Hydraulic Valve seat

In an earlier post I was trying to find a manual for a Polar 55 paper guillotine which had hydraulic problems. I never found a manual but found some info and dismantled the hydraulic valve block where I found the broken housing which has the valve stem running through it.

As a new part is unobtainable I was going to machine one. The valve spindle is 8mm dia and its about 28mm on the largest dia.

The existing material can just be filed and produces sharp sparks looking like carbon steel. I was hoping to avoid heat treatment.

The nearest material I can obtain is 24T, has anyone a better suggestion for material?

Peter

Well, the original was obviously fracture-prone. I'd try silver steel BS1407, untreated for a first go - then think about hardening it if the first one wears rapidly.

I'd use 4140, this can be heat treated if required, that is near to EN 19. EN 24T and 4340 are about the same, and if you want it a little tougher DIN. 1.2767 will take shock loading a little better.

Ian S C

I have some P20 pre hardened 38 mm dia bar which machines pretty good and is tough if you would like a piece. I am in Nottinghamshire if you want send me a PM.

David

As a rider to David's offer of P20 ( I have some here in Lichfield area if needed) P20 can be flame hardened to give a surface of 55/60 Rockwell and retain its core strength it also nitrides very well.

Thanks for the material suggestions, very helpful. I've managed to get hold of a small piece of EN19 and made one. I changed the design slightly to made radiused corners where the original broke at the sharp edges. Its now installed in the hydraulic block inside the machine and so far its now working and giving an adjustable pressure to the clamp (20-120bar) so I'm pleased with the progress. So pleased I forgot to take a pic!

Not sure if its going to hold also I'd like to make another better one just in case so I'd like to take up the offer of the P20, what the best way to arrange?

Peter

Where are you in the country send me a PM with address and I can send it to you.

David

Thanks David, just sent pm.