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Precise Measurement

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Forum topic by ajs349 posted 01-31-2011 03:21 AM 2023 views 0 times favorited 38 replies Add to Favorites Watch
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ajs349

4 posts in 1405 days


01-31-2011 03:21 AM

I’ve been search around for some time now but I can’t find any information on this, when using a tape measure/ruler do you include the width of the line in a measurement? Does one inch go from the left of the zero line to the right of the 1 inch line or something else? I know I can pick whatever I want and stay consistent throughout all my projects but I’m wondering if there is a standard method.

Thanks for the input.


38 replies so far

View GaryL's profile

GaryL

1080 posts in 1552 days


#1 posted 01-31-2011 03:26 AM

If your looking for a precise mark, don’t use a pencil. Use a marking knife, exacto knife or even a utility/box cutter. Just use light pressure. You just want to leave a visible mark that is removable if necessary.

-- Gary; Marysville, MI...Involve your children in your projects as much as possible, the return is priceless.

View NBeener's profile

NBeener

4806 posts in 1895 days


#2 posted 01-31-2011 03:56 AM

Get yourself one reference rule—say, a Starrett 12 inch'er .

Or a Pinnacle

Or anything with a good name, and high standards for design and manufacture.

Hook the “hook” of your tape measure onto one end of the Starrett, and run out a foot of tape. See exactly where the 6” mark on your tape measure hits the 6” mark on your Starrett. May as well check it as 12”, too.

THAT’s where you should make your mark.

I’m guessing, though, that most half-way decent tape measures use lines that are only a 100th or a 64th of an inch wide, so … you’re already achieving more precision that you need for probably 99% of woodworking operations.

-- -- Neil

View wseand's profile

wseand

2503 posts in 1763 days


#3 posted 01-31-2011 04:09 AM

I don’t have a scientific answer for you but I use the left edge on both for most purposes. My reasoning is, I assume that the left edge of the zero is your starting point so I use the left edge from there.
I guess it comes from my running days when you always started behind the line.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

View Loren's profile

Loren

7809 posts in 2369 days


#4 posted 01-31-2011 04:23 AM

You develop your own system in cabinetmaking for what a pencil
line represents, how you line up your cuts on it and so forth. I
usually mark with a .5 mm mechanical pencil and try to split the line
in half with the crosscut saw (carbide power saw). so a tiny bit
of graphite remains when the cut is done. Depending on the
amount of splintering the line may or may not remain at all. It’s
a mental standard.

I do use a marking knife sometimes and always when laying out joints
for hand-cutting and chisel work (the edge of a chisel can be set in
the groove of a cut line), but in general cabinetmaking with power
tools a pencil is usually handier for me. I use the mechanicals
so the width of the lead is always the same.

When using handsaws I almost always cut to the right of the line but
try to “split the line”, cutting away half of it.

Relative accuracy from part to part is more useful in furnituremaking than
trying for absolute accuracy with tapes, which have their problems (did
you know metal expands and contracts along it’s length with the weather?
it does and it means that a 12’ pull of your tape measure will vary in length
from day to day).

Accuracy is a state of mind. You’ll get in trouble if you always expect your
measuring tools to be dead-on all the time. Story sticks are useful and I
recommend making them and getting away from using ruler measurements
for multiple parts. You’ll discover why when you cut one side of a drawer
an inch too short do to relying on a tape and making the kind of unavoidable
human error we all do from time to time.

-- http://lawoodworking.com

View CharlieM1958's profile

CharlieM1958

15714 posts in 2940 days


#5 posted 01-31-2011 04:24 AM

Are you kidding me???

Don’t get me wrong… the question you ask is a valid one in theory. But given the inherent inaccuracies of trying to cut precisely on a line, does it really matter?

Loren said it beautifully!

