Find number
Printed as FIND NO ITEM ITEM NO
The row's number, repeated in a balloon on the views so you can find the part on the drawing. It is a reference within this drawing only; the part number is what identifies the part anywhere else.
How to read a bill of materials on a drawing
On an engineering drawing, the bill of materials is the parts list: a table, usually just above the title block, giving each item's find number, the quantity needed for one assembly, its part number, its description and often its material or specification. Each find number is repeated in a balloon on the drawing's views, pointing at the part it names.
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The table
Parts list or bill of materials?
The same table under two names: ASME Y14.34 calls it a parts list, and most companies and their software call it a bill of materials.
Where it is. On an assembly drawing the parts list usually sits just above the title block. A parts list can also be a separate document with its own number, one of the lists ASME Y14.34 covers.
What it lists. The parts of one level of assembly: what goes directly into the item the drawing defines. A subassembly is one row, with its own drawing and its own parts list; following those lists down level by level gives the full, multi-level bill of materials.
What it must say. At the least, for each item, the quantity required, its part number and its name. Most lists add the find number, the material or specification, and sometimes the CAGE code of the company whose part number it is.
ISO drawings follow ISO 7573 for parts lists and ISO 6433 for the numbers that tie rows to the views.
Sources: ASME Y14.34 (parts lists and other associated lists), ISO 7573 (parts lists), ISO 6433 (part references).
Column by column
What each column means.
A parts list as many ASME drawings print it, then each column with the headings it is printed under.
Quantity required
Printed as QTY REQD QTY
How many go into one of the assembly the drawing defines, never a total for an order. ASME Y14.34 makes it a required column. It is not always a number: AR and REF are explained below, and bulk material may be given in a length or a weight, with a unit of measure column beside it.
Part or identifying number
Printed as PART OR IDENTIFYING NO PART NO P/N
What the item is. ASME Y14.100 has it assigned by the company that designed the item or by the national standard that defines it, so it may be one of the company's own numbers, a standard part's number, or a supplier's, with that supplier's CAGE code beside it. Copy it exactly as printed, dashes and leading zeros included.
Nomenclature or description
Printed as NOMENCLATURE OR DESCRIPTION DESCRIPTION
The item's name, written like a drawing title: a noun or noun phrase, then modifiers after commas, as in PLATE, BASE. For a part with a drawing of its own, it usually repeats that drawing's title.
Material or specification
Printed as MATERIAL SPECIFICATION
What an item is made of, or the specification it is bought to. It matters most for items with no drawing of their own, such as a part cut from stock or a bulk material; a part with its own drawing has its material there.
Sources: ASME Y14.34 (parts list content; quantity required), ASME Y14.100 (part or identifying numbers; item names).
On the views
Balloons and find numbers.
A balloon is a circle holding a find number, with a leader line to the part it names: the bridge between the table and the picture.
Every row of the list is usually ballooned at least once, so every part can be found on the views; a part used several times may be ballooned once or at each place. A balloon number missing from the list, or a row with no balloon, is worth asking about.
Gaps in the numbers are normal. A revision that removes an item may leave its find number unused rather than renumber the rest, so a list can run 1, 2, 4, 5.
Sources: ASME Y14.34 (find numbers), ISO 6433 (part references).
Quantities
Quantities: per assembly, AR and REF.
A quantity is always for one assembly, and sometimes it is not a number at all.
- A number: how many go into one assembly. Multiply by the number of assemblies to build.
- AR, as required: the amount is set at assembly, for adhesive, sealant, shims or wire; an ERP system usually needs an estimate or a unit to plan with.
- REF, reference: listed for the reader's information and not supplied by this list, often because another item or drawing supplies it. Leave it out of what is ordered or picked.
- A length or a weight, such as 2.5 FT of tubing: bulk material, with its unit of measure.
- A dash or a blank under a dash number: that variant does not use the item (see tabulated parts lists below).
Source: ASME Y14.38 (AR, as required).
