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Supplementary Sources

At times, during the course of your work, you may require information not covered in OPs or ODs. Where you find this information depends upon the type of ordnance equipment with which you are working. If you are working with demolition equipment, for example, explosives ordnance demolition bulletins (EODBs) could help you. Other types of publications are special weapons ordnance publications (SWOPs), NAVSEA instructions and notices for general policy matters, and such other publications as ORDALTS-00 that supply information on all ORDALTs for aircraft, shore stations, and all classes of vessels.

The Army prepares several publications that are also applicable to Navy ordnance. These include field manuals (FMs), technical manuals (TMs), technical bulletins (TBs), and joint publications of the Army, Navy, and Marine Corps. These publications are listed in the Index of Doctrinal, Training, and Organizational Publications, DA-PAM 310-3, U.S. Army, or SL-1-3, Index of Publications Authorized and Stocked by the Marine Corps (PASMC).


LEARNING OBJECTIVES: Discuss the main types of drawings used in gun maintenance and overhaul. Discuss the purpose of the illustrated parts breakdown (IPB) publication. Discuss the purpose of the standardized symbols used in hydraulic diagrams.

To do any kind of maintenance work on your equipment, you must know it well. A good way to learn about it is to study the hardware itself. But you will learn faster and you will learn more by using certain source materials. This manual is such a source; so are the OPs, ODs, and other publications. In many ways, however, your most valuable source material could be ordnance drawings.

All manufacturers of ordnance equipment make drawings of all equipments they manufacture. Copies of these drawings, reproduced by blueprinting, Xerox process, or in some other way, are supplied to every naval ship or installation that either has the equipment or, for some other reason, requires copies of these drawings. Many drawings are reproduced in OPs and other technical manuals. Some of the drawings you will use are made by NAVSEA, but many others are made by the contractors who manufacture the equipment for NAVSEA.


Drawings differ depending on their purpose. The main types of drawings, as classified according to purpose by NAVSEA, are as follows:

1. General arrangement drawings. This kind of drawing shows the complete equipment assembled. It indicates general appearance and relationships of important component assemblies and identifies the drawings that describe the components of the equipment.

2. Installation drawings. These drawings show such features as mounting pads and brackets, shock mounts, points for entrance of cabling and mating mechanical parts, type of cable required, dimensions of mounting hardware needed, and directions for how to orient the equipment and secure it to its place on the bulkhead or deck. One variety of this type of drawing, called an outline drawing, shows overall dimensions and clearances required for operating and servicing equipment.

3. Assembly and subassembly drawings. These drawings show the constructional details of the assemblies that make up the complete equipment. In general, you can think of an assembly (or subassembly) as any group of two or more parts assembled to make up a unit. An assembly drawing is intended to enable a properly equipped shop to make up the finished assembly from the prescribed parts and assembly and finishing materials.

4. Detail drawings. When you disassemble any piece of equipment far-enough, you eventually get down to individual pieces that cannot be disassembled any further. These are represented by detail drawings that give all the information that a properly equipped shop will need to make the piece exactly as required.

5. Wiring drawings. The main purpose of a wiring drawing or diagram is obvious from its name-it shows you how to wire apiece of equipment or a system. There are several varieties of wiring diagrams.

An external wiring diagram shows how to connect an item of equipment to the ship's wiring system or to other pieces of equipment. It shows terminal boards, binding posts, plugs, jacks, and other connection points and devices, and identifies them by letters and numbers. Lines denote the electrical conductors to be installed. The drawing shows the size and type of wire to be used; the kind of insulation, shielding, ductwork, and armoring specified, as applicable; length needed; where ground connections are to be made; where joints must be soldered, welded, or clipped; and so on. It also specifies the kind of current (ac or de), frequency, and voltage for each conductor.

An internal wiring diagram does the same for wiring inside an equipment. It also identifies and shows where the fuses are, the size and type to be used, and their circuits. It locates and identifies, with standard symbols, all lamps, motors, synchros, resistors, capacitors, transformers, chokes, switches, relays, and all other electrical components in the equipment and gives their electrical values, as applicable. It identifies all the terminals and connection points. This is one of the most useful kinds of drawings for electrical maintenance and troubleshooting.

An elementary wiring diagram is about halfway between the diagrams we have just discussed and the schematic to be taken up shortly. It shows terminal and connection points, component locations and values, and soon, but it is also arranged so that it is much easier to follow and understand the circuit than with the usual wiring diagram. But note that the elementary, like the pure schematic, has little respect for the actual sizes and shapes of parts or equipment or for their physical location or orientation. The traceability of the circuit is a much more important consideration.

