Cylinder crosshatch general purpose vs. race

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createaaron
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Cylinder crosshatch general purpose vs. race

Post by createaaron » Tue Mar 14, 2017 11:15 pm

I've been doing some of my own research at school on our honing machines and with the profilometer. We have a Rottler setup with diamonds and a 616 setup with stones. We're taught to use to fixed brushes on the machine to finish with and create the "plateau". I don't have any RK numbers at the moment, my log is at school. Anyway, what do you guys like to see for RK, RPK, RVK (depending on ring type) for street engines vs all out race engines. We have a sheet at school we follow but its fairly broad. Obviously there is lots of variables but for sake of discussion say they have similair ring material and type, oil and naturally aspirated. I have compared fixed brushes to using ball hone and drill mounted brushes. Different finishing loads, different roughing loads etc... I realize a straighter, rounder bore is more important than finish. Would like this post to turn into a good discussion on cylinder finish as i couldn't find much on this site.

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Re: Cylinder crosshatch general purpose vs. race

Post by David Redszus » Wed Mar 15, 2017 1:07 am

To obtain maximum performance from any engine, the piston rings must seal properly
to the cylinder bore surface, so as to contain combustion gas pressure. A proper ring
seal not only reduces power robbing exhaust gas pressure losses due to blowby, but
actually reduces ring drag friction and extends engine life while virtually eliminating the
ring seating break-in period.

Proper cylinder bore preparation allows optimal ring sealing which will help reduce ring
wear, oil consumption, excessive piston heat buildup and greatly reduce cylinder bore
wear. Pressure leakdown tests have shown that it is very possible to obtain ring sealing
values of less than 1% leakage in a cold engine and even less in a warm engine. An
engine with superb ring sealing will retain its sealing properties for a longer period of time.

This workbook will provide the information necessary to obtain proper bore preparation
procedures, and a quantitative rating system for accurate cylinder bore evaluation.

The essential ingredients of proper engine cylinder pressure sealing involve
certain primary areas:
Piston to Wall Clearance,
Cylinder Geometry,
Cylinder Material,
Surface Preparation.

Piston to wall clearance is essential to avoid destructive piston and ring damage due
to dimensional size changes. As the piston and bore material become warmer, both will
expand but at different rates due to material properties and differences in temperatures.
The rate of expansion of both piston and bore will be a critical factor during warm-up.
While cold clearances are typically specified, it is the minimum hot running clearance
that really matters.

Traditionally, piston to wall clearances are determined by trial and error, either by the
engine builder or piston manufacturer. This method has several drawbacks; the cost of
damaged pistons being one of them. Most often, the engine builder does not know the
co-efficient of expansion of the piston material or cylinder bore. The piston manufacturer
usually does not know the actual operating conditions of the engine nor the geometry
of the cylinder bore. The usual technique is to provide excessive clearance to avoid
destruction while accepting a loss of performance.

The Piston Clearance workbook can be used to accurately predict the required piston
to wall clearances for any piston or bore material, as well as ring materials. The proper
cold clearance dimension will be determined by piston and bore materials, operating
temperatures and mode of operation. The workbook can then predict hot running
clearances and transitional warm-up clearances for both pistons and rings.

Cylinder geometry refers to the determination of the bore distortion. Bore distortion
has several forms: out of round called ovality, lack of straightness called taper, cylinder
perpendicularity called tilt and cylinder macrowaviness called waviness.

Cylinder bore ovality (out of roundness) cannot be totally eliminated but can be reduced
using proper preparation techniques. When a cylinder head is bolted to a block the
bore size and shape will be distorted. So even if a bore is perfectly round before
assembly, it will deform when placed under bolt tension load when the head is attached.
A bore that starts out round may take on the shape of a four leaf clover depending on
the number of head bolts, their location and cylinder position.

In order to obtain a round cylinder bore after assembly, it is necessary to distort the bore
before assembly by means of a preloading while the cylinder bore is being honed to size.

To correctly pre-distort the block and bore, a pseudo head called a deck plate is used,
bolted to the block. It is essential that a compressible head gasket be used, that deck
plate bolt length penetrate into the block the same depth as actual head bolts and that
the plate bolts are torqued the same as an actual cylinder head would be torqued. In
addition, main bearing caps, motor mounts and transmission bell housings are often
attached as well to pre-distort the lower cylinder bore.

