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Thread: Best bottom surface finish

  1. #1
    Join Date
    Dec 2015
    Location
    Johnson City, TN
    Posts
    10

    Default Best bottom surface finish

    Hello All,

    I have been doing a lot of multi layered relieved signs out of western cedar. It is frustrating to try and sand out tooling marks in tight spots.

    What can I do to achieve the best possible "pocket bottom" finish.

    What is the absolute ideal bit if the only concern is bottom finish in soft wood. I have been looking at Onsrud 60-200? (3 flute low helix finisher).

    Currently, on my final pass, I am using a double flute upcut spiral with about 30% overlap. The finish is ok but I think it could be better. Just looking for advice with someone with more experience.

  2. #2
    Join Date
    Sep 2006
    Location
    cnc routing, portland or
    Posts
    3,633

    Default

    usually up cuts are best part of it is just the machine and the slop that it has. going with the grain is the best to get the last marks.

  3. #3
    Join Date
    Apr 2013
    Location
    Kennebunkport, Maine
    Posts
    4,419

    Default

    Have you considered doing the pocketing at 45 degrees and leaving the mill marks in like Connor does for a Rustic look?
    http://forum.vectric.com/viewtopic.p...t=stacked+text
    scott P.
    2013 Desktop/spindle/VCP 11.5**
    Maine

  4. #4
    Join Date
    Jul 2011
    Location
    Atlanta, GA
    Posts
    197

    Default

    You can try a few things
    1) Do a finish pass with a low depth of cut. For instance if you are pocketing down to .750" then make your first pocket depth to .740" saving .010" to be cut on the last pass. This will greatly reduce tool deflection and give a much nicer finish.
    2) Make sure your spindle is square to the table. Try searching tram / tramming spindle z axis
    3) Bits with a corner radius give a nicer finish as well when pocketing

  5. #5
    Join Date
    Sep 2006
    Location
    cnc routing, portland or
    Posts
    3,633

    Default

    Quote Originally Posted by pkirby View Post
    You can try a few things
    1) Do a finish pass with a low depth of cut. For instance if you are pocketing down to .750" then make your first pocket depth to .740" saving .010" to be cut on the last pass. This will greatly reduce tool deflection and give a much nicer finish.
    I forgot to recommend that I do that on solid wood as going against the grain does not make large splinters that plug the dc hose then a finish pass. doing it this way you do a really course "roughing" pass then a finish pass this saves a fair amount of time too because if you need multiple pass for death your saving a lot of cutting time doing 60% setepover as the roughing.

  6. #6
    Join Date
    Dec 2015
    Location
    Johnson City, TN
    Posts
    10

    Default

    Scott, performing the raster at 45 degrees looks like a great idea, I will definitely try that on a project in the future.
    Pkirby, can you recommend a bit (brand and number) with the curved radius? The Tram looks like a good idea. I have a machinist dial indicator with magnetic base that I bet could be rigged up (not using the mag base).
    Thanks everyone for all the ideas, this gives me some options to try.

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