BRM's Flexible Honing, Surface Finishing, and Deburring Blog Blog

BRM's Flexible Honing, Surface Finishing, and Deburring Blog

BRM's Flexible Honing, Surface Finishing, and Deburring Blog is the place for conversation and discussion about how to solve difficult finishing problems. For over 50 years, Brush Research Manufacturing (BRM) has helped customers use brushing technology to clean, rebuild, and resurface components ranging from engine cylinders to brake rotors to flywheels to firearms. BRM's Blog on CR4 provides real-world examples of how flex hones and wire brushes work. It also evaluates related technologies and invites questions from the community.

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How Cylinder Honing Improves Piston Ring Seating

Posted October 06, 2014 1:34 PM by Brush Research

Piston rings are engine parts that seal the combustion chamber, transfer heat from the piston to the cylinder wall, and help regulate oil consumption. During normal engine operation, only small amounts of exhaust gases and unburned fuel escape the piston rings and enter the crankcase. If there are gaps between the piston rings and the cylinder walls, however, too much "blow-by" can enter the crankcase and overwhelm its ventilation system. The results range from power loss to engine damage.

"The piston ring is sort of the poor stepchild of the high-performance engine," explains Keith Jones of Total Seal, a Phoenix-based manufacturer of piston ring sets for street and racing engines. "They get blamed for just about everything." Without the proper fit between the piston ring and the cylinder bore, however, compression blow-by and oil leakage can sideline the kinds of car used in IRL, NASCAR, and World of Outlaws events.

High-Performance Surface Preparation

As an article in the October 2014 issue of Performance and Hotrod Business magazine explains, Flex-Hone tools from Brush Research Manufacturing (BRM) can help increase piston ring performance. In "Rings True", part of the publication's Precision Engine section, automotive writer Ed Sullivan describes how BRM's flexible hones "allow for the fine-tuning of cylinder bores", even in engine blocks made of harder metals that can make piston ring break-in challenging.

BRM Flex-Hone tools feature abrasive globules that are permanently laminated to flexible nylon filaments, and a sturdy metal stem that mounts in handheld power tools or CNC machinery. Self-centering, self-aligning to the bore, and self-compensating for wear, flexible cylinder hones are ideal for deglazing the walls of cylinders that are not out-of-round, and for improving the surface finish of bores that have been honed to size already.

Flexible honing tools aren't designed for heavy-duty material removal, however, nor should they be used for initial honing, cylinder resizing, or geometry correction (i.e., out-of-round bores). Instead, use BRM Flex-Hone tools to impart a plateau finish that optimizes engine lubrication for reduced friction and wear. The crosshatching that flexible honing imparts provides a uniform series of grooves for excellent oil retention, and a superior surface finish that supports piston ring seating and sealing.

Engine Hones and Cylinder Wall Surface Finishing

BRM's engine hones are available in 11 different abrasive types and 8 grit sizes. The Flex-Hone Resource Guide explains how to select and use ball hones, as Flex-Hone tools are also known. Industry experts such as Keith Jones of Total Seal also provide insights. As Jones told Performance and Hotrod Business magazine, "We recommend this type of hone because it works very well, is easy to use with a hand-held drill motor, and is really foolproof for someone who is not an experienced machinist."

Michael Miller, BRM's Vice President of Global Sales, adds that Total Seal "does its homework" when it comes to choosing specific Flex-Hone tools. The levigated alumina super-fine abrasive that the engine parts maker recommends "works best for their piston rings in harder engine block materials." Members of the automotive aftermarket and performance racing industries are encouraged to contact BRM with questions about flexible cylinder honing. "We provide this type of support all the time", Miller explains.

Author's Note: This CR4 blog entry originally appeared in BRM's Flex-Hone Blog.

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#1

Re: How Cylinder Honing Improves Piston Ring Seating

10/06/2014 6:42 PM

I've followed these ball hone articles for some time now, and fail to see any tangible advantage over other hones. Almost like a product searching for a market.

