Riveting Plywood to Metal

Today I'll give you a quick rundown of my experiment riveting aluminium to plywood.

2.8 mm Plywood Riveted to 1.4 mm Aluminium

If you've read my blog before you may know I like boxes and storage solutions.  I made some prototype storage boxes last year out of 19 mm pine and plywood, and since then they have been used quiet a lot.  The main problem I have with them is they are heavy, use more material than is really needed, and are complicated to make.  I wanted to simplify things and for inspiration I turned to an ammunition case that I have from 1958.  It's made from ply and is riveted together with metal edges.  All the components themselves are not specifically strong, but when assembled the case is rather sturdy.

Ammunition Box

I happened to find some brass rivets on AliExpress that are used for material, you may be wearing some now. Have a look at your jeans.  The type I purchased are called double capped, meaning they have flat rivets on both sides.  They consist of a cap and post that are pressed together.

Brass Rivet Cap

I ordered these because they were listed as 10 mm long.  I thought that this would mean I could join materials up to 10 mm (leaving room for compression of course).  Unfortunately I was mistaken. The length of the post is 10 mm but this only leaves 8.5 mm space for materials, and after compression of the rivets only about 5-6 mm are feasible.

Brass Rivet Post

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Rivet Test Compression

For my test I planned to join some 6 mm ply to a piece of aluminium angle, but because the rivets are smaller than I planned I used 3 mm plywood.  Two 3 mm holes were drilled into the aluminium and the posts were inserted. A hole slightly larger (about 3.75 mm) was drilled in the ply, the caps inserted and the the rivets clipped together. For the final compression step no fancy tools were used. They were placed in a vice and I squashed the hell out of them.

The results speak for themselves. I think they look awesome and they will not budge.

Aluminium Side

The dark wood and brass look nice together gives the strength I need. I think I'm on to something.

Plywood Side

I'm not actually building a box in this post. This is just a test, and besides I don't think the size of box I want to make will work with 3 mm ply. I need slightly bigger rivets. So now we wait the standard 2 or 3 weeks for a shipment from China. :-(

There are plenty of designs for storage boxes that may be better than mine, but what I'm aiming for is a good strength to weight ratio box that can be easily assembled by people at home without exotic materials and tools.  The idea is that if you want a box you go and buy some ply and metal and use rivets you've purchased.

Learning to use a Chisel

I use a lot of power tools but when it comes to hand tools I have a lot to learn.  So this week I decided to take it easy on my holidays and try to learn how to use a chisel.  There isn't much to this post.  It's mainly just to show that I'm still here, still working on things.

First of all I used a marking knife to score the wood in the area I wanted to remove.  This gives the chisel tip a starting point an it also cuts the wood fibre to prevent the wood splintering.

Scored Area

From there I slowly removed the wood, working my way down to the desired level.

Chiselled Rebate

The sides weren't completely straight and the cut ended up a little larger than I had hoped.

Chiselled Rebate

Next time I think I'll remove a lot of material from the centre before bring the rebate to the final size.  That should produce a better result.  I also need to use a sharper chisel.  Another tool that would come in handy would be a woodworkers vice and bench.  It would hold the wood in place better and prevent it from moving.

Chiselled Rebate

Thanks to Masters for the discounted wood to play with. :-)

Compound Mitre Cuts

It's funny how the seemingly easy can be ridiculously hard.  A relative wanted a replica of a serving tray that belonged to a family member, and I was asked to work out the mitre angles because I'm the math guy.  "Sure, no problem" I naively said.  All that was required was to tilt the tops of all the sides outward so that the timber was 25 degrees from vertical.

Angled Frame

Before going too far it seemed prudent to cut a test using some scrap wood.  The first step was to cut a 25 degree taper on the edge of the moulding that's in contact with the base.  That was easy.  I then came unstuck trying to calculate the angles required to make the corners fit together at 90 degrees.  I ended up using an awesome online calculator to calculate the angles for convenience.  It may seem easy, but in this case the mitre angle needed to be cut at about 22.9 degrees, while at the same time the head of the saw needs to be tilted at 39.9 degrees.  It took me a while to figure out where those numbers come from, but suffice to say it's not the simplest of maths.

Undercut Mitre

The moulding wasn't to easy to work with as it doesn't have many flat surfaces.

Undercut Mitre

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Mitre

The corners don't fit together that well as I didn't take extremely accurate measurements.  It also doesn't help that the parallel edges aren't exactly the same length.

Frame Corner

One problem I currently have is that I don't have a good way to measure angles.  That should be solved soon.  Combining the results so far with a little more accuracy should make the job a lot easier.

