An adjustable desk lamp made from old copper pipe. Using compression joints that are only hand tight means that joints can be moved as required to position the light. It has a 12volt dichroic bulb so that mains voltage is not mixed with the metal parts. The base is filled with lead to stop it tipping over.

Step 1: The Bits You'll Need

Here's a list of what you'll need. I have no idea how much all this lot would cost to buy new because I had everything I needed already in my shed.

The copper pipe I used was 15mm. So all the joints etc are to fit that size.

I give some links to places where they sell the bits you'll need. This is just to try to be clear about what parts i mean. I am not recommending that you use these suppliers.

1) About 1 metre of 15mm copper pipe (or tube if you're a plumber)

2) 90 degree soldered elbow joints - x6

3) Soldered equal tee joints - x5

4) Compression 90 degree elbow joints - x2

5) Compression stop end - x4

6) Endex female coupling, n2, 15mm.
In my picture this is already soldered to the bent pipe. The big end must be wide enough for
your bulb socket to fit inside.
eg: http://www.jellydeal.co.uk/ENDEX-yorkshire-endex-female-coupling-n2-15mm-x.htm

7) A mains (e.g 240volt, in the UK) to 12 volt transformer. Mine came out of a broken desk lamp.

8) A 12volt dichroic spot light.
e.g. http://www.lightbulbs-direct.com/product/1273/m268-12v-50mm-closed-dichroic-20w-10-degree-spot/

9) A socket for your bulb. Mine came from the same broken desk lamp as item 7.
e.g. http://www.buylighting.com/MR16-Round-Socket-with-6-Inch-Leads-and-Clip-p/hs70603-clip.htm

10) 2 metres 0.75mm 2-core round flex.

11) About 1lb old lead piping. This is to melt and pour inside the base.

12) Isolating ball valve. Bottom left in the picture.
e.g http://www.screwfix.com/prods/52623/Plumbing/Brassware/Isolating-Valve-15mm-Pack-of-2

13) Ultra miniture toggle switch
e.g. http://www.maplin.co.uk/Module.aspx?ModuleNo=2340

Step 2: The Soldering

Make the base as shown. It is 6 inches wide and 8 inches deep (i.e. from front to back.)

The bottom part of the arm is 9 inches long.

Bend the top part of the arm and solder on the15mm to N2 connector. This bit is 14 inches long (not allowing for the bend)

Either do a neat job or, like me, spend some time removing any spilt solder from the finished parts.

Step 3: Fill the Base With Lead.

This stage is dangerous. Make sure you wear gloves and goggles. Also make sure the inside of the base is clean and dry. I was worried that the molten lead might spit back at me, but it went in without any problem. I also thought it might melt the solder, but again I had no such problem.

There were two things I had to think about during this stage:

1) The base is open at the top and the bottom, so the lead might just run right out. I started by filling from the top, but with a wet cloth around the joints at either end of the rear cross member. This was to cool that part and make sure the lead set before it could run out the bottom. This worked OK and before I had put much lead in the top section started to fill up.
Once the top was filled I turned it over and poured lead into all four feet. For this I put my wet cloth where the solid lead was, just to make sure it didn't melt again.

2) The top section, where I started pouring the lead, needs to be hollow so I could fit the wires. This meant I had to be careful not to add too much lead. In fact, the first time I did it, it filled up much quicker than I expected. I had to heat the top section with my blow-torch, melt the lead again, then turn it all over to pour out the lead - straight into a big bucket of water.

My base is at least half full of lead and heavy enough to stop it toppling over. The whole thing, base and arm, weighs 4lb.

Step 4: Make the Switch.

This was the most fiddly bit. I was hoping I could slide the switch into the housing of the ball valve from the end once I removed the ball etc. but it wouldn't go. I had to cut a hole in the back. The housing is made of brass so it is easy to drill and file.

You could skip this and just put a switch on the electrical lead.

1) Remove the ball etc. Mine was held in with a circlip.

2) Cut a hole in the back (drill first then open it out with a file) big enough to get the switch through.

3) Make a small copper plate from a piece of pipe that will just fit inside the hole. You will solder this in place later, once the wires are all connected.

Step 5: Connect the Bulb Socket

1) Thread the wire through the arm, but don't screw the compression joints together yet.

2) Solder the socket to the wires.

3) Put electrical tape around the connections.

3) Cover the end of the socket with electrical tape keep the glue off it. (I used red tape; you can see it in the third picture.)

4) Wedge the socket in place with a couple of bits of plastic.

5) Mix up some epoxy glue and glue the socket in place.

6) Once the glue has set remove the plastic wedges and add more glue.

7) Before the glue is completely hard remove the tape from the end of the socket.

8) Now pull the wires through and screw the compression joints together.

Step 6: Connect the Switch and Assemble

Solder the one of the wires to the switch, then solder on the back plate that you made in step 4. You need to use a soldering iron for this. If you use a blow torch you'll melt the plastic bits on the switch, or the insulation on the wires. I thought I might have trouble getting the parts hot enough but a large soldering iron worked well.

I slipped a piece of plastic over the electrical connections before I fitted the back plate to keep everything insulated.

I joined the wires inside the lamp to external lead just below switch using a couple pieces from a terminal block. The pipe is too narrow for them to going side by side so I had to separate them, trim them down a bit and put one above the other.

The compression joints on the switch should be screwed up tight so that it can't rotate. The two elbow compression joints, however, need to be slightly loose so the arms can be adjusted. First screw then up tight so that the compression rings are squeezed tightly onto the pipe. This means that the pipe can't slide out, but only rotate. Then loosen the joints again so that they are just hand tight and the joint can move put stays where it's put.

Use a bit of old plastic tubing to protect the lead where it goes through the side of the pipe.

THIS IS A 12 VOLT LAMP. DON'T CONNECT IT STRAIGHT TO THE MAINS. IF YOU DO YOU'LL BLOW THE BULB, MELT THE SWITCH AND MAYBE ELECTRICUTE YOUSELF. YOU NEED A TRANSFORMER. YOU CAN GET 240 VOLT BULBS VERY SIMILAR TO THE ONE I HAVE USED. DON'T BE TEMPTED TO USE ONE OF THESE INSTEAD OF USING AN EXTERNAL TRANSFORMER. THE MIXTURE OF MAINS POWER AND WIRES RUNNING THROUGH COPPER PIPE WITH SHARP EDGES COULD RESULT IN YOU ELECTRICUTING YOURSELF.

MAKE SURE YOU PUT THE TRANSFORMER IN AN INSULATING BOX.

Step 7: Add the Feet - Then Stand Back and Admire

Stand the lamp on something flat and make sure it doesn't wobble, then tighten the compress fitings on the feet.

This bit worked really well for me. Without the feet the base wobbled because the legs were slightly different lengths. Once I added to feet, adjusted them, then tighted them up it was completely steady.