LumberJocks

Exposed Finger Joint Box #2: The base

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Blog entry by splintergroup posted 02-22-2017 05:44 PM 741 reads 4 times favorited 1 comment Add to Favorites Watch
« Part 1: Intro (The Body) Part 2 of Exposed Finger Joint Box series Part 3: The Lid »

The base of this box is where anyone can “go wild” with design options. The basics are simple, a frame with lap joints, filled with a plywood panel. The feet are simple squares.

A pdf file with dimensions for the base can be found here

The design allows for the base to have 1/2” of exposure along its perimeter with the box, basically it aligns flush with the boxes inside dimensions.
A felt covered plywood piece fits into a routed shelf to seal off the box bottom.

The box walls cover the seam between the plywood and base frame, hiding any missteps with the routing and securing the felt to the plywood.

Build a frame

It all begins with some 1/2” thick x 1” wide material cut to the proper lengths. I use a stop block setup to ensure all corresponding parts are the same.

At this point I go ahead and sand the edges (220 grit). Easier now then later!

The ends of this frame overhang by 1/4”. This means the half lap joint needs to be offset from the end of the “sticks” by 1/4”

I set my trusty box joint blade set 1/4” from the fence to make the first cut. The blade height is set to 1/2 the thickness of the stock (1/4”).

A good backer keeps any chip out from happening.

There are many tricks to accomplish the depth setting. My favorite is to set the blade height just shy of the half way mark, make a cut, flip the stock, make another cut. The blade height is bumped up slightly and the two cuts are made again. Repeat until the second cut removes the thin wood left by the first cut.

I have a secret weapon to make this “perfect”. The top and bottom of this frame needs to be flush, time spent on these half laps makes flattening in the easier in the end.

All pieces of the frame are passed over the blade to make the first cuts.

I use a scrap to check these setups. For the opposite side of the half lap, I make a pencil mark based on the width of the frame stock. This mark then is used to align the blade for the next cuts. I always cut slightly shy of the line and “sneak up” on the final position. The table saw fence is being used as my stop block reference.

”Dial” in the slot width
I clean out the material between the two cuts on my scrap with passes over the blade. This makes room for calipers to measure the width of the slot I have just created.

I compare the measured width to the actual width of my frame parts

1.001” – 0.962” = 0.039”

This is how far I need to widen the slot, basically I need to move the fence 0.039” away from the blade.

This is where my dial gauge and magnetic base come in handy. Dial gauges used to be pricey, but now they are quite inexpensive. A worthy addition to anyones tool collection!

Set the dial indicator against the fence, zero out the indicator, then “bump” the fence away until the indicator shows the correct value.

I moved the fence 0.04”. The dial is rotating CCW here so I had to go to the “60” mark. The extra 0.001” gives me some clearence for a slip fit between the parts. Actually this is wood working so the extra clearance allowed will vary depending on the wood, etc. I just happened to hit on the right numbers the first try 8^)

The scrap is cut again with this new blade position set and tested against a frame piece. The fit is good so I cut the remaining parts and clean out between the two cuts.

This is the resulting fit:

Nice and tight!

Chamfer and assemble

My secret to flattening is to fit the frame together and run it through my drum sander (cheating, I know 8^).

To remove the linear scratches let by the drum sander, I rub it around on my 120 grit disc mounted on a piece of melamine.

Now is when I take the frame pieces to the router table and chamfer the ends (just like on the box body).
The pieces are reassembled, this time with a spot of glue at each joint (not too much! don’t want any squeeze out).

After drying, I sand the surface as before on a 180 grit disc. The end grain is also squared up.

A further sanding with a 320 grit strip gives the end grain a polish.

Route the plywood base rabbet
A rabbet is needed to hold the base panel, The depth needs to be equal to the thickness of the plywood plus compressed felt.

I’ve done this different ways to achieve the same results. I started by doing stopped rabbets on each piece using a straight bit and the router table fence. This works, but is a bit of effort to get the start/stop points set accurately and handling the narrow pieces is difficult. By making a template I can get accurate and easy results with my router table or even a hand held trim router. This template method is my favorite so far.

I place a scrap on felt on my sanded plywood and compress it with the calipers.

Almost 1/4” (0.0240”).

-Make the template-

My router mortising bit cuts the same diameter as the bearing (some have a cutter larger then the bearing).

I need to make the template have a square “hole”. This is easily done with some hardboard strips.

I use two layers to get a proper surface for the bits bearing. These layers are interleaved. The layer on the left in the above photo has the long edges running the full length (the blue painters tape is spanning the seams, holding the strips together). The layer on the right has the short edges running the full length. These two layers are then joined with double sided tape into a stack. The overlap at the corners locks the square into place.

The new template is joined with the base frame using the same double sided tape.

A shallow pass on the router table, followed by raising the bit until I hit my target depth, completes the rabbet.

Clean radius corners are a benefit of using the template.

Felt the plywood and trim it to size

I cut the plywood for a good fit into the new rabbet. The corners are rounded on a disc sander to fit into the base.

Next is to apply the black felt. I like using the 3M “super 77” spray adhesive. Works great and one can goes a long way. Following the directions on the can gives good results. I spray the felt only to avoid getting overspray on the sides of the plywood.

After a minute or so, I place the felt onto the plywood (the felt is cut oversized). A “J” roller is used to smooth it all out, though just smoothing with your hand works well too.

The excess felt is trimmed away with scissors.

Finishing

As with the box body, I apply finish to the base now while access is easy for rubbing out. The box body will be glued to the base so I avoid getting finish in this glue area.

The feet also will be glued so I leave an area finish-free in the bottom corners as well.

The feet are simple 2” x 2” squares, 1/4” thick with the top edges chamfered. These are also finished with a glue area left exposed.

I made a simple fixture to square up a foot with the frame.

This is used with a clamp to attach the feet.

The finish is buffed and the prepped. The box body is now glued into position with the plywood, completing the assembly.

Next up, the lid.

Thanks for following along!



1 comment so far

View Roger's profile

Roger

20873 posts in 2619 days


#1 posted 02-23-2017 12:41 PM

Nice step by step

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed. Kentuk55@yahoo.com

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