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Re-Honing Piston Liner (Ringed)

Old 08-02-2022, 11:34 PM
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Eastflight
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Question Re-Honing Piston Liner (Ringed)

Hi all
I've just been told by a fellow club member that I should Re-Hone (cross hatching) with fine grit emery paper - the inside of the piston liner when replacing the piston ring.
Apparently it gives a better piston seal and engine output after the break-in period.
I've never thought of doing this before on model engines and wondered if it was a good idea to do so.
Feedback much appreciated.
Old 08-03-2022, 12:07 AM
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1967brutus
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Depends on what the liner material is and whether there is a coating of sorts. If it is plain steel, no problems, I do that all the time. Cross-hatch at an angle of between 45 and 60 degrees off the cylinder axis, not very critical. Won't hurt a bit unless you overdo it.
Can be done with some emery cloth and the plain old simple finger Mk 1.0
If it is a chromed liner, you have to be a bit more careful but can be done too. If you do, I would suggest using a honing tool like what you can buy to recondition brake caliper cylinder bores. Chances are a chromed liner is cross-hatched from factory and if so, most likely it is still intact. Then don't touch it.

If it is a Nikasil coating, ditto, the crosshatching most likely will still be there (one of my previous cars had that and the pattern was still visible all around the bore after 200K+ kilometres ((125K mi) I would not touch those. Nikasil is very rare in Model Engines.
But if it is an electroplated nickel coating, I would not touch it... Way too sensitive and/or fragile. Although chances are, with that type of coating the engine would not have a ringed piston to begin with and those sets are replaced as piston and liner matched sets.

Last edited by 1967brutus; 08-03-2022 at 12:17 AM.
Old 08-03-2022, 12:48 AM
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Originally Posted by 1967brutus View Post
Depends on what the liner material is and whether there is a coating of sorts. If it is plain steel, no problems, I do that all the time. Cross-hatch at an angle of between 45 and 60 degrees off the cylinder axis, not very critical. Won't hurt a bit unless you overdo it.
Can be done with some emery cloth and the plain old simple finger Mk 1.0
If it is a chromed liner, you have to be a bit more careful but can be done too. If you do, I would suggest using a honing tool like what you can buy to recondition brake caliper cylinder bores. Chances are a chromed liner is cross-hatched from factory and if so, most likely it is still intact. Then don't touch it.

If it is a Nikasil coating, ditto, the crosshatching most likely will still be there (one of my previous cars had that and the pattern was still visible all around the bore after 200K+ kilometres ((125K mi) I would not touch those. Nikasil is very rare in Model Engines.
But if it is an electroplated nickel coating, I would not touch it... Way too sensitive and/or fragile. Although chances are, with that type of coating the engine would not have a ringed piston to begin with and those sets are replaced as piston and liner matched sets.
Thanks Brutus for the info. I guess I'd better start doing this procedure on my future overhauls.
I Had this done on my car engine but didn't think it was necessary on these little boys!!
Old 08-03-2022, 02:23 AM
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Originally Posted by Eastflight View Post
didn't think it was necessary on these little boys!!
Size does NOT matter, it is what you do with it...
(sorry, could not resist...)

The weird thing is, running surfaces have an optimal smoothness range. Too rough is not good, but too smooth also is not OK. The oil needs something to cling to, and if the bore is polished, the oil wipes off and cannot do its job. And then that oil has the audacity to also put demands on the shape, size and form of that roughness. Hence the cross hatch pattern.

PS: for cars, it is imperative, or oil consumption will be higher than necessary (wet sump, and oil scraper rings). For everything else, it is just best performance and least wear.
Old 08-03-2022, 02:48 AM
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Originally Posted by 1967brutus View Post
Size does NOT matter, it is what you do with it...
(sorry, could not resist...)

The weird thing is, running surfaces have an optimal smoothness range. Too rough is not good, but too smooth also is not OK. The oil needs something to cling to, and if the bore is polished, the oil wipes off and cannot do its job. And then that oil has the audacity to also put demands on the shape, size and form of that roughness. Hence the cross hatch pattern.

PS: for cars, it is imperative, or oil consumption will be higher than necessary (wet sump, and oil scraper rings). For everything else, it is just best performance and least wear.
Touché .......I can see I've set you up nicely for that cheeky comment

Old 08-03-2022, 02:54 AM
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Originally Posted by 1967brutus View Post
Size does NOT matter, it is what you do with it...
(sorry, could not resist...)

The weird thing is, running surfaces have an optimal smoothness range. Too rough is not good, but too smooth also is not OK. The oil needs something to cling to, and if the bore is polished, the oil wipes off and cannot do its job. And then that oil has the audacity to also put demands on the shape, size and form of that roughness. Hence the cross hatch pattern.

PS: for cars, it is imperative, or oil consumption will be higher than necessary (wet sump, and oil scraper rings). For everything else, it is just best performance and least wear.
So would I be right in assuming that the manufacture would do this process of honing during production of the piston liner on something like a ringed OS engine?
If so, is it necessary to continue to do the honing if replacing the piston ring due to the smoothing of the liner from wear & tear?
or as and when you think it needs to be done by visual inspection rather than every time you do a 'strip down' (to be clear Brutus, ref to engines).

