Finger Joints

[Paul Fisicaro]

Hey Guys, Im making these wooden fly boxes with finger joints. After I cut the lid off and sand box sides I get a mismatched joint. Is there an easy way to ensure that doesnt happen again? I probably cant fix it on this box but I am making another one today. Im assuming is how you mark up the joints but Ive been sitting here for an hour trying to mark them out a certain way to allow for blade kerf and such but Im stumped. I could cut off an 1/2 inch (joints are 1/4") off the box to get even one walnut joint and one maple joint to match but I don't want to loose the space. Any suggestions or did I answer my own question?

Height of the box is 3 1/8"

Thanks!

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[glenn bradley]

Easier option but, more spoil - Build the box tall enough to remove a pair of fingers.

More involved option with less spoil - Space the fingers at the cut to result in an appropriate size after ripping.

[David Utterback]

If the box top could be a slider, the finger on the top of the front would hide the end piece that has been reattached to the top. The top joint end piece is removed with a band saw to create a narrow kerf. A groove on the inside face of this small piece can then be fit over a tenon on the end of the top. I can supply pictures if that might help.

[Paul Fisicaro]

Yes, David, please. Thank you.

[Chris Padilla]

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Is it this simple? Top board is what you want at the end with the pinkish lid on the yellowish body.

Below is adding the kerf of the blade into the picture (green kerf cut). I have it at a 1/8" kerf.

[David Utterback]

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Sorry this post is late. Attached are a couple of examples of 3/8" finger joints on boxes with slider lids. The cherry box w walnut burl lid has the advantage that grain pattern is continued on the end but the slots for the top are apparent when closed. With the maple and spalted walnut box, the grooves are not so obvious when closed but a new piece was required so the grain on the end of the box does not match.

Let me know if you have questions or comments.

[Alan Schaffter]

333392

Is it this simple? Top board is what you want at the end with the pinkish lid on the yellowish body.

Below is adding the kerf of the blade into the picture (green kerf cut). I have it at a 1/8" kerf.

I believe OP wants all fingers/slots to be the same width. Your technique won't do that because the box joint jig will still result in fingers and slots that are equal width, and depending on where you locate the lid cut, you will end up with a finger or slot that is not full width- it will be reduced by the width of the kerf (or half a kerf if the cut is centered exactly on the edge of a finger/slot.)

The simplest method is to do it like Glenn suggests- remove both a full finger and a full slot.

There may be another way that results in less waste. Use an I-BOX and cut a center-keyed box joint*. But, instead of a normal (symmetrical) center-keyed box joint cut an asymmetrical one so that the "key" is actually offset to where you want the lid break. I'm fairly certain this will work but I haven't tried nor fully wrapped my brain around it.

Start with boards that are slight more than a kerf width wider than the sum of the number of whole fingers and slots. When you follow the standard center-keyed box joint cutting procedure (cut half the slots from one edge, flip the board, and the other half from the other edge), the first and last fingers are always the same width as all the others, no "widows." The excess (board width) is forced to the center of the joint where there will be a wider finger/slot (see pic). (under certain conditions it is also possible for the center key (finger and slot) to be narrower than the others.) For a box with a shallow lid, instead of cutting a symmetrical pattern, cut an asymmetrical one- cut more fingers/slots from one edge than from the other. You should be able adjust the number of cuts from each edge so the wide "key" is offset to where you want your lid break located.

Regardless of what technique you use, you will never have a perfectly continuous grain pattern (across the grain). There will always be a kerf's width missing at the lid break.

* A center-keyed box joint is used when your stock must be a specific width, you want full width first and last fingers- no narrow fingers or slivers (no widows), or it is too hard or you can't adjust your dado blade or router bit to do that.

Examples of (symmetrical) center-keyed box joints and a (symmetrical) splined center-keyed box joint. Center finger and slot are slightly wider than the others. First and last fingers are full width.

http://www.incrementaltools.com/v/vspfiles/assets/images/ibox_body2.jpg

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQki-fa46z3X3IvK3qqtH_9wBR7C8bOeMNxaJN_0helJm-a4yKBJA

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTVZNLogzOyA_xZ4bO3bUs8Voe8piS3Y BeUhhwRz-7GGxYUPINvXw

[David Utterback]

These are great ideas on alternatives. At the time, I was trying various methods to joint the box corners with miters and splines and with box joints. Being the skinflint that I am, I was looking for ways to get around using high quality butt hinges that cost over $25 per pair.

Alan, I had a roommate who was from "Little Washington" when I was in the Triangle area from the late 70's through '83. We had many great times together.

[Pat Barry]

You have to make the area where you saw the box apart wider to accomodate the cutting line IMO, this is what Alan was showing above. You could do as you thought and cut out all the corresponding material for a pair of joints but then the grain matching around the box is likely to be too messed up. Are you cutting your joints with a router? If so, you could invest the time to make a pair of templates (One for the fronts and one for the mating side) that have the kerfing allowance factored in. You could cut with a bandsaw instead of a table saw to minimize the kerf and minimize the effect of that missing material on your grain matching. I think I would go with the template approach.