6. Schematic drawings. About the only general statement you can make about schematic drawings or diagrams is that their primary purpose is to help the user understand the functioning of the equipment. In ordnance, schematics of electric, hydraulic, and pneumatic systems are of great importance in assisting you as a repairman. Schematics often have very little to do with the actual physical appearance or construction of the equipment diagramed.

7. Lubrication drawings. A lubrication drawing or chart for naval equipment is often a general arrangement drawing, or a group of them showing several views, where lubrication fittings and other points are called out by labels. The OP on older equipment normally has a lube chart in its appendix.

8. Tool drawings. Special tools, such as spanner wrenches, for specific marks and mods of guns are described in tool drawings-usually assembly or detail type. These tools are listed in the specific OP.

9. Lists of drawings (LDs). LDs, as mentioned previously, is considered by NAVSEA to be a variety of sketches. In itself, this detail of classification is 'not especially important in your job, but it is worth remembering that an LD looks like and is treated like a kind of engineering drawing, rather than like a publication.

LDs are, in a sense, the key to the drawing system used by NAVSEA. Beginning at the top of the system, a master list of drawings, or master LD, is prepared for each major ordnance equipment (such as a gun mount). This list includes all components of the equipment concerned Each component is itemized by assemblies, subassemblies, and details on a separate LD.

The identifying number for each component LD is given, together with the general arrangement drawing number on the master LD for the equipment. Each component LD also shows the special tools required for servicing that component. By reference to the LD and the drawings for the mark and mod of a given assembly or subassembly, it is possible to work down to an individual part and to identify the correct nomenclature, drawing, piece number, design dimensions, tolerances, and all other necessary information.

When we refer to a drawing or engineering drawing without qualification, we usually refer to an assembly, subassembly, or detail drawing. Such drawings, as we have seen, explain how to manufacture some part or assembly. And they are also valuable guides for you in overhauling and repairing equipment. These drawings are valuable not only because they show how parts fit (though this is very important itself) but also because they describe and enumerate the fastening hardware you need to put the assembly together (including the proper bolts, nuts, patent fasteners, pins, etc.). They also show the minor, but essential, parts that the assembly must have so that it will continue to function as the designer intended. A watertight enclosure, for example, will leak if it does not have the exact gasket called for in the drawing; screws may loosen if they have not been assembled with the lock washers specified in the drawing; and nuts will work free if they have not been secured with the cotter pins listed in the drawing.

Other types of drawings are equally valuable. General arrangement drawings are good References for the exact nomenclature of major units and as guides to drawings on component assemblies. Installation and outline drawings contain just the information on clearances and dimensions that ship's personnel require when a new piece of equipment is to be installed, and they show how to arrange the piping and wiring to be connected to it. External wiring diagrams show just how to hook equipment into the ship's wiring. After installation, they aid in troubleshooting for faulty circuits and malfunctioning components and in electrical alignment of synchros and other data transmission devices. Internal wiring diagrams are equally valuable for making circuit checks in case of trouble in the equipment. Elementaries are helpful in training personnel and can be used in checking circuits. And, finally, LDs are valuable guides in tracking down the particular piece of information you maybe looking for.

Every ship carries copies of drawings on its equipment in the form of blueprints, photoprints, microfilm, or microfiche. These copies are assembled into sets, each set covering one item. Photoprints are usually bound in books. Aboard ship, both blueprints and photoprints are called ordnance drawings. Blueprints and photoprints are available to you either in a special file in the repair shop or in the custody of your department head. Make use of them; they will help you become familiar with the ordnance you will overhaul. (Remember to treat Confidential drawings as you would any other Confidential publication.)

Down in the lower right-hand corner of each drawing you will find a drawing number. On each detail pictured in the drawing, you will find another smaller number. These are the piece numbers. These numbers identify both the hardware and the drawing. Sometimes you will find a letter after the piece number showing how many times that piece has been changed or modified since the original design.

Every part of every ordnance device (unless it is very small) has a part number stamped on it. The first number is the drawing number; the second is the piece number. For example, you will find numbers like 120460-2. This should read: "drawing number 120460, piece number 2."

Look for these numbers and use them. Refer to them when you report on a particular piece or when you order new parts.


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