Some engine builders have advocated pre-heating the block in anticipation of operating
temperature expansion and distortion. For most engines, pre-heating has shown very
little benefit, compared to the bore distortion which results from combustion loading.

Depending on the cylinder bore size, the maximum permissible distortion due
to ovality should not exceed 0.01mm (.0004").

Piston rings that are radially flexible are capable of conforming to larger amounts of
piston bore distortion. Rigid (thick or wide) piston rings are much less able to flex
enough to adapt to the distorted bore shape. While a flexible piston ring might be able
to adapt to a simple shape distortion (such as an oval) it cannot adapt to a more
complex shape such as an apple, pear or clover leaf shape.

If a cylinder bore is out of round during loaded operation, the piston rings will not be
able to properly conform to the distorted shape, allowing combustion gas blowby that
will result in excess wear (indicated by bore surface polishing of cylinder cross
hatch areas), which will increase ring wear and cylinder bore wear.

Bore taper (straightness) is somewhat similar to ovality but in another direction; it is
the bore straightness in a vertical plane. A cylinder bore that is bell shaped, hour-glass
shaped, tapered or barrel shaped will cause the piston rings to slide excessively in a
radial direction. This will produce increased friction in the piston ring land often resulting
in stuck rings or excessive ring land wear.

The maximum deviation from straightness should not exceed 0.01mm (0.0004")
from the top to the bottom of the cylinder.

In order to determine ovality and bore straightness it is necessary to take several
diameter measurements of the cylinder bore at various angles and height locations.

Cylinder bore angle
In plan view (as viewed from the top) four measurements of diameter are necessary
in order to determine possible ovality. The usual measurement axis are at 0o or
along the crankshaft centerline, 45o from centerline, 90o from centerline and 135o
from centerline, although any similar angles may be used.

Cylinder bore height
In elevation view (as viewed from the side) four measurements of diameter are
necessary at various vertical positions in order to determine taper. Although any
vertical positions may be used for measurement some positions are more logical than
others. The most commonly used vertical positions are as follows:

Position A measures the diameter at the turnaround point of the piston
rings which is usually about 10mm from the block deck surface.
Position B is measured at the piston skirt edge height when the piston is
at its uppermost position. It is intended to measure possible cylinder
scuffing by the piston skirt caused by piston rocking at TDC crossover.
Position C is measured at the vertical position of the rings at the bottom
of the stroke.
Position D is measured at the very bottom of the cylinder, in an area
not scuffed by piston or rings. It is used to measure possible bore
distortion due to main bearing caps.

The measured diameters (16 in total) for each cylinder can be entered and recorded on
the Cylinder Geometry workbook data sheet. It will create a graphic for cylinder
ovality and straightness which may be saved as a reference for when the engine later
comes in for a rebuild.

Cylinder tilt (perpendicularity) refers to the angle of the cylinder centerline with respect
to the crankshaft axis. Ideally, the cylinder tilt axis should be at 90o to the crankshaft axis
in the longitudinal direction and intersect the crankshaft axis in the lateral direction. In
the real world, there will always be some deviation from the ideal value.

The amount of tilt angle that can be tolerated is highly dependent on bearing and piston
clearances. Consequently, the permissible tilt angle will usually be specified by the engine
manufacturer. If a new engine is being designed or modified, a good rule of thumb is to limit
cylinder tilt to a maximum of 5' deviation from perpendicular. Since 1 degree = 60' (minutes),
5 minutes deviation represents 5/60 or only .0833 degrees, which is a very small amount.

While most solid engine blocks are accurately machined by the manufacturer, the same
cannot be said when the crank bearing journals are align bored. Equally serious are
two stoke engines with separate cylinders which are clamped to crankcases and may often
exhibit a tilt deviation.

Cylinder waviness
Viewed in profile, refers to the deviation of the cylinder surface from a straight line. The
surface resembles a washboard effect superimposed on the surface roughness. The
maximum permissible waviness is often specified as one half of the surface roughness value.

