Metalworking Hand Tools and Techniques Guide

Posted on Oct 31, 2024 in Technology

ITEM 10: Filing and Sanding Techniques

Filing

Technical Filing: Aims to reduce areas where material removal is necessary. Metal removal can be done manually or mechanically.

Files:

  • Made of hardened, extra-hard steel plates.
  • Carved on their surface to facilitate the start of chips in the direction of file movement.
  • Carving consists of cutting teeth.

Characteristics of Files:

  • Size: Body length is the distance between the point and the heel of the file.
  • Shape: Flat, triangular, square, half-round, round, knife.
  • Cut: The degree of roughness on the file body (single-cut, double-cut, rasp-cut, special-cut).
  • Grade: Determined by the number of teeth per unit area (e.g., teeth per cm). Grades include extra fine, fine, semi-fine, bastard, and coarse.

Shaping

The shaper is a machine tool with a primary translating movement, allowing for the machining of flat surfaces. The movement occurs in successive cycles of tool advance and retreat on the workpiece surface. The cutting speed varies, being slower during advance and faster during retreat.

Sanding Techniques

Sanding aims to adjust or refine surface finishes by removing material through abrasion. It is often performed manually.

Sandpaper:

Sandpaper consists of three primary elements:

  • Backing: The base material on which abrasive grains are fixed (paper, fabric, fiber).
  • Abrasive: Minerals of different sizes and high hardness (natural, emery, etc.).
  • Binder: The compound used to bond the abrasive grains to the backing.

Particle Size:

Abrasives are marked on the back with their grain size, indicating their abrasive power. The letter “P” indicates a standardized abrasive, and the number indicates the grain size. Larger grain sizes have greater abrasive power and leave deeper grooves on the sanded surface.

Sanding Tools:

  • Sandpaper sheets, abrasive discs, pads.
  • Sanding blocks.
  • Sanding machines: Vibrating, eccentric, orbital, radial.
  • Emery stones.

ITEM 11: Drilling

Drilling is a cutting operation that removes material to create holes of different diameters. The primary machine used is the drill press, which utilizes a rotating cutting tool called a drill bit.

Drill Bits:

Drill bits are cutting tools made of very hard steel and metals, used for creating holes. They are cylindrical and have two helical grooves (flutes) that end in two cutting edges.

Parts of a Drill Bit:

  • Tip: The cutting part.
  • Body: The section between the tip and the shank.
  • Shank: The part that attaches to the drilling machine.
  • Neck: The section between the shank and the body.
  • Flutes: Helical grooves that allow chip removal.
  • Cutting Lips: The edges that perform the cutting action.

Drill Bit Materials:

  • HSS (High-Speed Steel)
  • HSS-Ti (Titanium-coated High-Speed Steel)
  • HSS-Co (Cobalt High-Speed Steel)

Drill Bit Types:

  • Metal
  • Wood
  • Masonry
  • Glass
  • Center drills

Drilling Machines:

Drilling machines transmit rotary motion to the drill bit. Depending on the job, you can choose between fixed (drill presses) and portable (handheld drills) machines.

Drill Presses:

Drill presses have a pulley system to vary the speed and a crank or lever to control the drill bit’s feed rate.

Portable Drilling Machines:

Portable drilling machines (e.g., corded drills, cordless drills, pneumatic drills) allow for drilling in various locations without a fixed setup.

Mini Drills:

Mini drills achieve high rotational speeds and are used for precision work and adjustments.

Drill Bit Holders:

Drill chucks are used to hold drill bits securely. They have jaws that are tightened using a chuck key.

Morse Tapers:

Morse tapers are conical fittings with different diameters that are used to connect drill bits to tapered holders in drill presses.

Countersinking:

Countersinking creates a conical recess in a drilled hole to accommodate the heads of screws or rivets, allowing them to sit flush with the surface.

Countersink Bits:

Countersink bits are cutting tools used to create countersinks. They are tapered and come in various types, including solid steel, multi-flute, and abrasive.

Reaming:

Reaming is a machining operation that removes a small amount of material from a hole to improve its accuracy, size, and surface finish.

Reamers:

Reamers are cutting tools made of hardened steel used to enlarge or refine existing holes. They come in two main types: manual and machine reamers.

ITEM 12: Screw Threads

A screw thread is a helical ridge formed on a cylindrical surface with a specific profile.

Classification of Threads:

  • Number of Starts: Single-start, multi-start.
  • Hand of Thread: Left-hand, right-hand.
  • Purpose: Fastening, motion transmission, fluid sealing.
  • Thread Form: Triangular, round, trapezoidal, square, buttress.

Characteristics of Threads:

  • Nominal diameter (major diameter)
  • Core diameter (minor diameter)
  • Pitch (distance between adjacent threads)
  • Thread flank angle
  • Thread depth

Thread Systems:

Metric ISO:

  • Based on an equilateral triangle with truncated crests and rounded roots.
  • Flank angle is 60°.
  • Pitch is measured in millimeters.

Whitworth:

  • Flank angle is 55°.
  • Forms an isosceles triangle.
  • Smaller side of the triangle equals the pitch.
  • Rounded crests and roots.

British Standard Pipe (BSP):

  • A variation of the Whitworth thread with a finer pitch.
  • Used in pneumatic and hydraulic fluid pipes.

Sellers (American National):

  • Similar to the metric thread with a 60° flank angle.
  • Truncated crests (1/8 of the triangle height).

Sheet Metal Thread:

  • Can be triangular or trapezoidal.
  • Wide thread form for use in sheet metal and plastics.