Reading and understanding a tape measure:
All the photos are clickable and you'll see the details needed if your having trouble viewing.
For first time woodworkers or anyone that needs to make a measurement. For most people you'll have to measure something sooner or later. You might as well sound like you know what your doing so you don't end up saying something like,"5 and three little little lines". Should be sounding more like "5 and 3/16 of an inch". After reading this you should have a good understanding of the following techniques:
1) Increments and steps
2) Reading a tape
3) Understanding fractions
4) General rules of thumb
Firstly I would like to make a note for all the beginners out there. The tip of your blade has a l shaped hook on the end. This piece is loose for a reason, don't tighten it or your tape is worthless. The purpose of this play is for an inside or outside measurement. The difference in the tip is actually the thickness of that tip. This is something that is set at the factory and should not be adjusted.
"What do all those lines mean anyway?". The standard or "imperial" tape measure is mostly used in the western world. Every one else in the world uses Metric. I will do a writeup about that another time. The imperial standard is an easy to use system that requires little to no thinking when it comes to math.
The way a tape measure is laid out is in such a way that inches are broken down to 16 equal step increments. those steps when multiplied are. 8 equal steps, then 4 equal steps, then 2 equal steps. 1/16th", 1/8th", 1/4", 1/2" respectively
Memorize fractions like this
1"= 2/2, 4/4, 8/8, 16/16"
1/2"= 1/2, 2/4, 4/8, 8/16"
1/4"= 1/4, 2/8, 4/16"
1/8"= 1/8, 2/16"
By remembering the fractions this way you'll easily be able to determine what your measurement is to the 1/16 of an inch, or even 1/32". To break it down visually I will demonstrate by marking out the lines on the tape. On the right we have an example of the 1/8" increments. This shows the actual numbers you would say or use.
And this example is broken down to the 1/16 of an inch increments. It's hard to put all this on one picture because it gets a little confusing. You can easily see that 1/2" would be 8/16". And 1/4" is equal to 4/16" This is what makes it easy. Then just remember to break down your measurement so you have a proper fraction.
When it comes time to actually read the measurement I do one of two things. I either round it up and subtract the number of lines or I count the steps and multiply. I will explain.
If I measure something that is 7/16" I look at the tape and see 1/2" is closest (which is 8/16 as we all know) subtract one little line ( equivalent to 1/16") And I get: 8/16" - 1/16" = 7/16" right?
If I happen to notice its center of 1/2" and 1" I can tell that its a quarter time 3 (because If i break an inch into 4 quarters I have 3 on my measuring side.) That would make it a 3/4" measurement.
The easiest way to measure is to follow these steps here:
Look at the big number that's nearest to, but before the mark you’re trying to read. It should be a whole number. That’s how many inches you’re measuring. If the mark you're reading falls on a whole number, then that number is all the information you need. Carpenters usually measure in inches. While framers use Feet, then inches, then fractions.
Count how many marks there are in between each inch if the mark you’re reading doesn't fall on a whole number. Most tape measures will divide an inch into 16 equal parts, or 16ths of an inch like the photo above.
Start at the whole number you found nearest your desired mark and count the number of marks between the whole number and the spot you're trying to read.
Read the final number as "inch and fraction." For example, if your nearest whole number is two and there are five marks between your spot and the whole number, then your measurement would be "two and five-sixteenths".
Reduce the fraction, if necessary. Fractions are expressed in the smallest numbers possible, so eight sixteenths would be reduced to half of an inch.
Sometimes a measurement ends up in between the lines, Now what? Well you say the line below your measurement the say heavy. and this is considered a 1/32 step from that line (ex. two and five sixteenths heavy)
You might have noticed that every 24" on the tape measure are marked with a contrasting black background and every 16" is marked with a red background. The marks are used by construction workers for spacing wood studs in a wall or joists in a floor/roof. 16" spacing is used most commonly for load bearing walls and 24" for non-load bearing walls. The small black diamonds represent a less common spacing scheme.
Rules of thumb and care for using a tape measure.
1. Don't ever let the tape slam back in when retracting. Always slow it down.
2. Try not to bend the tape against it's self. Bending the tape backwards shortens the life of the metal, and it creates slivers on the tape that will cut you when you least expect it.
3. Don't pull the tape out as far as it can go this ruins the spring mechanism inside rendering you tape useless much sooner than planned. I carry three tapes. 16', 25', 100'
4. Don't drop the tape measure on concrete. If you do measure up with someone around the job. You can bend the tip and create incorrect measurements.
5. Use a ladder when measuring in high places because an 1/8" can mean the difference between quality and crap.
6. The lock is over rated. Only use it if you have to walk away from the tape, or lay it down. this kinks and sometimes caused malfunction and the tape is useless.
7. Don't use a cut tape measure. If your blade has a tear or slice in it you need a new one. If you want to risk your own safety go ahead but I recommend against it. Too many times a job goes bad because silly tool related mistakes, and someone goes to the hospital for stitches. Is that really worth it?
For a video explanation check this out. Thank you to Tim Carter for this nice explanation.
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