Hydraulic DCV Spool-Sleeve Clearance


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If anyone would happen to know what the typical clearance between the sleeve and spool of a "sliding spool" type hydraulic dcv is, please let me know. Can't find this spec anywhere. Do know that a pneumatic lapped sleeve and spool is about .0002 in.

Thanks, Dan
for a 1/2" DCV mobile hydraulic control valve clearance varies from 8 to 10 microns.
when the spool is "concentric" in a "concentric" bore there is a radial clearance of 4-5 microns between the circumference of the spool and the inside bore dia.
BUT..... although the clearance fit of the spool drastically influences the leakage characteristic of the valve ,it is not the only determining factor, in production it is important to maintain a concentricity tolerance of about 2 microns,( both spool and bore )
also the length of the leakage path affects the performance ( valve land overlap )

try and get a copy of
" Using industrial hydraulics" by T C frankenfield
Rexroth Ltd.

DCV spool valve manufacture is a complicted business with diamond bore honing and laser measuring spool grinding being employed.

good luck