Keep a variety of common Renishaw stylus sizes, extensions, and tools on hand. When styli touch a workpiece, they trigger your probe to send a signal and measure geometric features.

Make sure the thread size of the styli in the kit you choose fits your application. Styli with M2 or M3 threads are often used in coordinate measuring machines (CMMs). Styli with M4 threads are often used on CNC machine tool probes.

Stylus type—These kits all include ruby ball styli, which can be used in a wide variety of applications, from touch-trigger to scanning probes. Ruby is second only to diamond in hardness, so the ball end won’t lose its shape or wear over time. It’s completely round and smooth to avoid touching your workpiece at more than one precise point, preventing inaccurate measurements. However, these probe styli don’t work well with aluminum or cast iron surfaces. Aluminum can rub off onto the ruby, and cast iron and ruby are prone to scratching each other during scanning jobs.

As a rule of thumb, you should use a stylus with the shortest length and largest ball end diameter that works for your application. If a stylus is too long, it’s more likely to move farther than it should, reducing measurement accuracy. Larger ball ends minimize the risk that the stem will accidentally touch your workpiece and interfere with the reading.

Disc styli fit in undercuts and grooves within bores that are too narrow for ball styli. However, because the stylus end is flat, they can’t measure in as many directions as ball styli. Use them with both touch-trigger and scanning probes.

Kit accessories—All kits come with stylus installation tools, which give you a handle to turn so it’s easier to thread a stylus into your probe. Slide them into the hole at the top of your probe stylus. The included stylus extensions are useful if you need to reach deep or difficult-to-access areas.

Break stems are designed to snap if your probe applies too much pressure on a workpiece, shielding the probe from damage.

EWL (effective working length) is measured from the beginning of the stem to the center of the ball or disc end.