A new attempt at making piston rings

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L98fiero

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I went down this path for a custom cutter. Not impossible & will save some bucks, but... you have to get the pocket milled correctly to contain the insert. I find getting the corner radius sharp for a proper fit is a bit fiddly. Also need the appropriate screw (available separately). Maybe you have that corresponding tap, maybe not... Model engineers can tackle anything. I can say from personal experience the shank steel is hardened, tough sh*t so maybe the stiffness & rigidity is part of why it works well. You can indicate off the shank & confirm its set up perpendicular.
I didn't find it much of an issue, mill the bottom of the pocket with a new, sharp 1/8" endmill, cut clearance for the tip and then clear the remainder, angle the vise for the end stop and that's done. Then it's just a matter of going to the, in my case, KBC catalog and find a toolholder/boring bar that uses the appropriate XXXT insert and buy a replacement screw, most are metric flat head Torx screws appropriate for the 60° countersink in the insert and then picking up the hole location for drilling and tapping. The hole location is a bit of a judgement call but you want it to pull back and down so it seats. If you're just going for function you can even use a socket head cap screw in a pinch.
As for how hard the holder is, if you're planning a long production run or heavy machining it would be something I'd be concerned about but keep the overhang limited and if it's only for a few ring grooves in cast iron or aluminum you'll have no problem.
 

DougB

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Hi Guys,


I have read a few of the comments about the use of custom cutters and while there is no doubt they will work I however found using a slitting saw and rotary table far more reliable and predictable.

Regards,

Doug
 

Gordon

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Gordon, you might actually be seeing a metric 1mm wide tool re-labelled for the N-Am market. Shars is famous for that, trying to being helpful I suppose. Parting tools are typically not precision ground for width though, its more of a nominal size thing. The N-Am basis is /64, /32" (unstated +/- tolerances). If you just suggesting this as starting point stock to finish grind then disregard. But I'm pretty sure the typical parting T profile has no side clearance on the upper portion, at least they don't show on sketch. That's typically what the thinning is about on the lower portion.
Actually, within reason the width is not important. If a .040 parting tool cuts .042 you just adjust the width of the ring accordingly. Not having side clearance could be a problem since you want smooth sides.

I just checked my .040 parting tool and it does have side clearance. The top section is tapered in a a slight angle.
 
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Brian Rupnow

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This is a video I made today, 11-june-2021 of my vertical i.c. engine 2021. I have been trying to make a set of cast iron rings for the piston, and as part of that I built a new cylinder and new piston to accept cast iron rings, but ultimately I was not successful. Finally I decided that I should put this engine back together, so I enlarged the top ring groove to .093" wide x 0.058" deep and put a Viton ring on it. This engine can now go up on the shelf with all of my other engines. I am still after cast iron rings that actually work, but will be trying them out on a different engine that is a lot simpler to take apart and access the piston.----Brian
 

Brian Rupnow

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And this is one of my other engines which I tried to run cast iron rings on and failed miserably. I have restored the original piston with a Viton ring on it, and of course it runs like a trooper. I wanted to make sure that both engines ran well before putting them back up "on the shelf". This engine is a noisy devil, because the spur gears are not enclosed in a metal housing. I am still pursuing the cast iron ring magic, but I'm not there yet. I have another engine to try cast iron rings on, but it is a much simpler engine to change pistons on.----Brian
 

Brian Rupnow

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I am going to try this one more time, but there is a possibility that the cast iron I purchased may not be right for the job. Does anyone know if there is a place in Ontario that sells "Meehanite"? I'm having a problem finding it.---Brian
 

Gordon

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I am not sure but is ductile iron a better choice for piston rings instead of grey iron? I think that Meehanite is a trade name as opposed to a type of cast iron.
 

