Honing of Gray Cast IronCylinder Blocks

2

Contents

Chapter 1: Honing 3

1.1 GeneralInformationon Honing 3

1.2 Adjustment of the

Hone 3

Chapter 2: Honing Today 4

2.1 Honing Angle 4

2.2 SurfaceRoughness 4

2.3 Honing Stonesand Honing Oil /

KS HoningAccessories 5

2.4 Hommel Tester 5

Chapter 3: Honing of State-of-the-artEngines 6

3.1 Advantages ofHoning plusBrushing 6

3.2 Honing andBrushingProcedure 7

3.2.1 Honing 7

3.2.2 Hone Brushing 8

3.3 RoughnessValues 8

Chapter 4: Examining theHoning Result 9

4.1 Why 9

4.2 Factors Influencing

the Honing Result 9

4.3 What to Check 9

4.4 How to Check 9

4.5 Next Follows theAssessement 9

4.6 Certificate 10

Page

3

1.2 Adjustment of the Hone

The honing stone length shouldcover 50–60% of the cylinderbore length. The most favorabletop overstroke is typically 25–30%of the hone stone length. At thebottom cylinder end, the designgeometry of the bearing supportsshould be taken into account.The applicable overstroke of thehoning stone is to be seen fromthe cylinder block drawing or theworkpiece. It may be between 15and 30 mm, (see Fig. 1).

Fig. 1

1.1 General Information on

Honing

The gray cast iron cylinder linersurface is typically finished byhoning. The surface should notbe too smooth, but exhibit finescores . Ensure a clean cut at alltimes.Chapter 2 shows the normalbasic honing procedure to beapplied for cylinder blocks ofgray cast iron. The surfaceroughness will be removed to acertain extent when the engineis run in and the sliding contact

surfaces adapt to each other.This condition is optimum for thepiston ring and cylindersurfaces. This run-in wear canbe anticipated by finishing thesurfaces by hone brushing, seeChapter 3.

Chapter 1: Honing

Sto

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ngth

Str

oke

M

achi

ning

leng

th

Honing stone projection

Honing stone projection approx. 25-30%

4

Chapter 2: Honing Today

Surface roughness completely newValue measured by instrument cylinder surface

Rt 3 - 6 µm

Ra 0,4 - 0,8 µm

Rz (DIN) max. 4 µm

Fig. 2

Fig. 4

2.2 Surface Roughness

In order to ensure the necessaryadherence of the oil film to thecylinder surface, especially inthe running-in phase, it is essen-tial for the cylinder to have a cer-tain roughness. Three measuringand valuation methods are incommon use for determiningroughness: Rt, Ra, Rz. Fig. 4 pro-vides a comparison of thesethree methods with the desirablevalues.

2.1 Honing Angle

The honing angle, Fig. 2, shouldbe between 40° and 80°. Theangle can be verified using thetransparent honing angle mask,Fig. 3.The metal smearing or deforma-tion produced in the honing pro-cess may lead to waviness of theliner surface which is again partlyremoved by the steep upwardand downward movement of thehone. The larger the honing angle,the less pronounced will the wavi-ness on the surface be. On theother hand, a smaller honingangle has the effect of reduced oilconsumption.

Fig. 3

Comparison of measured values

60° ±20“

40° ... 80°

5

2.4 Hommel tester

The surface roughness is reliablymeasured with roughness testerHommel T 1000 E, accuracyclass 1.It ensures surface measurmentsin the µm range satisfyingapplicable standards for all

2.3 Honing Stones and

Honing Oil

The right honing stones are:

•for rough honing: grain size 150.Provide for a material removal ofabout 0.06 mm referred to thediameter.

• for finish honing: grain size 280.Provide for a material removal ofapprox. 0.02 mm referred to thediameter (about 5-6 strokes)

The use of the right honing oil is aprerequisite for a satisfactoryhoning result. It is important al-ways to use the honing oil recom-mended by the honing stonemanufacturer.

KS Art.No.

50 009 857 Hommel T 1000 E

50 009 811 Hommel T 1000 E with P 1010

50 009 873 Honing angle test mask

Fig. 5

honing operations at cylinderliners and cylinder blocks, withdigital indication of Ra, Rz, Rtvalues. If the correspondinggraphic printer P1010 isavailable, the measurmentresults can be recorded on paperand documented.

6

Roughness Diagram

After brushing

Chapter 3: Honing of State-of-the-Art Engines

Before brushing

Fig. 7

Fig. 6

Hommel testerT1000 E

Dat.: . . . . . . . . . . . .Nr.: . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .Lt = 4.8 mmLC = 0.8 mmRa = 0.96 ymRzD = 7.17 ymRmD = 8.14 ymRt = 9.26 ymcut 0% = 0.00 ym

tPi 50% = 3.78 ym

R-PROFIL

-- 5ym 2000250ym 40

4.8 mm

0.8 mm

Hommel testerT1000 E

Dat.: . . . . . . . . . . . . . .Nr.: . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .Lt = 4.8 mmLC = 0.8 mmRa = 0.66 ymRzD = 4.90 ymRmD = 6.78 ymRt = 7.00 ymcut 5% = 0.54 ym

tPi 50% = 0.91 ym

R-PROFIL

-- 5ym 2000250ym 40

4.8 mm

0.8 mm

3.1 Advantages of Honing

plus Brushing

• After brushing, the surface is perfectly clean.• A high graphite exposure rate

of 50% is desirable, 20% hav-ing to be reached as a mini-mum. Fig. 6 shows a graphitevein exposure of 50%, scale500:1.

