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:
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
- Mark and drill an appropriately sized hole
- The hole should be in an area where fittings or pipe overlap (double thickness)
- Find correct hole size with a Tap/Drill Chart
- Insert the tap into the tap wrench
- If you don't have a tap wrench, a normal crescent wrench can be used
- 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.
- Drill hole slightly smaller than your fitting.
- Hold your fitting with a wrench and slowly turn it into the plastic, be sure to keep it straight.
- After the fitting is threaded in completly remove the fitting.
- Wrap teflon tape around the threads
- Thread the fitting back into your hole.