LAYOUT TOOLS AND PROCEDURES Section 6

Laying Out Process of scribing or marking center points, circles, arcs, or straight lines on metal Indicates shape of object Amount of metal to be removed Position of holes to be drilled Layouts made from baseline Layouts of two types: basic (semiprecision) and precision

Basic Layout Materials, Tools, and Accessories Unit 19

Objectives Prepare a work surface for layout Use and care for various types of surface plates Identify and use the main basic layout tools and accessories

Layout Solutions Layout very important to accuracy of finished product Surface of metal coated with layout solution to make layout lines visible Surface should be clean and free of grease Several types of solutions available

Types of Solutions Layout dye or bluing Copper sulfate solution Most common Quick-drying, good sharp background Copper sulfate solution Few drops of sulfuric acid added to solution gives copper-colored surface Used on ferrous metal only Surface must be absolutely clean of grease

Types of Solutions Mixture of vermilion powder and shellac Chalking Used for Aluminum Alcohol used to thin solution or remove it Chalking Mixture of lime and alcohol Used for castings and hot-rolled steel Readily clings to rough surface of castings

Layout Tables and Surface Plates Work performed on layout table or surface plate (Granite or Cast-iron) Granite considered better (Black, Pink, Gray) Do not become burred Do not rust Are not affected by temperature change Do not have internal stresses and therefore will not warp or distort Are nonmagnetic Can be used for checking near grinding machines Are cheaper than similar-size cast-iron plate

Care of Surface Plates and Layout Tables Keep working surface clean Cover plate or table when it is not in use Carefully place work on surface plate Use parallels under workpiece whenever possible Never hammer or punch any layout on surface plate Remove burrs from cast-iron plates and protect surfaces with thin film of oil when not in use

Scribers Has hardened steel point(s) and on some one end bent at angle for hard-to-reach places Point must always be sharp Honed frequently on fine oilstone Knife-edge scribers used for extremely fine lines Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Dividers and Trammels Dividers used for scribing arcs and circles on layout and transferring measurements Spring divider most common type Creates circles in sizes from 3 to 12 in Trammel Consists of beam on which two sliding or adjustable heads with scriber points are mounted Can do larger circles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Hermaphrodite Calipers One curved leg and one straight leg with scriber point Used for laying out lines parallel to an edge and locating center round or irregular- shaped stock For parallel lines hold scriber at 90º to edge Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Squares Used to lay out lines at right angles to machined edge, test accuracy of surfaces that must be square, and set up work for machining Adjustable squares used for general work Solid square: beam and blade Used where greater accuracy required Master squares Used to check accuracy of other squares

The Combination Set Used extensively in layout work Consists of steel rule, square head, bevel protractor and center head Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Combination Set Steel rule fitted to other three parts Square head Used to lay out angles at 45º and 90º and parallel to edge lines Bevel protractor used to lay out and check various angles (0º to 180º) Accuracy is ± 0.5º (30') Center head forms center square when mounted on rule Used for locating centers of ends of round , square, and octagonal stock

Used on surface plate to scribe parallel lines Surface Gage Consists of base, spindle, and scriber Used on surface plate to scribe parallel lines Some have a V-groove machined in the base, which allows them to be used on cylindrical work Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Layout or Prick Punches and Center Punches Difference only in angle of point Prick punch ground to angle of 30º to 60º Used to permanently mark location of layout lines Center punch ground to 90º Used to mark location of centers of holes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Layout Lines After scribed on workpiece, should be permanently marked by means of layout or prick-punch marks Ensures layout line location visible should line be rubbed off through handling Intersection of circle centerlines prick-punches then enlarge with center punch Automatic center punches produces uniform spacing of marks

Layout Accessories Angle plate and toolmaker's clamp Parallels Used when lines are required on face of plate Possible to scribe intersecting 90º lines accurately Parallels Used to raise workpiece and maintain work surface parallel to top of surface plate V-blocks Used to hold round work for layout and inspection Keyseat rules and keyset clamps Used to draw lines parallel to axis of shaft