Common Practices In CYLINDER BORING, HONING, AND WALL ...

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HOW THE FLEX-HONE ® DIFFERS FROM THE RIGID HONE Let’s review some of the disadvantages of using the rigid stone types: 1. A new set of stones are straight and in the initial application can be expected to hone straight. The first cylinder contours them, and each succeeding cylinder adds to the unevenness so that they just do not hone straight any more. 2. In honing a worn cylinder, the rigid stone has to grind out the high spots before it reaches the low spots. Sometimes you have to take out more material than you either want or need to. 3. In order to remove metal the stones must exert enough pressure against the wall. This pressure then often tears the metal, folds it over, cuts deeper grooves than is necessary or desirable. 4. The stones load up. When this happens they must be wire brushed out or the parts of the stone face that are loaded up with cut metal and varnishes will not cut. 5. If your honing device is worn in some of its fittings, then sometimes the hone body will not hold the rigid stone securely and square to the cylinder wall, causing them to cock to one side. This causes the rigid stone to gouge into the metal, so that one stone cuts differently than the other. 6. There is a problem in trying to get even pressures from each of the stones. Some hones have spring-loaded stones which try to equalize the pressure. Others have metal guides or felt pads. The pads certainly carry the honing oil, which helps, but being softer than the stones are not that good as a guide. 7. The stones break and crack which means a replacement. This means not only the cost of the new stones, but also the cost in labor from the time spent replacing them. 8. You really can’t run the rigid hone out of both open ends of a cylinder, though you should or you run the risk of creating a bell-mouth at the ends. Also, you should be able to remove the hone while it is still spinning to create the crosshatch finish where you need it - at the top of the ring travel. 9. Most rigid honing in a shop has to be done by the experienced mechanic. It is not an easy job and requires skill and training. This can create bottle-necks because all of the honing jobs have to wait for your honing expert. 10. There is no way that you can hone each cylinder the same. So much depends on the operator, that you really cannot be as exact as you should be from cylinder to cylinder and engine to engine. 11. Time. How long does it take to rigid hone your block It all depends, but it is quite an undertaking. And you better have a good supply of extra stones lying around. THE FLEX-HONE ® DIFFERENCE 1. Instead of two or three stones, such as in the rigid hone, we have hundreds of smaller stones that are flexible. You have 360 degrees of cutting medium going for you all the time. 2. It cuts very quickly and easily. No training necessary, no expensive machinery, not to mention any wasted time. 3. There is very little pressure on the walls. Only the pressure created by the modulus of the nylon filaments. This tool cannot gouge out the metal and cause torn or folded over edges. 4. The hone is self-centering and self-aligning thanks to its patented design. You get even pressure from each abrasive. 5. You can cut off the old surface and present a new surface with the proper ring-seating and oil retention WITHOUT a great deal of metal removal. A remarkable achievement. 6. The honing stones are practically unbreakable, and are self-wearing so that you always have abrasive on the outermost edge of the tool. 7. No loading, no wire brush cleaning. Just rinse the tool with water to clean. 8. You can (and should) have the tool rotating before entry into the cylinder. It enters more easily and doesn’t put vertical scratches in your upper cylinder. You’ll be able to properly create a cross-hatch finish from end to end without any bell-mouthing. 9. A balanced engine because every cylinder will have the same finish. The kind of consistency and quality you can rely on throughout your organization. ® Please ask for it by name: COARSE V.S. FINE FINISHES With a high performance engine where the maximum compression is wanted, and the running life is short, perhaps you may want an ultra-fine finish. Possibly with a large diameter bore engine with a slow RPM and a heavy viscosity oil, you may want a coarse finish. Care must be taken with coarse finishes, particularly in new engines. The increased friction causing excessive temperatures may promote scuffing and excessive wear on the rings. The greatest engine friction is the piston-ring/cylinder sliding-bearing interaction. Fine finishes reduce friction and oil retention capabilities. Today’s multi-viscosity high detergent oils do not need the deep finishes that yesterday’s paraffin based oils required. A deep (coarse) finish may carry up to ten times the oil needed to lubricate the cylinder wall (if multi-viscosities are used) resulting in excessive oil consumption. As an example, there happens to be a 1,000 cc twin motorcycle on the market today whose engine style has not changed for many, many years. The thin walled iron sleeve on the new bikes is subject to warpage if the new owner does not exercise great care in the breaking-in process.
There has been a lot of replacement of sleeves. Our local agency has discovered that before delivering the new bike or replacing new sleeves, that Flex-Honing the cylinder has cured this fault. This is perhaps due to the old thinking of a coarse finish to begin with. Excessive friction creating excessive heat between the piston rings and the cylinder wall undoubtedly caused the warpage, and may also have annealed the rings. CLEANING WALLS AFTER HONING If you are going to leave the crankshaft in, then of course be sure to mask off the journals. Some guys even cut an old rubber beach ball in half and push down into the bottom to catch the dirt. But catch it. That is why we recommend a light-weight oil, to lubricate and increase the life of the hone, to absorb the heat and prevent hardening of the metal, and to catch and hold the metal grindings, the abrasives that have chipped and been cast off and the other contaminants. We have compounded a Flex-Hone Processing Oil. It contains cutting oil, lapping oil, a wetting agent, a rust remover, a super lubricant, and the same stuff they would put in toothpaste to pick and hold all the “bread crumbs.” A few drops will do. But whatever you use, PLEASE DON’T use a solvent, kerosene, or diesel oil. They penetrate into the What is known as the “Flex-Hone Process” BEFORE wall finish and will fill the valleys of the finish with all the contaminants you want to get rid of. Also, NOT only should you not use solvents to hone with, you should NOT use them to wash out your cylinder for the same reason. After the honing job, just don’t wipe it out with an oily rag and smear the abrasive into the surface. Instead, use a good brush and some (preferably) hot water and some soap or detergent, and wash it out until the foam stays white. Then wipe it with a paper or cloth towel until the cloth or paper towel stays clean and white. Then dry it out so it won’t rust, and protect it with a swabbing of light oil. QUALITY CONTROL - MANUFACTURING SPECIFICATIONS When a new engine is being developed, somewhere in design engineering, somebody decides on the cylinder wall finish. It goes on the print, and becomes law. Manufacturing sets it up with the equipment that they have, quality control often checks in the beginning, but when things become routine….. As an example, we got 9 air-cooled two strokes right off the shelf, single cylinder, aluminum alloy with chromed cylinders. We ran them on a surface analyzer. We could only check the surface finish from the crank end as it was a closed jug and the stylus would not reach up to the top of the cylinder (plug end). The readings were: Cyl. No. FINISH A A µm Figure 10 OUT OF ROUND Top Bottom Inches mm Inches mm 1 5-50 .127-1.27 .0008 .0203 .0004 .0102 2 8-15 .203-.381 .0015 .0381 .0005 .0127 3 5-10 .127-.254 .0017 .0432 .0002 .0051 4 7-15 .178-.381 .0005 .0127 .0007 .0178 5 5-50 .127-.1.27 .0014 .0356 .0005 .0127 6 6-12 .152-.305 .0005 .0127 .0003 .0076 7 5-10 .127-.254 .0025 .0635 .0023 .0584 AFTER Their desired finish was 7-10 (.178-, .254 µm Ra). We sawed the top off the one of the cylinders and found a finish of 1-2 AA at the top of the ring travel.
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Common Practices In CYLINDER BORING, HONING, AND WALL ...

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