# How to create a clear bill of materials list?

I am required to create a Bill of Material for a steering system I am designing.

However, I am not entirely sure how to structure it. For example, what type of order are the parts listed as I have seen some that involve levels (I have posted below)?

I just require some knowledge from someone who has created a full list on how to write one up clearly. Also the parts circled are what I like help explaining.

• Who assigned you this task? I presume they would be the ones who should know that. Just looking at it, the levels are just the organization structure. Level 1 stuff is large systems, level 2 is components of those systems, level 3 is smaller components in those, etc. It's just breaking it down into smaller chunks until you get your ordered materials. – JMac Apr 10 '17 at 13:18
• I do not believe this should be on hold. All the engineers in my department make bills of material. I believe this question is clear and applicable to Engineering. – Gwydionforge Apr 10 '17 at 13:18
• The way we make bills of material (BOM) is to start with the main assembly part categorized by the model number or family it is associated with. Then under that main assembly are the parts that go directly on it and any sub-assemblies under it. Each sub-assembly is the same way, parts and other subs. We use a manufacturing program called Exact Max which tracks parts, materials and assemblies. It also has modules for part and assembly routing through the manufacturing shops. It also tracks and updates revisions as we update parts. It looks like you are using Excel to build your own. good luck – Gwydionforge Apr 10 '17 at 13:23
• @Gwydionforge Just in case it isn't clear why it was on hold, look at the time it was on hold and the edit history. This was originally extremely unclear. – JMac Apr 10 '17 at 13:30
• @Gwydionforge thankyou for the comment, would you happen to have a visual example? – Mcccccc Apr 10 '17 at 18:03

What you have have posted I believe is Bill of Materials that includes Assembly level representation. Below is the complete BOM which I believe is the one you have partially referenced.

Click on image for a larger version of the image.

So if you were to create a BOM from the attached spreadsheet I would remove following line items and to create the BOM.

All of the above higher level assembly part numbers that require components like capacitors, screws, labels etc to create higher level assemblies.

A bottom up or top down approach can be followed to create assembly drawings. Below is an example for bottom up assembly structure pseudo steering system.


+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
| BOM Level | 0 | 1 | 2 | 3 | Part Number | Part Name                                | Revision | Quantity |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   | * |   |   | 20-0001     | Steering System                          |     A    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   | * |   | 30-0002     | Steering Wheel Assmbly                   |     B    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-7911     | Spring                                   |     D    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-7984     | Bearing                                  |     D    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-7940     | Support                                  |     A    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-7952     | Screws                                   |     C    |    10    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-7912     | Screws                                   |     A    |     3    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-7918     | Hub                                      |     B    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   | * |   | 30-0005     | Steering Column Assembly                 |     B    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-6002     | Flange Nut                               |     B    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-6005     | Column Holder                            |     A    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-6010     | Flange Bolt                              |     C    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-6010     | Steering Joint Gromment                  |     A    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   | * |   | 30-0010     | Rack and Pinion Assembly                 |     C    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-5001     | Front Suspension Steering Ball Dust Seal |     B    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-5010     | Steering Gear                            |     A    |     1    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-5020     | Front Wheel Spindle Connecting End       |     C    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   | * |   | 30-0020     | Wheel Assembly                           |     C    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-8012     | Tire                                     |     C    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-8013     | Bolt                                     |     A    |    10    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   |   | * | 40-8015     | Cap                                      |     C    |     2    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   | * |   | 40-7952     | Screws                                   |     C    |    20    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+
|           |   |   | * |   | 40-7912     | Screws                                   |     A    |     5    |
+-----------+---+---+---+---+-------------+------------------------------------------+----------+----------+



Assembly drawing of a Steering Assembly

Click on image for a larger version of the image.

References: