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Small Projects #48: Jatoba Strong Box Finished!

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Blog entry by Madmark2 posted 06-14-2021 05:25 AM 850 reads 0 times favorited 6 comments Add to Favorites Watch
« Part 47: Walnut and Spanish Humidor with Hydrometer & C° gauge Part 48 of Small Projects series Part 49: 5 minute camera stand »

Friend asked me to build a cash box. Something small enough to fit under a bed but still capable of holding significant amounts of cash in a neat and orderly fashion.

Strong boxes have a long history. They are often metal banded and reinforced and are designed to resist attack. Being wood, fire can breach the structure. However, being a paper money storage strong box, fire will destroy the contents, defeating the purpose.


Completed Strong Box.

Build details below …

I tried to think of every potential attack, sawing, smashing, prying, dropping, etc. I think this strong box will hold up until the point of destruction. The strong box is heavy, has sharp edges, has no provision for being carried, is dark and designed to be low profile and generally impossible to open without the key.

I came up with this detailed, precision drafted, master plan:

Detailed CAD drawing.

The project was built in two parts. The interior bill till and the main strong box.

Interior Bill Till:
Inside the box has a removable four slot bill till. Each till opening is 6-1/4” by 2-3/8” and 3” deep. The till is 3-1/4” x 6-3/4” x 12-1/4”. The end pieces had 1-1/8” holes drilled 1” down as lifting points. The interior dividers have sanded finger spaces on top for easier access.

The till was made from 1/4” thick clear pine from resawn “one by” stock. A total of 11 pieces comprise the till. The pieces were sanded to 220 and edges were rounded slightly before glue up. After glue up the till was again sanded with 220 and the edges and corners broken slightly.

The till was finished with two coats of 50%-50% poly/mineral spirits applied with disposable foam brushes. A third coat of full strength poly is the final finish. The till needed a protective coat more than a cosmetic finish so there was no sanding between coats.


Bill till — designed to hold 5, 100 bill stacks per slot.

Strong Box:
The box is full 7/8” thick jatoba, 15-1/2” long. The top, sides and one end are full 8” high. The bottom is 7-1/8” wide for a full width of 8-7/8”.

The top is rabbeted on three sides and fits into matching dados with 1/32” to spare. The top is fitted snugly and level with the top. The rabbets were made with the two cuts at 90° method. The dados were 15/62” square and cut on the TS.


First dry fit.

After the box was dry fit with the 1/4-20 bolts the tolerances on the lid went to zero and the lid was immovable. After I shaved 1/32” off the top it became a perfect fit. No real gap but slidable (after waxing). The box was sanded flush to 220.

The center of the top has a low profile finger pull mortised in to make it easier to open but still essentially flat. The lid fit is snug and there isn’t a fingernail gap anywhere. The pull can only be used to open the sliding lid and cannot be used as a lift. I had thought about adding end handles but the goal is to make it harder, not easier, to carry.

The top was initially long because of the dado. It was trimmed and sanded flush before the slot for the lock was cut.

All five fixed parts of the box are attached to each other with both glue and a series of two dozen 1/4-20 1-1/4” long SS allen head machine screws. The machine screws are countersunk and back filled with JB Weld to prevent removal.

The screws are offset slightly to 5/8” from the outside edge, instead of the 7/16” nominal center on the 7/8” stock, to put more meat between the outside and the bolts. After all, the box doesn’t have to resist blowing the inside out. I say “nominal” because the jatoba is being used full thickness as supplied and not planed to a specific dimension.


Initial rough fitting.

Just finished tapping the 22 1/4-20×1-1/4” bolt holes. It was supposed to be 24 but a snapped drill and a snapped tap plugged two of the holes. The holes were drilled in stages. First the holes were laid out 5/8” in from the outside edges and piloted with a 1/16” bit. The box was dry fit and the pilot holes were extended into the mating piece. The pilot holes were redrilled to full depth in the mating pieces.

