Catalogue parts are components/items that are bought from a manufacturer and are not defined by a standard like ISO, DIN or similar.
Although the making of drawings for catalogue parts can take up some time (and is usually avoided for one-time projects), they are of very high importance in the case of product engineering and projects that get reproduced.
You might be asking yourself: Why don't you just order per code number?
Well, unfortunately not all companies have the same definition of interchangeability. It has often happened that the manufacturer of the catalogue part changed some crucial product dimensions but kept the ordering code the same.
In such cases, if we are only ordering per the code number we will get the wrong component which will influence the manufacturing process of our product.
Sometimes it can also happen that we need small customization on the catalogue part and the manufacturer's process to issue a new code number just for us is something that can take ages.
So, to avoid those traps it is always a good practice to also make drawings for catalogue parts because only with a clear drawing, we can define what features are important to us and only so we can control what we order.
This does not mean we need to make complicated drawings of the catalogue parts or that we should not include their code number. It only means that if we have a document on which we put all the important info, we have a clear reference per which we can order and are sure to get what we need.
Here are some examples:
TECHNICAL DRAWING OF A Load Sensor - Custom HOLE
In this case, the manufacturer had only sensors with a threaded hole in their catalogue. But we needed one that had a normal hole. So we took the order code of their standard sensor and added the information for the customization. We gave the sensor our custom item number just as we would with any other item.
TECHNICAL DRAWING OF A Chain - Custom Length
In this case, the chain consists of 156 standard chain links.
TECHNICAL DRAWING OF A Spherical Roller Bearing - NO CUSTOMIZATIONS
In this case, there was no customization needed. We only put the info on the drawing that was important at that time. But we also could have added some info about the maximum static/dynamic load if we wanted to.
As you can see, the drawings are pretty simple. They won’t take you much time to create but might bring a lot of value to your engineering process and your company.