Nobody has ever disputed that cylinder honing improves ring sealing/seating. Why else would we do it?

This statement, "the crosshatching that flexible honing imparts provides a uniform series of grooves for excellent oil retention, and a superior surface finish that supports piston ring seating and sealing" sounds more like a soap commercial than a technical justification for their use. A "superior surface finish" over what, bare steel? How could a flexible hone possible improve crosshatching?

If an untrained person is honing a perfectly smooth, round and true surface then the only advantage is............................................................................I can only say that in the hands of an untrained person using a hand held drill, they MAY offer an advantage.

Otherwise, they're just a "new and improved hone formula guaranteed to get your cylinder walls "up to 20% better" than rigid stone hones. Remember, "up to" also includes zero, as in none.

I don't see the advantage. Can anyone convert me?

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#5
In reply to #1

Re: How Cylinder Honing Improves Piston Ring Seating

10/07/2014 9:16 AM

I'm not going to pretend to be an automotive machine expert, but I have built and rebuilt many high performance engines and worked in an automotive machine shop. Being dedicated to my trade, I read many books and magazines. I remember reading a rebuilding article in a Mercedes 300-SL shop manual. They went into great detail on the importance of honing and also described, not only the optimum V-shaped hone pattern, but the included angle of the V-pattern. I figured that if Mercedes engineers went to the trouble of figuring that stuff out, I would take the time to read and understand their recommendations. That was about 60 years ago. That's still what I attempt to achieve and it hasn't failed. So, I don't see it as a soap commercial.

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#6
In reply to #5

Re: How Cylinder Honing Improves Piston Ring Seating

10/07/2014 9:38 AM

You failed to get the point.

The point wasn't about honing. I agree that a proper hone, and crosshatching is essential and said so.

My beef is with the claim that ball hones are better than conventional flat homes.

To that I say BS. Sounds like "new and improved" soap sales commercial to me. A product looking for a market.

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#2

Re: How Cylinder Honing Improves Piston Ring Seating

10/06/2014 8:19 PM

Actually I can see a place for flex hones (we called them dingle berry hones back in my hot rod days) when you have a bore that is worn a regular rigid hone tends to skip the upper part of the bore (IC cylinder bores wear in a taper) where the most wear occurs thus NOT allowing the crosshatch to completely "dress" the bore, we would hone the cylinder to get a lot of the imperfections out of it but not enough to allow piston slap, then we would take the dingle berry and finish the crosshatch for ring seating, granted it did not have the "ground" look to it but it did the job well.

We had some of the BIG BOY hot rodders that had us hone the cylinders for a certain diameter then knurl the piston skirts to match the bore claiming it "reduced drag" and allowed less parasitic horsepower loss, I don't know if it actually helped as I never got to do dyno pulls after such mods but it sounded feasible.

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#3
In reply to #2

Re: How Cylinder Honing Improves Piston Ring Seating

10/06/2014 9:02 PM

I'd use a ridge reamer to remove the ridge at the top and re-bore if there was too much of a taper. But I never tuned dragsters.

Knurling does increase the diameter by moving material around, but I don't see it aiding sealing of anything. All those grooves make a good leak path, seems to me.

We used to knurl pump impeller shafts to increase the diameter slightly, .005" to get a close slip fit into a sleeve. That made sense to me.

Anyway, I'm just an old man.

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#4

Re: How Cylinder Honing Improves Piston Ring Seating

10/06/2014 10:16 PM

If the taper was beyond .004 we'd recommend boring to oversize, and the knurl did hold a lot of oil but the idea of oil control was not high on the list of things the hot rodders worried about.

It was more compression seal and less drag, some even wanted a little bit of oil to impinge in the combustion chamber, these guys gas ported their pistons and used zero gap rings (usually double moly). Rings did not live long in these engines at all, high RPM, high compression, high octane, high ignition advance, high lift cams, Hell they were lucky to get through a weekend of racing without engine teardown.

All for the glory of the win light! (must admit I know that feeling)

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