Mitre Corner

In the image below you can see the complex shape of the wood I'm using for the test.  The actual serving tray will be made out of plain rectangular material making things a lot easier.

Profile Shape

I do have a method to calculate all the angles needed to make compound mitre cuts.  It makes use of vectors and exploits some of their abilities, but I'll leave that for another time.

Custom Storage Box Prototypes

In my last post I played around with an idea for mass producible boxes that can be manufactured with laser cutting and routing.  Before going too far down this path I wanted to test the form factor of the box, discovering what works and what doesn't.  Besides, I actually need some storage.

I started with a cheap 1.2 meter long piece of pine from Bunnings.  The external dimensions of the box (350mm x 275mm) were selected to minimise waste from a single board.  The timber is 184 mm wide and is close enough to the desired final height of the boxes, it therefore didn't make sense to change it.  Ideally I think 10 mm plywood is optimum for the box sides, but 19 mm pine will be fine for this test.  As the sides are thicker it also allows them to be joined with a dowels instead of cutting time consuming box joints.

Box With Sliding Lid

The construction is very simple, with two side panels placed between a front and rear panel.  All contain a rebate at the bottom to retain a piece of 7mm ply for the base.  The front and sides are also rebated at the top to hold a 7mm ply sliding lid.  The back panel is cut lower to allow the insertion and removal of the lid.  In the final design the groove for the sliding lid would also continue into the back panel, but it's quicker and easier to just cut it straight across.  Remember, the point of these boxes isn't for demonstrating my jointing prowess (still a beginner, but getting better) it's to quickly produce a box to use and test.  You'll also notice I wasn't too concerned about router tearout either.

Rear of Box with Smaller Back Panel

When inserted, the lid prevents dust entering the box and items falling out.  However, in this rudimentary test the main problem is that if the box is picked up from the front the lid slides out the back.  It definitely needs some sort of retention mechanism and it also needs a handle.  Both of these flaws were obvious from the start, but I haven't really settled on how I want that to work.

Top of Box

This is my favourite part of the design.  They're brass drawer pulls I bought on Aliexpress for about one Australian dollar each.  They allow small labels to be inserted and removed as needed.  The viewable area of the labels they hold are about 40mm by 20mm and you can fit a decent amount of text in there, but it's not that readable at a distance.  Unfortunately the proportions of the front panel look weird too.  As these boxes are designed to fit a specific location I had to make the long side the front, ideally the short side would be the front and these drawer pulls would be more suitable.  Luckily there are larger ones available, so next time I'll buy those.

Brass Pull with Label Insert

I also decided to experiment with interlocking removable dividers.  There theory was to split the box up into 9 equal compartments to allow better separation of small items.  Due to tool and jig issues, I had to make the centre compartment on the long side larger than the others.

Front to Back Dividers

With all the dividers in place you may notice a lot of space around some of the joints.  I was allowing a lot of clearance in this part of the job as I wanted everything to go together easily the first time.

Side to Side Dividers

The big problem I discovered is that there's a minimum usable compartment size.  I can get my hand in the smaller ones but I can't see what I'm trying to grab.  If the box was only 25 mm tall that wouldn't be a problem, but as each compartment is about 150 mm deep it isn't going to work.  I think if the box was divided into 6 (3 x 2) roughly equal square compartments the result would be more usable.

Compartments are too small

I cut the divider guides all the way across the board but they only need to extend to the top edge.

Guide at Top of Box For Lid

I think this next detail is the most important thing I learnt that'll help make a more enjoyable design.  When the lid is inserted it's in contact with all four side panels and any misalignment during assembly or even expansion and contraction of the wood will cause the lid to catch on edges when inserted.  You can see in the image below that when inserting the panel in the back slot there's a small lip due to assembly misalignment.

Misalignment of Back and Side Panels

This can also occur at the front.  To fix this, ideally the rebated guides in the sides should be tapered.  Let's say you have a 7 mm board for the lid and you're happy leaving 0.5 mm of clearance.  Instead of just routing a 7.5 mm slot, make it 8.5 mm at the back to allow for misalignment and then reduce it to 7.5 mm after an inch or two.  Then make the rebate in the front 8.5 mm wide.  By doing this the lid should slide in and out without hitting anything.

Misalignment of Front and Side Panels

The top lid won't be perfectly flat either, it could bow up or down.  So you may want to make the front slot a little larger in the centre where it will bow the most.  You could also taper the sides of the front rebate to allow the lid to locate into the front slot smoothly.

