A short guide to choosing contact probe tips
When measuring or gauging parts using contact probes, the choice of tip profile and material is important. It is integral to the accuracy of the measurement process and the overall performance of the part.
To help you make the right decision, we have put together the following short guide to choosing contact probe tip profile and material.
How to choose your contact probe tip material
For most applications, the probe tip touches the part being measured in a single place. When this is the case, the recommended contact probe tip material is tungsten carbide or nylon. Providing the probe tip force is not excessive, the part is unlikely to be damaged by the process.
However, when measuring an aluminum part, even with touch contacts using these materials, over time aluminum will adhere to the tip, which can change the measurement data. This wear and tear should be factored into measurement system planning.
If part profiling is being performed, then the situation is different: adhesive wear can occur that both marks the part being profiled and alters the tip geometry. With regard to aluminum parts, material can pass from the relatively soft aluminum material to the tip, leaving marks on the part that may degrade performance. To prevent this, it is recommended that silicon nitride tips are used.
Tips for very hard materials
With regard to parts made form very hard materials, such as cast iron, measuring or gauging parts using contact probes can cause wear in profile applications, so a diamond tip may be more suitable.
Ruby tips are an alternative to tungsten carbide tips for contact probes, although these tips are not recommended for profiling aluminium as again they interact with the surface and may have an impact on performance.
Nylon tips are naturally softer and as a result are a good choice for glass measurement that requires contact probes with low and very low tip force.
How to choose your contact probe tip shape
The right shape and style of tip is important because it has a direct impact on the quality of your measurement process. Typical gauging is performed using a ball tip with a diameter of 3mm. However, in some cases, it may be necessary to probe into smaller spaces and in these circumstances, a pin, cone, blade or knife-edge tip can be used.
Larger ball tips are also available and have the advantage of mechanically averaging surface finish effects. Where a larger ball may not give the required access, a smaller dome or flat tip may provide the solution.
Flat tips are particular useful for measuring diameters in circumstances where measurement with a ball tip should not be attempted – for example, if it is likely that the true diameter may not be found but rather an adjacent cord. For moving material, it is recommend to use a rolling tip.
How to look after your contact probe tip
Tips are often the forgotten part of the gauge sensor and yet they are key to sensor performance and, therefore, overall gauge performance.
A gauge should be inspected regularly for tip damage and wear, in particular with regard to manual gauges where the clumsy insertion of the part can damage probe tips. Pneumatic actuation is a better solution if the cost can be justified.
A damaged or loose tip will change readings and prevent gauges operating correctly. If a tip needs to be replaced, it should be replaced with a tip of the same profile. Replacing tips should be performed in accordance with the instructions included in the gauge probe user manual to prevent causing other damage to your sensor.
Choose your contact probe tip today
Solartron Metrology provides a wide range of contact probe tips in different materials. To view our full range, go to this page on our website, scroll down to the Ball Tips section and click on the Technical Spec button.
To find out more about what Solartron Metrology can do for your business, contact us on +44 (0)1243 833333 or sales.solartronmetrology@ametek.com.