SE Holcomb with a crooked bridge and no help

Discussion in 'PTC - PRS Tech Center' started by TheRealSteveRose, Oct 3, 2019.

  1. Mozzi

    Mozzi https://imgur.com/user/BAMozzy

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    CNC is used for all the big holes and cavities. Finish would clog up the small holes and would need to be redrilled anyway so its pointless to do these pre finish. CNC is used to get a body to shape and do the basic routing necessary that templates would of been used to do. Templates were not used for the small holes things like stopping the tuners from rotating, fitting the pick up rings, drilling through the cavities for the wiring and the output jack etc. After a CNC has been used to get the body and neck into the rough shape and carve, with all the cavities (pickups, electronics, trem) and any 'big' holes (6 tuners, tuner-o-matic post holes, pot/switch holes), the rest is totally done by hand. They have a jig made so that the output jack is drilled in exactly the same spot every time.

    Any small holes are not drilled because they would fill up with sawdust from all the hand sanding and clog up with the finish too so would still need to be hand drilled when the guitar ends up at 'assembly' - the people that fit the tuners, the pickups, etc would drill the holes needed for those screws.
     
  2. jak3af3r

    jak3af3r Slightly Older Than New Member

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    Has anyone in the "CNC does it better" or of the opinion that CNC doesn't deviate actually machined anything with a CNC machine (milling, lathe, etc?)

    I've worked with similar machines as what PRS uses and some beyond what woodworking would require and even those have a tendency to deviate slightly because of coding issues, electrical problems, not properly warming a machine before use, stepper motors skipping a step or series of steps. It's amazing the machines are as accurate as they are to begin with.

    Most commonly I had parts out of tolerance because a tool would begin to wear beyond its usefulness.
     
    Black Plaid, Alnus Rubra and bodia like this.
  3. Mozzi

    Mozzi https://imgur.com/user/BAMozzy

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    I guess it depends on what you are making with a CNC machine. With a guitar made of wood, the tools being used to machine are likely to be much harder and therefore wear is not going to be significant - over time maybe but I doubt its deteriorated, become blunt after a week or even a month. Tolerances too aren't necessarily going to be incredibly small - like to the nearest thousandth of a mm and, in the case of shaping, only a 'rough' cut because its going to need sanding by hand to remove the tool marks. Even the cavities aren't necessarily needed to be exact and to the thousandth of a mm accurate. If something does go badly wrong, its very early in the production that its a minor loss - inc all the man-hours that its occupied. Its far worse if something drastically goes wrong during the final test phase, dropping it and cracking the neck for example.

    I think it does depend more on the materials you are working with and the accuracy/tolerances required. I can see wood being less of an issue than metal and building a guitar that is still going to have a lot of sanding done having a higher tolerance threshold than other products.
     
  4. Alnus Rubra

    Alnus Rubra Loving nature’s wonders

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    If I remember correctly, the CNC machinery at Maryland is designed for metal milling. So therefore it’s probably pretty hardy.

    Hopefully the OP gets the guitar he wants.
     
  5. jak3af3r

    jak3af3r Slightly Older Than New Member

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    Wood tools aren't and harder than metal cutting tools like carbide. They'll either be the same or softer as wood is typically a softer material. The silica content of wood is what wears tools down and can do so after a few bodies have been run. In particular the tool that has the potential to wear the quickest would be one that is fully engaged (180 degrees of cutting action at a time) which is a possibility on the outline cut provided bandsaw work isn't close or clean. Even then you run the risk of a tool dulling and cutting a curve wide or slightly crooked and when it goes in a form everything else becomes crooked.

    Then if you wait to drill bridge hole until after the body is finished you have all the possibilities of crooked bodies, over-sanding, under-sanding, and finish thickness that could cause the body to sit crooked in a form while a machine drills.

    On the matter of metal milling, I've seen a brand new, recently calibrated, multi-million dollar machine drill a straight programmed hole crooked because of the shape and density of the metal pushing the drill inside the material.

    I can't say why exactly the holes may be crooked on that body. I'm more curious as to how that passed QC along the way. And if it were mine and it played better than all the other guitars I had, I'd keep it.
     
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