• Fig. 7, Roughness Diagram,shows a plateau-like surface.

Already some time ago, enginemanufacturers started finishingengines for trucks and passengercars by honing and brushing.Brushing has an advantage inthat it reduces the oil consump-tion and provides for an easierrun-in of pistons, piston rings andcylinders. What is more, it pre-vents problems in connectionwith plateau honing with regard tothe defined minimum materialremoval.

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3.2 Honing and Brushing Procedure

3.2.1 Honing

If the cylinder block is to bebrushed after honing, it is es- it is es- it is es- it is es- it is es-sential not to hone to too fine asential not to hone to too fine asential not to hone to too fine asential not to hone to too fine asential not to hone to too fine agrain. That is why honinggrain. That is why honinggrain. That is why honinggrain. That is why honinggrain. That is why honingstones with grain sizesstones with grain sizesstones with grain sizesstones with grain sizesstones with grain sizesbetween 120 and 180 shouldbetween 120 and 180 shouldbetween 120 and 180 shouldbetween 120 and 180 shouldbetween 120 and 180 shouldbe used:be used:be used:be used:be used:Bond of honing stones:• for parent bore engines: bond

5-7• for liners (centrifugal casting) bond 5 max.

Material removal:0.03 - 0.05 mm referred todiameter

Fig. 8

8

Fig. 9

3.2.2 Brushing

Honing brushes consist of nylonfibers with silicon crystals. Atleast 10 strokes are required,using honing oil. This cleans the

3.3 Roughness values

Allowable roughness:

bores and removes the peaks(see roughness diagram, Fig. 8).Brushing does not involve anyfurther dimensional changes!

R3Z Cars 2-5 µm

Trucks 3-5 µm

Rmax 11 µm

KS Art. No. Article

50 009 864 Hone brush set, Sunnen C 30 PHT 731

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Chapter 4: Examining the Honing Result

4.1 Why?

Today, a state-of-the-art engine iscomposed of heavy duty compo-nents. For diesel engines, for ex-ample, a performance increasewas achieved through turbo-chargers and charge-air inter-cooling. The piston ring material(steel rings) has changed, thenumber of piston rings was re-duced and the piston ring widthdecreased.The treatment of the cylinder run-ning surface by honing is there-fore critical for the quality of thereconditioning operation.

4.2 Factors Influencing the

Honing Result

Regular checking of the honingresult is essential in order to de-tect and remedy various sourcesof defects.

Sources of defects :• too little or the wrong honing oil• contact pressure of honing

stones too high• too little material removal for the

honing process• selection of wrong honing stones• incorrect feed + revolutions

The service offered by KS Motor Service International for

engine reconditioners

4.3 What to Check

The service range ofKS Motor Service internationalcomprises the checking of :

•honing angle• roughness values• graphite exposure rate (metal

smearing)

4.4 How to Check

• Customer will send us a cut-outof a honed surface, approx. 5x3cm.

•The honing angle and rough-ness are measured.

•The exposure of graphite veinsis determined under the micro-scope at a magnification of500:1 (micrograph).

4.5 Next Follows the

Assessment

•The customer receives a honingcertificate attesting to the honingquality.

•If necessary, suggestions forimprovement are made.

•As the costs of such an exami-nation are very high but it is ex-tremely important for the cus-tomer, we charge a share in thecost.

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Honing angle:

Target value 40-80 degrees

Actual value degrees

Roughness of cylinder

surface:

Target value Rt 3-6 µm

Actual value µm

Target value Ra 0.4-0.8 µm

Actual value µm

Target value Rz max. 4 µm

Actual value µm

Graphite exposure rate

Target value 20% min.

Actual value 21 %

4.6 Certificate

Honing Certificate

for

in

6060606060

44444

0,50,50,50,50,5

Roughness record:

Micrograph at a magnification of 500:1

KS Motor Service

International GmbH

P.O. Box 13 51

D-74150 Neckarsulm

Phone +49-71 32-33 33 33

Fax +49-71 32-33 28 64

msi@kolbenschmidt.de

Place

Date

NeckarsulmNeckarsulmNeckarsulmNeckarsulmNeckarsulm

10. September 199810. September 199810. September 199810. September 199810. September 1998Signature

Schmidt

Specimen CompanySpecimen CompanySpecimen CompanySpecimen CompanySpecimen Company

Specimen TownSpecimen TownSpecimen TownSpecimen TownSpecimen Town

33333

11

50 0

03 8

22

03/9

9

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