Making a Finger Joint Drawer to An Exact Width

[algale]

When cutting finger joints, it is often advised to cut the fingers a little long (or more accurately to cut the notches a little deeper than the stock is thick) in order to be able to sand or plane the fingers down flush to the sides (rather than risk the fingers being too short and having to shave down the entire side of the drawer to make it flush to the fingers).

My question is this: when you need to make a drawer to an exact width (to fit with extension slides installed in a case), is there a "simple" method for determining the length to cut the stock to be used as the drawer front and back?

For instance, if with the slides installed in the case, the finished width of the drawer has to be exactly 20 inches, how do you easily determine the length to cut the drawer front and back? It seems to me if you cut the drawer stock to exactly 20 inches but then cut the notches for the fingers even slightly deeper than stock is wide, your assembled drawer will be less than 20 inches wides. In fact, the assembled width will be 20 - (2 x A) where A is the amount beyond the thickness of the stock that the notch was cut (since you cutting notches on both ends).

So what is your method for accounting for this "error"? Do you always cut your notches to some predetermined depth beyond the thickness of the stock -- say 1/16th -- and then cut your front and back drawer pieces 1/8th longer than the finished width (20.125 for a finished length of 20?)?

I am probably over-thinking this but is there an easier/better/simpler way to approach this?

Al

[JPG]

Quit thinking 'short' and concentrate on long.

You need to determine how much longer to make the front(initially) and how much deeper to make the finger cuts.

Obviously you start with the opening width.

Then decide how much 'extra' finger length you will sand off(extra finger cut depth).

Double that 'extra' and add it to the opening width for the initial front/back length.

Make the finger cut(s) 1x 'extra' deeper than the side thickness.

Two interdependent variables here.

1) Initial length.

2) Finger length(finger cut depth).


Finger cut depth = opening width + (1 x 'extra').

Initial length = opening width + (2 x 'extra').






So! Think 20 + 2A. Where 'extra' = A as before!;)


IIWM, I would make 'A' very small(< 1/32").


Oh!!! and test finger cut depth on scrap before cutting fingers on drawer sides.

[charlese]

Yes, this could be brain buster if you want to over think it. Just build the drawers a little bit wider than they should be then plane or sand the sides to the correct width.

Using 1/2" sides, you shouldn't have to remove over a sixteenth from both sides. Drawer slides should have a little play in them to allow for slightly smaller drawer width.

Measuring is good, but I always wind up doing a little fitting to offset the errors in measuring.

[keakap]

[quote="charlese"]
Measuring is good, but I always wind up doing a little fitting to offset the errors in measuring.]

Ah, so, how did that old 'saw' go--
"measure once, cut, shim, glue, cut, plane, shave, scrape, sand..."

[reible]

Just remember your old friend the shopsmith belt sander.

When doing drawers most of the joints are hidden, possibly all of them so don't sweat the little stuff. The hardware for mounting will have some amount of play so do check the information with the slides and make sure you stay within that.

You might want get experience by making some samples and getting a feel for the process using some scrap pieces of similar wood. Experience counts.

If you do magazine boxes or other projects where you will have exposed joints you need to be more carefully. Charlese has some excellent examples posted here if you care to look them up.

Good luck with the project.

Ed

[charlese]

Ah, so, how did that old 'saw' go--
"measure once, cut, shim, glue, cut, plane, shave, scrape, sand..."

EXACTLY THAT'S THE PROCESS! Sometimes it isn't necessary to do all those things, but each one has merits.