Then the holes were countersunk 3/8” deep and dia. The box was dry fit and a couple holes drilled with a #7 pilot. These holes were threaded and the countersunk piece was thru drilled to 1/4”. The box was screwed together and the process repeated for all 22 usable holes.

Two of the bolts couldn’t be installed because of the broken tap and drill bits stuck below the surface. (Sigh.) But I’ll just fill the two empties with JB Weld to look like the others so no one will know (except YOU, my dear readers, and I know YOU won’t tell! LOL!)

  • I drilled and tapped 22, 1/4-20 holes, 1” deep. Tapping a 1/4 turn at a time with a wrench is 4 turns a rotation times 20 threads is 80 quarter turns to tap. 1760 quarter turns later there is a reason my shoulder is achy!

One of the things that makes the box hard to carry is its weight (~30# empty) and the intentionally sharp edges. Without handles its a grunt to grab.


Its HEAVY!

Someone pointed out that a portable hand saw could easily cut thru the box. To thwart that I mortised 1” x 1/4” steel bars into three inside faces, both side and the non-lock end. This should break the teeth off any blade as well as add more weight (2-1/2#).

Lock:
I gave a lot of thought to selecting the lock. Various types of high security locks were considered, round keys, half circle (unduplicatable) keys, magnetic keys, etc. Most of them are designed to be thru mounted in sheet metal and require a D-hole. Since a bored hole in wood doesn’t have anti-rotation flats, the D-lock can be grabbed with pliers or a wrench and physically rotated, turning the entire lock 90°, defeating the security. To prevent this a lock is needed that mounts with a flange on one side to stop rotation attacks.


Desk lock and keys.

A desk deadbolt is installed in the short end. Even if the top is sawn in half the lock will keep it from moving. The lock is a five tumbler, uniquely keyed unit. It mounts with a pair of #6 1/2” screws in the jatoba. The face of the lock is recessed slightly. The lock spec sheet says mount thickness max is 7/8” (which is where the jatoba is) but the actual physical lock barrel is only 13/16” long so it finishes out as recessed 1/16” so there is no projection at all.

A slot is cut in the lid with a biscuiter for the tongue on the lock. The slot was cut double wide to make it easier for the lock to catch. An 1/8” piece of scrap was used to offset the tool for the 2nd cut. This is a fast “no measure” technique. I keep assorted known thickness small scraps kicking around for just this purpose.

I goofed on the lock install and piloted the holes on the face. It looks a little odd and I’m thinking of adding a decoration to cover the goof and make it a feature.


Oops!

Trunk Hardware:
The bottom four corners are fitted with black powder coated trunk corners to protect against someone trying to smash it open. The corners are attached with black head screws.

Because of the sliding lid, the top cannot use trunk corners. So I’m using four black powder coated edge bumpers mounted just below the dado. This will prevent breaking the box at the ends. Mounted, again, with more of the same black hardware.


After first coat of 50%-50% poly/ms mix.

The top gets an inset pull. The fit of the top is so tight there is not even a gap you can get a fingernail into. The pull had to be mortised in. I did a test on a piece of scrap with my new plunge router. You can see the holding jig made from scraps, clamps, an assembly corner and the fence. Most of my jigs are temporary like this and get built and torn down out of scraps as needed.


Ad hoc routing jig.

I got all set up to cut the mortise and went to put the bit into the router only to discover I didn’t have a 1/4” shank straight cutter (sigh.) So I ordered what was available (3/8” x 1”, non-plunge) for pickup locally. Well one thing leads to another, they didn’t have the bit I wanted for plunging. So that led me to having to drill some flat bottomed starter holes to drop the bit into instead in of plunging down into the surface directly.


Test mortise needed hole to plunge into since bit wouldn’t!

After all that when I went to inset the handle I misread my marks and really boogered the mortise. Trying to fill it in would look like the bad patch it would be. To make matters worse the mortise was off center.