Cylinder material
Cylinder bores may be constructed of various metals including aluminum, or cast iron.
In addition, the cylinders may be run naked (without coatings) or may have some type
of wear protective coating applied to the surface.

For most engines, cylinders of cast iron with lamellar graphite, are the most common
because of their cost and excellent running surface characteristics. For some applications,
cast iron bores may be chrome plated to provide a harder running surface.

Aluminum, because of its light weight, thermal conductivity and thermal expansion
characteristics which are similar to piston materials, is finding increased use in stock
based engines as well as racing engines. When aluminum bore material is used, it is
common to apply a wear resistant surface coating such as nickel with disbursed silicon
carbide particles (Nikasil).

New metallurgical techniques have produced high silicon aluminum alloys that can be
used without surface coatings.

Whichever cylinder or block material is used, it is imperative that the thermal expansion
properties of the material be known and taken into consideration

Perhaps the most important consideration regarding cylinder material is the hardness of
the metal or coating being used. The surface hardness will significantly affect the type
of surface that can be obtained and the honing techniques that must be used. The
harder the surface, the more difficult it becomes to obtain a proper surface texture,
particularly to obtain a deep scratch or honing groove.

The surface hardness will determine which type of honing stones must be used.
Diamond stones can be used for iron or aluminum for basic bore shape and size but
are not desirable to obtain a proper surface finish, even with harder surface materials.
Diamond abrasives, while they may last longer, tend to become dull and do not cut
with a sharp edge and will produce a shallow oil groove.

Ceramic abrasives such as silicon carbide or silicon boron will break off with use to
expose new and sharp abrasive edges. The drawback is their shorter useful life and
resultant higher operating cost.

A discussion of honing abrasive materials and the type of finishes which can be
produced with various grit stones can be found in the Abrasives workbook. Many
abrasive manufacturers publish data sheets that indicate the type of surface finish
that can be obtained on materials with various Brinell hardness values. These charts
must be taken with a grain of salt since honing oils, rotational and stroke speed, and
stone pressure, all effect the surface finish which is produced. When in doubt, hone
a test cylinder and send it to a metallurgical lab for measurement and evaluation.

Surface preparation
Perhaps the most significant advancement in the science of cylinder bore preparation
has been the development of measurement techniques of surface finishes. Accurate,
electronic measurement of running surfaces has permitted rapid microsurface evaluation
and cost effective production techniques.

Surface preparation consists of two parts, groove preparation and surface
roughness. Both parts are equally important and must be carefully
considered if optimum cylinder sealing is to be obtained.

Groove preparation evaluation is primarily visual and has several categories, each
with target values to be met and weighted features. The condition of the groove, its
shape and openness account for 40% of the total cylinder groove preparation rating
and must be considered very important.

Factors to be considered regarding groove preparation include the following:
Honing Angle
Groove orientation
Plateau formation
Groove condition
Macrowaviness

Surface roughness evaluation is primarily by measurement and also has several
categories, each with target values to be met and weighted features. The value of the
bearing surface area carries 45% of the total cylinder roughness rating and must be
considered equally important.

Factors to be considered regarding surface roughness include the following:
Groove width
Peak to valley height
Groove distance
Bearing surface area

Bearing surface area is sometimes called Abbotts Bearing Curve or simply Plateau Honing.
The first step is to bore to size and hone to shape.
A rough (120 to 180) hone is then used to obtain near net size and to provide a deep scratch
which intended to hold oil below the surface. A very smooth surface cannot hold oil.
A finish fine hone (400 to 600) is then used to remove the peaks of the cylinder surface, leaving
the deep scratches.
For a street engine, the top or plateaued surface target value is about 70%. For applications
subjected to heavier ring to wall loading, (race or turbocharged engines and diesels) a higher
percentage of plateau (80-85%) is necessary to provide adequate support for the rings.

Rigid stones, ball hones, and abrasive brushes all have their supporters. The tool being used is not as
important as the skill of the workman using the tool.

Remember that if you can't measure it, you don't know what you have.

