LumberJocks

The Importance of Measurement Accuracy

  • Advertise with us

« back to Woodworking Skill Share forum

Forum topic by CRAIGCLICK posted 04-26-2018 06:09 PM 1925 views 0 times favorited 26 replies Add to Favorites Watch
View CRAIGCLICK's profile

CRAIGCLICK

117 posts in 223 days


04-26-2018 06:09 PM

Hi All.

I’ve been wanting to get myself some measuring tools for the shop…but MAN…the prices can be crazy!

I know that accuracy is important…that’s a given…but is a 100 dollar engineer’s square from Woodpecker THAT much more accurate than…say…the 27 dollar one from Woodcraft or 20 dollar one from Lowe’s?

More to the point…just how vital is thousandth of an inch accuracy in woodworking? I don’t want to buy less expensive measuring tools only to have it come back and bite me in the butt later on.

-- Somewhere between raising hell and amazing grace.


26 replies so far

View Loren's profile

Loren

10477 posts in 3797 days


#1 posted 04-26-2018 06:33 PM

You may want to acquire a dial or digital
caliper at some point. Old fashioned vernier
calipers are accurate too but fussier to read.
They can be useful in calibrating thickness planers,
cutting tenons, making dados. If you make a
crosscut box and want to check it for square using
the 5-cut method a caliper is essential.

Combination squares can be adjusted with a narrow file
to make them square enough for woodworking.
If you dropped an expensive one you might have
to do it anyway. I have a cheap one from Harbor
Freight that I made square this way. Over the
years the rule has become spider webbed all over with
rust lines though. I have other finer quality squares
I have not seen this happen with.

Lee Valley is a good source for quality measuring
tools that will do a good job and hold up well.

The squares with the lines cut in them for .5mm
pencil leads sold by Woodpeckers and Incra can
be useful. It depends on the sort of work you’re
doing. They ellimate errors caused by variances in
pencil sharpness and the angle at which it is held.
If you take a combination square and set it to mark
3” from the end you’ll incur an error by setting it
by eye because you won’t always set it the same.
When you line up your pencil with the end of the
rule the line will not always be the same because
the pencil is not always the same and in any case
the thickness and offset of the line introduces an
error factor too. You can learn to work around it
most of the time.

It can get to be rather academic debating these things.
You can make furniture without measurements at
all using story sticks and marking gauges.

View jmartel's profile

jmartel

8158 posts in 2299 days


#2 posted 04-26-2018 06:38 PM

Pick up a factory 2nd PEC combination and a small 6” Double square from here and you’ll be all set.

https://www.harryepstein.com/index.php/12-3-pc-combination-square-16r-usa.html
https://www.harryepstein.com/index.php/6-double-square-16r-usa.html

Also, focus less on the measurements themselves, and use the workpiece itself for measurements. The actual numbers don’t matter. Who cares if it’s 3” or 3 1/32”? Use a reference off of the piece being worked and your accuracy will go way up.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View HokieKen's profile

HokieKen

6299 posts in 1288 days


#3 posted 04-26-2018 06:45 PM

The actual measuring and how critical it is is subjective IMO. As Loren alludes to, there is always error in any measuring device. For me, I don’t worry so much about being precise in my measurements as I do about using the same devices throughout a project. So if my measuring tape is off by 1/32” or only .0001, it doesn’t really matter as long as I use the same one to measure everything.

On the other hand, you want to be precise when setting machines up to reduce the error that transfers to your projects. So dial indicators and calipers also have their place in your shop.

But, where I wouldn’t skimp on cost/quaility is that I would make sure you have at least one good square that is known to be square. No one will ever know if the table you built ended up 1/8” wider than you intended because your measuring tape was a freebie from Harbor Freight. But they’ll definitely notice if your top’s a parallelogram but not a rectangle ;-))

-- Kenny, SW VA, Go Hokies!!!

View HokieKen's profile

HokieKen

6299 posts in 1288 days


#4 posted 04-26-2018 06:46 PM



The actual measuring and how critical it is is subjective IMO. As Loren alludes to, there is always error in any measuring device. For me, I don t worry so much about being precise in my measurements as I do about using the same devices throughout a project. So if my measuring tape is off by 1/32” or only .0001, it doesn t really matter as long as I use the same one to measure everything.

On the other hand, you want to be precise when setting machines up to reduce the error that transfers to your projects. So dial indicators and calipers also have their place in your shop.

But, where I wouldn t skimp on cost/quaility is that I would make sure you have at least one good square that is known to be square. No one will ever know if the table you built ended up 1/8” wider than you intended because your measuring tape was a freebie from Harbor Freight. But they ll definitely notice if your top s a parallelogram but not a rectangle ;-))

- HokieKen

Edit: jmartel was posting while I was… I agree completely on the PEC seconds being great tools and a great value.

-- Kenny, SW VA, Go Hokies!!!

View Rich's profile

Rich

3670 posts in 738 days


#5 posted 04-26-2018 07:36 PM

Square is square. You can find squares at Lowe’s, Home Depot, Harbor Freight, wherever that are as square as you’ll find on the premium brands. Bring one home, do one of the tests for squareness and if it’s off, go exchange it.

What you get when you pay more for the name brands is better finish, more solidly build and so more durable. Look for sales. I’ve gotten Woodpecker tools on sale at Woodcraft for what was a pretty reasonable price.

