Control Cavity Question

Discussion in 'Luthier's Corner' started by Flynman, Sep 10, 2017.

  1. Flynman

    Flynman Senior Member

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    I was watching Freddy's Youtube video and i finally got around to making the control cavity floor routing jig that he uses. Previously i was just angling the Pot holes and then using a thin medium soft rubber washer to get the pot tilted in the right direction. It has worked well so far but i figure i will try using the angle jig. My question is: The jig is angled 8 degrees and the route is cut slightly smaller than the cavity route in the body. From the left (outer} edge of the jig to the right side of the jig it looks like the router bit will drop about 3/8 inch. It seems like that is a little steep and i am afraid it will cut too deep into the maple. I left 1/8 inch of mahogany thickness over the maple. Does that 3/8 inch slant seem to be too much??

    Thanks,
    Keith R JoeA2.jpg JoeA3.jpg JoeA2.jpg JoeA3.jpg
     
  2. pshupe

    pshupe Senior Member

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    The angle directly relates to the carve of the top. It should be about 8 degrees, slightly more. Place your jig on the top and see if it creates a flat surface. Conversely place it on the back and see if the top then is parallel.

    Cheers Peter.
     
  3. nuance97

    nuance97 Premium Member

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    Looks right to me
     
  4. Flynman

    Flynman Senior Member

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    The angle seems right. Was just wondering if the 3/8 inch drop from one side of the pocket to the other was too much?
     
  5. pshupe

    pshupe Senior Member

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    If you still have mahogany showing you haven't gone deep enough. As long as your carve is a typical 5/8" - 3/16" over the 7 carve steps. You should be a bit deeper than 3/8", pretty much another full 1/16", actually. If you have already cut the cavity. Measure the thickness at the pot holes and see where you are. A little less than 1/4" works well for most short shaft pots.

    Cheers Peter.
     
  6. nuance97

    nuance97 Premium Member

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    I shoot for a paper thin whisper of mahogany before the secondary angle route. As far as the 3/8" depth-the angled portion only extends approximately 2/3 across the full width of the cavity...at an angle, but not across the whole width so it's a bit deceiving. If your angles are correct and your template is approximately 15* of the centerline of the body and approximately 8* elevated then it should be flawless.
     
  7. ARandall

    ARandall Senior Member

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    If the pic you have posted is your control cavity....why on earth don't you have the pot holes drilled already??

    As the positioning of them is best done with a flat maple top, and the best chance of eliminating tearout is drilling into flat wood I can't see any need for you to not do this step the instant your maple top is glued on - certainly before you go any further. Do the switch hole too. If indeed you drillbit is a little blunt or cheap, any tearing on backside or in the maple will get eliminated by the wood removed in the carve or the subsequent rear wood removal.

    Then the carve gets done.

    The whole idea of the angled rout in the cavity is to make a consistent thickness for the pot shaft to the carve surface. I cannot see why you would not complete the one step that would eliminate the guesswork in knowing how deep your rout has to be. The pots sitting on an angle is simply a byproduct of this.
     
  8. cmjohnson

    cmjohnson Senior Member

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    If you're really concerned about it, drill the control shaft holes thru. Maybe with a smaller diameter drill and finish them out later. Then you KNOW how much thickness you have to work with, and you'll trust your eyes more than you'll trust your measurements no matter how carefully you make them.
     
    Flynman likes this.

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