How to Measure a Replacement Part for 3D Printing

A broken plastic component does not always mean the whole product needs replacing.

Sometimes the missing piece is a simple clip, knob, bracket, cover, spacer or adapter. When a suitable replacement is no longer available, a custom 3D-printed part may be an option.

The important first step is getting enough information to establish what the part needs to do and whether it can be made to fit. Here is what helps when you are looking into a replacement part.

Start with the part’s job

Before measuring, think about what the part actually does.

Is it mainly decorative, such as a trim piece or cover? Does it hold two components in position? Does it need to clip on, thread into another part, carry a load or sit near heat and sunlight?

A replacement part needs to suit its intended use, not simply look similar to the original. A small clip on a household appliance and a mounting bracket on outdoor equipment may require very different design and material choices.

If the part failed, it is also useful to note how it broke. This may point to an area that needs strengthening or redesigning.

Keep every piece you have

Even a broken part can provide useful information.

Bring together all available pieces, including screws, inserts, seals, caps or adjoining components. The original part is often the best reference for its shape, dimensions and fit.

If the original is missing completely, photos of the location where it fitted can still help. Measure the surrounding area, mounting points and the part it connected to.

Take clear photographs

Photos help show details that measurements alone can miss.

Take pictures:

• From the front, back and both sides
• With a ruler or tape measure beside the part
• Of any holes, clips, threads or mounting points
• Of the place where the part fits
• Of any damage or worn areas

Good lighting and a plain background make the images easier to assess. Close-up photos are useful, but include at least one wider photo for context.

Measure the important dimensions

You do not need specialist equipment for an initial enquiry, but accurate measurements make a real difference.

A ruler is useful for overall length, width and height. Digital calipers are better for smaller features such as hole sizes, wall thicknesses, shaft diameters and the width of a slot or clip.

The most useful measurements often include:

• Overall length, width and height
• Diameter of holes, pins or round openings
• Distance between mounting holes
• Thickness of walls, tabs and clips
• Internal dimensions where another part needs to fit inside
• External dimensions where the part fits into a space
• Thread type and size, where applicable

Write down which dimension belongs to which feature. A photo with measurements marked on it can be especially helpful.

Check the fit, not just the shape

Two parts can look alike but still be incompatible.

For example, a cap may appear to fit a container but use a different thread. A bracket may have the same overall size but place its fixing holes a few millimetres apart. A replacement knob may fit over a shaft only if the internal profile is correct.

Where possible, measure the component the new part will connect to as well as the original part. This is particularly important for adapters, mounts, covers, replacement clips and threaded fittings.

Tell us about the environment

Material choice depends on where and how a part will be used.

Let us know if the replacement will be used:

• Indoors or outdoors
• In direct sunlight
• Near heat, moisture or chemicals
• Around moving parts
• Under repeated force or vibration
• For a light decorative purpose or a practical task

This helps identify suitable options and any limits that should be considered before making the part.

What 3D printing can help with

Custom 3D printing is often well suited to one-off replacements and small practical parts, especially when an item is discontinued or difficult to source.

It can be useful for items such as:

• Appliance clips and covers
• Workshop organisers and holders
• Mounting brackets
• Spacers and feet
• Handles and knobs
• Cable guides
• Non-critical adapters
• Replacement trim pieces

Some parts may need redesigning rather than copying exactly. A weak tab, thin wall or awkward shape can sometimes be improved when the part is remade.

When a replacement part may not be suitable

Not every component should be reproduced.

Parts used for safety-critical, high-pressure, drinking-water, food-contact, electrical or heavy-load applications require specific assessment. A 3D-printed replacement should not be assumed suitable for these uses without appropriate evidence and testing.

If there is uncertainty about what a part does or what it needs to withstand, it is better to check before proceeding.

Send through what you have

An initial enquiry does not need to be perfect. Photos, measurements and a short explanation of the problem are usually enough to start a conversation.

If you have a broken part, clear photos and a few key dimensions, FarmFab3D can help assess whether a custom replacement is practical and what information is needed next.

Have a part in mind? Get in touch and let’s look at turning it into a practical replacement.