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.

Using A Dial Gauge To Measure The Shape Of A Surface

Recently I've been trying to measure the shape of a vintage plastic cupboard handle.  For those that aren't up to speed, check out my previous post on how to use a radius gauge, where I explain the motivation for the project.  I was able to determine the basic shape of the profile on the face of the handle, but wanted to quantify it a little more.  After a lot of thinking I figured out a way to do this using a dial gauge with a magnetic base attached to the carriage of a lathe.  It takes patience but gives great results.

Measurement Setup

The first thing to do is rigidly mount the object you want to measure in the toolpost of a lathe. In this case I've fitted the handle to a thick sturdy bracket.  The screws in the toolpost weren't long enough to reach it so I've used a lathe tool between the bracket and the centre screw to space it out.

Handle Mounting

The next step is to place the magnetic base and dial indicator in a position on the lathe carriage so that they won't get hit if you move the topslide.  Do some tests to make sure that the tip of the dial indicator can reach all parts of the surface you want to measure.

Probing The Handle

Then comes the tedious part.  Position the handle so that the indicator tip is just to the side of the surface you want to measure.  You then raise the indicator tip, move the topslide a set amount by turning the dial, lower the indicator tip, and then take a reading and repeat.

In my case I decided to take a measurement every 0.1 mm.  In the image below, this means that I had to turn the dial 5 divisions between every reading.  Make sure that you always travel in the same direction when doing this, otherwise the backlash in the topslide will make the measurements worthless.  It's also important to lift the indicator tip when moving the topslide.  If you don't, the surface will push the indicator tip to the side, once again making the readings meaningless.

Cross Slide Dial

When taking readings off the dial, estimate the position of the needle if it's between marks.  It may not be exact but it's better than rounding.

Dial Indicator

Depending on what dial indicator you have, you may need a new tip for it.  The one I was able to use had a tip that was very round and wasn't sharp enough to access all the areas of the surface I wanted to measure.

Dial Indicator

You can see the difference between the tip I used in the above process and the one that comes with the indicator.

Contact Points

I was able to get a set of dial indicator contact points on eBay for 20 dollars Australian.  They aren't the highest quality things I've ever seen, but they do exactly what I want and that's all that matters.  If you're looking for a set yourself, search for "indicator contact tips" or "indicator contact points".  Searching for 4-48 UNF threads also leads you to these as it seems to be pretty much the only thing that thread is used for.  Some dial indicators use an M2.5 thread, so you may need an adapter.

Contact Point Set

The point of the tip I used looks to be round, but using radius gauges I was able to tell that it had a radius of less than 0.3mm.  I'm fine with that.

Sharp Contact Point

When performing measurements I wrote down my results as I went.  I then went way back to the beginning started again and took a measurement every 2.5 mm to make sure that the dial indicator didn't move during the process.  This was just to verify the setup and are the circled data points.

Data

The data was then plotted to reveal the shape of the handle.  When looking at the shape it's important to remember the limitations of the tip geometry.  The three sharp crevasses will appear round because the tip is slightly round and can't get all the way to the bottom of them.  As the tip is conical it will also have trouble measuring the vertical part to the left and right of the central bumps, so these sections will also be slightly distorted.

The red dots in the image below are the verification data points.  This makes me confident that the setup didn't move during the measurement process.

Profile with verification points

Another thing to look out for is that you might not have mounted the object perfectly flat.  Because my object is symmetrical. I can mirror the data, overlay it and see that I do indeed have a small misalignment.

Profile with its mirror image

By lining the two up, I was able to determine that the part was off flat by about 0.5 degrees.  I can now compensate for that later.

Profile with its mirror image rotated 1 degree

Another thing that may happen is that the handle is not mounted perpendicular to the motion of the top-slide.  This would have the effect of stretching the shape side to side.

To be honest this turned out a lot better than I expected.  I need to do more work to clean up the data, but I now have a good reference to work from.

Using A Radius Gauge

I recently managed to buy unused original 1950's stock of a handle that was used on my grandparents kitchen cupboard and I want to be able to reproduce it in the future.  The first step in this process is measure measure measure!

Replicating the exact mechanical operation of the handle isn't that important, what I'm mainly interested in is being able to reproduce it's aesthetics.  The first part I'm measuring is the radius of the beading on the outside of the handle.  One problem, I had no idea how I was going to do it.

Acetex 44L Handle

My go to tool for something like this would normally be a caliper.  Unfortunately in this case there isn't really anywhere to get the jaws of the calipers around the curve of the beading.  Not even 180 degrees of the beading is available to measure.  So to measure the curve you need to compare it to a set of reference curves.  It turn's out that the tool to use is a radius gauge.  After a longer than expected wait for $10 gauge from eBay, I was able to get started.

Radius Gauge

The gauge comes with external and internal feelers with radii ranging from 0.3mm to 1.5mm in 0.1mm increments.  The concave gauges can measure radii where around 70 degrees or more of the total circle is available.

Concave Gauges

The convex gauges can measure radii where 180 or less of the circle is available.

Convex Gauges

Ideally when using these gauges you hold them against the surface you want to measure, hold everything up to the light and look for light leakage around the edges.  To take photos I've just put them on the table and placed the gauge against the handle.  You can see that the 1.2mm gauge is slightly too small.

