Wood with Tom¶
Tom goes over the fundamentals of wood finishing after the material comes out of the CNC router.
Tips and Tricks -
Shearing Your Wood - Card/cabinet scrapers and hand planes slice wood fibers. Slicing these fibers in a uniform manner allows oil/stain to be absorbed in a more uniform manner thus preventing blotchy finishes.
Uphill vs Downhill - A wood board's surface will never be perfectly parallel to the fibers that form the grain: these will rise into the surface with some inclination. You can attack them head on, or from their back. One of these is called "uphill" planing and the other is "downhill" planing, altough there is not universal agreement on which is which. Attacking them head on will tend to pull the fibers up rather than shaving them cleanly and will result in a more uneven, more porous surface.
Figured Boards - Undesired by larger manufacturers but sought after by professional woodworkers to create artistic pieces. These are pieces of wood that have unique non-uniform patterns.
Dented Wood - Some woods come damaged or are damaged while being worked on. Dents are essentially compressed wood fibers that can potentially be decompressed. A good way to remove these dents is by applying water to the spot and then steaming it with an iron to "pop" out. The wood fibers in this spot will retain water. This will affect your finishing with oil/stain. The wet and steamed location will present a different oil/stain consistency, all other unwet and unsteamed locations with have a more uniform consistency. To avoid this, have the mentality that "what I do here, I do everywhere." Lightly dampen all over with water all over to have the same consistency.
Adhesives and Tape - Even if you do not realize it, when used in your project, they will leave residue behind. This residue, once it is sanded will be burnt into the wood fibers. This will produce blotchiness once your wood is finished. To remove leftover tape residue, it is recommended to use acetone.
Sanding - Start with a lower grit, move forward with a higher and finer grit. If using a random orbital sander, move your tool slowly and apply even pressure. Make sure your sandpaper is clean. If any particulates are stuck to it, they can leave pigtail/spiral marks on your wood.
Stable Work Surfaces - Friction mats, or other materials (like used yoga mats) are good work surfaces. When sanding/finishing a piece you finish one surface/side of your workpiece while the other surface is making contact with the mat. This prevents dragging your workpiece on uneven or damaged surfaces with further prevents damaging your workpiece.
Finishing Workflow - Use in this order. Hand Plane, Card/cabinet Scraper, Sandpaper, Abrasive scratch pad (gentler than sandpaper)
My creeping realization was that... [finishing] is most of the job!
Tom Bodett
Film vs penetrating finish and sanding - For film finishes like shellac or polyurethane-based finishes you want to stop at around 240 grit. If you don't the wood surface will be too smooth for good adhesion of the finish. Penetrating finishes like Tung oil or hardwax oil don't care about this, so you can go as fine as you want.
Odie's oil.
Plywood and CNC Compression Bits - Compression bits while useful for plywood, should not be used to drill holes, Tom mentioned a member at his shop created a fire in the dust collector this way. The design of a compression bit leads to poor chip evacuation, causing excessive heat buildup and potentially resulting in burning the workpiece or even a fire hazard.
3D Surfacing on a CNC - Downcut bits may be better for certain scenarios. Upcut bits increase the possibility of tearout.
"Invisible" Cavities - Sometimes your wood looks perfectly sanded and smooth. A good way to test it one final time is to used a 400 grit piece of sandpaper. This grit produces fine sawdust of a lighter color that will occupy any cavities in your wood. If any cavities are highlighted by the lighter sawdust, now you know where you need to plane/sand again to have a uniform surface.
Scraping 3D Prints - Tom mentioned that card/cabinet scrapers can be used to help finish 3D Prints. Attached below is a video he recommended for those situations.