Last edited by Eastflight; 08-03-2022 at 03:00 AM.
Old 08-03-2022, 03:59 AM
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We used Flex Hones extensively at our shop for de-glazing when replacing rings in bores of various types:

Flex Hone, Cylinder Hone
(Available from Amazon in most sizes and grits)

There are differences between honing to size a bore and the simple de-glaze operation as performed to facilitate ring seating.

Some RCers use a pad of Scotch Bright red or grey and a bit of finger pressure.

Always take care to clean the bore well after de-glazing.



Last edited by Jesse Open; 08-03-2022 at 04:25 AM.
Old 08-03-2022, 04:36 AM
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Originally Posted by Jesse Open View Post
We used Flex Hones extensively at our shop for de-glazing when replacing rings in bores of various types:

Flex Hone, Cylinder Hone
(Available from Amazon in most sizes and grits)

There are differences between honing to size a bore and the simple de-glaze operation as performed to facilitate ring seating.

Some RCers use a pad of Scotch Bright red or grey and a bit of finger pressure.

Always take care to clean the bore well after de-glazing.
Thanks J.O, Well noted .
Old 08-03-2022, 05:17 AM
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Originally Posted by Eastflight View Post
So would I be right in assuming that the manufacture would do this process of honing during production of the piston liner on something like a ringed OS engine?
Yes, they usually do.
Originally Posted by Eastflight View Post
If so, is it necessary to continue to do the honing if replacing the piston ring due to the smoothing of the liner from wear & tear?
or as and when you think it needs to be done by visual inspection rather than every time you do a 'strip down' (to be clear Brutus, ref to engines).
I only do the cross-hatching after visual inspection. If you can see the pattern, it is still there. In fact the effectiveness of the pattern goes slightly beyond the capabilities of the naked eye, which means, if you can see it, it still is OK, if you cannot see it, that does NOT mean it is NOT OK, you just can't be sure. Hence, hone/deglaze in case of doubt.

I have to warn against using Scottish Bright, it does leave a too fine pattern (basically no pattern at all). Scottish bright derives its name from being a fast polishing material, and is more intended for quickly creating a smooth shiny surface than anything else. And a shiny bore is not what we want to see. for hand use, Emery cloth works the best is my experience, better than a honing tool. A honing tool however is easier in use for people with less experience.

For the record: Honing and deglazing are the exact same procedure: rotating a fixture of springloaded abrasive stones in an internal bore. You can deglaze with a honing tool, but you can not "hone to size" with a flexhone, But the damn thing is STILL called a "hone", and the process still is honing. It is the purpose that is different, not the process.
Honing to size has no place in model engines unless you are fabricating parts: there are no oversized pistons availlable for these little things, so there is no need for honing to size: if the bore is worn out, it is worn out and that is the end of it.
Old 08-03-2022, 06:06 AM
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The de-glazing (verb) and sizing (verb) operations are different in several ways.
Honing (verb) to size should not be undertaken with a Flex Hone . Rigid stones are used, usually with a controlled, incremental , micrometer type feed.
The initial metal removal starts with coarse grits and finishes with the fine stones to leave the desired cross hatch.

De-glazing should be done with minimal metal removal, ideally no change in the bore diameter.
This may be done with spring loaded pivoting stones, beaded hones like the Flex Hone (noun) or in some cases simply by hand. Again, the goal is usually not to alter the bore size, the mission is to simply create a specific surface,on a burnished, or glazed, previously used bore.

De-glazing and sizing bores are indeed different operations. Regardless the nomenclature of the tools involved
Other types of "Hone" (noun) stones are often flat and used to create keen cutting edges on straight cutting tools as well. Same name, different tool, different operation.

Scotch Brite pads are available in a wide range of grits and materials. They are made specifically to produce a uniform surface finish in industrial applications and yes, frequently used in RC engine work to create a surface to seat new rings.
They can and do work well for that application.
People use them every day with fine results. Glaze broken, minimal metal removal, uniform finish.

Just as with any other method, choose the correct grit from the broad selection they offer.


Last edited by Jesse Open; 08-03-2022 at 08:18 AM.
Old 08-03-2022, 01:15 PM
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Originally Posted by Jesse Open View Post
The de-glazing (verb) and sizing (verb) operations are different in several ways.
Honing (verb) to size should not be undertaken with a Flex Hone . Rigid stones are used, usually with a controlled, incremental , micrometer type feed.
The initial metal removal starts with coarse grits and finishes with the fine stones to leave the desired cross hatch.

De-glazing should be done with minimal metal removal, ideally no change in the bore diameter.
This may be done with spring loaded pivoting stones, beaded hones like the Flex Hone (noun) or in some cases simply by hand. Again, the goal is usually not to alter the bore size, the mission is to simply create a specific surface,on a burnished, or glazed, previously used bore.

De-glazing and sizing bores are indeed different operations. Regardless the nomenclature of the tools involved
Other types of "Hone" (noun) stones are often flat and used to create keen cutting edges on straight cutting tools as well. Same name, different tool, different operation.

