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Backstreet Engineering...

Soldering

I am given to understand that a staggering 80% of failure in constructing a project is due to poor soldering.

Good soldering is a skill that is only learned by practice.

The first thing you need is a good soldering iron. I find that irons made by Antex to be an extremely good choice. Choose one with a fairly high wattage.

The second thing you need is a soldering iron stand, preferably one that incorporates a sponge pad sunk into a small water trough.

Another alternative albeit more expensive is a soldering station where the irons temperature can be variably controlled, and even have a digital display to show the current temperature of the iron. These units also usually contain a cleaning sponge and trough. Those made by Vann Draper are very good.

The end of the iron is called the “bit” or “tip”

The temperature of the tip is between approximately 330 ˚ C and 350 ˚ C although the latest lead free solders will require more heat.

Dribble some water into the trough (an old shampoo dispenser is good for this.) Switch on the iron and wait for the iron to reach its full temperature, before doing anything. Apply solder to the flattened working area of the tip and wipe it off on the sponge. This is called “tinning” the tip. The iron will now have a thin film on the tip.

Apply a little more solder to the iron and put the tip of the iron at an angle that allows the heat to flow quickly from the iron to BOTH parts of the joint.

The heated soldering iron should then be placed in contact with the joint and allowed to heat them up.

Once they are heated the solder can be applied. The solder should flow through and around the joint.

The finished joint should be shiny and clean.

Too much solder on the join represents a waste and too little may not physically support the joint.

The joint should take no more than 3 seconds. (5 seconds maximum.) Try and get into the habit of wiping the tip each time you make a joint.

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Some Ideas for Enclosures

Good quality purpose made boxes can be very expensive when purchased new; therefore it is a good idea to be on the look out for new unused boxes at you favourite rallies where they can be found at a much lesser price.

Another idea at a rally is to be on the look out for a scrap piece of gear for the purpose of using just the case. Assuming the design of the case allows the old front and rear panel to be detached you can then replace these with new aluminium panels or copper clad board, to be marked out and then drilled to suit your needs.

I have found some really good quality enclosures using this method.

It’s always a good idea to ask the stallholder if he would mind you removing the cover to see how the case has been constructed.

If the case has removable front and rear panels then the case has great possibilities. This means that the front and rear panels could be replaced with new aluminium or copper clad board panels and drilled to suit your requirements.

I never go to a rally without a couple of screwdrivers in my pocket!

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Useful Tools

  • Steel set square
  • Steel Rule in Millimetres and Inches
  • Digital Vernier Callipers in Millimetres and Inches
  • Sharp pencil
  • Decorator’s masking tape
  • Punch and Hammer
  • Reamer
  • Electric Drill
  • Pillar Drill
  • Drill Bits

Marking Out Front and rear Panels

Irrespective of the panel being new or old, if it is not covered with a protective covering put one on now, this will save the panel from getting unnecessarily scratched during drilling etc.

This can easily be done by using decorator’s masking tape.

     

 

Lay all the hardware like Knobs, Switches, Led’s, Meters etc out on the front plate and using a sharp pencil mark out their placement (make sure at this stage you leave enough room for your fingers to comfortably turn the knobs)

Replicate for the rear panel.

Before attempting to drill any holes, mark out on the masking tape with a sharp pencil two perpendicular intersecting lines to indicate the required hole centre, and make a fairly deep centre-punch mark. This will help stop the drill bit point from skating around. Do this in three stages; first make a light centre-punch mark exactly where the lines intersect. Next, scrutinise the mark, and you will invariably find that it is slightly off from where you intended it to be. Don't worry; you can move the punch mark to where it should be by driving it across the surface with light hammer blows applied to an angled centre punch. When you are satisfied the mark is correctly positioned, set the centre-punch vertical and give it a firm knock to make a nice deep indentation.

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Drilling

Make sure your drill-bits are sharp.

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Most metals require a slow drilling speed. This is best done with a Pillar Drill.

