Not much experience with tiny little hydraulic rams.  Usual choice is a chromed rod if the seal is under high pressure or exposed to moisture.  Is this a double acting hydraulic ram?

If double acting, there is no problem with a little leakage by the piston ring(s) in this application.

Piston seal leakage is NOT fine, though as wear occurs some may have to be accepted. In most cases internal leakage will not be obvious until it is serious and then a rebuild will be needed. Re machining pistons, piston rods or cylinder ends to take newer or different seals is common. One company I have used is All Seals at Norwich, very helpful fellows ! Good Luck. Noel.

Piston seal leakage is NOT fine

Expected in this application.  It is not high pressure (even with several piston rings in the case of an engine), compression will leak down slowly past the rings- as there will be a gap on each ring.

Please see this thread:

CBN inserts

I suggested a fairly random UK supplier that Google found for me and the OP replied that they had ben extremely helpful to him.

On 13 August 2024 at 18:59 Peter Cook 6 Said:

Depending on the size you want, the hardened chromed rod used for linear bearings and building 3D printers might be the cheapest source.

Gas springs or car shock absorbers are probably better sources. I have a couple of 500mm(ish)lengths of 20mm hard chrome rods from some front struts that took about a minute with an angle grinder to harvest. Provided some nice tubing too, although the process is a bit messy…

On 13 August 2024 at 22:44 Nick Wheeler Said:

On 13 August 2024 at 18:59 Peter Cook 6 Said:

Depending on the size you want, the hardened chromed rod used for linear bearings and building 3D printers might be the cheapest source.

Gas springs or car shock absorbers are probably better sources.

Think a little about the age and place of manufacture of the machine. Are the required hydraulic rods more likely to be metric or imperial?

On J and S grinders the cylinder rod is 3/8″ diamiter and have packing seals on the rods which are a ruberised cloth in a circular V shape with a plastic formed spacer. when under pressure the hydraulic oil presses the seal on to the rod with little friction and loads of wear space so they last for ages. The central piston has two Hydraulic round nosed ruberised cloth seals back to back. O ring seals will cause to much friction and will wear to soon.

David

This company do a huge range of seals, but you would probably fall foul of minimum order charge https://eriks.co.uk/en/products/sealing-and-polymer/industrial-seals/