L98fiero

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I am going to try this one more time, but there is a possibility that the cast iron I purchased may not be right for the job. Does anyone know if there is a place in Ontario that sells "Meehanite"? I'm having a problem finding it.---Brian
Brian;
Here's a link discussing what Meehanite is, can't say for sure but you probably don't really need Meehanite, just good cast Durabar. Meehanite As I've posted before Terranova Steel sells it and probably Metal Supermarket, McKinnon in Woodbridge and even AtoZ in Barrie
 

doc1955

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I am not sure but is ductile iron a better choice for piston rings instead of grey iron? I think that Meehanite is a trade name as opposed to a type of cast iron.
You are correct on both counts.
 

Tim1974

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I was told gray iron not that dura bar stuff ? Hard to find I no but when you do is cheep post cost me more than the 800 mm bar I got ?
 

Fidlstyks

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Brian, I am a new member here. Have read posts here a few years now, I belong to several web pages and have not taken the time to post everywhere.
I always liked making rings, so this thread has caught my eye.
Several things come to my mind to try and help you along. Sorry I have not the time to read all the posts here, so I may be redundant in some advice.

Here are somethings that come to mind.
Please note I think of things later or in post-proof reading and change my words. So if I misspell or quote, look later, I may change what I said. I finally learned to shut off the auto correct which got me in trouble a time or two.

So here is my advice.
Remeber in the begining, all engines ran on tempered cast rings, it is O rings new to engines.
One important point is when using rings, get it clear in your mind, the cylinder breaks into the rings. Rings do not break into the cylinder. That is why they hone a cylinder. It must have swirls to wear in. This is a problem with alot of people. You need to have a nicely honed cylinder, and fit the piston to the cylinder. If you make a piston first, you cannot set a close tollerance, honing later makes an improper clearance.

This breakin may not be happening in your case, as I believe you did not temper the ring. Very important. It takes a harder than the cylinder ring to break in.
If you look at any new cast iron ring, they have a blue tint to them. And they snap when forced to do things they not want to do. This color is the temper, not a snazy paint job.
To make a ring and temper it, I machine a cylinder to my bore diameter and anywhere from square to .050 ring depth. So engine bore 1.250, make cast iron tube 1.250. It then has 1.200 bore, to make a ring .050 thick. It is nice to make all engine bores to hone fit to the same size. But the ring can fit slightly different sizes of bore.
I part the ring with a tool bit ground to look like a parting tool, with relief on each side behind the cutting edge to be sure and not damage the ring edges.
I set the compound at an exact right angle to lathe center line. Then I run the bit past the front of the tube I of cast iron. That way then you shut off lathe. Pull bit back, then turn compound down .062 plus width of tool bit which is usally .0625 so I get as many rings as are wasted.
I have already cut my piston groove at .0625 wide x .0625 deep.

After the ring is parted off, where I drug the tool bit back there usually is a scratch. I take an exacto blade and cut-groove in the cast ring all around. Like glass cutting, the cast breaks where the scratch is. Some times I use a jewlerys saw.
I then place the ring in a machinist vise with the scratch at the edge of vise. I then tap the ring at this edge with a drift and hammer. It usually just snaps there. I then raise the ring a bit, using a point file I flatten the roughness and reverse the ring and flatten the other end. This becomes my ring gap. Which is an absolute must as when a ring heats, it expands length like as if the ring were a straight piece. Sometimes I think I make .002 gap, per inch of bore. I think in large hot operating engines people use .007 per inch of bore. A minimum is very important, the maximum us not as important as too much gap makes very little difference. Side clearance looses more compression than end gap. Always out the gap up as the pistons in engines rise under compression. Don't ask me who figured that One out. They say like air in the atmosphere, compressed air rises.
I run the ring through the groove to test fit. And place on oil stone to get a nice fit. 1/4 of .001 makes a better fit. But carbon buildup seizes tight fits. I have made the ring exactly the same size as the groove. But I am not a professional and just make every thing hand fit.
On a bore of 3.500" a ring side clearance over .0015 looses compression according to ring manufacturers. I am not a real authority on this measurement for side clearance.
The tempering is important than anything. One needs spring in a ring and The ring needs to be harder than the bore to break in a bore.
Next I place the ring on a flat piece of steel. Maybe what I have or 1/8" thcik. I cut and place a wedge in the ring gap, thicker as the bore increases. I use 1/8" gap creating wedge on 1.250 bore.
Then with a torch, I heat from the bottom the steel and ring to an orange color and dunk it into oil to freeze it. Ring is very hard and brittle at this point. Do not manipulate.

