< Valve Liner 2 >
In order to remove terrible burrs around 240 holes, I.D. and O.D. are finished here. First, the basket section is finished. The liner has diameter-shift between the two sections both in O.D and I.D. The photo shows cutting a slope between two inside diameters, using a ball-point end mill as a taper boring tool. Only I.D. must have such a slope so as to squeeze piston rings in assembly.
The liner is reversed and its working section is finished. I employed new 22mm boring tool which has 20mm shank and can be held in the body of 'slotter'.
This is the slotter which I prepared for cutting key way of the driving wheel. I never dreamed such a convenient use of the instrument.
Note the knife tool is hold in the tool post. Both I.D. and O.D. can be cut without tool change.
I.D. of the liner is larger than the tailstock center. So I prepared center extension jig. It was turned from a gunmetal round bar.
Grooves for O-rings are cut by a parting tool. After that, the cutting edges are rounded with a fine file so as to guard O-rings.
The end of I.D. is slightly chamfered. It is also for squeezing piston rings in assembly.
Finally, I.D. is finished with 'lapping'. I made an aluminum lap which has a slit and its O.D. can be adjusted. The lap is held in three-jaw, suitable abrasive oil is embedded to the lap, and the liner is held around the lap by hand. Turning the lap at 300 rpm, the liner is moved back and forth until rotating resistance disappears. Then the lap's O.D. is adjusted and I repeat the operation.
Finished valve liners with Viton O-rings: We need very thin O-rings here. I employed JASO-1028 in JIS (Japanese Industrial Standard).