Tool path strategy for clean dados/rabbets

[jTr]

Problem: Square vectors for pocket cuts such as dados/rabbets will have rounded inside corners due to tool radius. A majority of the time, these vectors terminate flush with the cutout vector for the cabinet part being produced and the dog bone filet does not always cooperate.

Manual solution: chop straight with a chisel prior to assembly.
Current solution: stretch selected vectors ~ .125" off work piece into cutout kerf path where it will do no harm. This causes bit to over-cut, pulling that radius off the work piece, thereby leaving a straight, crisp edge once cutout is completed. This is a bit time-consuming and tedious. Screen shot shows the cleaned up edges and tool path tracer lines that are deliberately over cutting in order to achieve the clean lines shown:

Over cut dados and rabbets.jpg

Thinking there could be a better way?

The dog bone filet occasionally works, but most of the time it's throwing the arc in the wrong direction. Is there a way to trigger the dogbone filet into a different orientation?
Perhaps a much easier solution eludes me?


jeff

[Burkhardt]

Good question. I do that the same way and it is not really elegant.

Additional problem: I usually import my drawings from a dxf or dwg file and the boundary of the dado overlaps the cutout boundary, i.e. the same vector snippet. I need to create the extended dado boundaries first, close them individually and then close the cutout vector pieces. It works well enough but I would appreciate to learn a better better way of doing that.

[adrianm]

Are you cutting the dado with a tool the same width or are you using multiple passes with a smaller tool? If it's the former then I made a gadget (http://gadgets.vectric.com/dado_creator.html) that automatically creates the overshoot.

[jTr]

Adrian: I do use a .375 bit for faster, cleaner plowing out of rabbets and dados, as they vary from .125 depth to as much as .500 x .750 wide. However, I am not opposed to altering my plywood master to utilize the full size bit if the gadget proves useful. Thanks for sharing!

G: I'm using Sketchup, so dxf's are imported for me as well. However, I import a layer at a time, assign dxf's to appropriate layer, close them as a batch, then repeat for next layer. Upon completion, I save as a multiple sheet dxf "master" for the given project. I then select multiple rabbets with identical size and orientation whenever possible. Using select tool, I often can grab 2-4 closed dado vectors for instance, and use the pull point to "stretch" the rectangles as a group, making it much faster. Just be certain they are perfect rectangles, as any "L" shaped items will be distorted in the process. No, this is not precise, but eye-balling the overhang has always worked fine.

An additional strategy is to lay cabinet sides out so all rabbets are in line as they lay flat. Pair the sides as book-matched sets. In some instances, multiple sets are able to be paired on a single sheet. This way I can stretch one rectangle across multiple cab sides on the sheet, dump the remaining short rectangles, and the machine sweeps all the way through 2-4 dados as one, eliminating many stop/re-plunge events. This saves machine time, reduces component wear, and cleans up a batch of the pesky arcs in one shot.

Wish I was more savvy with screen exports/video, as it would be much easier to show the process than describe. Hopefully you get the gist from above.

Jeff