Hi Barry, I've made solid piston valves from PEEK HPV which is a high performance bearing grade plastic filled with PTFE, Carbon, and Graphite with some success, apart from the difficulty of getting the correct fit at working temperature due to the expansion (not a problem with slide valves!). Using this for slide valves should be no problem as it will stand the temperatures involved and it's very easy to machine. I've used it for all sorts of bearings including coupling rod bushes etc. I made a set of slide valves for my brother's Rob Roy from solid PTFE which seem to be ok so far although it hasn't run a great distance yet. I have heard mention of PTFE valves distorting but as mentioned above, the ones I made haven't. The carbon filled variety would probably be more rigid and perhaps more suitable. John Barrie Purslow wrote: > I am currently refurbishing a 5" gauge Simplex which has non ferrous > cylinders. The slide valves are rather badly scored so I have skimmed the top > of the cylinder block no problem but I am reluctant to skim the valve itself > as it is obviously not made of a material with good rubbing characteristics > against the cylinder block. > I have it in mind to make new valves out of carbon filled ptfe which I have > previously used for a regulator valve with good results but this duty is a > little more onerous. > Any thoughts anybody? > Barrie > MODEL ENGINEERING DISCUSSION LIST. > > To UNSUBSCRIBE from this list, send a blank email to, > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject > line. > > > > MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.