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Surface Finish Information |   |
| Function and working life of a seal are affected greatly by the surface finish
of the sliding surfaces to be sealed. The minimum surface roughness with largest
possible profile bearing length ensures optimum work life. The following table gives an overview of the permissible surface roughness and of the machining process possible. | |
| 1. Cylnder Walls | |
| Material: | St 52 or better |
| Tolerance: | H 8-H 11, dependent on seal (see individual specification) |
| Peak-to-valley-height: | R max=< 2.5 µm R a= < 0.05-0.3 µm M r50-90 % in a cutting depth c=0.5x R zstarting from reference line of C ref=0%. |
| Machining process: | Honing and roller burnishing (rolling). Material should be removed at the concluding process stage, rather there ought to be a reshaping. Scratches, scores, machine scoring running concentrically or spirally are not permitted. |
| 2. Rods | |
| Material: | CK 45 or better |
| Tolerance: | Is determined by individual application and sealing component (see individual specification) |
| Peak-to-valley-height: | R max=< 2.5 µm R a= < 0.05-0.3 µm M r50-90 % in a cutting depth c=0.5x R zstarting from reference line of C ref=0%. |
| Machining process: | Non-oriented, ground or roller burnishing (rolling) |
| Corrision protection: | Hard chrome with coating thickness 30-50 µm |
| Severe true stress: | Hardening (55-60 HRC) and hard chroming. Re-work (finishing, grinding among others) to required surface quality after hard chroming. In doing so, developing scratches, scores, machine scoring running concentrically or spirally are not permitted. |
| 3. Housings | |
| Material: | St, cast steel (free of cavities/blow-holes) |
| Tolerance: | Can be taken from respective groove drawings. |
| Peak-to-valley-height: | Base of groove: R max=< 6.3 µm R a=< 1.6 µm M r50-90 % in a cutting depth c=0.5x R zstarting from reference line of C ref=0%. Sides of groove: R max=< 15.0 µm Some types allow a rougher groove base: (e.g. KI 310, KI 320: R max=< 10 µm, R a= 2.0 µm, see individual specification) |
| Machining process: | Turning and grinding |
| Comment: | Phospated and nitrated surfaces (bonding, chemical nickel plating) are not suitable as contact surfaces for seals without mechanical re-work. |