Scotch Brite pads are available in a wide range of grits and materials. They are made specifically to produce a uniform surface finish in industrial applications and yes, frequently used in RC engine work to create a surface to seat new rings.
They can and do work well for that application.
People use them every day with fine results. Glaze broken, minimal metal removal, uniform finish.

Just as with any other method, choose the correct grit from the broad selection they offer.
What grade/grit would you recommend for doing the job
Old 08-03-2022, 01:38 PM
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What is the material?
Old 08-03-2022, 02:22 PM
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Originally Posted by Jesse Open View Post
What is the material?
Steel Liner
Old 08-03-2022, 02:49 PM
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I usually use 7447 Pro grade or 8447. The 8447 is a bit more aggressive.
Old 08-03-2022, 03:11 PM
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Great....!
Thanks
Old 08-03-2022, 10:51 PM
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Originally Posted by Jesse Open View Post
I usually use 7447 Pro grade or 8447. The 8447 is a bit more aggressive.
I have 220 grade emery available. Would that be okay to hone the steel liner of an engine size of .50 to .61 ?
Old 08-06-2022, 10:34 AM
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Originally Posted by Eastflight View Post
I have 220 grade emery available. Would that be okay to hone the steel liner of an engine size of .50 to .61 ?
I had to check visually what 220 grade is, but that would be about the coarsest i would go. Many light cuts are better than a few rough ones, so go light. About the pressure of rubbing an itchy nose, I'd say...
Old 08-06-2022, 01:56 PM
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Originally Posted by 1967brutus View Post
I had to check visually what 220 grade is, but that would be about the coarsest i would go. Many light cuts are better than a few rough ones, so go light. About the pressure of rubbing an itchy nose, I'd say...
Okay, thanks for checking. I shall get some finer grade to be on the safe side.
Old 08-06-2022, 03:36 PM
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Originally Posted by Eastflight View Post
Okay, thanks for checking. I shall get some finer grade to be on the safe side.
Don't get too much finer either. I have here in my workshop on board 240 and I would be perfectly happy with that, but 180 is too coarse for my taste.
Old 08-07-2022, 12:53 AM
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Well noted thank you
Old 08-07-2022, 08:29 AM
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If you are using cloth backed abrasives; 320 grit emery is a reasonable choice. Again, remember the idea is primarily removing the glaze. Minimal metal removal

If you care to send me your address, I will be happy to send you a sheet of Scotch Brite.
Old 08-07-2022, 08:47 AM
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Frank Bowman specifically stated in his instructions to use 400-600 grit emery cloth abrasive to prep the cylinder liner for the new ring. Anything coarser than that is too coarse. Maroon scotchbrite is 320 grit - AND - it doesn’t hold that for very long. While it will deglaze —just—okay, it won’t make any scratches capable of holding oil - which is necessary for the ring to properly seat. Green scotchbrite is non-abrasive and will be useless compared to maroon scotchbrite, which is close to useless in this situation.

Old 08-07-2022, 09:10 AM
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Originally Posted by 1QwkSport2.5r View Post
Frank Bowman specifically stated in his instructions to use 400-600 grit emery cloth abrasive to prep the cylinder liner for the new ring. Anything coarser than that is too coarse. Maroon scotchbrite is 320 grit - AND - it doesn’t hold that for very long. While it will deglaze —just—okay, it won’t make any scratches capable of holding oil - which is necessary for the ring to properly seat. Green scotchbrite is non-abrasive and will be useless compared to maroon scotchbrite, which is close to useless in this situation.
I was not aware of that info (the 400~600 thing). I have always used 240 or similar on larger engines and compressors and the likes, and simply pushed less hard when doing model engines. I'll have a look next time such a job comes around how 400~600 will work.

The Scottish Brite I have never managed to make a good pattern with (and yes, the green ScottishBrite is for kitchenware, has IMHO no place in a workshop... ).

Old 08-07-2022, 09:34 AM
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Originally Posted by Jesse Open View Post
If you are using cloth backed abrasives; 320 grit emery is a reasonable choice. Again, remember the idea is primarily removing the glaze. Minimal metal removal

If you care to send me your address, I will be happy to send you a sheet of Scotch Brite.
That's very kind of you to offer to send a Scotch Bright. Fortunately I am able to obtain it from a supplier over here
Old 08-07-2022, 09:38 AM
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Originally Posted by 1QwkSport2.5r View Post
Frank Bowman specifically stated in his instructions to use 400-600 grit emery cloth abrasive to prep the cylinder liner for the new ring. Anything coarser than that is too coarse. Maroon scotchbrite is 320 grit - AND - it doesn’t hold that for very long. While it will deglaze —just—okay, it won’t make any scratches capable of holding oil - which is necessary for the ring to properly seat. Green scotchbrite is non-abrasive and will be useless compared to maroon scotchbrite, which is close to useless in this situation.
So I should prep first with 400-600 then finish with a 320, Right?
On the liner I have there is only a miniscule amount of glazing.

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