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Re: Cylinder crosshatch general purpose vs. race

Post by modok » Wed Mar 15, 2017 8:10 am

No, I think surface finish and trueness are both important. Rings can follow a lot of taper, and some out of round, but if the surface is wrong they are doomed in any case.
Surface you can get away with DEPENDS on rings used.
If they are chrome, iron, or ESPECIALLY wide chrome rings, what may do well is 180-220 base finish with aluminum oxide, then do a limited number of strokes with 280 silicon carbide. Step one gets it STRAIGHT, step two gets you a nice surface and a clean bore.
No matter if you are finishing a crank, a cylinder, or even buffing your paint, it always pays to start coarse and work your way finer. "Rough it up then smooth it out". That always works better, and the reason why should be clear. It may not be clear to measure after the fact, as some degrees of wavi-ness cannot be measured with common tools.

if rings are moly faced may consider a shallower croshatch angle, plateau with 400 grit or brush type plateau tool.

It is very interesting IMO.
Rings that are pre-lapped or moly faced will not wear the cylinders much, they require minimal "break-in", so you can make the cylinder surface closer to what it will be like after broken-in, BUT IF you plateau the surface too much for the tings used, may see some scuffing.

On the other hand Hastings says a good cylinder finish will work with most any kind of ring. "what???' well, that is also true to a degree. There are many different kinds of rings but for the most part engines all use similar oil. A surface that is conductive to good lubrication is very important. OIL lets the rings break-in without scuffing, so you want a surface that "holds" oil well. The oil will not want go into grooves that are too small, so that is why 180-220 is so popular for a base finish and no finer, and it will not want to stick to an overly smoothed surface, which is why you have to be conservative with your plateau and above all the last few strokes must be cutting SHARP with light pressure, making a good clean bright cut that will INVITE oil.

And all that is a very crude and subjective description, but reading it may make the post above make a lot more sense
Glen Urban

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Re: Cylinder crosshatch general purpose vs. race

Post by pamotorman » Wed Mar 15, 2017 8:40 am

OEM rings are broken in in a cylinder at the ring manufactures before being shipped to the engine assy factory.

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Re: Cylinder crosshatch general purpose vs. race

Post by David Redszus » Wed Mar 15, 2017 11:07 am

On the other hand Hastings says a good cylinder finish will work with most any kind of ring. "what???' well, that is also true to a degree.
Surface finish does not depend on type of ring, but rather on ring unit pressure. For a given gas pressure, a thin ring will exert more pressure against the wall and require more surface support. Higher gas loading will do the same.
The oil will not want go into grooves that are too small, so that is why 180-220 is so popular for a base finish and no finer, and it will not want to stick to an overly smoothed surface, which is why you have to be conservative with your plateau and above all the last few strokes must be cutting SHARP with light pressure, making a good clean bright cut that will INVITE oil.
A smooth surface or shallow scratch will hold oil, but not much. The task is to determine the volume of oil that the surface will hold, which can be calculated from surface finish measurements.

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Re: Cylinder crosshatch general purpose vs. race

Post by David Redszus » Wed Mar 15, 2017 11:23 am

Sorry but I left the following information out of my earlier post.
Each rating factor must be weighted in importance; some are simply more important than others.

Cylinder bore finish rating is divided into two groups; groove and surface condition.
Grooves
Honing Angle..........0.20
Groove orientation...0.15
Plateau formation....0.20
Groove condition.....0.40
Macrowaviness........0.05

Surface roughness evaluation is primarily by measurement and also has several
categories, each with target values to be met and weighted features.

Factors to be considered regarding surface roughness include the following:
Groove width............0.15
Peak to valley height...0.15
Groove distance.........0.10
Bearing surface area....0.45
Macrowaviness...........0.05

Clearly, the two most important rating factors are groove condition and bearing surface area.
But hone angle and plateau formation are too important to ignore.

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Re: Cylinder crosshatch general purpose vs. race

Post by MotionMachine » Wed Mar 15, 2017 1:00 pm

I think this thread is a little more technical than the OP wanted, he's looking for actual values that his profilometer measures. These are the Rpk, Rvk, and Rk. Ra and Rmax also should be considered but I've found that if the 1st 3 are where they should be, those 2 always are also. It is a wide range if you listen to all the different manufacturers and experts on the topic. Numbers I shoot for are 8-12 on Rpk, mid 30's to mid 40's on Rvk, and mid 30's for Rk. I have had requests for a super slick surface, I got Rpk of mid 7's and Rvk in the mid 20's, which are still in the wide range of suggested numbers but generally I don't go that low. As far as crosshatch angle, the longer the bore, the steeper the angle.

