ASME B18.21.1 Type A Plain Washers — Inch Series, Narrow / Regular / Wide (0.072 – 4 in)
ASME B18.21.1 Type A plain washer dimensions for inch-series bolts — inside diameter, outside diameter and thickness with tolerances per nominal size in narrow, regular and wide series, from 0.072 in up to 4 in, transcribed row-for-row from the collected chart.
Last updated: 2026-11
Specifications
Type A is the common plain washer of the inch world: a flat annulus whose job is to distribute bolt load, bridge oversized or slotted holes, and give the nut a true bearing face. ASME B18.21.1 defines it, and the collected chart prints the three series that matter when ordering: narrow (N), regular (W in the source's series note) and wide — the same bolt size gets progressively more outside diameter as the series widens, buying bearing area at the cost of washer weight and clearance around the joint. Reading a row, a regular-series washer for a 1/2 in bolt: inside diameter limits 0.531/0.515 in, outside diameter 1.000/0.969 in, thickness 0.095/0.080 in — each carrying max/min because washers are stamped or machined and the limits are what a receiving inspection actually checks. The chart covers nominal sizes from 0.072 in through 4 in; note the source's two flagged footnotes carried on the table below: the series column values (which size gets narrow vs regular vs wide) and an anti-coin thickness note on the large sizes. Metric plain washers on this site follow ISO 7089 (see the ISO 7089 page in this catalog); hardness, finish and material are not tabulated by the collected chart — per RFQ.
| Standard | ASME B18.21.1 — lock and plain washers, inch series; Type A (plain), narrow / regular / wide series per size as printed |
|---|---|
| Size range | Nominal bolt sizes 0.072 – 4 in, 40 printed rows |
| Tabulated limits (in) | Per row: inside diameter max/min, outside diameter max/min, thickness max/min; example regular 1/2 in: ID 0.531/0.515, OD 1.000/0.969, thickness 0.095/0.080 |
| Series note | The source flags which series (narrow/regular/wide) applies per size group — carried as a table footnote; series choice is an ordering decision, state it at RFQ |
| Hardness / finish / material | Not tabulated by the collected chart — per RFQ (state material, hardness range and finish together) |
| Nominal Washer Size | Nominal Bolt Dia. (basic) | Series (N narrow / W wide) | A — Inside Dia. (basic) | A (plus) | A (minus) | B — Outside Dia. (basic) | B (plus) | B (minus) | C — Thickness (basic) | C (plus) | C (minus) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No.0 | - | - | 0.078 | 0.000 | 0.005 | 0.188 | 0.000 | 0.005 | 0.020 | 0.025 | 0.016 |
| No.2 | - | - | 0.094 | 0.000 | 0.005 | 0.250 | 0.000 | 0.005 | 0.020 | 0.025 | 0.016 |
| No.4 | - | - | 0.125 | 0.008 | 0.005 | 0.312 | 0.008 | 0.005 | 0.032 | 0.040 | 0.025 |
| No.6 | 0.138 | - | 0.156 | 0.008 | 0.005 | 0.375 | 0.015 | 0.005 | 0.049 | 0.065 | 0.036 |
| No.8 | 0.164 | - | 0.188 | 0.008 | 0.005 | 0.438 | 0.015 | 0.005 | 0.049 | 0.065 | 0.036 |
| No.10 | 0.190 | - | 0.219 | 0.008 | 0.005 | 0.500 | 0.015 | 0.005 | 0.049 | 0.065 | 0.036 |
| 3/16 | 0.188 | - | 0.250 | 0.015 | 0.005 | 0.562 | 0.015 | 0.005 | 0.049 | 0.065 | 0.036 |
| No.12 | 0.216 | - | 0.250 | 0.015 | 0.005 | 0.562 | 0.015 | 0.005 | 0.065 | 0.080 | 0.051 |
| 1/4 | 0.250 | N | 0.281 | 0.015 | 0.005 | 0.625 | 0.015 | 0.005 | 0.065 | 0.080 | 0.051 |
| 1/4 | 0.250 | W | 0.312 | 0.015 | 0.005 | 0.734 | 0.015 | 0.007 | 0.065 | 0.080 | 0.051 |
| 5/16 | 0.312 | N | 0.344 | 0.015 | 0.005 | 0.688 | 0.015 | 0.007 | 0.065 | 0.080 | 0.051 |
| 5/16 | 0.312 | W | 0.375 | 0.015 | 0.005 | 0.875 | 0.030 | 0.007 | 0.083 | 0.104 | 0.064 |
| 3/8 | 0.375 | N | 0.406 | 0.015 | 0.005 | 0.812 | 0.015 | 0.007 | 0.065 | 0.080 | 0.051 |
| 3/8 | 0.375 | W | 0.438 | 0.015 | 0.005 | 1.000 | 0.030 | 0.007 | 0.083 | 0.104 | 0.064 |
| 7/16 | 0.438 | N | 0.469 | 0.015 | 0.005 | 0.922 | 0.015 | 0.007 | 0.065 | 0.080 | 0.051 |
| 7/16 | 0.438 | W | 0.500 | 0.015 | 0.005 | 1.250 | 0.030 | 0.007 | 0.083 | 0.104 | 0.064 |
| 1/2 | 0.500 | N | 0.531 | 0.015 | 0.005 | 1.062 | 0.030 | 0.007 | 0.095 | 0.121 | 0.074 |
| 1/2 | 0.500 | W | 0.562 | 0.015 | 0.005 | 1.375 | 0.030 | 0.007 | 0.109 | 0.132 | 0.086 |
| 9/16 | 0.562 | N | 0.594 | 0.015 | 0.005 | 1.156 | 0.030 | 0.007 | 0.095 | 0.121 | 0.074 |
