I made an experiment with my smallest centre drill (provably 0.7mm or so) and enlarged the hole to 1mm.


Right: faulty hole.
Left: the hole with above method.
Large burrs were produced, but the hole was nicely centred.


I rechecked my stock of drills and found 1mm centre drill. I drilled holes with this to halfway and penetrated it with 1mm twist drill.


I removed the burrs with spotting drill as much as possible and completely removed them by turning the work with a very fine file. Removing burrs is important to prevent wear of valve bodies and smooth operation.


Connecting parts to operation rod were made from 3mm brass rod and bonded to the valve rod with Loctite. The angle of holes must be in 90 degrees. They were positioned by help of pieces of brass rod.


The valve rod was installed. This shows the valves closed. The tightness between body and rod cannot be so good, but may be sealed reasonably well with steam oil. Anyway small leakage may look nice while operation.


This shows valves open.



inserted by FC2 system