Finding Replacement Screws for Blue Robotics Products

Introduction

Blue Robotics uses a variety of screws in its components and assemblies. Because Blue Robotics does not sell individual screws except those that are included with retail packed products, this guide may be used as a reference of where to find replacement or additional screws for your project.

General Screw Characteristics

Blue Robotics generally uses metric-size screws, as they follow international standards and are easier for customers outside the U.S. to source. In cases where metric screws are impractical to obtain—typically for thread-forming applications—imperial-size screws are used instead.

Dimensions

The key dimensions that characterize a screw are thread diameter, thread pitch, and thread length.

Shorthand Description

Because thread pitch is standardized for both metric and imperial screws, we often leave it out of screw size descriptions. Screw sizes are written in shorthand using this format:

• M3x12 → Metric screw: thread diameter × thread length (in millimeters)
• #4×0.5″ → Imperial screw: numbered diameter × thread length (in inches)

For metric screws, if the thread pitch isn’t specified, you can assume it uses the standard coarse pitch. A list of commonly used metric screw sizes and their corresponding coarse pitches is included below.

Material

Stainless Steel – We use stainless steel for most of our screws. They offer high strength and good corrosion resistance.

• 316 stainless steel has the highest corrosion resistance and should be used for any screws exposed to the outside, especially in marine environments.
• 304 stainless steel is slightly less corrosion resistant than 316 and is suitable for internal screws that aren’t exposed to water or the outside environment.
• 18-8 stainless steel has lower corrosion resistance than 304 and can be used for internal screws when 304 is not available.

Aluminum – Corrosion resistant, but weaker than stainless steel. We only use aluminum screws when galvanic corrosion may be an issue.

Locating Where Screws are Used in Blue Robotics Retail Packaging (RP)

Screws used in all Blue Robotics products can be found in two locations:

• The “Contents” section of a product page.
• The assembly guide steps for the relevant product.

Contents Section of a Product Page

The “Contents” section of each product page lists the loose screws that come with each product in its retail packaging. Screws already installed on a product assembly are not included with this list.

Assembly Guides

Screws used during the assembly or integration guides are called out during each step.

Locating Where Screws are Used in Blue Robotics Assembled Products (ASM)

For screws on pre-assembled products, the type and dimensions may be determined by following these steps:

1. Remove the screw from the assembly. Remember where it came from for reassembly. Taking pictures along the way may help.

2. Measure the thread diameter using a set of calipers.

3. Measure the thread length from the base of the head to the end of the end of the screw, unless otherwise specified from the screw characteristics.

Screw Sourcing

McMaster-Carr: McMaster-Carr is Blue Robotics’ preferred hardware store when prototyping. The company has one of the most complete collections of fasteners and other items for rapid project work.

Amazon: For smaller numbers of screws it may be more beneficial to find what you need on Amazon.

Screws Used in Blue Robotics Products

Socket Head Cap Screws

These standard socket head screws have a head height that matches the screw’s thread diameter.

Low Profile Socket Head Cap Screws

With half the head height of a standard socket head, they fit where space is limited, but their low profile makes their head weaker.

Button Head Cap Screws

These screws have rounded heads and are suitable for use on exterior surfaces to reduce snags.

Set Screws

Cup point set screws have a thin edge that digs into the contact surface for a secure hold on a wide range of surfaces.

Flat Head Screws

These screws are angled under the head to sit flush within countersunk holes. Length is measured from the top of the head.

Thread Forming Screws

These screws have a rounded head, excellent resistance to chemicals and salt water and may be mildly magnetic. They press tightly against formable plastic to resist loosening.