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Exposed Finger Joint Box #1: Intro (The Body)

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Blog entry by splintergroup posted 02-21-2017 07:20 PM 1519 reads 11 times favorited 5 comments Add to Favorites Watch
no previous part Part 1 of Exposed Finger Joint Box series Part 2: The base »

I’ve had several inquiries for plans or more info into the details of my exposed finger joint boxes I’ve been building of late.
Plans get complex and are often best explained in some detail, hence this project blog.

Lots of pictures and details, hopefully clear and not too boring 8^)

A set of dimensional drawings (4 pfd files) can be downloaded here

It’s next to impossible for drawings like these to contain all the details. These boxes have simple structure, but a lot of “what’s what” is in the process, so hopefully in the next few parts I’ll sort this process out.

It should finish in three parts, the box body (this entry), the base, and the lid.

This is what the final box looks like:

The wood is cherry. A bit light right now, but it’ll darken up.

No hard/fast rules, the dimensions are entirely arbitrary and simple to alter without adding too much confusion. Feel free to be free!

Let us begin.

The “box” portion of the box

I like the look of exposed finger joints, they add detail and are simple to cut, but they take more time then simple miters.

Prepping the stock

It all begins with resawing the cherry to 1/2” thick and the four sides being cut to size.

I select where to cut the pieces from to avoid the “cathedral” grain and use care to orient assembly to keep the grain patterns simpatico.

For this box, I opted for a 45 degree chamfer. Fingers extend out 1/8” past the sides and these chamfers are about 3/32”.
The routing is done on all ends and sides at this step, though no need to route the top/bottom edges on the box sides since they get removed later.


I find his a great time to sand the end grain as well. It is easier to stack the boards together now and hit the end grain with a ROS then do it later. The chamfers are hit with some strip paper and a small, flat piece of wood as a sanding block.

Ganging up the pieces helps keep the edges crisp:

Making the fingers

Divide one of the sides into thirds ( I usually start with a front or back piece ). “Thirds” is arbitrary, but for purposes of discussion….

For the finger cuts, I use a tenoning jig. It allows fine tuning the cut position and has provisions for clamping and backer boards to prevent chip-out. You can also do this with a simple stop block on a sled or miter gauge.

I use my best blade for these cuts to keep the edged crisp. The depth of the cut is the board thickness (1/2”) plus the finger protrusion (1/8”). Make the cut so the blade removes material from the inboard side of the line.

Place the board in the tenon jig (or against a stop block), make the cut, rotate the piece, make the cut. This method ensures that the finger is now exactly centered.

Repeat the process for each end of the front/back pieces.

Do the same with the side pieces except set up so the blade removes material from the outboard side of the line, leaving the center finger a tad wide.
I usually make the cuts a bit further out initially then sneak up on the perfect fit.

Here is a front/back (bottom) butting up to the side piece just cut (top). You can see the reason to correctly position the cuts on the proper side of the lines.

I bandsaw away some of the waste material to get a test fit. Be sure to mark what gets removed! I’ve messed up before at this step 8^(

I return the side to the tenon jig with any slight adjustments for the cut dialed in. Once I have the fit I want (gapless), I finish the cuts on all remaining ends of the side pieces.

Of note here is the side pieces should have the center fingers. This allows the lid to hinge back properly without hitting the finger ends.

I trim the waste from the sides with a miter gauge just like one would cut tenon shoulders.

I trim the waste on the front/back parts with a flat tooth blade on my sled. This Freud box joint blade set gives perfectly flat/smooth bottomed cuts and excellent shoulder cuts. The 3/8” kerf finishes things up fast.
A backer board is critical here for clean cuts!

The fingers fit well!
Results of taking time and fine tuning the cuts:

The finger chamfers are finished with a miter gauge set to 45 degrees (front piece shown).

One nice thing about choosing chamfers instead of radiuses edges is I can do all the cuts with a machine. These edges would otherwise need to be done by hand with a rasp.

The trick here is knowing when to stop pushing 8^)

Pre-finish (optional)
Finish sand all the surfaces (except for the sides, done later) and apply the finish now when it is easy to do.

The finish I’m using is Homer Formby’s wiping varnish and requires a final rubbing with #0000 steel wool. This is so much easier to do without the box body being assembled and having the fingers in the way.
I only finish the outside, the interior gets wax.

Art? Is that you???? (or are you really Homer?, hmmmmm….)


Assembly
I use epoxy to simply tack the parts together. 30 minute epoxy gives me plenty of time to apply and get everything set up in the clamps, less stress is nice 8^).
Epoxy is only applied where the fingers contact the bottoms of their corresponding sockets. Glue applied to the sides of the fingers would just get smeared, I want to avoid any squeeze-out.

Clamps and cauls. I also have a machinists square spring-clamped in place for reference.

Once the epoxy has set, the box can be handled.

I now reinforce and lock the joints together with these 1” long copper rivets and epoxy. These are what really hold the box together!

Note that I filed small notches on the rivets to give the epoxy a good mechanical grip.

Masking tape is applied and marked for the rivet holes. The holes for the 1/8” diameter rivets are bored on my drill press with a #30 bit. This provides perfect clearance for inserting the rivets and getting a film of epoxy on their sides. The holes are about 1/8” deeper then required to provide a place for excess epoxy to collect when installing.

Don’t remove the tape after drilling! It protects the surface while placing epoxy into the holes.

I use a toothpick to place several “globs” of epoxy into each hole, then pull the tape. A rivet is pushed into the hole while rotating it to help cover it with epoxy. Applying epoxy only to the hole lets the rivet be installed without any excess epoxy getting scraped off (and creating a real mess!). If the fit is good, the rivet will spring back up a bit due to trapped air. Clamps or tape hold the rivets down in place until the epoxy sets.

I added a thin (3/16” x 1”) ledge to the interior to act as a tray support. Pieces are cut to length for a tight fit and clamped until set.

Care is taken to keep the top edges of these strips aligned.

Final box prep
Last step is to flatten the entire box body on a cheap 20” sander PSA disk applied to a flat 3/4” melamine board.
First 120 grit, then 180.

I just sand in circular motions until the entire surface is even.

I now have a perfectly flat box body!

No finish on the bottom edge which gets glued to the base. The top gets finished after I cut the hinge mortises.

Thanks for following along.

Until next entry!



5 comments so far

View AandCstyle's profile

AandCstyle

2885 posts in 2072 days


#1 posted 02-21-2017 10:33 PM

Hey. Splint, you are close. Actually, he was my dad and I learned a ton about woodworking and finishing from him and my grandfather who was a cabinetmaker.

Thanks for the tutorial. I have added this to my list of future projects.

P.S. JK re the family tree. :D

-- Art

View splintergroup's profile

splintergroup

1649 posts in 1038 days


#2 posted 02-21-2017 10:38 PM

Hah!

View Roger's profile

Roger

20873 posts in 2619 days


#3 posted 02-22-2017 12:03 AM

Nice blog Splint. Thnx for the link as well. Very nice box

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

View CaptainSkully's profile

CaptainSkully

1517 posts in 3374 days


#4 posted 02-22-2017 12:47 AM

Ha! I actually remember when Mr. Formby starred in his own commercials…

Awesome box, BTW!

-- You can't control the wind, but you can trim your sails

View JimYoung's profile

JimYoung

269 posts in 1402 days


#5 posted 02-22-2017 05:20 PM

Thanks for sharing, I might have to try one of these.

-- -Jim, "Society is well governed when its people obey the magistrates, and the magistrates obey the law." -- Solon

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