Best bottom surface finish

[TheRuggedLab]

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.

[knight_toolworks]

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.

[scottp55]

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.php?f=5&t=22609&hilit=stacked+text

[pkirby]

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

[knight_toolworks]

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.

[TheRuggedLab]

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.