I also agree that PEC is a great choice. I have PEC and Starrett and PEC is just as good for a lot less money.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View Gene Howe's profile (online now)

Gene Howe

10917 posts in 3578 days


#6 posted 04-26-2018 07:56 PM

Personally, I really try to get by without doing a lot of measuring with any thing that has a number on it.
Story sticks, 1,2,3 blocks and an array of key way stock pieces are what I use for most machine set ups. Open end wrenches are my thickness gauges. My combo squares have numbers but, they are not used for measuring, just for checking square. My tapes are only for gross measuring.
As to accuracy, I cut to fit. As my dad used to say, when it fits, nail it.

-- 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 shipwright's profile

shipwright

8086 posts in 2947 days


#7 posted 04-26-2018 10:40 PM

+10 Gene.
You beat me to it. To answer the original question, my answer is that the measurements aren’t all that important at all. What is important is the fits. Numbers get in the way.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View Gene Howe's profile (online now)

Gene Howe

10917 posts in 3578 days


#8 posted 04-26-2018 10:46 PM

I had to chuckle when I read that, Paul. One only needs to take a look at your body of work to realize what “fit” really means.

-- 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 jonah's profile

jonah

1845 posts in 3448 days


#9 posted 04-26-2018 10:47 PM

I have two $3 plastic speed squares. Both are absolutely as square as my 20/15 vision can tell.

I have various cheap, moderate (PEC is great here), and expensive (a used Starrett) layout tools, and they’re all square.

Spending a bazillion dollars for some layout tool from woodpeckers is pretty much the worst deal imaginable for me. You don’t gain anything in accuracy. You gain fit and finish which you can also get on that $25 PEC square.

View jonah's profile

jonah

1845 posts in 3448 days


#10 posted 04-26-2018 10:49 PM

Also, the term for what people have described in this thread is relative dimensioning. You use the work pieces themselves to set up, measure, and make layout lines. That way you don’t compound measurement errors.

All you need is a sharp pencil, some basic spacial reasoning skills, and decent vision.

View bbasiaga's profile

bbasiaga

1240 posts in 2144 days


#11 posted 04-26-2018 11:03 PM

I have one of those woodpeckers saddle squares with the holes for a .5mm pencil every 32nd of an inch. It was expensive, but it is very handy for some things. Necessary? No. Useful? Yes. Worth it? IMO yes.
As others have said, a square square is a square square, regardless of how much you paid for it. Some other things that are nice to have are the digital height, depth and angle gauges. All the tasks they perform can be done other ways, but they do speed things up and aid a lot in repeatability. So they are clearly in the “nice to have” category.

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View Kelster58's profile

Kelster58

670 posts in 689 days


#12 posted 04-26-2018 11:30 PM

I have purchased a few of SHINWA measuring tools off Amazon. I love them. They are my go to measuring tools and are very reasonably priced.

https://www.amazon.com/gp/product/B00LY9OYSU/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B003CMRSRG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

-- K. Stone “Tell me and I forget, teach me and I may remember, involve me and I learn.” ― Benjamin Franklin

View Andybb's profile

Andybb

1288 posts in 753 days


#13 posted 04-27-2018 12:41 AM


Square is square. You can find squares at Lowe s, Home Depot, Harbor Freight, wherever that are as square as you ll find on the premium brands. Bring one home, do one of the tests for squareness and if it s off, go exchange it.

- Rich

“Square IS square”. I have one of those $100 24” WP squares. I use it as my reference. (as seen in my avatar) My $9.99 HF digital caliper reads the same as the guys at the machine shop and my $7.99 HF 12” combo square is square according to my $100 WP. Save your money for other stuff. Square is square. One thing I do love is this..

-- Andy - Seattle USA

View darthford's profile

darthford

612 posts in 2073 days


#14 posted 04-27-2018 12:57 AM

Depends what you are measuring. If you are setting up/tuning a machine to be square and parallel then you need accurate measuring tools otherwise you will become frustrated with your machines. I don’t skimp on measuring tools I buy once and buy for life.

I have Mitutoyo digital calipers, sealed and coolant proof. Are they the cheapest calipers you can buy heck no. Will they last pretty much forever heck yes. Mine are dang at least 10 years old and still going. I have a Starrett combination square with 12 inch and 24 inch satin chrome rules, 20 plus years old and still in fine shape.

View woodbutcherbynight's profile

woodbutcherbynight

5559 posts in 2558 days


#15 posted 04-27-2018 02:57 AM

Calipers are your friend. They need not be the $2000 gold plated version to do the job. Ones that give fractional, decimal and metric are a bonus but not needed to get the job done.

Squares that are reasonably accurate a must for machine set-up.

Squares for working with, if it tests square it’s good. I have several in the shop, each has a job I prefer to use it for. You can get by with one, if so inclined. LOL Thanks to my Father I own a Starrett combo square.

Tape measures, grunt work anything will do, as others stated fine tune with the does it fit idea.

Marking and layout, hey story sticks work but a decent tape will suffice. Take in mind we are NOT building the space shuttle here. Wood moves with the weather etc etc.

For those reading this and just getting started. Be reasonable with your approach. Buy a square or whatever tool and learn how to use it effectively. Wear it out, drop it,or hurl it in frustration and upgrade as you go.

-- Live to tell the stories, they sound better that way.

showing 1 through 15 of 26 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com