Quote Originally Posted by Dornfelderliebe View Post
Nice one Evert. Not having any engineering facilities or suitably sized wood. I searched for another 25mm tube. Low and behold I found 25mm plastic conduit in the screwfix catalogue, wondering whether plastic is strong enough I tried it.
I glued a section of 400 grade wet & dry to it and gently had a go. I usually use different tubing with a slit to secure wet & dry wrapped around to polish cylinders so I was not worried about doing this carefully.
Whilst rotating it, I could feel alternating resistance then free movement. When moving forwards/backwards with a few degrees movement each time. I felt no difference.
Sadly my glue is not waterproof and after 5 minutes each on the two Mk3 cylinders I am working on, the paper came loose.
This may point to the uneven profile. I currently waiting for he glue to dry for a second attempt.
Sounds like a good approach.
Ed Canoles who showed O-ring experimentation on a lot of the forums some years back used an approach similar to yours to true up HW95 cylinders for o-ring piston noses.