Hi Tom,
Sorry for the delay in replying to your query but only got back to the UK early this morning and for some reason didn't get a notification of your post while away.
Could you please say a little about the ball seating jig you show in post#14. I expect it's use is fairly self evident, however, what wasn't clear to me was how you determine the "maximum clearance" - by the angle of the valve stem, by measurement with feeler gauges, or something else and what the 2.9 stamped on the jig referring to?
I ask the questions because I understand that the clearance (i.e. how far the ball protrudes from it's carrier) is critical to the correct operation of this type of safety valve.
The 2.9 on the jig refers to the size of the hole that the ball sits in. The size hole means that a 5/32" (4 mm ish) ball will be resting in it on its radius. This measurement is arrived at by dividing the balls diameter 3,969 mm by 1.41 which gives 2.815 mm and I usually use the next drill size up. I have always done this when making safety valves, I must have read it in the ME in the dim and distant, it seems to work. The clearance of the cup needs to be very little about 10/15 degree lean or as little as can be managed and the ball still seats. I seem to remember that the article I read about making them suggested 5 to 10 thou clearance possibly to allow for wear?
I hope this helps.
Regards Tony.
