The sketch above shows how to calculate the offset between the dovetail path on the lid and the dovetail path on the box. It will vary with the thickness of the lid as well as the angle of the dovetail bit.
It is also a bit tricky to machine the lid since you can't use tabs with a dovetail bit. Consequently I had to divide the toolpath into three sections. The order you cut these is important so that you maintain your reference datums until the last cut. It is also important how you hold the lid down to avoid having your bit collide with the hold downs.
Here are the basic steps assuming you are starting with pieces having dimensions specified in the sheets tab:
Start by cutting out the lid:
- Create fixed datum references on the bottom and left edges that you can bump to.
- Machine the top surface by engraving the name and cutting out the finger pull slot
- Flip the top over and bump to the same datum references
- Clamp down on the top and bottom edges very firmly
- Trim off the curved end of the lid
- Then cut the dovetail on the curved end of the lid
- Now securly hold the lid down with clamps at both ends, then remove the hold downs from the top edge
- Now cut the dovetail along the top edge
- Bump to the new top edge and securely clamp down
- Remove the bottom clamp that also provides the datum
- Cut the dovetail along the bottom edge
- Delete the toolpath in the layer "Box Dovetail"
- Turn on visibility to the layer "Dovetail Master", and then ensure the layer "Box Dovetail" is active
- Create an offset toolpath from the "Dovetail Master". The amount of offset will depend on your lid thickness and dovetail bit angle. Reference the formula listed in the sketch above.
- Extend the top and bottom vectors about 1 inch to the left of the box to provide a place for the dovetail bit to plunge before making the cut. You should also add a vertical line at the left end to close the loop on this toolpath.
- Run the "Pocket Box Lid Profile" toolpath using this new toolpath
- Run the "Pocket Pencil Cavity" toolpath
- Run the "Profile Box Dovetail" toolpath using the new toolpath
- Now test the lid to see if it slides easily in the box dovetail. If it doesn't, you need to create an additional pocket toolpath using the same path used to cut the first dovetail in the box. Now that you have a pocket toolpath instead of a profile toolpath, you can add a very small pocket allowance to widen the dovetail slot. If the lid still doesn't fit you can increase the pocket allowance and try again until it fits properly.
- Once the lid fits nicely you can finish up by cutting the pocket for the magnet.
Hopefully the above description will make sense after you have the VCarve file open and have a chance to review it. As always, you may need to edit the toolpaths to use your bits and the appropriate feeds and speeds for your machine.
One final note, I ended up using a 1/16" endmill bit to pocket out the magnet holes in order to get a flat bottom hole. If you use a larger bit then there isn't enough motion in the XY plane to sweep over the center of the hole and you end up with a hump in the middle that will cause the magnet to wobble, which will make it difficult to glue it into place.