I decide to do a big purpleheart inlay as a “decoration” to cover the botch. Cutting the inlay slot with the TS and getting a perfect fit with the Incra was easy. The inlay dimensions were dead on and had a gentle rubber mallet fit once the glue was added.

I flattened the bottom of the inlay dado with the detail “finger” sander. Its just the right tool for cleaning the bottom of TS dados.

My scrap for the patch is what I call 1/4” (0.252”) and I cut the dado at 0.241” to leave the inlay ~0.010” proud. This makes sanding easier than if the dado were 0.010” too deep.

The inlay now appears as:


Its an architectural detail. That’s my story an’ I’m stick’n to it!

I’ll tell the cust its part of the design for strength. The crossing inlay helps protect the lid from splitting lengthwise.

Anti-Chainsaw:
To frustrate someone with a chain saw the inside of both sides and one end have been reinforced with lengths of 1” x 1/4” mild steel bars. The sides are laid out so the bars hit between the 1/4-20 screw holes.

I bought a 36” length of bar stock. It cut slowly but cleanly on my jig saw with the appropriate “thick metal” cutting blade. I put a drop of 3-in-1 oil on the cut lines to ease cutting.

Holes were drilled in the bars for the mounting screws on the drill press, again with a little oil to ease the drilling. The holes were started dry until the bit started to cut and the oil was added a couple of times. Once the holes were drilled they were chamfered for flat head wood screws.

The bars were put in place and outlined. The outline was drilled with a forstner bit to provide several starting points and to hog out some of the bulk material. The rest was cleaned out with the router.


Anti-chainsaw bar installation.

  • [email protected]#$%&() router collet started to slip during one of the cuts, fortunately I noticed before it got out of hand. I had cranked down on the collet but is is single wrench with lock button and I guess I hadn’t torqued the bit down tight enough. After some blue language and a grunt the collet was tight.

The pieces were glued and the screws power driven in — hard. You can see the difference between the initial glue drops and after being spread to 100% coverage. Once the glue squeezeout was cleaned up the heads are clogged & filled with JB Weld to prevent backout.


Final glue up and bolt backfill.

Since JB Weld is runny at first I had to fill one side at a time. Its a real mess and gets everywhere and it smears! (Blecch!) Fortunately I had put a slop coat of poly on before the JB Weld. This kept the JB Weld from getting deep into the pores and once it was dry it sanded off without a trace (other than where it was supposed to be.)


JB Weld mess sanded right off.

The top of the JB Weld was a little rough where it was sanded flat and shiny where it was a little shallow. But the poly evened the epoxy finish out. The epoxy looks like conventional walnut plugs.

The bottom corners had to be rounded to fit properly into the trunk corners. Any irregularities will be covered.


Looks like walnut plugs.

Final Steps:
The till rests on four 3/4” x 2” corner posts, 2-3/4” tall. Sloped spacers keep the till centered and allow access to the finger holes to make it easier to remove for access to the lower compartment. The space below is undivided and can easily hold additional cash or something a little more lethal — potentially very useful if the strong box is being opened under duress.

The end spacers are sloped so that if you just drop the till in place the 45° slope automatically centers the tray. This leaves the finger holes open. The slopes were cut with a 45° router chamfering bit and ripped off the edge of the wide board.


Pedestal & sloped end spacers.

Here you can see how the till moves into position when released. This also keeps the till from binding on removal. I don’t know about you, but I hate a sticky till!


Till auto centers when dropped in place.

The till doesn’t bind at all.

Finishing:
A slop coat of 50%-50% poly/ms coat was applied to the outside before final glueup. This helped tame any squeezeout and prevented the JB Weld from getting in the grain. The excess JB Weld sanded off with nary a trace.

Once the epoxy mess was cleaned off two additional coats of the 50%-50% poly/ms mix were applied. The inside was also finished with two coats of the 50%-50% mix.

The box was left inverted with the fans churning so it should be ready for the final coat of full strength poly tomorrow. Once that coat is done all thats left is to remount the final hardware and on from there.

Finis:


Hope he likes it!