Curved Lid Not fitting into Front Slot

Dimensionwise, I was flying by the seat of my pants on this project and just making it up as I went.  Most of my rebates were 6 mm but that introduces a tiny problem.  You want the rebate for the dividers to be a small as possible.  If they're too deep, you leave a small hole that dust or insects can get into.  Just a minor thing.

Divider Guide as Seen From the Top

While I was at it I made 8 of them. :-)  It took about three days of work and the the total price for each box comes to around $20.  The funny thing is that making 8 boxes takes about as long as making 6 boxes.  Most of the time was spent setting up tools, measuring and marking things.  That's partly why I'd like to use CNC equipment to cut out the parts for the boxes.  In the time it took me to make 8 boxes I could assemble 50 pre-cut boxes.

Usage Example

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Idea For A Mass Producible Wooden Storage Box

I like things to be organised.  Over time, I've found the best way to accomplish this is to store similar things in labelled boxes.  It looks neat and tidy and makes it easy to find exactly what you want when you want it.

The exact form factor of the boxes has so far been an iterative process where I learn the pros and cons of each design as I use it.  I currently use cardboard boxes, but the long term goal was always move to wooden boxes.  I have only a few requirements.  They need to be big enough to hold a sheet of A4 paper (297mm x 210mm), and they need to have a lid to prevent dust covering the items I want to store.

The title of this post mentions the term "Mass Producible".  I should clarify that I mean making about 100 boxes, not millions.  With that in mind, I also want to be able to use automated manufacturing methods like CNC routing and laser cutting to make the parts of the boxes.  It would be great if I could get some furniture grade plywood delivered to a workshop, have them cut the pieces, and all that was left was a bit of assembly.  I haven't been able to find that capability yet, but it'll happen one day.

So what have I come up with?  Nothing too ground breaking.  In the image below you can see that there are standard box joints in the corners.  For this job, box joints are pretty much the only way to go.  Although the image below has been rendered with a plain piece of timber, I actually want to use plywood and making the thickness of the ply as small as practical is important as it reduces the weight of and size of the box.  With thin pieces of ply, nailing or screwing into the ends can cause problems with splitting, the box joint eliminates this as an issue.  It also make assembly easy.  Glue and clamp.

Storage Box with Sliding Lid

With the lid removed you can see the rebate that allows it to slide in and out.

Rear View of Box with Lid Removed

With the back and side removed you can now see a couple of extra features.  There are grooves cut into the sides that allow removable dividers to be added and removed as needed.  The shape of the base is now visible as well.  Traditionally you would just cut a rebate all around the bottom for the base.  So why have I gone for the convoluted tabs?  Once again, plywood.  Depending on the depth of any rebate and the direction of the grain in that layer of the ply, there is a risk that when a heavy item is placed in the box, the ply could fail.  This stitches the base and sides together for greater strength.

Rear view of Box with Back and Side Removed

Of course this creates some problems.  If you're laser cutting the tab holes and they go all the way through, everything is fine, but if they only go half way, they need to be routed and need t-bone fillets added to allow the tabs to be inserted.  This is because you can't cut an internal square corner with a router bit.

Box with Base Removed

I don't have the capability to manufacture these at the moment.  Ideally I'd start off by routing all the features that don't go all the way through on a 1200mm x 2400mm sheet of plywood.  At this point it's still one sheet that's easy to move.  It would then be laser cut to produce the final pieces.  I don't even know if this is something that's done commonly.  The reason for this is that you need the nice square internal corners that a laser produces for nice box joints.  I might be able to play around with the joints to make it a one step process by routing though.

So what's next?  Like I said, I can't manufacture them they way I want yet.  That doesn't mean I can't play around with the form factor though.  Stay tuned.

Designing My Ultimate workbench

If you're like me, at some point you've dreamt of how you'd build your ideal desk or workbench. Everyone will have a different vision depending on their needs, but I think most people, even if they don't know it, have a list of requirements floating around in their head.  As a bit of an exercise in CAD, I decided to visualise my ideas so that when I have the space, time, and money I'll be able to build it without too many problems.

Workbench Design

My design is fairly straight forward.  I wanted a lot of open space and also wanted it to be easy to add extra features in the future.  To accomplish this there are equally spaced pre-drilled holes in the rear uprights.  These also allow the desk to be made in bolt together sections so that a single person can transport and assemble it without help.  At this point I've used 50mm x50mm square sections of steel, but I'm not sold on bolting across a hollow tube.  I prefer to bolt flat plates together, but I think it'll be fine though if the steel section is thick enough.

