TPD 1399E Chapter 2
Page 5
Propeller shaft couplings
Flanged shaft couplings can be supplied with any
gearbox. The couplings are pilot bored and must be
machined to suit the propeller shaft, and provision
must be made to take thrust, both ahead and astern.
The following machining procedure is recommended.
1. Machine the propeller shaft end to reduce the
diameter by about 2mm, over a length to suit the
coupling, as shown on (A1). Machine keyway slot
in shaft (A2).
2. Bore the coupling to give a transitional t on the
shaft end and broach to suit the key.
3. Assemble the coupling and shaft with the key,
ensuring that the shaft is pushed fully home (B1).
4. Drill a hole (1/4” diameter) so that it extends at
full diameter for not more than 2mm into the shaft
(measured on the shaft diameter) (B2).
5. Remove shaft, then open up the hole in the coupling
to 5/16” or 8mm, and tap 3/8” UNC. Clean up the
bore of the coupling as necessary.
6. Reassemble the shaft to the coupling. Fit the half
dog 3/8” UNC grubscrew (C1) (supplied with the
coupling). The grubscrew locks the coupling to the
shaft and will accept astern thrust (C).
Alternative methods of providing for astern thrust (in
place of the grubscrew) include:-
• Drilling right through the coupling hub and shaft
(close to the ange) and tting double roll pins (one
inside the other).
• Using a washer secured by a bolt threaded into
the shaft end. The coupling will require machining
to accomodate these components, and the shaft
engagement within the coupling will require
adjustment.
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