

At Brewster, we have manufactured custom-made washers and custom metal washers for over 100 years across aerospace, medical, defense, automotive, and industrial applications, and our engineering team has seen every specification mistake there is to make. We review your drawings and specifications before quoting, flagging issues that would affect production, performance, or cost before they become problems. Contact us today to learn more about how we can help you with your custom-made washers.