1.2mm Gauge

It's hard to tell from the below photo, but the 1.3mm gauge is almost perfect.  A little to big. but close.  This now gives a range for the radius of 1.2-1.3 mm.

1.3mm Gauge

It should be said that I haven't verified these gauges against a standard, but I plan to take a few measurements in different ways and use them to build up confidence in the profile I measure.  From what I've been able to tell there are 4 beads that make up the central reeding.  They are evenly spaced and there is 7mm between the centres of the outer ones.  The radii of the beads is as seen before about 1.25mm.  The shoulders of the profile are made of two sections.  Coming from the beading is a flat section that I've eyeballed to be about 5 degrees less than horizontal.  I've tested the flatness of this section by placing a razor blade against it and checking for light leakage.  After this section is an unknown curve that is tangent to the other section but stops abruptly at the edge.

Handle Profile

Still a lot of measuring to do. No idea how to do, but I'll figure it out.

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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Mounting a Changeover Switch on a Generator Frame

Over the last month or so I've been intermittently working on adding a changeover switch to my grandmothers generator.  This will allow the battery to switched between a solar charger or the starter motor of the generator, and although it's not complete, it's 90% there and the interesting work work is all done.  Before I wrap things up you can catch up on my efforts so far in these couple of posts.

13/10/2014 Blade Switch Modification

24/10/2014 Blade Switch Modification - Part 2

The generator is a small backup unit to power fridges in the event of a power outage.  It's mounted on a steel frame with wheels that allows it to be easily moved.  Mounting the changeover switch on the frame is the easiest option that gives the best result.  The image below shows the general arrangement of the frame.  The switch is going to be mounted just above the electrical generator, in the image this is where the black and red cables are coming from.  It needs to connect to the battery in the black case on the ground, the solar charger mounted on the roof (cabling above to the right and not in frame), and the starter motor.   The starter motor connection point can be seen to the left near the yellow oil fill point on the motor.  Unfortunately I didn't have the cabling or the time to install it today, but it's a trivial task I'll complete in the near future.

Generator Frame Layout

This is the part of the project that really annoyed me.  Making a bracket to hold the switch.  I don't have the metal fabrication tools that are needed to do a professional job.  As usual I went to my fall back plan of finding a metal plate from the local hardware and making it do what I needed it to.

The plate below is just a standard joining plate used in the building industry.  I added five small holes to it.  The two on the left allow a saddle clamp to attach the plate to round tube on the frame, the bottom two holes allow metal screws to connect it to a rectangular tube, and the centre hole is the mounting point for the switch.  Two of these plates are needed, one for each side of the switch.

Mounting Plate

The mounted switch can be seen in the highlighted section of the image below.  It's mounted on the left to keep it away from the motor exhaust.  I need to make a couple of cables to connect everything together, but the hard part is over.  I could have done things better, but when you're building something in one place and installing it in another, it makes things a little difficult.

By the way, if Santa happens to read this I could really do with a water jet cutter, press brake, and a milling machine.  Yeah, I'm aware how much that would cost, and yes it's a want not a need, but I've been reasonably good.

Mounted Switch

Blade Switch Modification - Part 2

My last post laid out how I planned to modify a high current DPDT blade switch, making it easier to connect eye terminals from a solar charger, starter motor, and battery.  The goal is to add threaded posts to the terminals by soldering some screws through them.    This post is just an update of my efforts.

I started by drilling a hole in the end of each terminal plate and tapping an M5 thread in it.  It may seem strange to tap a thread for something I'm going to solder in place, but I thought it would be an easy way to hold everything together while I soldered the screw to the plate.  I originally intended to use 20mm long brass M5 hex bolts, but they were over a dollar each, while M5 cheese head screws the same length were 20 cents.  The head didn't really matter so I went with those.

To solder the parts together I used a 2% silver solder and a MAPP torch.  The image below shows the results from soldering the brass screws to the plates.  Those of you with a keen eye may notice the first four look like crap.  After I did the first two, I took some time to reassess things and thought my surface preparation could be improved.  So I spent some more time thoroughly filing all the surfaces to be mated.  You can see from parts three and four, things didn't get much better.

It was at this point I realised I'd been using the wrong flux.  I'd been applying the stuff for just basic plumbing work using lead free tin solder.  I needed something a little bit more powerful for silver solder brazing rod.  Luckily I had some flux that contained boric and phosphoric acid.  The poison warning on the bottle was bigger than the brand name so it had to be good, right?  Indeed it was. My last two joints were a lot better.  Joint five is almost perfect, but I think joint six got too hot.  It was going well and then the solder started spitting (always wear goggles).  I was tempted to rework the first four parts, but even though they were they ugly, they were electrically and mechanically connected.  I didn't have spare parts, so if I made a mistake it would be a month before new parts arrive from China.  I played it safe and left them alone.  If I had to do 100 of these I think I'd know what I was doing after a few more attempts.

Brass strips with screws soldered in place

It was almost easy sailing from then on.  Joint 6 caused me some problems.  The solder wicked its way through the thread and about 5 mm down the bolt.  This was easily fixed by running an M5 die down the thread to re-cut it.  The flux was then removed and the entire switch was reassembled.

Screw Terminal

All I need to do now is make a mounting bracket and finish the wiring.

Reassembled Blade Switch

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