Aluminium however is an exception to the rule, it is a very soft metal and swarf very soon builds up on the drill-bit if driven to slowly, therefore a faster speed seems to produce a much cleaner hole, providing the feed rate is slow. In other words if you are using an electric Hand Drill, do not apply to much pressure to the surface of the metal. The same applies to the Pillar Drill.

Take care if drilling through thin sheets of metal. Make sure the sheet it is well fixed in position, otherwise it is quite easy for the drill-bit to snatch the work as it breaks through. This can result in a nasty cut if a metal sheet spins out of your grip, so do not hold it in bare hands, instead clamp it firmly to the bench! Drilling sheet metal into a block of scrap wood (MDF is ideal) will result in a cleaner exit hole and less chance of the metal "climbing" up the flutes of the drill-bit immediately after breakthrough.

Drilling Large Holes

Best done in stages. Start with a smaller drill-bit, and then work up to the final size using progressively larger drill-bits. This will reduce the strain and wear on the drill and drill-bit, and reduce the chance of you ending up with a triangular shaped hole!

Drilling Odd Size Holes

I find the best approach is to drill a hole slightly undersize and then insert a reamer into the hole and by gently turning clockwise will increase the diameter to the required size.

Metals are often best drilled using a fixed machine drill (such as a pillar drill or a lathe), with the work clamped into a drill vice or similar. If a fixed machine is not available then a conventional hand held drill mounted in a drill stand would be the next best alternative.

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Cutting Out Squares and Oblongs

This can be time consuming.

Using a pencil, mark out the required shape on the masking tape.

Then with a punch and hammer, make dents inside the marked out shape (at this point bear in mind that the final holes to be drilled must not exceed the marked out area.

Once the majority of the unwanted aluminium has been removed, carefully file away the remainder using a fairly course file until you are close to the marked out lines.

Now change to a fine file to finish.

Step Drill-bits

For holes in thin sheet metal up to 3mm thick, a ‘step drill’ is a great choice. It will produce a fairly clean hole.

First drill a pilot hole, some step drills will have a pilot built into the end.

Then drill through, pushing each step through until you reach the step that is the size you want. These will need to be used with your drill set on a fairly low speed, and always with plenty of lubrication. Another option is a cone drill. Very similar to the step drill, except that it is tapered rather than having steps.

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Large Diameter Holes

Hole saws are also used for drilling larger diameter holes. Suitable for thicker material than a step drill.

Available in many sizes from about 16mm to 150mm diameter. You will also require an arbour to use these. They come in two types, the first simply screws into the hole saw tight.

The second, for sizes above 35mm, screws in until about half a turn from tight, and then a collar with 2 pins is screwed down. This prevents the arbour from jamming into the hole saw. One of the best ways to buy hole saws is in a kit, with a selection of sizes and usually both types of arbour.

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Countersinking

Countersinking will require a very slow speed and quite a lot of pressure. Lubrication is essential. Once you have drilled your hole use a ‘countersink’ to make the recess for the countersunk screw head. You will need to hold your drill as square to the job as possible to make an even countersink. You will need a HSS countersinking bit.

If you need to countersink holes in thin sheet metal it is a good idea to drill the holes slightly smaller than you will need, as the countersink will make them slightly larger.

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Lubrication

Lubrication is needed quite frequently for drilling metal; there are a few different one available.In liquids, aerosols and pastes. Apply it liberally to the cutting tool as required. If you have only a couple of holes to drill, a brush of clean engine oil or a drop of 3in1 oil is better than nothing. Penetrating oils, such as WD40 are not cutting oils.All of these types of tool are okay for use on steel, aluminium and stainless steel with the correct speeds and lubrication.

Speaker Grill Ideas

Perforated matrix circuit board is a great material to use. Cut an oblong or square from the main sheet of matrix board, to the required size using a junior type hacksaw.

Lightly spray paint the top side of the board in the required colour. Be careful to spray lightly otherwise you could end up clogging the tiny holes.