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Re: Cylinder crosshatch general purpose vs. race

Post by statsystems » Wed Mar 15, 2017 3:36 pm

David Redszus wrote:To obtain maximum performance from any engine, the piston rings must seal properly
to the cylinder bore surface, so as to contain combustion gas pressure. A proper ring
seal not only reduces power robbing exhaust gas pressure losses due to blowby, but
actually reduces ring drag friction and extends engine life while virtually eliminating the
ring seating break-in period.

Proper cylinder bore preparation allows optimal ring sealing which will help reduce ring
wear, oil consumption, excessive piston heat buildup and greatly reduce cylinder bore
wear. Pressure leakdown tests have shown that it is very possible to obtain ring sealing
values of less than 1% leakage in a cold engine and even less in a warm engine. An
engine with superb ring sealing will retain its sealing properties for a longer period of time.

This workbook will provide the information necessary to obtain proper bore preparation
procedures, and a quantitative rating system for accurate cylinder bore evaluation.

The essential ingredients of proper engine cylinder pressure sealing involve
certain primary areas:
Piston to Wall Clearance,
Cylinder Geometry,
Cylinder Material,
Surface Preparation.

Piston to wall clearance is essential to avoid destructive piston and ring damage due
to dimensional size changes. As the piston and bore material become warmer, both will
expand but at different rates due to material properties and differences in temperatures.
The rate of expansion of both piston and bore will be a critical factor during warm-up.
While cold clearances are typically specified, it is the minimum hot running clearance
that really matters.

Traditionally, piston to wall clearances are determined by trial and error, either by the
engine builder or piston manufacturer. This method has several drawbacks; the cost of
damaged pistons being one of them. Most often, the engine builder does not know the
co-efficient of expansion of the piston material or cylinder bore. The piston manufacturer
usually does not know the actual operating conditions of the engine nor the geometry
of the cylinder bore. The usual technique is to provide excessive clearance to avoid
destruction while accepting a loss of performance.

The Piston Clearance workbook can be used to accurately predict the required piston
to wall clearances for any piston or bore material, as well as ring materials. The proper
cold clearance dimension will be determined by piston and bore materials, operating
temperatures and mode of operation. The workbook can then predict hot running
clearances and transitional warm-up clearances for both pistons and rings.

Cylinder geometry refers to the determination of the bore distortion. Bore distortion
has several forms: out of round called ovality, lack of straightness called taper, cylinder
perpendicularity called tilt and cylinder macrowaviness called waviness.

Cylinder bore ovality (out of roundness) cannot be totally eliminated but can be reduced
using proper preparation techniques. When a cylinder head is bolted to a block the
bore size and shape will be distorted. So even if a bore is perfectly round before
assembly, it will deform when placed under bolt tension load when the head is attached.
A bore that starts out round may take on the shape of a four leaf clover depending on
the number of head bolts, their location and cylinder position.

In order to obtain a round cylinder bore after assembly, it is necessary to distort the bore
before assembly by means of a preloading while the cylinder bore is being honed to size.

To correctly pre-distort the block and bore, a pseudo head called a deck plate is used,
bolted to the block. It is essential that a compressible head gasket be used, that deck
plate bolt length penetrate into the block the same depth as actual head bolts and that
the plate bolts are torqued the same as an actual cylinder head would be torqued. In
addition, main bearing caps, motor mounts and transmission bell housings are often
attached as well to pre-distort the lower cylinder bore.

Some engine builders have advocated pre-heating the block in anticipation of operating
temperature expansion and distortion. For most engines, pre-heating has shown very
little benefit, compared to the bore distortion which results from combustion loading.

Depending on the cylinder bore size, the maximum permissible distortion due
to ovality should not exceed 0.01mm (.0004").