Next I polish this hard ring. Like in blacksmith shops where as my grandpa had when he hammered plow shares on a trip hammer, which I have, you always see a polishing wheel on the grinding mandrel, you must polish the ring to temper it at the right temp. The science here is to be able to control the tempering temperature of the ring by eye-color.
To prevent easy snap breaking and create spring, you must temper the ring. To temper, one anneals the ring to a heated temperature that turns polished steel to a desired temp, dark black blue to a deep blue or bright blue color. I forget the colors-temps. I have a color chart I look at by a forge where I usually do this. Old age is hard on my memory. I think it is around 810° and dark blue.
I do this back on the flat piece of steel I have also polished to be sure and watch the temperature change closely. This is a very interesting scientific way to develop a temperature by eye-color change, rather than a lieing needle on a furnace or pyrometer.
Some people say that like when they temper a knife blade, they dunk the piece at this blue color into water. I drop them on a rag, but one may dunk the whole thing. I have made many rings and knives, and hardened and tempered many pieces of steel, mainly spring making and determined that once a piece hits the blue color desired, it cannot keep getting hotter if the heat source is removed. If you have not polished the piece holding the ring? you can loose control and over heat. I like it to set at the tempered color a bit as it is sure to remove internal stress, rather than dunking again. When making a knife I use a 1" long piece of steel. When making springs I Some times cheat and hang it on a wire.
 
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dsage

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Not that any of the following will help you make rings but you may be interested in what "the big boys" do for rings.
This is Steve Morris of Steve Morris Engines in Michigan. He makes engines with turbos making upward of 3000hp.
Interesting what he uses for rings in his engines. Most of it not within our model sized machining capabilities.
But is interesting that he use a steel first ring. In one of the Model engine builder magazines there is an article on making rings from steel (rather than cast iron).
So Brian - You are not limited to cast iron. Another wrench in the works. LOL.
BTW this is a new video as of today. You might want to watch the next one that he says will have to do with cylinder bore finish.
As a matter of fact you should subscribe to him and go to his channel. He has a lot of really interesting information on engine internals.

 
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Fidlstyks

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I make castings in cast iron. I can mail you a sprue to make rings and pistons from if you like. What size bore do you have. Most of my sprues are under 1.250.
As far as material, you may have gotten something bad. Some people use window weights. They claim the no 2 cast springs wider. Another guy who made them stumbled across some weigts made of fine no 1 cast. I like the no 1. No 2 was usually almost throw away cast when new in my opinion. I think they had weight molds made when they poured, so if they had good cast left in the pot, they made some weights rather than pig iron?
 

dsage

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Proper cast iron whether it be ductile cast or gray cast - whatever you choose to use in continuous cast bar form is cheap from a reputable dealer. Don't use scrap iron. You'll just be in a world of hurt.
As they say. Garbage in - garbage out.
 

James Barker

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I can not take it anymore. At 20 pages in length, and countless methods and opinions about what materials and processes to use, Brian is still no closer to producing live functioning rings. May I suggest to you Brian, that you go back to basics and just do what your instincts tell you is the proper thing to do and forego all of the mumbo-jumbo, "scientifical" -ish methods. Good Lord. I am by no means an expert here, but I have been successful in making several sets of rings following simple instructions such as outlined in the articles and examples that I sent along to you. Everyone it seems has their "perfect", "surefire" recipe for success in making rings. Good for them if it works, but to me quite a bit of unnecessary labor is expended by many. Not to mention the added expenses incurred along those paths. Cut the rings to size, remove the burrs, split them, gap them using a fixture, wrap same in iron wire and place in the charcoal BBQ fire. Go to bed. In the morning, retrieve, unwrap, polish and install. Simple as that. All of these numbers and what-not, are I believe clouding the issue. Piston rings are being made, not a rocket launch to the moon. I will sit down and shut up now, but I would really like to see you have success in overcoming your challenge.

