A Big Secret About the Diameter Tape Measure

The Diameter Tape Secret
The Diameter Tape Measure Secret

Diameter tape measures are made for wrapping around pipes and poles, to find the diameter. That’s a good enough reason to keep one in your tool box, garage, and vehicle. But there’s one feature that no one talks about, until now….

The other side of the diameter tape measure is a regular tape measure, in inches or centimeters. It measures length, not diameter. So, even though it is a special tape, it is also a handy every day tape, too. Lufkin, and the other manufacturers, thought of everything when they designed these handy pocket tapes. Everyone should have one or two.

Lufkin Y906PD pipe diameter tape measure, not Barlow W906PD Lufkin Diameter Tape

 

What Will Pipe Diameter Tape Measures look like in 2030?

Measuring Techniques
Measuring Techniques

There are distance measuring apps out there, but measuring the diameter of a pipe presents a unique measuring situation.

  • Calibration. There will need to be some way of checking to see if the app is working correctly. You will need to measure a known standard to see if the app is measuring right. If not, there needs to be some way of calibrating or adjusting the reading, to make it accurate. In other words, if you measure a 2 inch pipe, and the app says 2.1 inches, you need a way to adjust the setting to read 2.0 inches. Otherwise, when you measure a 3 inch pipe or any size pipe, the measurement would be off.
  • Calibration should be done with different sizes of pipe, to make sure you will get an accurate reading at any of those sizes.
  • The curvature of the pipe needs to be considered. You aren’t taking a picture of a 2D object. The pipe is 3D, so your camera may not see the top and bottom of the pipe as being 180 degrees away from each other. If you are too close to the pipe, you wouldn’t see the full 180 degrees. So your measurement would be too small.
  • Resolution of measuring. A pipe diameter tape measure normally has a resolution of 100th of an inch diameter. Can a smart phone app be that accurate?
  • The nearness of the object. For calibration, we would need some standard distance from the cell phone. Maybe this could be accomplished by using an object like a 12″ ruler, placed between the pipe and the phone. Hopefully, a less mechanical method will pop up.

If you know of an app that can accurately measure pipe diameter, please let me know. If one does not exist, I’m sure it will be invented in the near future.

Who Makes Diameter Tape Measures?

Lufkin Pipe Diameter Measuring Tape
Lufkin Pipe Diameter Measuring Tape

There are 4 main manufacturers of diameter tape measures.

  1. Lufkin® has a world-wide reputation for making high quality tape measures. They used to make them in the USA, but they have shifted the production facilities to Mexico. Some of the tapes are made out of a cast case, which is highly polished and chrome plated, like the w906pd. Others, like the w606pd have a stamped case, which is shiny and chrome plated.  A third type of case is black plastic, like the asw616pd. However, the tape blade inside is the same in all 3 types of cases. It is capable of measuring diameters up to 23 inches.
  2. Pi-Cobra is a brand name for diameter tapes made with

    Pi-Cobra Diameter Tape, Metric Pi-Cobra Diameter Tape, Metric

    a cast case which is chrome plated. It can hold a longer tape blade, capable of measuring diameters up to 38 inches. The case is very durable. These are manufactured in China.

  3. 24inch-od-tape
    24inch-od-tape

    Various other Chinese manufacturers make versatile OD tapes like the 416-04-024-P. The back side of the tape measures diameter up to 24″ in 100ths of an inch or 610 mm. The case is plastic, and has a key ring attached to it.

  4. The UT-56675 is made in the USA. It is capable of
    diameter-tapes-com
    diameter-tapes-com UT-56675

    measuring pipes up to 45 inches in diameter. This is a belt tape, not a pocket tape. The calibrations are in tenths of an inch diameter.

 

The Mystery of Pipe Diameter Tape Measure Codes

Mystery of Diameter Tape Codes
Mystery of Diameter Tape Codes

Lufkin pipe diameter tape measure products are available with different scales. To find the right tape for your needs, here is how to read the codes that are embedded in the SKU numbers.

  • “P” means that it is a “pi” tape, also known as a diameter tape.

Examples are w606p, w906pd, w606pm, asw616pd, w606pd, w906p.

  • “D” means that it measures in tenths of an inch. If the “D” were missing, it would measure in 64ths of an inch.

Examples are w906pd, asw616pd, w606pd.

  • “M” means that it measures in metric scale.

An example is w606pm.

Celebrate Pi Day 2019 With A Diameter Tape Measure

pi symbol
pi symbol

Pi Day is March 14. This year you can help celebrate by answering the question at the bottom.

Pi is the constant ratio of a circle’s circumference to its diameter, no matter what size the circle is. This is useful knowledge when you work with water pipes or oil or gas pipelines, and you need to replace part of it. You can measure the circumference and divide by pi. But there’s an easier way to do that.