Piston rings that are radially flexible are capable of conforming to larger amounts of
piston bore distortion. Rigid (thick or wide) piston rings are much less able to flex
enough to adapt to the distorted bore shape. While a flexible piston ring might be able
to adapt to a simple shape distortion (such as an oval) it cannot adapt to a more
complex shape such as an apple, pear or clover leaf shape.

If a cylinder bore is out of round during loaded operation, the piston rings will not be
able to properly conform to the distorted shape, allowing combustion gas blowby that
will result in excess wear (indicated by bore surface polishing of cylinder cross
hatch areas), which will increase ring wear and cylinder bore wear.

Bore taper (straightness) is somewhat similar to ovality but in another direction; it is
the bore straightness in a vertical plane. A cylinder bore that is bell shaped, hour-glass
shaped, tapered or barrel shaped will cause the piston rings to slide excessively in a
radial direction. This will produce increased friction in the piston ring land often resulting
in stuck rings or excessive ring land wear.

The maximum deviation from straightness should not exceed 0.01mm (0.0004")
from the top to the bottom of the cylinder.

In order to determine ovality and bore straightness it is necessary to take several
diameter measurements of the cylinder bore at various angles and height locations.

Cylinder bore angle
In plan view (as viewed from the top) four measurements of diameter are necessary
in order to determine possible ovality. The usual measurement axis are at 0o or
along the crankshaft centerline, 45o from centerline, 90o from centerline and 135o
from centerline, although any similar angles may be used.

Cylinder bore height
In elevation view (as viewed from the side) four measurements of diameter are
necessary at various vertical positions in order to determine taper. Although any
vertical positions may be used for measurement some positions are more logical than
others. The most commonly used vertical positions are as follows:

Position A measures the diameter at the turnaround point of the piston
rings which is usually about 10mm from the block deck surface.
Position B is measured at the piston skirt edge height when the piston is
at its uppermost position. It is intended to measure possible cylinder
scuffing by the piston skirt caused by piston rocking at TDC crossover.
Position C is measured at the vertical position of the rings at the bottom
of the stroke.
Position D is measured at the very bottom of the cylinder, in an area
not scuffed by piston or rings. It is used to measure possible bore
distortion due to main bearing caps.

The measured diameters (16 in total) for each cylinder can be entered and recorded on
the Cylinder Geometry workbook data sheet. It will create a graphic for cylinder
ovality and straightness which may be saved as a reference for when the engine later
comes in for a rebuild.

Cylinder tilt (perpendicularity) refers to the angle of the cylinder centerline with respect
to the crankshaft axis. Ideally, the cylinder tilt axis should be at 90o to the crankshaft axis
in the longitudinal direction and intersect the crankshaft axis in the lateral direction. In
the real world, there will always be some deviation from the ideal value.

The amount of tilt angle that can be tolerated is highly dependent on bearing and piston
clearances. Consequently, the permissible tilt angle will usually be specified by the engine
manufacturer. If a new engine is being designed or modified, a good rule of thumb is to limit
cylinder tilt to a maximum of 5' deviation from perpendicular. Since 1 degree = 60' (minutes),
5 minutes deviation represents 5/60 or only .0833 degrees, which is a very small amount.

While most solid engine blocks are accurately machined by the manufacturer, the same
cannot be said when the crank bearing journals are align bored. Equally serious are
two stoke engines with separate cylinders which are clamped to crankcases and may often
exhibit a tilt deviation.

Cylinder waviness
Viewed in profile, refers to the deviation of the cylinder surface from a straight line. The
surface resembles a washboard effect superimposed on the surface roughness. The
maximum permissible waviness is often specified as one half of the surface roughness value.

Cylinder material
Cylinder bores may be constructed of various metals including aluminum, or cast iron.
In addition, the cylinders may be run naked (without coatings) or may have some type
of wear protective coating applied to the surface.

For most engines, cylinders of cast iron with lamellar graphite, are the most common
because of their cost and excellent running surface characteristics. For some applications,
cast iron bores may be chrome plated to provide a harder running surface.