BC1
Jim
 

Fidlstyks

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I could agree that 20 pages is enough. But it really goes to show how we all are infatuated with the subject of rings. I finally joined the site so I could comment on the subject matter.

At 18 yo, I made drawings, wood patterns and cast my own kits starting back in 1980. It always amazed me when some ones model would not run. It seemed that no one ever wanted advice. They would talk about it like Brian, weigh the thoughts of others and then do their own thing. The reason most models never ran is usually either the compression or the cam timing. I have tried to show people how their cam was off, and they said they would figure it out. Must be my dumb look.
For a first post, maybe I went on too long. But I have read several of Brian's posts and just was surprised he never tackled the ring-compression issue. I learned to make rings from Bob Manske of Kansas. He was a great model maker. I also knew personally all of the greats from the LeSuer Mn show and when they had the NAMES show at the Domino's Farms Office Park at Anarbor Mich. Which is an event center S of Detroit owned by the former owner of Domino's Pizza, Tom Monaghan . I think they said he was worth 10 billion back then.
But of course with me, I knew his brother, James, who was a model maker too. He had a steam launch and a separate-buddy fridge in his shop, full of beer and cheese. Back early on he traded his half the business for the VW Beetle they started deliveries with. Poor me.
I met Georg Luhrs there who taught me to lap the piston to .0005 to .001 fit with a small oil groove and no ring.
When I started in 1980, you could buy rings for like 2-3 dollars. Fred Ellis formerly of Deperse Mo sold them, (ask me someday what happens when you store fireworks in your basement-foundry, such a sad story, what a waste). As did Coles, whose owner now just lets everything set. Or have things changed there? They both being no more, I am not even sure where people buy rings.
When I started it was a matter of scrounging and making everything. If I wanted to buy it, I would not have wanted it. I liked seeing what I could do. It is a "The journey is the destination" thing for me, and would love to see Brian make rings.
If I had a CNC operation, I would buy new cast iron. It is just the achievement thing for me. I use to buy castiron rounds that were pressure cast in carbon dies. Very good material. If they are 40 bucks a foot now, it is still a good deal, I am sure.
The casting sprues lay around here until I melt them down again. People used to buy them from me. I just think it is fun to make some thing of them. The tall 1 1/4" are usually hole free . I also use the vents for welding rods. I poke holes in the sand with a 3/16" rod for vent holes, they fall off of the castings, and I store them up, using Brazealoy no 5 flux. I weld alot of cast iron, collecting hit and miss engines.
If you use a piece of scrap, cut off a bit and break it. Then look at the crystal structure. A few times makes one an expert. I look for fine grains. Number 2 cast like most window weights have large looking structures. As I had said, the one man liked the large structure grains. He swore they sprung better. But the window weights are made of Garbage iron for the most part. Always full of holes and grains that very from one end to the other. They used what ever would melt in them to save money.
I like making things from anything John Deere. But it is hard to find anything now. Always staying away from anything that was run in oil, as the oil stays in the cast like a seasoned skillet. I melted the wheels from cast mowers to start with in my early days. Fine grey iron.
I have turned my dials wrong and ruined more castings than where I had the iron be bad, when once I would have a part almost all machined out. But I did learn the hard way to never melt motor blocks of HP Dodge's, Pontiacs or diesel. They do have nickel in them. It makes a good ringing bell though, no machining! I like 350 Chevy blocks, not truck blocks. They are so soft one can carve them with a pocket knife.

