Valve dimensions
Body from 1/2" AF HEX (Circlip didn't grasp this simple fact) brass bar 30mm long.

  1. Turn down the end 6mm to 5/16" diameter. Thread.
  2. Turn the workpiece round and drill 5.3mm hole 21mm deep.
  3. Now bore with a 7mm endmill for 7mm and thread 5/16" X 32 for 5mm. Thread right up to the end at M6 X 0.75
  4. Drill right through 3mm
  5. Turn the outside of the body down to 12 mm for 12mm of the length
  6. In the milling machine, cross drill for the plug 3mm on one of the hex flats 12mm from the end which was turned down and threaded 5/16" X 32. Then follow through with a 7mm endmill to a depth of 2.5mm.
  7. The plug is made from 5/16" diameter bar bored 3mm for 11mm with a 60° countersink for the nipple. Thread 5/16" X 32 for 8mm then with the parting tool, turn down 2mm to just under 7mm diameter before parting off at a total length of 10mm.
  8. The plunger is from stainess steel - chuck a bit of 1/4" ss bar and leave about 30mm protruding from the chuck - grip it very tightly, and turn down 20mm of the length to 4mm, then turn down the first 3mm to 2.5mm diameter and thread for the nut. Pontificator Circlip says I should tell you to turn down the 2.5mm bit before you turn down the 4mm bit - BOLLOCKS - I did another one today and it worked fine with small cuts!
    Now turn about 9mm of the 1/4" bit still protruding from the chuck to about 5.8mm and thread M6 X 0.75. Run the die back and forth to make the thread as loose as possible. Start to part off with 8mm of the thread on the shaft. Clean that end of the thread with a file and run the die over it again. Now finish the parting off.
  9. A 1mm thick brass washer 7mm diameter, plus a 3mm bit of ptfe also 7mm OD with a 3.8 mm hole to be a good push fit on the 4mm shaft of the plunger.
  10. Make the square on the end of the plunger 3mm long on the mill.
  11. Gland nut is made from 3/8" hex bar with 6mm of it threaded 5'16" X 32, the last 1mm turned down th the core depth of the thread so it screws in more easily. The hole should be fairly loose fit on the plunger - 4.2mm seems good.
  12. Silver solder the plug into the side and it's done.


    13. Note: For the bypass valve which is not screwed into the manifold, start with a 32mm body and make the 5/16" thread 8mm long with the contersink for a nipple connection. The other end of the body which was turned down to 12mm is threaded to fit through the back of the tank.