For parallel keys in Grade 8.8 Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for Grade 8.8 Steel (class 8.8) is summarized below together with every size supplied.
Why Choose Grade 8.8 Steel for Parallel Keys
The workhorse medium-carbon alloy grade for structural joints. For parallel keys, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating (zinc) for corrosion protection |
Corrosion Behavior in Service
Carbon and alloy steel parallel keys require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Galvanic & Galling Considerations
For parallel keys in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.
Sizes of Parallel Keys Available in Grade 8.8 Steel
| Shaft diameter range (mm) | Key width b (mm) | Key height h (mm) | Key length range (mm) | Shaft groove depth t1 (mm) | Hub groove depth t2 (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| 6~8 | 2 | 2 | 6~20 | 1.2 | 1.0 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 8~10 | 3 | 3 | 6~36 | 1.8 | 1.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 10~12 | 4 | 4 | 8~45 | 2.5 | 1.8 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 12~17 | 5 | 5 | 10~56 | 3.0 | 2.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 17~22 | 6 | 6 | 14~70 | 3.5 | 2.8 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 22~30 | 8 | 7 | 18~90 | 4.0 | 3.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 30~38 | 10 | 8 | 22~110 | 5.0 | 3.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 38~44 | 12 | 8 | 28~140 | 5.0 | 3.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 44~50 | 14 | 9 | 36~160 | 5.5 | 3.8 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 50~58 | 16 | 10 | 45~180 | 6.0 | 4.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 58~65 | 18 | 11 | 50~200 | 7.0 | 4.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 65~75 | 20 | 12 | 56~220 | 7.5 | 4.9 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 75~85 | 22 | 14 | 63~250 | 9.0 | 5.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 85~95 | 25 | 14 | 70~280 | 9.0 | 5.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 95~110 | 28 | 16 | 80~320 | 10.0 | 6.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 110~130 | 32 | 18 | 90~360 | 11.0 | 7.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 130~150 | 36 | 20 | 100~400 | 12.0 | 8.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 150~170 | 40 | 22 | 100~400 | 13.0 | 9.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 170~200 | 45 | 25 | 110~450 | 15.0 | 10.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 200~230 | 50 | 28 | 125~500 | 17.0 | 11.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 230~260 | 56 | 32 | 140~500 | 20.0 | 12.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 260~290 | 63 | 32 | 160~500 | 20.0 | 12.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 290~330 | 70 | 36 | 180~500 | 22.0 | 14.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 330~380 | 80 | 40 | 200~500 | 25.0 | 15.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 380~440 | 90 | 45 | 220~500 | 28.0 | 17.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |
| 440~500 | 100 | 50 | 250~500 | 31.0 | 19.5 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square |