Material Take-Off and Fit-Up Documentation

What Is a Material Take-Off?

A material take-off (MTO) is a complete, itemized list of every piece of material required to build a structural assembly. In a shipyard, the MTO is the bridge between the engineering drawing and the shop floor: it tells the material handler what to pull from stock, tells the fitter what to expect at the work site, and gives the project manager cost and weight data. An incomplete or inaccurate MTO causes delays, rework, and wasted material—all of which cost money and time on a production schedule where vessel sections must flow smoothly through the build.

For the NCCER Shipfitting credential, you are expected to read a fabrication drawing, identify every part, and record the information on a standard take-off form without missing any item and without introducing significant errors.

Reading the Drawing Before You Write Anything

Before you fill in a single line of the MTO form, study the entire drawing:

1. Title block – Confirms the assembly name, drawing number, revision level, scale, and applicable material specification (for example, ABS Grade A plate or ASTM A36 structural steel).

2. Bill of materials (BOM) block – Usually located in the upper-right corner or along the right border. It lists each part by part mark (sometimes called item number or piece mark), description, material designation, quantity required, and often the raw size.

3. Detail views and section cuts – Clarify geometry that the plan view cannot show. Check every view before recording a dimension.

4. General notes – May specify painting, surface preparation, edge treatment, or weld quality class that affects fit-up.

Never scale dimensions from a drawing unless the drawing specifically authorizes it and you are using the stated scale. Always read printed dimensions.

Completing the Material Take-Off Form

A standard shipyard MTO form contains at minimum these columns:

| Column | What to Record |

|---|---|

| Part Mark | Alphanumeric identifier from the BOM (e.g., P-1, F-2) |

| Description | Plate, flat bar, angle, T-bar, etc. |

| Material Grade | ABS Grade A, ASTM A36, 5083-H116 aluminum, etc. |

| Quantity (Qty) | Number of identical pieces required |

| Thickness or Size | Flange width × web height for shapes; thickness for plate |

| Length | Cut length per piece in inches or millimeters |

| Unit Mass | Weight of one piece (lb or kg) |

| Total Mass | Unit mass × quantity |

Common errors to avoid:

• Transposing digits in a dimension (writing 63 mm instead of 36 mm).
• Forgetting to multiply unit mass by quantity when totaling.
• Recording the nominal section size instead of the actual cut length.
• Missing a mirrored part (port vs. starboard) that has a separate part mark.
• Using the wrong material grade when the drawing shows a revision that changed the spec.

A quantity error of more than 5% on any line means the downstream material pull will be wrong. Check every line against the BOM before submitting the form.

Producing the Fit-Up Sketch

A fit-up sketch is a freehand, dimensioned drawing—not a CAD plot—that a fitter uses at the assembly table to orient parts correctly, confirm sequence, and identify each weld joint before the first tack is struck. A good fit-up sketch shows:

• Part orientation: Which face is up, which edge is the reference edge, port vs. starboard.
• Part marks labeled on each piece so anyone picking up the sketch can match it to the MTO.
• Weld symbols per AWS A2.4: the reference line, arrow, tail, and the correct symbol for joint type (fillet, groove, plug, etc.). Weld symbols on a sketch must match the drawing—never improvise.
• Assembly sequence (numbered steps or a sequence table): for example, tack the keel plate first, then add frames, then attach the face bar. Sequence prevents distortion and access problems.
• Fit-up tolerances called out in general notes or the applicable code (ABS rules, AWS D1.1 for steel, or AWS D1.2 for aluminum).

Safety Points for the Shop Environment

Even a documentation task connects to shop safety:

• When you verify dimensions in the shop, you may be near active welding or grinding operations. Wear your full PPE: safety glasses, hearing protection, and steel-toed footwear as a minimum.
• Never handle plate or structural shapes without cut-resistant gloves; edges are sharp from the cutting table.
• If you must access a confined space or elevated platform to read a part mark, apply the proper fall-protection and confined-space entry procedures before entering—documentation work does not exempt you.
• Keep your sketch and paperwork away from welding arc flash zones. Arc flash can ignite paper and damage your eyes even at a distance.

Why Accuracy to 5% Matters

A 5% quantity error threshold is not arbitrary. If a 100-piece assembly ships to the build dock short by six pieces, the fitter stops work, the crane is tied up, and a rush material pull disrupts the cut shop schedule. Accuracy on the MTO is a direct production-efficiency requirement, not a classroom standard alone.