Chapter 5 Measurements and Service Information Objectives Explain

Chapter 5 Measurements and Service Information

Objectives • Explain the many types of measurements needed in collision repair • Make accurate linear, angle, pressure, volume, and other measurements • Compare SAE and metric measuring systems • Identify and use basic measuring tools common to collision repair

Objectives (continued) • Use conversion charts • Summarize how to measure with a paint mixing cup • Use printed and computerized service information

Introduction • Measurements are number values that help control processes in collision repair • Measurements are used to evaluate and correct structural damage, adjust a spray gun, etc. • Vehicle manufacturers give specifications for body dimensions and mechanical parts • In the course of your work you will have to refer to and understand factory specifications

SAE and Metric Systems • Society of Automotive Engineers measuring system (SAE) is also called the English, U. S. , customary or conventional system • SAE system uses fractions and decimals – Fractions divide the inch into thirty-seconds, sixteenths and larger parts of an inch – Decimals are for high precision • Metric measuring system is also called the scientific international (SI) system • Metric units are related by a factor of ten

Conversion Charts • Conversion charts are handy for changing from one measuring system to another • SAE-metric conversion chart gives multipliers to convert from SAE to metric or vice versa • Decimal conversion chart allows you to change from fractions, to decimals or millimeters • Decimal conversion used for tasks such as selecting drill bits

Linear Measurements • Linear measurements are straight line measurements of a distance • Commonly used when evaluating major structural damage after a collision • Many types of tools used for linear measurements

Scales • Scale or ruler is a tool for linear measurement and has an accuracy of 1/64 in, or 0. 5 mm – SAE rule is marked in fractions or decimals – Metric rule is marked in millimeters, centimeters • Parallax error occurs reading a rule at an angle • Pocket scale is small and clips into a pocket • Tram gauge – Body dimension measuring tool – Pointers are aligned with reference points • Determine direction of misalignment damage • Determine amount of misalignment damage

Figure 5– 6. A tram gauge is used to measure across points on a damaged vehicle. If point measures are too close or too far apart, the vehicle must be put on a frame rack to pull out the unibody or frame damage.

Dividers and Calipers • Dividers have straight, sharp tips for taking measurements or marking parts for cutting – Sometimes used for layout or marking cut lines – Scribe circles and lines on sheet metal and plastic – Transfer and make surface measurements – Sometimes used when fabricating repair pieces for corrosion repair

Figure 5 -7. Calipers are used when fabricating sheet metal for custom repairs. Study their use.

Micrometers • Micrometers are used for measuring mechanical parts when precision is important – Also called a “mike” – Can easily measure one-thousandths of an inch or one-hundredths of a millimeter – Might be used to measure thickness of a brake system rotor

Dial Indicators • Dial indicator measures part movement and outof-round in thousandths of an inch • Mount the tool base so it will not move • Position tool arm and indicator stem against part • Turn the outside of the dial to zero the needle • Move or rotate the part and take reading

(B) Mount the indicator on a heavy base and adjust the point up against the wheel. Rotate the wheel slowly while reading the dial. If the runout is beyond specs (about 0. 020 inch), the wheel must be replaced or straightened. Figure 5 -9. A dial indicator is commonly used for measuring part movement. They are often used to check for bent wheels that were damaged in collision.

Feeler Gauges • Feeler gauges measure small clearances inside parts • Blade thickness is given in thousandths of an inch or hundredths of a millimeter • Flat feeler gauges are for measuring between parallel surfaces • Wire feeler gauges are round are for measuring slightly larger distances between curved surfaces

Pressure and Flow Measurements • Pressures are important for air tools, spray guns and other equipment • Adequate airflow is important when working in a paint spray booth, for example • Pressure gauge reads in pounds per square inch (psi) kilograms per square centimeter (kg/cm 2) or kilopascals (k. Pa) • Air pressure gauges are used on compressors, pressure regulators or at the spray gun • Excessive pressure can damage parts

