• 9.15.1.1Keys for propeller shafting shall be of the round ended or sled-runner type (see Figure 6 and Figure 7) and shall be of material compatible with the shaft to which they are to be fitted. The bottom of the keyway in the boss and shaft shall be parallel to the taper cone of the shaft.
• 9.15.1.2Keys of the sled-runner type shall incorporate means to prevent the key from sliding in the keyway.
• 9.15.1.3Sled, runner keys shall have 2 screwed pins for securing the key in the keyway, and the forward pin should be at least one-third of the length of the key from the large end of the taper. The depth of the countersink for the screwed pins should not exceed the pin diameter, and the edges of the hole should be slightly bevelled.

• 9.15.2.1The distance between the large end of the taper and the commencement of the keyway shall not be less than 0.2 times the required diameter of the shaft. A keyway for a round ended key shall be contained wholly within the length of the taper. A keyway for a sled-runner key may run through the small end of the taper provided the keyway remains clear of both the propeller or taper flange coupling nut thread and the groove or radius at the transition between the thread and taper.
• 9.15.2.2The depth of the keyway shall be 0.5 times the required thickness of the key (see subparagraph 9.15.6). The keyway shall have smooth fillets at the bottom. Any sharp edges at the top shall be removed. The radius of the fillet shall be at least 0.0125 times the fitted diameter of the shaft.

Figure 6 — Round-ended key and keyway (diagram shows arrangement suitable for a shaft of high-tensile material)

Figure 7 — Sled-runner key and keyway

The inward end of the keyway in shafts of high-tensile material shall be “relieved”. On round-ended keyways the relieving shall be chamfered to an angle of 45° from side to side to a depth at least 0.7 times the keyway depth. The edges so formed shall be rounded. Refer to Figure 6.

The calculated key width shall be determined in accordance with the following formula—

w = d4

Where—

• w = calculated width of key, in millimetres
• d = required diameter of propeller shaft or intermediate shaft (calculated in accordance with subparagraph 9.14.3, and 9.14.4 or 9.14.5 respectively), in millimetres.

The calculated key length shall be determined in accordance with the following formula—

l= l. 6 d

Where—

• l = calculated length of the key, in millimetres
• d = required diameter of the propeller shaft or intermediate shaft (calculated in accordance with subparagraph 9.14.3, and 9.14.4 or 9.14.5 respectively), in millimetres

The thickness of a key shall be determined in accordance with the following formula—

• (a)For shafts less than 150mm diameter—

  t=0.633w+0.94

• (b)For shafts of 150mm diameter and over—

Where—

• t = required thickness of key, in millimetres
• w = width of key, in millimetres, calculated in accordance with subparagraph 9.15.4

The Actual width and length of a key shall comply with the following—

• (a)The Actual key width w _a shall be within 15% of the calculated key width w, and

Where—

• l _a = Actual length of the key, in millimetres;
• w _a = Actual width of key in millimetres;
• d = required diameter of the propeller shaft or intermediate shaft (calculated in accordance with subparagraph 9.14.3, and 9.14.4 or 9.14.5 respectively), in millimetres;
• UTS _key = ultimate tensile strength of the key material, in megapascals (MPa); amd
• UTS _shaft = ultimate tensile strength of the shaft material, in megapascals (MPa).

NOTE:

The key material should have a UTS similar to that of the shaft material.