| 9/16 | 0.562 | W | 0.625 | 0.015 | 0.005 | 1.469 | 0.030 | 0.007 | 0.109 | 0.132 | 0.086 |
| 5/8 | 0.625 | N | 0.656 | 0.030 | 0.007 | 1.312 | 0.030 | 0.007 | 0.095 | 0.121 | 0.074 |
| 5/8 | 0.625 | W | 0.688 | 0.030 | 0.007 | 1.750 | 0.030 | 0.007 | 0.134 | 0.160 | 0.108 |
| 3/4 | 0.750 | N | 0.812 | 0.030 | 0.007 | 1.469 | 0.030 | 0.007 | 0.134 | 0.160 | 0.108 |
| 3/4 | 0.750 | W | 0.812 | 0.030 | 0.007 | 2.000 | 0.030 | 0.007 | 0.148 | 0.177 | 0.122 |
| 7/8 | 0.875 | N | 0.938 | 0.030 | 0.007 | 1.750 | 0.030 | 0.007 | 0.134 | 0.160 | 0.108 |
| 7/8 | 0.875 | W | 0.938 | 0.030 | 0.007 | 2.250 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 | 1.000 | N | 1.062 | 0.030 | 0.007 | 2.000 | 0.030 | 0.007 | 0.134 | 0.160 | 0.108 |
| 1 | 1.000 | W | 1.062 | 0.030 | 0.007 | 2.500 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 1/8 | 1.125 | N | 1.250 | 0.030 | 0.007 | 2.250 | 0.030 | 0.007 | 0.134 | 0.160 | 0.108 |
| 1 1/8 | 1.125 | W | 1.250 | 0.030 | 0.007 | 2.750 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 1/4 | 1.250 | N | 1.375 | 0.030 | 0.007 | 2.500 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 1/4 | 1.250 | W | 1.375 | 0.030 | 0.007 | 3.000 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 3/8 | 1.375 | N | 1.500 | 0.030 | 0.007 | 2.750 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 3/8 | 1.375 | W | 1.500 | 0.045 | 0.010 | 3.250 | 0.045 | 0.010 | 0.180 | 0.213 | 0.153 |
| 1 1/2 | 1.500 | N | 1.625 | 0.030 | 0.007 | 3.000 | 0.030 | 0.007 | 0.165 | 0.192 | 0.136 |
| 1 1/2 | 1.500 | W | 1.625 | 0.045 | 0.010 | 3.500 | 0.045 | 0.010 | 0.180 | 0.213 | 0.153 |
| 1 5/8 | 1.625 | - | 1.750 | 0.045 | 0.010 | 3.750 | 0.045 | 0.010 | 0.180 | 0.213 | 0.153 |
| 1 3/4 | 1.750 | - | 1.875 | 0.045 | 0.010 | 4.000 | 0.045 | 0.010 | 0.180 | 0.213 | 0.153 |
| 1 7/8 | 1.875 | - | 2.000 | 0.045 | 0.010 | 4.250 | 0.045 | 0.010 | 0.180 | 0.213 | 0.153 |
| 2 | 2.000 | - | 2.125 | 0.045 | 0.010 | 4.500 | 0.045 | 0.010 | 0.180 | 0.213 | 0.153 |
- Row 10 (1/4): Source prints the 5/8-step outside diameter as "0.734Note2" — the anti-coin OD of source Note 2 (0.734/1.156/1.469 in ODs avoid washers usable in coin-operated devices); the numeric value is tabulated as printed.
- Row 19 (9/16): Source prints the outside diameter as "1.156Note2" — anti-coin OD of source Note 2; numeric value tabulated as printed.
- Row 20 (9/16): Source prints the outside diameter as "1.469Note2" — anti-coin OD of source Note 2; numeric value tabulated as printed.
Materials
- Material and hardness specified per RFQ — plain washers are commonly low-carbon steel; through-hardened grades pair with high-strength bolts and are an RFQ line, not a chart lookup
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASME B18.21.1 Type A Plain Washers — Inch Series, Narrow / Regular / Wide (0.072 – 4 in)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Narrow, regular or wide — how do I pick the plain-washer series, and why do the dimensions carry max/min limits?
The series is a bearing-area decision. Regular is the default: its OD gives the standard load distribution under a hex or socket-fastener bearing face. Narrow exists where clearance or weight rules — tight enclosures, moving joints, or where the washer must not overhang the mating part. Wide buys spreading power for soft or thin base material (aluminum, plastics, sheet) where the limiting failure mode is the washer digging in rather than the bolt breaking — the extra OD also bridges oversized or damaged holes in repair work. Because the same bolt size takes all three, order the series explicitly; "just a washer for a 1/2 bolt" leaves the most consequential dimension undefined. The max/min limits are the receiving-inspection answer: stamped washers vary, and the chart's limits (e.g. regular 1/2 in ID 0.531/0.515 in) define what is acceptable at goods-in — a washer that measures outside them is a nonconformance regardless of how it fits by eye. For load-critical joints, thickness matters as much as diameter: an undersized-thickness washer loses its ability to resist rotation and embedment, which is why the source flags thickness limits explicitly on the large sizes.
What is the MOQ and lead time for washers on this standard?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common inch sizes are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support