-- Charlie M. "Woodworking - patience = firewood"

View Sailor's profile

Sailor

534 posts in 1986 days


#6 posted 01-31-2011 04:46 AM

I use my tape measure and mark with a mechanical pencil when I am looking for accuracy. I check my tapes before I buy them on a straight rule of some sort. I make my mark at the center of the line on the tape and then try to cut through the center of the mark, leaving half of the mark and taking half of the mark.

-- Dothan, Alabama Check out my woodworking blog! http://woodworkingtrip.blogspot.com/ Also my Youtube Channel's Facebook page https://www.facebook.com/SailingAndSuch

View Dez's profile

Dez

1121 posts in 2799 days


#7 posted 01-31-2011 09:55 AM

As important as the accuracy of the tape is that the SAME tape or measuring device be used throughout the project. Consistency is second – IE always mark, cut etc to the same place on the tape – center right or left edge, you pick. Accuracy in wood is relative as everyone here has mentioned, the most critical time is when making matching parts like sides, ends so that they come out the same.

-- Folly ever comes cloaked in opportunity!

View ajs349's profile

ajs349

4 posts in 1405 days


#8 posted 01-31-2011 02:39 PM

Thank you all for the great information, I’m going to buy myself a starrett as well as a digital caliper just so I know that things are exact. After that I’ll just be concerned with consistancy.

I’m looking for a Starrett ruler, what is the difference between a 4R graduation and 5R?

View Gene Howe's profile

Gene Howe

5924 posts in 2150 days


#9 posted 01-31-2011 02:55 PM

Loren is right about story sticks. I might use a tape or ruler once during the beginning stages of a project. From there on, every size is gauged with one of my sticks.
Lee valley advertised a tape without markings as an April Foll’s joke. It became so popular that they began stocking and selling them. Think about it. A flexible, roll up story tape. Great idea!

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View Howie's profile

Howie

2656 posts in 1644 days


#10 posted 01-31-2011 03:01 PM

Beener has it right…you start with a precision measuring instrument.

-- Life is good.

View NBeener's profile

NBeener

4806 posts in 1895 days


#11 posted 01-31-2011 03:54 PM

The various kinds of gradations (into what smaller units the rule is divided) are listed here

No downside to calibrating and aligning, but … it can easily be overdone.

3,000 woodworkers, annually, are institutionalized for inappropriately obsessing over accuracy and precision.

But … before that … they cut some squeaky-clean dovetails ;-)

-- -- Neil

View Gene Howe's profile

Gene Howe

5924 posts in 2150 days


#12 posted 01-31-2011 04:18 PM

Hey Neil, if it fits, it’s good. All else is fraught with frustration and irrelevancies. Commonly known as OCD.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View canadianchips's profile

canadianchips

1836 posts in 1719 days


#13 posted 01-31-2011 04:42 PM

The only calibration I do with my tape measure is 1 measurement with it hooked over end of board, 1 measurement with end of tape butted against something. IF my little metal thing at end of tape hasn’t been bent, or rivets slopped out that measurment should read the same. Any other micro-measuring while working with wood is unecessary !A scribe mark works if you can cut that accurate with your tools.

-- "My mission in life - make everyone smile !"

View PurpLev's profile

PurpLev

8476 posts in 2370 days


#14 posted 01-31-2011 04:52 PM

for a real precise measurement, don’t use tapes, or numerical values. instead use gauges or batch cut all ‘same’ parts at the same time using the same setting. relying on numerical measuring devises and eyesight will get you close, but will never get you to a perfect match on it’s own.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View GaryK's profile

GaryK

10262 posts in 2710 days


#15 posted 01-31-2011 07:14 PM

vonhagen says “the 10ths and 100ths are for aircraft industry and are useless in woodworking”

Useless in woodworking? Far far from it.

I have a 24” 5r scale and the 10ths and 100ths is only side I ever use. It’s the scale I use for everything under 24”.

For longer things I use the the same with a tape measure. Here’s a review I did on one:Tape Measure

If you still think they are useless in woodworking then check out my projects to see what I made with them, then let me know what you think.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

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