Optimas Parts Imperial Blog Series: Technical Insight Into Hardened and Unhardened Flat Washers
Optimas designed the Parts Imperial Blog Series to provide detailed information about the fasteners you use and the ones you may need. Curated to help you find the right parts, these technical releases supply information on components’ specifications, applications and standards. This Imperial Series is comprised of five types of components: flat washers, hex cap screws, locknuts, machine screws and tapping screws. Once you have determined the parts suited for your application, Optimas can source them through manufacturing and distribution, ensuring you get the parts you need.
Hardened Flat Washers
Hardened flat washers are designed for assembly with a Grade 5 or higher strength bolt between the bearing surface of the fastener and the part to which it is attached. They are made of carbon steel and may either be thru-hardened to Rc 38-45 or carburized (case hardened) to a minimum depth of .015” and have a surface hardness of 37-45 Rc with a minimum core hardness of Rc 30.
Unhardened Flat Washers
Unhardened flat washers are designed for assembly with Grade 2 or lower strength bolts or tapping screws between the bearing surface of the fastener and the part to which it is attached. Narrow (SAE) and wide (USS) flat washers are available for specification—depending on the preferred outside diameter needed.
Hardened and Unhardened Flat Washers Are Used To:
- Improve stress distribution on the mating surface
- Span larger clearance holes
- Protect the mating surface from damage during assembly
- Provide a consistent bearing surface between the mating surfaces for torquing
Dimensional characteristics are covered by ANSI B18.22.1* and mechanical properties are covered by ASTM F844.
Top and side views of a hardened or unhardened flat washer with the dimensional attributes listed in the charts below.
Hardened Flat Washers Specification Chart
NOMINAL SIZE** (BOLT SIZE) |
A INSIDE DIAMETER |
B OUTSIDE DIAMTER |
C THICKNESS |
|||||
---|---|---|---|---|---|---|---|---|
NOM | MIN | MAX | NOM | MIN | MAX | MIN | MAX | |
1/4 (.250) | 9/32 | .281 | .312 | 5/8 | .594 | .656 | .051 | .080 |
5/16 (.312) | 11/32 | .344 | .375 | 11/16 | .657 | .719 | .051 | .080 |
3/8 (.375) | 13/32 | .406 | .437 | 13/16 | .781 | .843 | .051 | .080 |
7/16 (.438) | 15/32 | .469 | .500 | 59/64 | .891 | .953 | .051 | .080 |
1/2 (.500) | 17/32 | .531 | .562 | 1-1/16 | 1.032 | 1.094 | .097 | .177 |
5/8 (.625) | 11/16 | .688 | .719 | 1-5/16 | 1.281 | 1.343 | .122 | .177 |
3/4 (.750) | 13/16 | .812 | .843 | 1-15/32 | 1.438 | 1.500 | .122 | .177 |
7/8 (.875) | 15/16 | .937 | .968 | 1-3/4 | 1.719 | 1.781 | .136 | .177 |
1 (1.000) | 1-1/8 | 1.125 | 1.156 | 2 | 1.969 | 2.031 | .136 | .177 |
*Sizes indicated in this chart are generally available.
**These are common dimensions in inches.
Unhardened Flat Washers Specification Chart
NOMINAL SIZE** (BOLT SIZE) |
SERIES | A INSIDE DIAMETER |
B OUTSIDE DIAMTER |
C THICKNESS |
||||||
---|---|---|---|---|---|---|---|---|---|---|
NOM | MIN | MAX | NOM | MIN | MAX | NOM | MIN | MAX | ||
#10 (.190) | Narrow | 7/32 | .214 | .227 | 1/2 | .495 | .515 | 3/64 | .036 | .065 |
Wide | 7/32 | .214 | .227 | 1/2 | .495 | .515 | 3/64 | .036 | .065 | |
#12 (.216) | Narrow | 1/4 | .245 | .265 | 9/16 | .557 | .577 | 1/16 | .051 | .080 |
Wide | 1/4 | .245 | .265 | 9/16 | .557 | .577 | 1/16 | .051 | .080 | |
1/4 (.250) | Narrow | 9/32 | .276 | .296 | 5/8 | .620 | .640 | 1/16 | .051 | .080 |
Wide | 5/16 | .307 | .327 | 3/4 | .727 | .749 | 1/16 | .051 | .080 | |
5/16 (.312) | Narrow | 11/32 | .339 | .359 | 11/16 | .681 | .703 | 1/16 | .051 | .080 |
Wide | 3/8 | .370 | .390 | 7/8 | .868 | .905 | 5/64 | .064 | .104 | |
3/8 (.375) | Narrow | 13/32 | .401 | .419 | 13/16 | .805 | .827 | 1/16 | .051 | .080 |
Wide | 7/16 | .433 | .453 | 1 | .993 | 1.030 | 5/64 | .064 | .104 | |
7/16 (.438) | Narrow | 15/32 | .464 | .484 | 59/64 | .915 | .937 | 1/16 | .051 | .080 |
Wide | 1/2 | .495 | .515 | 1-1/4 | 1.243 | 1.280 | 5/64 | .064 | .104 | |
1/2 (.500) | Narrow | 17/32 | .526 | .546 | 1-1/16 | 1.055 | 1.092 | 3/32 | .074 | .121 |
Wide | 9/16 | .557 | .577 | 1-3/8 | 1.368 | 1.405 | 7/64 | .086 | .132 | |
5/8 (.625) | Narrow | 21/32 | .649 | .686 | 1-5/16 | 1.305 | 1.342 | 3/32 | .074 | .121 |
Wide | 11/16 | .681 | .718 | 1-3/4 | 1.743 | 1.780 | 9/64 | .108 | .160 | |
3/4 (.750) | Narrow | 13/16 | .805 | .842 | 1-1/2 | 1.462 | 1.499 | 9/64 | .108 | .160 |
Wide | 13/16 | .805 | .842 | 2 | 1.993 | 2.030 | 5/32 | .122 | .177 | |
7/8 (.875) | Narrow | 15/16 | .931 | .968 | 1-3/4 | 1.743 | 1.780 | 9/64 | .108 | .160 |
Wide | 15/16 | .931 | .968 | 2-1/4 | 2.243 | 2.280 | 11/64 | .136 | .192 | |
1 (1.00) | Narrow | 1-1/16 | 1.055 | 1.092 | 2 | 1.993 | 2.030 | 9/64 | .108 | .160 |
Wide | 1-1/16 | 1.055 | 1.092 | 2-1/2 | 2.493 | 2.530 | 11/64 | .136 | .192 |
*Common dimensions of unhardened steel washers are given in inches.
Get a Technical Consult
For more information on hardened and unhardened flat washers or any type of fastener, contact one of our experts at optimas.com/contact.