Bolting the bench frame to the uprights.

A welded frame is bolted between uprights to form the bench.  It's made mostly of square steel with some rectangular section cut on an angle welded to the bottom for brackets.

Bench frame

The workbench is made of inch thick pine with a rubber antistatic mat on top.  Once again these components are all easily managed by one person.  Cross bars are also used to mount computer monitors so that they are off the desk.  In the rendering below the monitors are bolted directly to the cross bar.  In reality it's likely that they will be mounted to a swing arm so that they can be moved closer to the user.

The pre-drilled uprights also allow shelves and lights to be easily mounted.  In this case the brackets for these aren't shown, but it's not too hard to imagine a triangular shaped support with internal bracing if needed.  The lights used are 600mm x 1200mm LED panel lights.  The nice even spread of light minimises reflections and shadows cast on the work area.  Ideally I'd also like to have a camera mounted on a swing arm to record any work I'm doing.  That's why I also don't mind over sizing the rear supports as this will minimize vibrations the camera may experience.

Monitors and Lights

The lights are set forward to allow maximum illumination of the bench without wasting light on the shelving.

Location of shelving and lights

At the moment the thing is built like a tank.  I can afford to reduce the size of certain elements to reduce the weight, but at this point it's just to get a feel for the concept.  My bolt holes in the upright are 50 mm apart and 10 mm in diameter.  This is just a first guess and will eventually be different.

Bench Frame

OH NO!!!  Someone broke in and replaced two of my uprights with light sabers.  OK, I may have got a little carried away with the self illuminating materials in Fusion 360.

Add caption

I'd love to know if you have any ideas or examples of your own.  If you have any ideas for things to mount at the back let me know.  I've been thinking along the line of small parts bins or something like that.

Cheap and Easy DIY TV Stand

Recently my mother asked me to sort out a problem she was having.  On top of a cupboard in the kitchen she has a 26 inch LCD TV she likes to watch.  It's at a height of about 2.5 meters, and when sitting, she's looking up at an angle of about 30 degrees.  At such an extreme viewing angle the image becomes unwatchable.  What she wanted was a way to tilt the TV so that the screen was facing her when she sat down.

I thought this would be easy, the TV has 200mm x 100mm VESA mount points on the back, it's not too heavy (8kg), all that was needed was a stand that allowed it to be tilted down.  The cheapest bracket and stand that met our criteria was over $150 and that was more than we were willing to pay, so it wasn't going to be as easy as I thought.  I decided to just buy a tilting wall mount bracket for $35 and figure out what to do with it when it arrived.  Building my own tilt mechanism would've taken way too long and wouldn't have been as good.

B-Tech BT7522B LCD wall mount bracket

After receiving the tilting bracket I went to the local hardware and walked around to see if I could find something to mount it to and make a TV stand.  It wasn't long until I found the post stirrup section.  Just in case you don't know, post stirrups are metal brackets used to keep timber posts of buildings elevated above ground to prevent rotting. They're concreted into the ground or bolted to a concrete base and the post is then attached to the top part.  Perfect, for $7 I get a sturdy metal bracket that can be mounted to a ply base to complete the job.

Post stirrup TV display stand

I just happened to have an offcut of 19mm plywood under my bed that was perfect for the base.

Ply base

It always pays to keep large offcuts.  Originally the ply was left over from my removable drawer project.

Drawer slide holder

It then became a side of my standing desk experiment.

Standing desk add-on

As the stand sits on an L shaped cupboard in a corner, I had to cut out a section so there wouldn't be an overhanging bit.  To attach the post stirrup to the base board I used 4 bolts and a metal plate as a washer.  This meant that the bottom was no longer flat and needed to be elevated.  To do this I used a hole saw to cut some circular feet out of the scrap ply section that was removed.  These were glued and screwed in place.  The parts that were going to be visible when installed were then painted white.

Base with feet and washer plate attached

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Washer plate

The tilting bracket was then attached to the post stirrup with some metal screws and lock nuts.  It's not the most attractive piece of furniture, but it's not too hard to imagine how to make it look like more like a professional product.  A new piece of ply the right size and a bit more time planning, painting, and sanding, this wouldn't be out out place in a living room.  Depends how good you are at finishing wood though, I took some shortcuts because I wanted this to be a one day build.  The TV hides all of the ugly stuff anyway.  The only part you can see is the edge that I painted white

The best part however is that it only cost me $50 maybe $65 if you bought everything new.

Tilting bracket attached to post stirrup

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Tilting bracket attached to post stirrup

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Assembled TV stand

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