Variants
Tabulated parts lists and dash numbers.
One assembly drawing can define several variants, each a dash number, and its parts list gives each variant a quantity column of its own.
Assembly 10050, its two variants
| Qty -1 | Qty -2 | Find no | Part no | Description |
|---|---|---|---|---|
| 1 | – | 1 | 10045-1 | PLATE, BASE |
| – | 1 | 2 | 10045-2 | PLATE, BASE |
| 2 | 2 | 3 | 10046 | BRACKET |
| 4 | 8 | 4 | 10047 | SCREW, CAP |
A made-up tabulated parts list. To build 10050-2, read down the -2 column: one 10045-2, two 10046 and eight 10047.
The variants are part numbers of their own, the drawing number with a suffix: 10050-1 and 10050-2. The drawing usually also says what makes each variant different, in a table of dash numbers. A revision of the drawing applies to every variant at once; revision history blocks explains how dash numbers and revisions differ.
Taken into a spreadsheet or an ERP system, a tabulated list becomes one bill of materials for each dash number, each listing only the rows with a quantity in its column.
Into your systems
From the drawing into ERP or PLM.
ERP and PLM systems generally take a bill of materials as rows of parent, child, quantity and unit, so loading one is mostly a matter of mapping columns and settling the rows that are not plain numbers.
- The parent is the assembly: the drawing number with its dash number, at the revision you read.
- Each row becomes a child: its part number exactly as printed, its quantity per parent, and a unit of measure: EA (each) for counted parts, a length or a weight for bulk material.
- Keep the find number, so anyone can go from the system back to the balloon on the drawing.
- Settle the rows that are not numbers: give AR items the planning quantity your system needs, and leave REF rows out.
- Split a tabulated list into one bill of materials per dash number.
- Go down a level for each subassembly, from its own drawing, to build the multi-level BOM.
Engineering BOM and manufacturing BOM. The drawings give the engineering BOM: the product as designed. A manufacturing BOM is how it is built, and may regroup parts and add what the shop needs that the drawing does not show, such as packaging or consumables.
Getting the parts lists out of a stack of PDF drawings is a question of its own: see Parts lists from PDF drawings to Excel, or An API for drawing data for a system that should read them itself.
Questions
What people ask about parts lists.
What is the difference between a parts list and a bill of materials?
On a drawing they are the same table. ASME Y14.34 calls it a parts list; bill of materials, or BOM, is the name most companies and their ERP and PLM systems use. A parts list may be printed on the assembly drawing or kept as a separate document with its own number.
What is a find number on a drawing?
The number that ties a row of the parts list to the part on the drawing's views: the same number appears in a balloon, a circle with a leader line pointing at the part. Some drawings call it the item number; ISO 6433 calls it a part reference.
What does AR mean in a bill of materials?
As required. The quantity is decided when the assembly is made, for material such as adhesive, sealant, shims or wire, rather than counted in advance. AR is the abbreviation ASME Y14.38 gives.
What does REF mean in a parts list quantity?
Reference: the item is listed so the reader knows about it, but the list does not supply it, for example because it is supplied under another item or another drawing. A REF row is not counted when the assembly is built.
Is the quantity in a parts list per assembly or in total?
Per assembly: the quantity needed to make one of what the drawing defines. For ten assemblies, multiply. On a tabulated drawing, each dash number has its own quantity column.
What is a tabulated parts list?
The parts list of a drawing that defines several variants, each with a dash number. It has one quantity column per dash number, so to build one variant you read down its column: a dash or a blank means that variant does not use the item.
From SpecCapture
Parts lists by the hundred?
SpecCapture reads the title block, the revision history, the bill of materials, the hole table, the application block, the tabulated dash numbers and the general notes off 2D engineering drawings, with a box on the drawing around every value it reads, so checking it takes a glance.
It reads every row of the bill of materials, column by column: item number, quantity, part number, description and material. It reads every row of the tabulated dash numbers, column by column: dash number and description.