Mirtered Lightbox corner question.

[nappy1]

Well here is a brain teaser for sombody, including ME.
I am making a light box for a lithopane. The actual size of the litho is 17.5 x 12.5 inches.I cut a channel into the material that is 1/4" deep. it will allow me to bury the 1/4" border into the box so there is no backing needed. That means the viewable lithophane will be 12 x 17".
Now I want to use a 1" v bit and cut the mitered ends to make the box.
What dimension do I use for the v bit toolpath. I'm thinking it should be the 1/4" recess plus 1/2" to equal the thickness of the material which is 3/4".
Any suggestions?

[myxpykalix]

Without running to the shed to test this, the answer should be figured out by measuring the diamter of the bit at 3/4" of an inch from the point of the bit, give or take a few thousandths.

If you visualize taking that bit and plunging it down the thickness of the material (3/4") then measuring the hole, it should be the same measurement as outlined above.
Or am i wrong?

[gene]

You will use a 90 degree v bit , the size of the top and bottom pieces will be 18.5 long x the width and 13.5 high by the width . something that will effect the length measurement will be the depth the bit goes into the spoilboard . this is for 3/4" thick material . if i were you i would oversize about 1/16" to allow for glue and fitting it together. Let me know the outcome. Hope this helps

[nappy1]

Thanks Guys,
I did get it after I did a test cut. Its just one of those projects that causes brain lockup.

[myxpykalix]

Ok tony so share your results! lol. Because when i read it i thought i understood the question being basically "How wide do i make my toolpath for this vbit?" But then i read Gene's response and his answer sounded like he was giving you the deminsion for the overall length of your piece and where to cut, and mine was focusing on the "kerf" of the cut.
Sounds like we were both right!
I just got thru making another box for a litho but have made all mine on the tablesaw that was why i was interested in the answer to this post.
Be sure to post pictures of your finished project.