witout wanting to sound rude, do a search, its been discussed in finr detail many times

Search for an essay on piston rings on your choice of search engine and you should stumble upon a usefull article by walshaw.

I don't blame fizzy as some subjects re occur with regular monotony , which lathe to buy is a classic example .

I too would like to see some input by the more experienced engine builders in regards to the process of making rings more easily and with a higher success rate for beginners .

Yes sure i could go and dig through my library and find what i need to know but that doesn't help anyone else as they may not have access to the same books as i do .

Ian.

Here is what I do.

Make the liner first so you can use that to gauge the OD of the rings.

Chuck a bit of suitably sized CI bar in the lathe, face off and then turn sufficient length for the 4 rings, a couple of spares and the parting cuts until it just slips into the liner. Open up the hole with various size drills followed by a boring bar until you get the desired wall thickness.

Zero a thin parting tool against the end of the work, feed along the lathe to get the required width of ring and part off. Repeat by feeding along the ring width plus the parting tool width until you have enough rings. It helps to put a bit of wire or one of those angled scribers in the tailstock chuck to catch the rings as they drop off.

I find that a pair of end cutters will split the rings OK, even quite thick/wide ones. Use the cutters on the two edges hot the inside & outside faces. The black lines are where the ring has fractured not cuts.

Next spread the rings apart, some methods describe fancy jigs but I just pop a bit of scrap flat bar between the ends, about 4mm thickness per 1" dia seems to work OK for me. Not having an oven I just lay the spread rings on the hearth and heat with a blowtorch. Keep the heat even otherwise you will get egg shaped rings if one small area get hot first. I heat to red heat and hold it there for 3-4 mins then allow to cool slowly. The packer will now be loose as the ring will have taken the "set".

Lay a bit of wet and dry on a flat surface and rub the edges of the rings on that to clean them up and remove any burrs and scale from heating. To gap the rings hold them on the edge of the bench with the gap hanging over the edge then pinch the two ends together onto a needle file which can be worked up and down. To test the fit put the ring into the bore and use the piston to push it in so it is not angled in the bore, test the gap with feeler gauges, I go for about 0.002 per 1" bore.

Finally fit the rings to the piston and off you go. Ring grooves about 0.005" deeper than the ring thickness and 0.001" wider than ring width. This pic will also answer your other question

If all else fails revert to O rings like on the drawing

Edited By JasonB on 17/04/2016 14:02:49

I think the other two take care of that and the third is to scrape a bit of oil off the cylinder wall to lub the pin. There is a drip feed oiler into the open end of the cylinder. The full size had it so the model has the same 3 rings.

Edited By JasonB on 17/04/2016 16:15:31

Hi Andrew, thanks for your reply , all good information there for the beginner especially using a saw to split the rings .

I must admit i have never considered grinding the OD ! Do you think there is a benifit in doing this?

Hi Jason ,

Wow ! Thanks for taking the time to post such a comprehensive answer! There are two bits of information in there that i think most beginners are looking for :

The size of the spacer to spread the rings for heat treatment and the ring groove clearances .

Most articles tell you to insert a suitable spacer in the ring gap and heat etc but never explain what suitable is !

It would be nice if on the home page there was a link to a page/pages for info like that ,probably never happen though as anything submitted would have to be proof read before adding to the library – but one can only hope .

Ian

Strictly no, especially for steam, but I've got a cylindrical grinder so why not use it? The piston rings are for a hit 'n' miss engine. Given that I'd gone to the trouble of honing the liner to get a smoother finish it seemed sensible to grind the rings.

Andrew

Yes i feel this website could be more than just a forum and some advertising !

But this depends on those that run it and what they want to do with it , it could be the number one place for info and communications among model engineers with a few adjustments and some hard work from those in the know engineers that are prepared to give their knowledge and time to make it happen..

Think of like a wkipedia of model engineering on this website!

Ian