54 Machine Trades Print Reading Copyright Goodheart-Willcox Co., Inc. New revisions appear underneath the previous revisions as they occur. A revision history block contains the following information as shown in Figure 4-9: ■ ZONE (column A)—identifi es the revised area of the drawing. Details on a large drawing can be hard to locate. Separating a large drawing into smaller areas called zones makes locating features on a drawing easier. Zones appear in a grid formation using numbers and letters located outside the border for identifi cation. Refer to Figure 4-2(10). ■ REV (column B)—identifi es each change with a symbol, starting with the letter A. Numbers also identify the changes. In addition, the symbol appears on the drawing to locate and identify the change. ■ DESCRIPTION (column C)—explains the revision. REVISION, CHANGE, or REVISION RECORD are alternate terms for this column heading. ■ DATE (column D)—records the date of a revision. ■ APPROVED (column E)—contains the authorizing initials of the person responsible for approving the revisions. Some companies may require additional information for their drawing revisions. Additional columns can easily provide the necessary space for the information. Revision Status of Sheets A project with multiple sheets may require a revision status of sheets block. The revision status of sheets block records the revision status for each sheet. See Figure 4-10. The block is located at the top of a sheet, next to the revision block as shown in Figure 4-2(7), or on top of the title block as shown in Figure 4-4(S). The revision status of sheets can also be a separate document. Goodheart-Willcox Publisher The revision history block shows a list of revisions made to the original drawing. Figure 4-9 A B C D E A drawing revision is often ordered by an Engineering Change Order (ECO) or an Engineering Change Request (ECR). The ECO or ECR contain the data, notes, and sketches required for the changes on the drawing. Changes include anything that affects the finished product such as dimensions, materials, processes, notes, features, and finishes. The ECR or ECO is usually a separate document in digital form. The document’s reference number (ECO NO.) can be included in the revision history block. PRO TIP