Analysis of a Three-Tiered Auger Bit Box

I bought a set of auger bits about 5 years ago and was lucky that they came in the original box.  Not all the bits were original to the set, but that's OK.  Last year I came across an almost-complete set of bits and they've been rolled up in a towel since then, so I wanted to give them a better home.  That's why I'm studying the box from my first set.  I've always loved the 3-tiered box and wanted to know a bit more about what makes it tick.

The Russell Jennings Mfg. Co auger bit box for their "Fig 100" bits (double thread lead screw)
The box is 10 1/2" x 4" x 3 7/8" high and the walls and lid are 7/16" thick

Underside of lid has the label.  Top tier has bits #4 to 9 (1/4" to 9/16").
Second tier has #10-13, bottom has #14-16.

The box is put together with with box joints, each finger is about 5/32" wide

But note that there are three nails reinforcing each corner - one nail for each tier

Note in the previous two pics that the lid has a spline running front to back at each end.  My guess is that this was to keep the single-piece lid flat.  But that creates a cross-grain situation if it's glued in, which could cause the lid to crack.  And guess what?

The lid has a crack
(At one time I sanded the lid, removing the patina.  The horror!)

The bottom of the box is inset and is flush with the bottom of the box sides and ends.

Box bottom inset within carcase

Note the two nails holding the box bottom in place

You may also notice in the above pic that there are two nails in the top two tiers as well.  I'll get to that more later but they are nailed through grooves in the sides that house a lip of the bit trays.

The hardware on this box is interesting.  Each tier is secured to it neighbor with small clasps.

Clasps on front of box - all work perfectly.  They are attached with round-headed nails.
It looks like the upper nails on the middle clasp are not original.

The hinges on back are awesome!  They are continuous from bottom tier to top tier and then to the top of the lid.  Clearly these were custom made for this box.  I'm sure many thousands of these boxes were made, so it made sense to have a specific hinge mass-produced for them.

The back of the box showing the hinges

Back portion of the three-knuckled hinges.
Hinges affixed with round-headed screws (not "clocked" - an obvious faux pas).

Where the hinge comes up on top of the lid, it is affixed by a single countersunk flat-head screw

Let's get to the bit trays.  The top tray is low enough in its tier that the bits don't stick up higher than the sides, allowing the lid (which is not relieved on its underside) to close.  But for the second and third tiers, the bits are higher than the rims of their respective tiers.  The tier above them has a relief in its underside to account for that.

First tier bits below the rim of that tier

Second tier bits higher than the rim of the tier

5/16" recess in underside of first tier

Third tier is similar, except the recess in the underside of tier 2 is only 1/4"

Now, how are the trays held in place?  The following pic shows the bottom tray and you can see in the left-most bit compartment that some of a groove is showing.

See the groove?

And this shows the underside of the middle tier and it's clear that it fits into a groove

One of the grooves can be seen from the outside of the box

What I don't know is if the bit tray and the piece that fits into the groove are one and the same.  That is, does each bit tray have a single-cheeked stub tenon that fits into the groove, or is there a thin shelf extending from the left side groove to the right side groove and the tray is just glued to the shelf?

No matter which it is, there is a cross-grain situation in this connection.  It certainly wouldn't need to be glued, but it seems solidly in place.  There is plenty of room for the tray to expand and contract, as there is about 1/32" of space between the tray and the front/back of the box.

An 0.029" shim fits between the tray and the back of the box

As far as construction is concerned, it's pretty clear that the box was made full size and then the tiers were cut apart.

The saw kerf split the finger I'm pointing to

One final detail and I'll wrap this up.  The top tray has 6 "half-pipe" compartments for the bits to rest in.  But the smallest three don't extend all the way to the right.

This was because the square tapered parts of the #4, #5 and #6 bits' shanks are too
large to fit in their half-pipe compartments.

It was a feat of engineering to fit 16 bits in a box this size and have them all be easily accessible.  Great stuff!