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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › Shipbuilding / Marine Fabrication › Shipfitting Layout › Lesson 12
MFG-SHIP13-04 · Lesson 12 · 34 clock hours · practice

Integrated Layout and Fit-Up Practical

Objective. Students will independently complete the full layout, template development, and fit-up sequence for an assigned multi-part hull-section assembly, satisfying all dimensional tolerances and producing a complete documentation package, which serves as the primary skills assessment for the course.

Integrated Layout and Fit-Up Practical

This lesson is the capstone assessment for Shipfitting Layout. You will work independently through the complete sequence a professional shipfitter performs on the job: reading the drawing package, laying out the assembly, developing templates, fitting parts in order, and producing the documentation that follows the work. Every step builds on skills practiced earlier in the course, and every step will be checked.

Reading the Drawing Package

Before touching a tool, spend time studying your drawing package. Identify the bill of materials, the reference datums, all dimension strings, and the weld symbols. Note which dimensions are toleranced and which are reference-only. Mark the sequence in which parts must go down—generally keel bar first, transverse frames next, longitudinals, then brackets—because each part locates the next. If anything is unclear, ask before you start; an error caught on paper costs nothing; one caught after cutting costs material and time.

Setting Up on the Shop Floor

A clean, flat surface is the foundation of accurate layout. Sweep the plate table or layout floor and verify it is free of weld spatter and debris that could rock a straight edge. Snap or scribe your baseline and centerline from the drawing datums. Use a calibrated tape measure, combination square, and framing square. Check your 90-degree corners with the 3-4-5 rule or its multiples. Transfer all primary dimensions to the floor before developing any template.

Template Development

Templates translate curved or complex shapes from the drawing to the material. Cut your cardboard or Masonite slightly larger than the finished part, then trim and fit it to the scribed lines on the floor. Mark every template with part number, heat number if applicable, orientation (forward/aft, port/starboard), and "this side up." Present each template to the instructor for approval before it touches steel. An approved template carries the instructor's signature and date. Cutting from an unapproved template is a gate violation that stops your progress.

Fit-Up Sequence and Tolerances

Fit parts in the sequence shown on the drawing. Tack-weld only after verifying each part is plumb, square, and at the correct height. Use clamps and strongbacks to hold parts against movement before tacking. Check root gaps against the weld procedure specification before calling the instructor to the milestone gate. All primary dimensions in this assembly must fall within ±1/8 inch of the nominal drawing dimension. If a part is out of tolerance, remove it, identify the cause, correct the layout error or re-cut the part, and document what you did and why on the correction log.

Documentation Package

Documentation is not optional and is not done at the end—it runs in parallel with the build. Complete the following forms as you go:

The instructor signs three milestone gates: layout complete, templates approved, and tack fit-up complete. All three signatures must appear on your package for the final grade to be awarded.

Safety on This Practical

Wear your full PPE at all times on the shop floor: hard hat, safety glasses (shade-appropriate goggles when tacking), leather gloves, and steel-toed boots. When operating the MIG welder for tacking, add a welding helmet with the correct shade lens, flame-resistant clothing, and hearing protection. Apply lockout/tagout procedures to the MIG machine before changing wire, cleaning the gun, or performing any maintenance—de-energize the machine, lock the disconnect, and tag it before working on it. Keep the area around the strongback clear of trip hazards; scrap drops from cutting are a slip risk. Have a fire extinguisher within reach whenever you arc. Never grind without a face shield over your safety glasses.

Milestone Gate Process

At each of the three gates, stop work and call the instructor. Do not advance to the next phase until you receive a written sign-off. The gates are checkpoints, not interruptions—use the wait time to update your documentation. At the final inspection, the instructor will measure all critical dimensions with calibrated tools. Pass means every primary dimension is within ±1/8 inch and the complete documentation package is present and correct.

