Installing Aftermarket Gauges is one of the best ways to monitor your engine's critical indicators, but proper sensor installation starts with using the correct Drill and Tap Size.

If you're adding a boost, intake temperature or exhaust gas temperature EGT pyrometer, creating accurate NPT threads ensures a secure, leak-free connection.

NPT, or National Pipe Thread, is the standard thread type used for most automotive gauge sensors. Unlike straight threads, NPT fittings create a tight seal by tapering as they thread into the port.

Before tapping, you'll need the correct drill bit size for the sensor's thread specification. For example, a 1/8-27 NPT sensor—the most common size for aftermarket gauges—requires an 11/32-inch drill bit before tapping. Larger sensors, such as 1/4-18 NPT, require a 7/16-inch drill bit.

Using the proper drill size is essential. A hole that's too small can damage the tap or create incomplete threads, while a hole that's too large may prevent the sensor from sealing correctly. Always drill carefully, apply cutting oil while tapping, and remove any metal shavings before installing the sender.

GlowShift offers a wide selection of Install Accessories designed to simplify aftermarket gauge installation. If your vehicle doesn't have an available factory sensor port, using the correct drill and tap combination allows you to create a reliable mounting location for accurate readings.

Before beginning your installation, keep an NPT drill and tap size chart nearby. Having the correct dimensions on hand will save time, reduce installation errors, and help ensure your GlowShift gauges deliver precise, dependable performance for the long term.