Pressure and Flow Measurements (continued) • Tool might not work with low pressure • A vacuum gauge reads suction – Inches of mercury (in. Hg) – Kilograms per square centimeter (kg/cm 2) • Flow meter measures the movement of air, gas, or liquid past a given point • Airflow meters register in feet per minute or meters per minute • Liquid flow measured in gallons or liters per hour

Angle Measurements • Angle measurements divide a circle into 360 parts • Each part of the circle is called a degree • Angles are measured when doing wheel alignment

Temperature Measurements • Temperature is usually measured in degrees Fahrenheit (F) or Celsius (C) • Thermometers measure temperature • Surface temperature thermometers are available in several designs – magnetic, paper, digital • Before applying any type of material, the vehicle and the material must be room temperature • If the vehicle is not at room temperature, condensation may form on the surface

Paint-Related Measurements • Mixing scales are used to weigh the various ingredients when mixing paint • Manual scales weigh ingredients as added • You must look up the paint formula to see how much of each material is needed • Most manual scales have been replaced by computerized scales • Electronic scales use computerized technology to calculate the amount of each ingredient

Paint-Related Measurements (continued) • When mixing paint you must measure and mix accurately or serious problems result • Graduated pail has measurement lines like a kitchen measuring cup • Mixing instructions are normally given on the material’s label • Percentage reduction means for a specific volume of paint a specific amount of another ingredient must be added • Proportional numbers denote the amount of each material needed

Figure 5 -12. This chart shows a range of possible mixing percentages and converts them into parts. Fifty percent would equal 1 part paint to 1 part solvent, for example.

Paint Mixing Sticks • Graduated paint mixing sticks have conversion scales to convert ingredient proportions into part proportions – Used by painters to help mix colors, solvents, catalysts and additives • Paint mixing sticks should not be confused with stirring sticks for mixing the contents after they are poured into the spray gun cup

Figure 5 -13. Mixing sticks, discussed in detail later, also have graduations so you can mix the ingredients in paint correctly.

Viscosity Cup Measurement • Viscosity cup measures thickness or fluidity of the mixed refinishing materials • Dip the cup into the mixed paint until submerged • Lift the cup out and hold it over the container • When cup is lifted out start timing how long it takes to empty • Paint will leak out of a small specific size orifice in the bottom of the cup

Paint Material Thickness Measurement • Paint thickness is measured in mils or thousandths of an inch • Original equipment manufacture finishes are typically 2 -6 mils thick • Basecoat is about 1 -2 mils thick • Clearcoat is about 2 -4 mils thick – About the thickness of a piece of typing paper

Paint Material Thickness Measurement (continue) • Paint buildup should be limited to 12 mils • Mil gauge measures paint thickness on a vehicle • Pencil mil gauge measures paint with calibrated magnet and spring setup • Electronic mil gauge shows thickness with a digital readout

Vehicle Identification Number (VIN) Numbers • Vehicle Identification Number (VIN) plate identifies data about the vehicle • VIN plate is riveted to the upper left corner of the instrument panel, visible through the windshield • Prior to 1981 and on foreign vehicles check the service manual for the location of the VIN plate • Body ID number or service part number gives information about how the vehicle is equipped

Collision Repair Publications • Service manuals are published yearly and describe construction and repair of the vehicle • Aftermarket repair manuals give enough information for most repairs • Diagnosis charts give logical steps for finding the source of problems • Collision estimating guides give are used for calculating the cost of repairs • Vehicle dimension manual gives frame measurements of undamaged vehicles

Computerized Service Information • Computerized service information places manuals and other data on compact discs • Most shops have service info on computer – If a technician needs dimensions for a specific vehicle the info can be found on the computer • Printout of the vehicle dimensions can be made and taken to the repair area

Color Matching Manuals • Color matching manuals contain information to make the old and new paint color look the same or match when painting panels – Include paint code information, color chips, blending and tinting data, tinting procedures and other information

Summary • Vehicle manufacturers give specifications for body dimensions and mechanical parts • SAE measuring system is used in the U. S. • Metric system is used worldwide • Pressure measured in pounds per square inch, kilograms per square centimeter or kilopascals • Temperature measured in Fahrenheit or Celsius • VIN number accurately identifies the body style and other data about the vehicle