Professionalism and Time Management

You have a fixed number of hours to complete this practical. Plan your time: allocate time for study, layout, template work, cutting, fit-up, and documentation. Professional shipfitters estimate time before they start and adjust as they go. If you fall behind, communicate with the instructor early—do not rush fit-up to make up time, because a hurried fit is an inaccurate fit.

Key terms9

DatumA reference point, line, or plane from which all other dimensions on the drawing are measured; establishing the correct datum before any layout begins prevents cumulative error.
TemplateA full-scale pattern, usually cut from cardboard or Masonite, used to transfer a complex or curved shape from the drawing to the steel before cutting.
StrongbackA rigid structural member clamped or tacked to the assembly to hold parts in position and resist distortion during tacking and welding.
Fit-Up SequenceThe prescribed order in which parts are assembled and tacked, determined by the drawing and weld procedure so that each part locates the next correctly.
Root GapThe opening between two pieces to be joined, specified by the weld procedure specification; too small or too large a gap causes defective welds.
Material Take-Off (MTO)A written list of every part needed for an assembly, including mark number, material grade, thickness, and cut dimensions, used to order or verify stock before work begins.
Milestone GateA defined checkpoint in the build sequence where an inspector or instructor verifies that work meets requirements before authorizing the student to proceed to the next phase.
Dimensional ToleranceThe permitted variation from a nominal drawing dimension; in this practical all primary dimensions must be within ±1/8 inch of nominal.
3-4-5 RuleA method for verifying a 90-degree angle on a layout floor: if one leg measures 3 units and the other 4 units, the hypotenuse must measure exactly 5 units for the corner to be square.

Worked examples4

1. Your drawing shows a transverse frame that must be positioned 24 inches from the centerline. You measure the scribed line and get 24 3/16 inches. Is this within tolerance, and by how much is it off?
  1. Step 1: Identify the nominal dimension: 24 inches.
  2. Step 2: Identify the allowed tolerance: ±1/8 inch = ±0.125 inch.
  3. Step 3: Convert your measured value to a decimal: 24 3/16 = 24 + 3/16 = 24 + 0.1875 = 24.1875 inches.
  4. Step 4: Calculate the deviation: 24.1875 − 24.000 = 0.1875 inch.
  5. Step 5: Compare deviation to tolerance: 0.1875 inch > 0.125 inch, so the line is OUT of tolerance.
  6. Step 6: Determine the correction needed: move the scribed line 0.1875 − 0.125 = 0.0625 inch (1/16 inch) closer to centerline before proceeding.
Answer: The scribed line is 3/16 inch from nominal, which exceeds the ±1/8-inch tolerance by 1/16 inch. Re-scribe the line 1/16 inch toward centerline before fitting the frame.
2. You are developing a template for a bracket that must span a rectangular opening 18 inches wide by 12 inches tall. Verify the template is square using the 3-4-5 rule.
  1. Step 1: Scale up the 3-4-5 ratio to suit the opening. Use a 3-4-5 multiple: choose 12-16-20 (multiply each by 4), which fits within the 18 × 12 opening.
  2. Step 2: From the lower-left corner, measure 12 inches along the bottom edge and mark point A.
  3. Step 3: From the same lower-left corner, measure 16 inches up the left edge and mark point B.
  4. Step 4: Measure the diagonal distance between point A and point B. It should equal 20 inches if the corner is exactly 90 degrees.
  5. Step 5: If the diagonal measures exactly 20 inches, the corner is square. If it differs, adjust the template edge until the diagonal equals 20 inches, then re-check.
Answer: A diagonal of exactly 20 inches between the two marked points confirms the corner is square. Any other measurement means the corner is not 90 degrees and the template edge must be adjusted.
3. Your material take-off requires three pieces of 3/8-inch plate. Piece A is 12 × 24 inches, Piece B is 10 × 18 inches, and Piece C is 8 × 8 inches. What is the total area of steel you need to list on the MTO?
  1. Step 1: Calculate area of Piece A: 12 × 24 = 288 square inches.
  2. Step 2: Calculate area of Piece B: 10 × 18 = 180 square inches.
  3. Step 3: Calculate area of Piece C: 8 × 8 = 64 square inches.
  4. Step 4: Sum the three areas: 288 + 180 + 64 = 532 square inches.
  5. Step 5: Convert to square feet if required: 532 ÷ 144 = 3.69 square feet (rounded to two decimal places).
Answer: The total material area is 532 square inches, or approximately 3.69 square feet of 3/8-inch plate, to be listed on the MTO before cutting begins.
4. The drawing shows a longitudinal running parallel to the keel, offset 9 inches to port. After fitting, you measure the offset at the forward end as 9 1/16 inches and at the aft end as 8 7/8 inches. Is the part within tolerance at both ends?
  1. Step 1: Nominal dimension: 9.000 inches. Tolerance: ±1/8 inch = ±0.125 inch. Acceptable range: 8.875 to 9.125 inches.
  2. Step 2: Convert forward measurement: 9 1/16 = 9.0625 inches. Check: 9.0625 is between 8.875 and 9.125. PASS.
  3. Step 3: Convert aft measurement: 8 7/8 = 8.875 inches. Check: 8.875 equals the lower limit exactly. PASS (at the boundary).
  4. Step 4: The longitudinal passes at both ends. Record both actual measurements on the fit-up inspection checklist.
Answer: Forward end (9 1/16 in) and aft end (8 7/8 in) are both within the ±1/8-inch tolerance. Document both readings on the fit-up checklist and proceed to tacking.

