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Thread: Extra holes in prop?

  1. #1
    skukum12's Avatar
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    Extra holes in prop?

    Excuse my ignorance, but what are the extra holes for? (frontside of prop only)
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    TurboBeaver's Avatar
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    Quote Originally Posted by skukum12 View Post
    Excuse my ignorance, but what are the extra holes for? (frontside of prop only)
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    Pin positioners for hub extension.......

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    Quote Originally Posted by TurboBeaver View Post
    Pin positioners for hub extension.......
    Interesting that they would be on the front of the prop, not the rear?

  4. #4
    skywagon8a's Avatar
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    That is a good question. What are the exact model numbers which are stamped on the hub? The answer should be in the propeller Type Certificate data sheet.

    Pin position holes are generally on the side where the extension spacer is mounted and closer in alignment with the other holes.

    Is this a special pusher prop? Those holes are in an unusual location. They are located in the least stressful location.
    N1PA
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    Balancing


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    skywagon8a's Avatar
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    Quote Originally Posted by dgapilot View Post
    Balancing
    I don't buy that theory in this case. Fixed pitch props are balanced by removing material or by screwing weights on the side. These two holes are the same on opposite sides of the hub.
    N1PA

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    Quote Originally Posted by skywagon8a View Post
    I don't buy that theory in this case. Fixed pitch props are balanced by removing material or by screwing weights on the side. These two holes are the same on opposite sides of the hub.
    But are they the same depth. Another possibility would be fixturing for the machining operations


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    skywagon8a's Avatar
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    Quote Originally Posted by dgapilot View Post
    But are they the same depth. Another possibility would be fixturing for the machining operations
    That is possible, but have you seen one drilled in a similar manner for that purpose? I have not.
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    Can’t say I’ve seen the fixturing, but I’ve seen several props with the extra holes.


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    These are the new props, I like the old ones without the needless ugly holes. These have been around for some time too, at least the last ten years. I was told for balance, but like one poster said, I agree, it’s hogwash. I guess you could fill the holes with bondo sand smooth then paint. Since after all they don’t even paint the middle part anymore. So you put a skull cap on and it’s f’ing ugly.
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    My Borer prop has the holes. I thought it was typical.


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  12. #12
    skywagon8a's Avatar
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    Quote Originally Posted by sjohnson View Post
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    My Borer prop has the holes. I thought it was typical.
    Is this a 1A175GM82-4X ? If so then perhaps they are tooling holes for some new CNC propeller making machinery? The new props are very precise.
    N1PA

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    Maybe indexing points for the actual drill?
    Remember, These are the Good old Days!

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    holes for mounting when they become wall clocks.
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    skukum12's Avatar
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    The prop in the picture I posted has balance weights attached already. If the extra holes are for machining, it sure is a shame they are on the front side.
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    BC12D-4-85's Avatar
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    Internet BS is Sensenich makes McCauley fixed pitch props. I've looked but can't confirm. Maybe truth or not? This could be new tech for machining that's better - like Catto and Whirlwind' complex shapes. Rumors of course.

    Gary

  17. #17
    skywagon8a's Avatar
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    Quote Originally Posted by skukum12 View Post
    The prop in the picture I posted has balance weights attached already. If the extra holes are for machining, it sure is a shame they are on the front side.
    Once more: What is your model number? go to: https://www.faa.gov/

    NOTE 2. Propeller Model Designation. The propeller model designation consists of a series of numbers suffixed to the basicdesign number to indicate propeller diameter and geometric pitch at the .75 radius. Basic Model Designation Suffix *1A170E/ DF 76 48 Inches pitch at .75 radius Propeller diameter in inches CFA denotes SAE No. 2 flange modified (six ˝” mounting bolts); 4” integral doweled spacer DF denotes SAE No. 3 flange; elliptical tips LM denotes SAE No. 3 flange; square tips L denotes SAE No. 3 flange with 2.188” diameter pilot; elliptical tips LL denotes SAE No. 3 flange with 2.188” diameter pilot; square tips GM denotes SAE No. 2 flange; square tips SFA denotes SAE No. 2 flange modified (six ˝”mounting bolts) SFC denotes special flange 4” B.C.; square tips FC denotes special flange 4” B.C.; square tips GMA denotes SAE No. 2 flange with 2” integral doweled spacer; square tips MFC denotes special flange 4” B.C.; square tips ATM denotes SAE No. 2 flange modified (six 7/16”mounting bolts); 3.5” integral doweled spacer; square tips EFA denotes SAE No. 2 flange modified (six 7/16”mounting bolts); 1.5” integral doweled spacer; square tips ETM denotes SAE No. 2 flange with 3.5” integral doweled spacer; square tips FFA denotes SAE No. 2 flange modified (six ˝”mounting bolts); 2.65” integral doweled spacer; square tips BMS denotes SAE No. 2 flange modified (six 7/16” mounting bolts); 1.375” integral doweled space; square tips TCD denotes TCM O200D flange Basic design number: “E” when present is a minor change letter that indicates elliptical tips and does not effect interchangeability or eligibility. * Some propellers of these models may have been marked with a hyphen following the basic design number in lieu of a diagonal line (i.e. 1A170-DF764
    N1PA

  18. #18
    Clyde Barker's Avatar
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    I purchased my McCauley 1A90CF7538 in 2007. It has the same holes. When I unpacked it and saw those ugly holes I called McCauley. The guy I talked to said it was for balancing.

    I also had to paint my hub.


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  19. #19
    skywagon8a's Avatar
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    Quote Originally Posted by Clyde Barker View Post
    I purchased my McCauley 1A90CF7538 in 2007. It has the same holes. When I unpacked it and saw those ugly holes I called McCauley. The guy I talked to said it was for balancing.
    Thank you, Direct from the horses mouth is the best answer. They must have changed some of their manufacturing processes. It does seem strange that two identical holes would be placed opposite to each other and then say it was for balancing. Maybe it is just a place to put some lead if needed?
    N1PA

  20. #20
    Clyde Barker's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Thank you, Direct from the horses mouth is the best answer. They must have changed some of their manufacturing processes. It does seem strange that two identical holes would be placed opposite to each other and then say it was for balancing. Maybe it is just a place to put some lead if needed?
    Yes, my understanding is that the holes are for future balancing after the prop leaves the factory. Not sure what material is used to add weight. Wouldn't be surprised it the EPA has banned lead for that purpose.
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  21. #21

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    Quote Originally Posted by Clyde Barker View Post
    Yes, my understanding is that the holes are for future balancing after the prop leaves the factory. Not sure what material is used to add weight. Wouldn't be surprised it the EPA has banned lead for that purpose.
    More than likely they would use Mallory.

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