Aluminum, because of its light weight, thermal conductivity and thermal expansion
characteristics which are similar to piston materials, is finding increased use in stock
based engines as well as racing engines. When aluminum bore material is used, it is
common to apply a wear resistant surface coating such as nickel with disbursed silicon
carbide particles (Nikasil).

New metallurgical techniques have produced high silicon aluminum alloys that can be
used without surface coatings.

Whichever cylinder or block material is used, it is imperative that the thermal expansion
properties of the material be known and taken into consideration

Perhaps the most important consideration regarding cylinder material is the hardness of
the metal or coating being used. The surface hardness will significantly affect the type
of surface that can be obtained and the honing techniques that must be used. The
harder the surface, the more difficult it becomes to obtain a proper surface texture,
particularly to obtain a deep scratch or honing groove.

The surface hardness will determine which type of honing stones must be used.
Diamond stones can be used for iron or aluminum for basic bore shape and size but
are not desirable to obtain a proper surface finish, even with harder surface materials.
Diamond abrasives, while they may last longer, tend to become dull and do not cut
with a sharp edge and will produce a shallow oil groove.

Ceramic abrasives such as silicon carbide or silicon boron will break off with use to
expose new and sharp abrasive edges. The drawback is their shorter useful life and
resultant higher operating cost.

A discussion of honing abrasive materials and the type of finishes which can be
produced with various grit stones can be found in the Abrasives workbook. Many
abrasive manufacturers publish data sheets that indicate the type of surface finish
that can be obtained on materials with various Brinell hardness values. These charts
must be taken with a grain of salt since honing oils, rotational and stroke speed, and
stone pressure, all effect the surface finish which is produced. When in doubt, hone
a test cylinder and send it to a metallurgical lab for measurement and evaluation.

Surface preparation
Perhaps the most significant advancement in the science of cylinder bore preparation
has been the development of measurement techniques of surface finishes. Accurate,
electronic measurement of running surfaces has permitted rapid microsurface evaluation
and cost effective production techniques.

Surface preparation consists of two parts, groove preparation and surface
roughness. Both parts are equally important and must be carefully
considered if optimum cylinder sealing is to be obtained.

Groove preparation evaluation is primarily visual and has several categories, each
with target values to be met and weighted features. The condition of the groove, its
shape and openness account for 40% of the total cylinder groove preparation rating
and must be considered very important.

Factors to be considered regarding groove preparation include the following:
Honing Angle
Groove orientation
Plateau formation
Groove condition
Macrowaviness

Surface roughness evaluation is primarily by measurement and also has several
categories, each with target values to be met and weighted features. The value of the
bearing surface area carries 45% of the total cylinder roughness rating and must be
considered equally important.

Factors to be considered regarding surface roughness include the following:
Groove width
Peak to valley height
Groove distance
Bearing surface area

Bearing surface area is sometimes called Abbotts Bearing Curve or simply Plateau Honing.
The first step is to bore to size and hone to shape.
A rough (120 to 180) hone is then used to obtain near net size and to provide a deep scratch
which intended to hold oil below the surface. A very smooth surface cannot hold oil.
A finish fine hone (400 to 600) is then used to remove the peaks of the cylinder surface, leaving
the deep scratches.
For a street engine, the top or plateaued surface target value is about 70%. For applications
subjected to heavier ring to wall loading, (race or turbocharged engines and diesels) a higher
percentage of plateau (80-85%) is necessary to provide adequate support for the rings.

Rigid stones, ball hones, and abrasive brushes all have their supporters. The tool being used is not as
important as the skill of the workman using the tool.

Remember that if you can't measure it, you don't know what you have.


Where do you buy a copy of the Piston Workbook?

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Re: Cylinder crosshatch general purpose vs. race

Post by hoffman900 » Wed Mar 15, 2017 6:03 pm

I haven't read all the posts on here (will when I get a moment to actually sit down), but the OP really needs to call the ring manufacturer and get the number from them. It's variable based on material, coatings, thickness, cylinder wall material, etc.