The math in this lesson2

Learners total plate area for three pieces in the material take-off.
7.G.68.G.7
Brush up in the math halls at newSchoolWorks.com:
In class: Each student receives a drawing package for a small hull section (keel bar, two transverse frames, one longitudinal, one bracket); they independently lay out the assembly on the shop floor, develop any required templates, cut or request pre-cut material, and fit the parts in correct sequence over the allotted hours. · Students complete all required documentation in parallel with the build: material take-off, layout record, fit-up inspection checklist, and a brief written description of any corrections made and why. · Instructor conducts a progressive check at three milestones—layout complete, templates approved, tack fit-up complete—signing off at each gate before the student advances; final assembly is measured against the drawing at the end.
Materials: Full drawing package (unique per student), steel layout floor or plate table, full precision-tool kit, cardboard or Masonite for templates, clamps, strongbacks, MIG welder for tacking, full documentation forms, safety PPE (hard hat, safety glasses, leather gloves, steel-toed boots)
Check: Final assembly measured at all critical dimensions by instructor using calibrated tools; all primary dimensions must be within ±1/8 inch, all templates must have been approved before cutting, documentation package must be complete—all three gate sign-offs required and final dimensional check must pass to receive a passing grade on this lesson.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Shipfitting – Layout and Template Development
1. Before cutting steel from a template you developed, the most important step required in this practical is to:
NCCER Shipfitting – Dimensional Tolerances
2. You measure a frame position and find it is 3/16 inch from the nominal drawing dimension. The tolerance is ±1/8 inch. What must you do?
NCCER Shipfitting – Layout Mathematics
3. When verifying that a layout corner is square using the 3-4-5 rule, if one leg is 3 feet and the other is 4 feet, the hypotenuse should measure exactly:
NCCER Shipfitting – Assembly Sequence
4. The correct fit-up sequence for a basic hull-section assembly is generally:
Safety – Lockout/Tagout (OSHA)
5. Which lockout/tagout action is required before changing MIG welding wire or cleaning the welding gun?
NCCER Shipfitting – Documentation
6. A material take-off (MTO) is best described as:
Safety – Welding PPE
7. During tacking with a MIG welder, which additional PPE item is required beyond the standard hard hat, safety glasses, and leather gloves?
NCCER Shipfitting – Dimensional Tolerances
8. A student's aft longitudinal offset measures 8 13/16 inches against a nominal of 9 inches with ±1/8 inch tolerance. The deviation is:
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