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CNC machined prop shaft versus old style machine shop techniques

Discussion in 'Props, Shafts & Seals' started by dogsharks, May 18, 2007.

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  1. dogsharks

    dogsharks Guest

    Hi guys,
    I know it's sort of difficult to get excited about a new prop shaft, but when my new one was delivered the other day, I was pretty astounded at the quality of the work. The CNC robotic machine process can do things to a speed and precision that would take someone by hand a LONG time to do. Just look at this photo. I appreciate fine workmanship whether it is in a vintage automatic watch, a fine Colt pistol, automobiles, whatever, and this work here is just outstanding. Just take a look at that first photo! Have you EVER seen a prop shaft looking this good?? It came directly from the shop, shipped in a tube, fast turn-around, complete with lock nuts and keys. I thought the price was reasonable, especially considering the quality of workmanship.

    The second photo is what I would normally expect to see for a shaft this size. This one happens to be a 1" shaft. As you can see, the keyway slot in the old style shaft extends all the way through the threads, and the CNC machined shaft does not. The CNC product is going to be a LOT easier on those brass nuts, because the old style tends to cut and strip metal off the nuts as you might imagine from looking a these pics.

    The photo (Bottom) showing the hand work in the machine shop is from some 80" long 1-3/8" shafts I had made up last year. These were traditionally done by hand in a machine shop. Here the shaft is being trued for mating up to the hub, which is something you'll want to do BEFORE you are standing on your head in the boat bilge. In any case, the old style "by hand" process will still work, and work well, but the machined final product from a CNC machine is just positively awesome by comparison.

    If anyone is interested in seeing more photos of the CNC machined prop shaft, or more photos of the "by hand process" shown above, you can check the following link for more.

    Regards, Paul

    Attached Files:

  2. K1W1

    K1W1 Senior Member

    Sep 30, 2005
    My Office

    Unfortunately your pics are taken from different angles so it is difficult to compare apples for apples.

    The thread count at 13 visible on each indicates that they are the same size and pitch, the old one was drilled for a castleated nut and the new has two nuts with a pin to retain them not penetrating the nut.

    I would say that the keyway cut was done on the old one with an end mill and hazard a guess as I can't see the keyway that the CNC (Computer Numerically Controlled) one was done with a saw blade type tool- this could have been done by hand as well if the milling machine was set up accordingly.

    What surprises me is the second split pin hole in the old shaft, it would worry me if I couldn't get the nut back where it was on an existing prop. I would find out why and correct it before reaching for the drill motor. If a new prop was used the boss length could affect this but it's a lot easier to whip 0.050" off the face of the nut than drill a hole through an installed SS Shaft.

    CNC Machining is generally beneficial to the operator if more than one item the same is being made as someone has to sit and type the code to run the operation in the first place. There is no substitute to hand machineing and finishing if you are making something to fit an existing used component. Files,Emery Tape and lapping paste are the true jobbing machinists best friends.
  3. Hello Paul,

    Whow - i think those shafts are exactly what i need for a project which is on for september

    Cheers, Wilfried