Cutting Speaker Holes

Hold the Speaker in its intended location and draw around it.

Find the exact centre of the circle and make a punch mark.

Draw a line straight through the centre of the circle and beyond.

Now reduce this diameter by a sufficient amount to allow the Speaker to be comfortably fixed in place.

Small Speakers are best held in place by small fixing clamps. With the speaker still held in position, lay the clamps on the line dissecting the circle and mark the fixing clamp holes.

Punch the holes.

Drill the main Speaker hole in the panel using a hole saw and remove any burr.

Drill the Speaker clamp holes.

Painting the Enclosure

All Wrapped Up
With some careful painting and the appliance of legends can make a very professional appearance to a project. Sometimes to such an extent it will be difficult to tell the difference between homebrew and factory produced.

Painting
Wherever you decide to paint don’t do it inside the house, divorce proceedings will be imminent.

In the garden is not a good idea either. I tried this once, on a summer’s day with no breeze. Ideal conditions I thought, so I covered the garden table and started to spray my box, when I finished it looked really good and so I left it to dry. When I checked on it about an hour later I found kamikaze Gnats and Flies had come to investigate and stuck themselves to my tacky paint. All in all a waste of time, so a re-think was required. I resorted to the garage.

I have found the best method is to make a painting box. This is simply a large cardboard packing case with the front cut away. This helps greatly by reducing the film mist of spray paint in the air from settling on those surrounding things in the workshop that you had no intention to paint in the first place.

****Picture of Spray” paint box****



Spray paints sold by Halfords are very good and the range of colours is enormous.

If you fancy White as a colour then always buy “Appliance White” this is intended as the name suggests for touching up white goods such as washing machines and tumble dryers etc. The reason I have found this to be so good is for the simple reason that the paint is very thick and has the capability of filling in any small blemishes in the surface with just one coat.

Whichever colour you go for Spray painting gives a far better finish than using a brush.

Remember
Preparation of the surface is the key to getting a good finish.

Be sure to paint in a well ventilated area.

Bare Aluminium Preparation
Thoroughly de-grease the surface, using surgical spirit and kitchen roll.

Provide a “Key” to the surface using steel wool. Rub the surface with the wool in one direction only. Clean the surface using a piece of kitchen roll. Do not be tempted to run your fingers back over the metal, as this will only add more grease to the surface.

Place the surface into the painting box.

Bare Aluminium Painting
Apply the undercoat first and remember to shake the spray can for at least four minutes prior to use and continue to shake regularly during use.

Hold the can vertically and about 12 inches from the surface. Apply the paint by spraying thin and even coats in a steady back and forth motion, slightly overlapping with each stroke.

Allow to dry for at least 1 hour.

Once dry inspect the panel for any blemishes, it will be quite normal to find some. These are easily removed by very lightly rubbing them with very fine emery paper, remember to remove any dust.

Spray a second coat and allow drying for at least one hour.

****Picture of undercoated panel****

Top Coat Painting
Choose your colour and repeat the above method.

****Picture of top coated panel****

Producing the Legends
For this job I use a rather dated P-touch labelling machine with one of these you can produce very professional legends. You are able to choose the required font size and print accordingly.

I tend to use a cartridge that gives white text on a clear background.

Applying the Legends
Once printed, cut off the excess tape above and below the text with the aid of a sharp scalpel and repeat the process for the excess tape left and right of the text.

It is important to make all your cuts “square”.

From the right hand side of the legend, carefully remove the legend backing tape using a scalpel. The legend should now be hanging off the edge of the blade.

Lightly offer the legend to the panel and again make sure it is offered “square”. Once you are completely satisfied, press down the legend. Repeat this process for the rest of the panel.

Clear Lacquer Coat
At this stage all Drilling, Undercoat Painting, Topcoat Painting, and Legend work should have been carried out.

All that remains is for the Clear Lacquer spray to be applied. This is done by using the same method as for spraying paint except that only one coat should be used.

****Picture of finished panel****