Tapping

A set of pipe taps

Tapping is the process of cutting threads on the inside diameter of a hole with a tool called a tap. It is used to thread holes for mounting:

• Pressure gauges
• Fuel meters
• Electrodes (Bolts)
• Safety valves
• Other

Types of Threads

There are a few different thread systems that are used in spudgun construction

• NPT (National Pipe Taper)
• BSP (British Standard Pipe)
• NF (National Fine)
• NC (National Course)

The Process for metal

1. Mark and drill an appropriately sized hole
   • The hole should be in an area where fittings or pipe overlap (double thickness)
     

     An appropriate cutting fluid for tapping holes. It is usually available at tool stores.
   • Find correct hole size with a Tap/Drill Chart
2. Insert the tap into the tap wrench
   • If you don't have a tap wrench, a normal crescent wrench can be used
3. Cut the threads
   • Be careful to keep the tap straight or you will end up with crooked threads
   • When tapping plastic (or any other material) be sure to use an appropriate cutting fluid such as RapidTap® made by Relton.
   • Apply downward pressure while slowly turning the tap clockwise 180 degrees, then back out 90 degrees counterclockwise to clear the chips
   • For tapered threads, stop as soon as the entire length of the hole is threaded

Process for plastic

When taping into plastic a pipe tap is unessasary.

1. Drill hole slightly smaller than your fitting.
2. Hold your fitting with a wrench and slowly turn it into the plastic, be sure to keep it straight.
3. After the fitting is threaded in completly remove the fitting.
4. Wrap teflon tape around the threads
5. Thread the fitting back into your hole.

external links

wikihow's article on tapping