Materials
  • Jatoba 1×9, 5.5 bf @ $9.95/bf — $54 + $19 shipping = $73
  • Clear Pine — $10
  • Drawer Lock — $12
  • Trunk Corners & Trunk edge protectors — $32
  • 1/4-20×1-1/4 SS Allen head machine screws — 24 @ $0.40 ea. = $9.60
  • Black screws for corners, edges and the pull — $10
  • Mild steel flat bar, 1” x 1/4” x 36” — $8
  • Finger pull — $12

Matl Total: ~$167

Labor: (so far)
  • Bill till — 2 hrs @ $20/hr = $40
  • Strong box — 13 hrs @ $20/hr = $260

Labor Total: $300

COGS: $467 — SOLD!

Misc. Shop Items Consumed:
  • JB Weld
  • Broken 6-32 tap
  • Broken #6 pilot drill
  • 3/8” x 1” 1/4” shank router bit
  • glue
  • poly
  • 6 foam brushes, assorted sizes

I’m sure there’s more but my memory is Swiss cheese …

-- The hump with the stump and the pump!



6 comments so far

View Ocelot's profile

Ocelot

3250 posts in 3803 days


#1 posted 06-14-2021 08:30 PM

it looks like a real nice box, but I personally would not store money like that.

-- I intended to be a woodworker, but turned into a tool and lumber collector.

View Madmark2's profile

Madmark2

2973 posts in 1753 days


#2 posted 06-14-2021 08:52 PM

Yeah, and everyone carries one. Its designed with the option of thru bolt holes for floor mount. If you cut into it and encounter one of those two dozen 1/4”-20 bolts there should be sparks a-plenty!

Cust understands its wood and not steel. But for the casual thief it should be a stopper.

I previously made one out of 5/4×12 jatoba that weight 50# or so empty. The client kept guns & ammo in it and it took two people to lift it.

No one is going to get into it without making a ton of noise. Its the same idea as plate glass. Breaking it is the alarm!

-- The hump with the stump and the pump!

View HowardAppel's profile

HowardAppel

110 posts in 4199 days


#3 posted 06-25-2021 11:08 PM

I want the cash.

View John Smith's profile

John Smith

2984 posts in 1327 days


#4 posted 06-27-2021 06:46 PM

excellent build documentary – thanks for sharing

-- there is no educational alternative to having a front row seat in the School of Hard Knocks. --

View LeeRoyMan's profile

LeeRoyMan

1954 posts in 892 days


#5 posted 06-29-2021 04:09 AM


No one is going to get into it without making a ton of noise. Its the same idea as plate glass. Breaking it is the alarm!

“I tried to think of every potential attack”

“and generally impossible to open without the key.”

- Madmark2


I think you missed the mark, Mark

I think using the metal “anti chainsaw” bars was redundant.
I don’t know how many thief’s show up with a chain saw.

Using a three dollar lock that can be punched in in about 3 seconds?

I think anybody that would put 1/3 of a million dollars in it is Loonier than Mr. Magoo

That all said, it would be a nice box for minimal security items.
In other words, what’s the saying? It keeps an honest man honest.

Nice score on the sale.

View Madmark2's profile

Madmark2

2973 posts in 1753 days


#6 posted 06-30-2021 07:00 PM

It’s not a “three dollar” lock. It’s a five tumbler cut key lock that was specifically selected to not be punchable or capable of being rotated with pliers. It was the best, non-rotatable lock I could find.

The bars were added in direct response to a poster mentioning that it could be easily cut with a battery saw. And while I mentioned that not everyone carries a saw the threat was real enough to take countermeasures.

The most important safety feature is in not bragging to people that you’re storing large amounts of cash.

The box looks good enough to be left out on a shelf as a decoration. If you put the lock side to the wall no-one will know what it is. You could tell someone that it’s a fake “treasure chest” you found at Pier 1 Imports or at The Bombay Co. & put a lamp on it.

-- The hump with the stump and the pump!

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