Essential Machining Operations: Sawing, Filing, Chiseling, Reaming, and Drilling

Posted on Jan 5, 2025 in Geology

Sawing

The saw blade. The first operation of sawing permits the removal of leftover pieces. A saw consists of a sheet of tempered steel with a smooth part and a toothed part.

Types of saw blades:

  • Bimetal saw blades
  • Bilateral saw blades

Bimetal saw blades are tempered. Bilateral saw blades present teeth on each side.

Tooth pitch. It is the distance between teeth. If the pitch is fine, the teeth will be smaller, otherwise, they will be larger.

What is tooth set? To avoid wedging and eventual damage to the blade, the teeth are alternately bent to one side and the other, allowing the blade to move without difficulty.

What effects does a loose saw produce? A loose saw can cause:

  1. Imperfect cuts due to deviations and deformations.
  2. Difficulty moving the blade in the cutting slot.
  3. Possibility of excessive breakage of the saw.

What if the saw is too tense? On the contrary, a very tense blade can generate a risk of breakage due to the great traction efforts.

What tooth pitch is required for soft or hard materials? For soft materials, a larger tooth pitch is required to remove the surplus. Unlike hard materials, which need a finer tooth pitch.

If it is hard or difficult to cut, should the speed of movement be increased or decreased? The speed of movement should be decreased to approximately 30 cuts per minute.

How should tubes be cut? When cutting tubes, they should be turned as the cut progresses.

Filing

Parts of a file. Files are tempered steel bars that present a surface composed of small teeth in the form of cutting wedges, which constitute the file’s teeth.

Classification of files by form. Files can be classified as:

  • Flat
  • Triangular
  • Square
  • Half-round
  • Round
  • Knife

Classification of files by size. File sizes are normally expressed in inches, the most common being: 3″, 4″, 5″, 6″, 7″, 8″, 10″, 12″, 14″, 16″.

Classification of files by cut. There are two types of cuts: single and double. Single-cut files have one set of parallel teeth at an angle of 60° to 75°, and double-cut files have two sets of teeth.

What technique is applied when filing hard materials? Double-cut files are used for hard materials.

How should the piece be placed in the vise? The part should be placed perfectly centered in the vise jaws, protruding as little as possible to avoid vibrations that make filing difficult.

How is the file handle attached to the tang? It should be slid and hit on a workbench until it is perfectly attached to the file.

Chiseling

Parts of a chisel. In the chiseling operation, cuts are made by means of a tool endowed with an edge at one end. It consists of three parts:

  1. Body
  2. Edge
  3. Head

Burin. Uses. The burin or chisel is used to cut grooves, keyways, etc.

Chiseling in a vise. The following steps should be followed:

  1. Grip the part in the vise along the cutting line.
  2. Hold the chisel at a 30° angle with the cutting line.
  3. Firmly strike the chisel to shear the metal.
  4. The chisel is also used to shear a rivet.

Reaming

Reamer. Types of reamers. Reaming is an operation that smooths the surface of a hole and gives it a precise finish. Reamers can be classified into three categories:

  1. Manual reamers
  2. Machine reamers
  3. Special reamers

Reaming techniques. To proceed with reaming, act as follows:

  1. Drill a hole smaller than the final size.
  2. Hold the piece in a vise with the hole vertical.
  3. Attach a tap wrench to the reamer.
  4. Maintain the reamer at a right angle and apply light pressure.
  5. Insert the reamer and turn it uniformly.
  6. Steadily advance the reamer through the hole.
  7. Use cutting fluid as a lubricant.
  8. When turning the reamer, follow the direction of the clock’s hands.
  9. When using machines, the cutting speeds should be lower than those of drilling.

Drilling

The drill. How can holes be drilled? Drilling is a machining operation that uses chip removal to make circular or conical holes, with the help of tools called drill bits and machines called drills. Holes can be:

  1. Through
  2. Blind
  3. Countersunk

Countersinking. It is a machining process that consists of tapering the outer edge of a hole.

Drill bits. Parts of a drill bit. The main element of drilling is the drill bit, and its mission is to remove material by making the hole.

Main cutting edges and transverse areas of drill bits. The transverse edge is the edge that joins the two main cutting edges, forming an angle of about 55°. The transverse edge does not cut but scratches the piece.

Classification of drill bits. There are many types of drill bits. Some of the most important are:

  1. Glass drills
  2. Wood drills
  3. Multi-purpose drill bits
  4. Drill bits with internal cooling ducts
  5. Step drills
  6. Sheet metal drill bits
  7. Universal milling drill bits
  8. Spot welding drill bits
  9. Tapered drill bits
  10. Tapered step drill bits
  11. Crown drill bits

Drilling types. Drilling machines generate the rotational movement necessary for the holes, using drill bits as cutting tools. There are two types of drilling:

  1. Stationary drills, where the drill bit is held.
  2. Mobile drills, where the piece is held.
  3. Use a center punch to mark the center of the hole.
  4. For large holes, pre-drill with a smaller drill bit.
  5. Select the rotation speed.
  6. During the operation, the drill bit is subjected to two movements: one of rotation around its axis and another of advancement.
  7. During the operation, the type of chip will be determined by the material being worked on.
  8. Properly cool the contact area with the drill bit.

What is the drill bit’s advance? It is the introduction of the drill bit into the piece.

How is the speed of the drills determined? It can be determined electronically or by means of pulleys and gears.