Also I melt in crucibles, never use Carbon Bonded Silicon Carbide Crucibles. Always use the Clay Graphite ones. I treat my iron with 3 different aditives too. Mostly it machines. But have had to toss a couple of pots in the past.
Kinda like a mistake I made when I put a stick of stressproof in the mill and started cutting gears. On tooth 25 of a 28 th gear, the cutter got dull, I then seen sparks fly. The stick turned hard in an instant. A dull bit will make stressproof with manganese hard in an instant. Looking back 30 years, all I had to do was skip that area, use a new cutter and finish the 12" stick. Instead I always thought it looked cool laying around the shop. If in a good mood when people asked me what it was, I told one story. If it was a cloudy day, I just grumbled.
Some people also make rings eliptic, (turn the outside, then move over the blank in the chuck a little ways to make it off center, the idea is so they spring out more, like a feathered edge. Others cast the cast iron blank, with a pollywog on the inside. A lump that makes the cast iron have a different structure in that place, by having a mass that lengthens cooling time changes the casting structure, which when machined with the gap cut at 180° away caused the ring to spring in the center more.
I have had people tell me they heated the finished ring like discribed being put into the fire. But studying metallurgy I see no point in that. Maybe if done prior to machining. If not queenched first, I see no point in that.

There are steels people make knives of where they Normalize the steel prior to heating and quenching and then tempering which is done by annealing to your color chart. One guy heats his finished blade then cools in lime twice before he heats and quenches. Then he tempers by annealing his polished blank to a specific color.

Of course to quench harden one checks for the heated piece to become nonmagnetic with a magnet, plus then estimate 50° hotter before quenching in oil, slicing the oil to keep it uniform. Which is a said standard. I quench my springs and knives that way. Then polish and anneal to color for my temper. The darker the color, the harder your piece stays. Light blue makes a lighter duty spring.b
As I was saying before, lay a new factory ring by your ring being tempered for color range reference and anneal your pre-polished ring on the steel stick, heating till the same color as the factory ring is achieved. Then your ring will spring and wear the cylinder into a proper fit.

It takes a break-in period you know. Some times the compression developes immediately, but usually it requires turning an engine over for a few minutes to start break-in. They use to show shots at Ford where they spun model T engines for breakin. Some of that was burning in the babbitt too. But new cast iron rings need spun over for a period of time before being fired up for the first time. Always oil well too.

One of the reasons they use crome molly, (I think that the material) rings is they require no breakin time.
 
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Nerd1000

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I am not sure but is ductile iron a better choice for piston rings instead of grey iron? I think that Meehanite is a trade name as opposed to a type of cast iron.
Ductile iron will be stronger and stiffer than grey iron but its 'nodular' graphite inclusions provide less self-lubrication than grey iron's flake graphite.

Ductile iron is commonly used for the top ring in full sized engines that run high compression ratios or forced induction that could break a grey iron ring. Such rings are usually coated to improve their friction properties so they don't gall up the cylinder walls.

For a model engine I think grey iron would be superior as no coating is required, plus continuous cast grey iron is usually slightly harder than the ductile iron equivalent.
 

Gordon

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I certainly do not agree that this thread should end. Many of us have learned a lot. Many of us who have built engines have had very erratic results when making rings. Brian did not have 6 or 8 failures, he found 6 or 8 ways that do not work. It just amazes me that some folks seem to use rather crude methods and seem to have success and others who try to do everything right cannot find the magic combination. I am sure that some things were done correctly and had offsetting incorrect operations. It is like getting an engine to run the first time. Nothing seems to work and suddenly we get ignition, valves, carburation, and compression right and everything takes off and runs but we do not know which adjustment finally made the difference.

Carry on Brian.

Gordon
 

ozzie46

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No body sys you have to keep reading this thread. those of us that want t keep up with it can and those that don't can just stop.
 

minh-thanh

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I certainly do not agree that this thread should end. Many of us have learned a lot. Many of us who have built engines have had very erratic results when making rings. . It just amazes me that some folks seem to use rather crude methods and seem to have success and others who try to do everything right cannot find the magic combination. I am sure that some things were done correctly and had offsetting incorrect operations.

Carry on Brian.

Gordon
With a little bit of my experience : When I make cylinders and rings , of course the cylinders and rings they are not perfectly round and straight , but they can combine to create compression .
I think the important thing is that the cylinder is not the ring !
 

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