What is the drill size for a 1/8 NPT tap?
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In this article, I'll help you determine the correct drill type and size for your 1/8" NPT tap.
NPT taps have tapered threads and are available in a variety of sizes. As an experienced craftsman, I know how important it is to choose the right size drill to make the perfect hole for 1/8 NPT taps. Otherwise, the depth and diameter of the hole will prevent the NPT tap from seating well.
Check the correct metric chart to determine the correct drill size for the 1/8 NPT tap. The 11/32″ “R” drill is ideal for installing 1/8″ NPT taps.
I'll tell you more below. Let's go deeper.
Correct size drill bit for NPT taps
It is extremely important to use the correct size drill to install the 1/8 NPT tap. Otherwise, the 1/8 NPT tap will not hold. It can even break away from the material and cause damage.
So which drill size should you choose?
You must select a 11/32, "R" drill when using a 1/8 NPT tap.
Taps 1/8 NPT
NPT (National Pipe Thread) taps often recreate damaged threads or make new threads in pipes.
For NPT, the actual thread section is tapered. The numbers do not correspond to inch sizes because they (NPT taps) are based on sector and pipe sizes. (1)
In this sense, the diameter of a 1/8" NPT tap is not 0.125". It is based on threads on the end of a 1/8" pipe. Therefore, it is approximately 0.405" in the "large" diameter.
The threads, pipe ends, and holes of 1/8 NPT taps are tapered. The narrowing makes them less leaky when put together.
So if you put tape or pipe grease on the 1/8 NPT tap parts and tighten them tightly, you won't see any leaks. (2)
important Notices: Do not cut the 1/8 in. NPT tap like a regular tap. It should not crash into the material. Just tap it enough to get a good taper for the fitting.
I recommend tapping it down to 3/4 inch. Pressing all the way down will enlarge the cone, making it too big.
How to Drill a 1/8 NPT Tap
Drilling a 1/8 NPT tap is easy:
Step 1: Mark the spot you want to drill
You can use any suitable tool, such as a marker, to mark the location.
Step 2: Get the right size drill
As already mentioned, take an "R" drill, that is, a drill with a diameter of 11/32 inches.
Step 3: Drill a Hole
Carefully drill into the spot you marked in the first step. Since you are using a 11/32 drill, the depth and diameter of the hole will be ideal for a 1/8 NPT tap, which will fit snugly into the hole.
Step 4: Install the 1/8 NPT tap
Finally, install the NPT tap on the drill and place it on the material. During installation, tap it on 3/4 of the threaded part as above.
Summing up
Having the correct drill bit is critical when using a 1/8 NPT or other NPT size tap. This ensures a perfect opening and faucet installation. You can always refer to the metric chart if you forget the drill size to use for a given NPT tap size.
Take a look at some of our articles below.
- What is the size of a 1/4 tapcon drill?
- How to drill out a broken bolt in an engine block
- How to use left hand drills
Recommendations
(1) pie sizes - https://www.kingarthurbaking.com/blog/2019/05/28/the-best-pie-pan-youll-ever-own
(2) leak - https://www.sciencedirect.com/topics/earth-and-planetary-sciences/leakage
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