Valve Spool and Bore Tolerances 2

[Cyclefrog]

Can anyone point me to a good reference on acceptable cavity bore and spool OD tolerances for a pilot-operated spool moving in a closed-end cavity? The valve body is aluminum, the spool is mild steel. The system typically runs under 1,000 psi with AW-32 fluid.

We're changing vendors on the valve body machining, and would like to avoid over-specifying.

 

[unclesyd]

Here is an example for a Al valve body. I have some more, older, literature from Engis that shows a lot of similar values, but also show some with tighter tolerances. Both of these companies were very good at supplying information on their products.
Engis supplies a lot of honing equipment for the auto and aircraft industry so they might be able to help you out with getting an economical bore for your end use.

http://www.engis.com/techsupport/bfcasestudy6.html

http://www.helicallap.com/

 

[meintsi]

Even with the low pressure you can't make this determination until you know the required gpm, pressure drop across the valve, the expected operating temperature range, and the allowable leakage.

Remember...
[navy]"If you don't use your head,[/navy]
[navy]your going to have to use your feet."[/navy]