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Part Numbers

Posted on in the basics

Part numbers aren't essential for the cutting process.  However, if you have more than a few parts you need cut, especially if any of them are similar (a left and right pair, for example), part numbers are a very useful way to track them. We may need to discuss a particular part or set of parts with you, or you may need to know which part is which for ease of assembly.  Neal's CNC is happy to write the part numbers on the parts for you, either directly or on a piece of masking tape, for no additional charge.  We can also engrave them on each part with a V bit, although this does add to the cut cost.

You may think, why not just use a description of the part?  For simple constructions with few pieces, "left side" "top" "right side" "bottom" are fine.  As the part count increases, "left upper flange with large holes" starts to get harder to handle.  Which of the five upper flanges on the left side has large holes versus, say, medium sized holes?  Is it the left side when looking at the front of the piece, or looking out from it?  The descriptive phrases are too long, and simultaneously not detailed enough.  Errors become increasingly likely, and it's just harder to think about.

Many organizations have policies around part numbers.  For those that don't, here is a simple part numbering scheme that can extend to thousands of parts.  We have used this successfully on many projects over the years.  The scheme consists of three sections: an alphabetic component label, a numeric or alphabetic material code, and a numeric incremented part.  In many cases the material code or component label can be omitted.  Here are some examples:


This is a part number from a van conversion project.  On the left, two letters indicating the assembly the part belongs to.  "FC" stands for Front Cabinet.  Next, a single digit indicating the type of material used.  In this van scheme, "1" means 3/4" plywood, "2" means 1/2" plywood, "3" means clear 1/4" acrylic, and so on.  Finally on the right, two digits indicating which part in the FC assembly this refers to.  None of the assemblies in the van have more than 25 pieces, so two digits is plenty.


This is a part number from a large freestanding pergola, constructed of many individually shaped slats that slot together at right angles.  Here, "A" stands for nothing in particular, but indicates slats that all go in one direction.  There are two more codes, "B" for the slats perpendicular to the A set, and "U" for Uprights, which are the support structure.  Here, the entire structure is built from the same 3/4" plywood so a material indicator isn't needed.


This is a part number from a full size model of an airplane.  There are components WNG (wing), H (hull), S (seats), BW (bulwarks), BC (baggage compartment), OC (overhead compartment) and more.  Materials used include four thicknesses of plywood in both finished and unfinished versions, three kinds of plastic, and aluminum in two thicknesses, so a double digit material code is used.  Some of the components have only 10 or 15 parts, but a few have over 100 so three digits are used for the incremented number.

We do recommend keeping the incremented number section to the same number of digits across all assemblies.  If the number of numbers varies, this can cause confusion.  This hasn't been as much of an issue with the component letters, for some reason, perhaps due to the frequent use of mnemonics for those codes.

For some jobs, part numbers are assigned early in the design process and tracked with revision numbers as the design drawings progress.  The above schema could be extended to indicate a version number, but the primary focus of this schema is to track and identify final part drawings with the cut piece.  If your cut job is complex enough to need part numbers and you don't have them, we will often ask if we can assign them for you, and we'll provide a copy of your drawings with the part numbers we assign marked as reference.  We'll often do this if, for example, we need to break up a large piece into smaller ones for cutting purposes: a 15' tree sculpture, templates for a subdivision sidewalk, concrete forms for a multi-story stairwell.

A final advantage of part numbers is that you can send us one drawing with the parts and their numbers, and then a table with the part numbers and the quantities needed.  There is no need for the customer to agonize over a cutting layout, we are happy to do that here.  And we often rearrange any layouts that customers send anyway, to reduce the cut risk or save material.

All that said, for your own part numbering, any schema that makes sense to you will likely be fine.  It just needs to identify each part uniquely, and be short enough to write down easily.