Working in dimensional metrology and machine inspection means matching the tool to the job. You may be repairing a coordinate measuring machine (CMM) that needs a replacement safety switch, or you may be looking for a quick handheld gauge for daily part checks. This head-to-head compares the Mitutoyo BHN506 pressure switch assembly with the 6-inch/150mm digital caliper. Both have a place, but they are not interchangeable. Understanding what each is designed to do will help you avoid spending money on a component that doesn't solve your problem.
Quick verdict: Need a replacement pressure switch for a CMM? The Mitutoyo BHN506 is the part to consider. Need a general-purpose digital caliper for inside, outside, depth, and step measurements? The 6-inch model is a new, economical option. If you want to keep the machine running safely, the switch matters most; if you need to take a dimension reading, the caliper is the tool.
| Feature | Mitutoyo BHN506 Switch | 6\" Digital Caliper |
|---|---|---|
| Listed price | USD 399.00 | USD 5.52 |
| Condition | Used | New |
| Country of Origin | Japan | China |
| Primary purpose | CMM safety switch part | General dimensional measurement |
| Key capability | Adjustable SPS-8T switch | Four measuring modes with inch/mm conversion |
Where each product wins
The Mitutoyo BHN506 is the part to choose when you need to protect a CMM's air bearings. It is designed to monitor pressure and send a fault signal if pressure drops, helping prevent damage to guideways and axes. Because it is a used component from Japan, it's a service part rather than a new measuring instrument. Its whole purpose is to add a layer of safety to a machine that relies on monitored air pressure.
The 6-inch digital caliper wins for everyday shop measurement. It gives you a complete, new measuring tool with a zero-setting function for differential checks and a large LCD readout. It's also priced low enough to keep as a spare or use for quick inspections. You can grab it off the bench and get a reading without setting up a larger inspection system.
Mitutoyo BHN506 Pressure Switch (Sanwa Denki SPS-8T)
This replacement assembly is the specific part to source if your CMM uses an SPS-8T adjustable pressure switch to monitor the air supply for air bearings and pneumatic counterbalance components. Its job is to trigger a fault when pressure falls below safe levels, which can prevent costly damage to the machine's guideways. At USD 399.00, it is a meaningful purchase, but it earns its keep when you're keeping a critical CMM online. The limitation: it's a switch, not a measuring tool, and it's used, so it's only worth the investment for its intended machine. If you don't service a CMM with this switch, the part has no function on your bench.
6\" 150mm Digital Caliper Micrometer LCD Gauge
For general inspection work, this digital caliper delivers a practical set of functions at a very low price. It measures inside and outside diameters, depth, and step, and it switches between inches and millimeters with one button. The zero-setting capability is useful for comparing one part to another, and the large LCD makes readings easy to see. Its listed accuracy of ±0.2mm/0.01\" is suitable for everyday checks, but if your work demands tight-tolerance metrology, you'll likely want a higher-grade instrument. As a portable, battery-powered tool, it's a convenient addition to any shop station.
Final choice by use case
Buy the Mitutoyo BHN506 when you need a replacement pressure switch for a CMM that relies on this part to protect its monitoring system. Buy the 6-inch digital caliper when you need a low-priced, portable tool for routine dimensional inspection and comparison. Because they serve different roles, the right choice depends entirely on what your inspection station requires. For machine maintenance, the switch is the answer; for part inspection, the caliper gets the job done.