Diameter Tape (pi Tape)
Diameter Tape (pi Tape)

Let a Lufkin Diameter tape measure do it for you. You just wrap it around the pipe, and read the diameter. Mathematicians call pi an irrational number, since it goes on for an infinite number of decimal places, but using a diameter tape is a very rational and easy way to find the diameter of a pipe. To see a little video on How to measure the diameter of a pipe, just click here.

 

Trivia: What famous scientist was born on Pi Day?

 

 

 

3 Easy Steps to Use a Pipe Diameter Tape Measure

How To Use A Diameter Tape
How To Use A Diameter Tape

This time, we won’t get into the geometry theory of pi that we had in high school. The magic of a pipe diameter tape measure is its simplicity of use. Here are the 3 steps to find the diameter of a pipeline:

  1. Clean the pipe surface. Soil and any other contamination, of course, will make the pipe seem bigger than it really is.
  2. Wrap the diameter tape around it, with the diameter scale visible to you.
  3. Simply read off the tape. This will be the diameter, even though the tape is wrapped around the circumference. That’s all!

Some things to watch for…..Some OD tapes (diameter tapes) are marked in 100ths of an inch. Some are marked in 64ths of an inch. On the 64ths of an inch tape, 32/64 would be 1/2″. 16/64 would be 1/4″. 24/64 would be 3/8″. For convenience, you can use a magic marker to mark some of these common, but confusing measurements.

For a 2 1/2 minute video with more detail, click How To Use A Diameter Tape.

 

Give A Diameter Tape Measure For Christmas

Give Diameter Tapes for Christmas
Give Diameter Tapes for Christmas

A diameter tape measure can save you a lot of time and frustration when you want to find the OD (outside diameter) of a pipe, post, or tree. This special tape has the inch scale (or metric scale) stretched out by a factor of pi (3.14159). So, if you wrap it around the pipeline, you will not see the “circumference”. You will see its diameter. You don’t need to divide your answer by 3.14159.

This Weird Diameter Tape Measure Can Make Your Life Easier

You may be part of a special group of people. We can call this group, FDTU, for “future diameter tape users”. To be in that group, you would have these three qualifications:

  1. You never heard of a Diameter tape measure.
  2. After you get one, and learn how to use it, you will use one every week for the rest of your life.
  3. You won’t believe how you ever got along without one.

To help you on this fun journey as a FDTU, let’s find out…

  • What is a diameter tape.

    It is a measuring tape that, when you wrap it around the circumference of a round object (pipeline or tree), it reads the “diameter”. If you would use a regular tape measure, you would have to divide by pi (3.14159) to get the diameter.

  • How to use a diameter tape.

    How To Measure the Diameter of a PipeYou simply wrap it around a pipe or shaft, or tree, and have the diameter scale face outward, so you can read it. Make sure you don’t use the other side, because it would give you the circumference. 

  • What you will use it on from now on, to make your life easier.

    If you need to replace a car heater hose, but you want to have the new hose on-hand before you remove the old hose, use your diameter tape to measure the diameter (and length) of the old hose. You can do the same routine when replacing plumbing.

My friend owns a marina. He never heard of a diameter tape. I gave him a diameter tape and told him what it was for. He was in the FDTU group, and now he uses this valuable diameter tape measure every day.

Are you in the FDTU Group? Now you know how a simple tape can make your life easier.

 

5 Pipe Diameter Tape Measure Tips

When you use your Lufkin or Pi-Cobra pipe diameter tape measure, here are 5 tips to keep you out of trouble.

How to Measure the Diameter of a Pipe
How to Measure the Diameter of a Pipe
  1. Make sure the pipe is free of dirt and mud. You don’t want to measure those things, just the pipe.
  2. Use the right tape. Do you want your answer in 100ths of an inch, 64ths of an inch, or millimeters? There is a tape for each purpose.
  3. Use the right side of the tape. The other side is probably a regular linear tape. It will give you the circumference, not the diameter.
  4. Wrap the tape around the pipe straight, not at an angle. If it is not straight, you will get an elevated result. You can test this by wiggling the tape so that it gives you the lowest reading.
  5. Be familiar with the scale. It can be tricky on a 64ths of an inch diameter tape. 48 on the scale means 3/4 ” diameter. The easy one is 32, which is of course 1/2″ diameter.

3 Tricks With A Pipe Diameter Tape Measure

Many people don’t use a pipe diameter tape measure because they never heard of one.

Here are 3 tricks that will make you a user:

Want To Know The Diameter of Your Arm?
Want To Know The Diameter of Your Arm?
  1. Wrap a diameter tape around a car heater hose that you intend to replace. Read the diameter, and the length. Go buy the correct hose, because you know the exact size. Remove your old leaky hose and immediately replace it with the new one. There’s no need to take the old hose to the parts store and leave your vehicle without a hose for a while.
  2. Use the tape to find the diameter of a copper water pipe in your basement that is leaking a little.  Go get the pipe, and have it ready to install when you remove the old pipe.
  3. Need a new rope for your boat? Get one that is the same size as your old one, by measuring the diameter with your “OD tape”.