Ernie Elliot posted a schematic of bore distortion on Instagram:
https://www.instagram.com/p/BRXEvLAg4Ee ... elliottinc

You shouldn't need to be a member to view this. Keep the scale in mind when looking at that as it looks a lot more distorted than it actually is, but it does illustrate the point.
-Bob

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Re: Cylinder crosshatch general purpose vs. race

Post by createaaron » Wed Mar 15, 2017 11:48 pm

David Redszus wrote: For a street engine, the top or plateaued surface target value is about 70%. For applications
subjected to heavier ring to wall loading, (race or turbocharged engines and diesels) a higher
percentage of plateau (80-85%) is necessary to provide adequate support for the rings.
.
What is meant by the percentages?

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Re: Cylinder crosshatch general purpose vs. race

Post by createaaron » Thu Mar 16, 2017 12:04 am

I realize what I originally posted was kind of broad as far as what I'm looking for or where I wanted this post to go. I enjoy the technicalities, it makes me think. David, what book/article is your post quoted from, unless its original? This is great info Im getting from you gurus. I have begin to think about recently, in racing applications where cylinder pressure is high and PtoW to more loose, does the ring knock down some of the initial peaks left by the fine grit stones? How much can your RK values change from finish hone to running to high loads etc...

Ive also noticed going from the 220 grit stones or from 20% motor load on the diamonds, depending on machine, using the ball hone then running the drill bush in reverse leaves a very clean bore and gives me slightly better values than using the fixed brushes. Not that any of this really matters, once i get a job im gonna do it the way my boss wants me too lol. :D

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Re: Cylinder crosshatch general purpose vs. race

Post by modok » Thu Mar 16, 2017 5:34 am

People "race" all kinds of engines, in all kinds of different ways.
Street VS race, there may not be any difference, in a lot of cases.
Some kinds of racing, they want to use cheap rings and make them seat as soon as possible!
Glen Urban

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Re: Cylinder crosshatch general purpose vs. race

Post by modok » Thu Mar 16, 2017 5:52 am

David Redszus wrote: Surface finish does not depend on type of ring
Did you mean to say:
Surface finish does not depend -entirely- on type of ring
?

Same width, same app, different designs of rings usually have very different instructions, but same "unit pressure"
WHY? because the ABILITY of the ring to wear the cylinder, it's need to wear-in, and lubrication requirements differ.
Glen Urban

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Re: Cylinder crosshatch general purpose vs. race

Post by MotionMachine » Thu Mar 16, 2017 7:50 am

"Ive also noticed going from the 220 grit stones or from 20% motor load on the diamonds, depending on machine, using the ball hone then running the drill bush in reverse leaves a very clean bore and gives me slightly better values than using the fixed brushes."

Even though ball hones appear to be low tech, they actually do give good results. I've had blocks before that I just could not get the numbers I wanted until I hit it with a 400 grit ball hone.

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Re: Cylinder crosshatch general purpose vs. race

Post by racear2865 » Thu Mar 16, 2017 8:48 am

MotionMachine wrote:"Ive also noticed going from the 220 grit stones or from 20% motor load on the diamonds, depending on machine, using the ball hone then running the drill bush in reverse leaves a very clean bore and gives me slightly better values than using the fixed brushes."

Even though ball hones appear to be low tech, they actually do give good results. I've had blocks before that I just could not get the numbers I wanted until I hit it with a 400 grit ball hone.

WEll yall put in your 2 cents worth and as well I gots to put in mine. Ive used ball hone, feather duster with carbide filaments and fixed bruses. First fixed brushed. I tried double and single sided fixed brushes. Absolutely did not like the double brushes. If just one or 2 strokes too much and cylinder actually changed colors from laying over the peakes (I think) but single was more forgiving and still left "white" finish and easily passed fish scal pull and seated quickly on dyno. Feather duster with right diameter did better than any of them but only if tips do the cleaning. If use too large a diameter, it rolls over and does work on side and actually hurts finish, but if used properly does better job. 400 ball hone works also but same thing. Cut on the od and not on the sides of the ball. But what Ive found to be best is to use a rather stiff bristle brush and run forward and backward in cleaning. It will finish breaking and reidue peaks off and remove. Use good detergent so as to clean into the cross hatch. You have to get to the bottom of crosshatch. Am trying new type brush now. Is a filament brush that has carbide embedded into the "hair" . Looks promising but having problem finding all the diameters
reed

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