Because most tap wrenches wont fit in the tight space where the thermocouple is located, you may have to come up with some way to extend the reach of your tap.  Shown here is a 1/4" NPT tap with it's 7/16" square drive.  An 8 point 7/16" socket is used with an extension and slide bar handle.  NOTE:  We now include a 1/8"NPT threaded thermocouple will all complete gauge kits.  If you purchase our 1/8"NPT tap a 11/32" square drive socket can be used to fit the square drive of the tap.  Not all taps have the same size square drive on their end, so if you already have one, check it before you buy an 8 point socket to fit.  Tip: You can tape the tap to the socket with electrical tape to hold it in place.