Combination Square Accuracy

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Forum topic by ChunkyC posted 08-29-2010 05:02 PM 6817 views 0 times favorited 14 replies Add to Favorites Watch
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856 posts in 3249 days

08-29-2010 05:02 PM

Topic tags/keywords: square

The accuracy of my Combination Square is less than perfect. I’ve passed a couple emails back and forth with Brian over at discussing:

(1) if a combo square can be “tuned” to 90 degrees and
(2) is it worth it?

I had the idea that one could file, sand, and cuss the inside of the square head until you got it square. My combo squares have small ridges in the head at the leading edge (where the rule enters the head) and trailing edge (where the rule leaves the head) that I thought could be coaxed to make it more square.

My problem is that my combo square is the most used tool in my shop by far. It’s always in my apron pocket ready for service. So if I need to check a joint for square, guess what the closest square at hand is?

I have gotten better at this one but I used to always seem to layout my marks on the wrong edge of the board. So, beings that I’m fat and lazy, I would use the square to translate the measurement to the other edge. If the square is out, then the marks on the opposing edge will be off, even more so if you flip the square over during the process.

Anyone have any thoughts on this?

-- Chunk's Workshop pictures:

14 replies so far

View Rick  Dennington's profile

Rick Dennington

5854 posts in 3189 days

#1 posted 08-29-2010 05:53 PM

Greetings Chunk, Hey bud, haven’t seen you on in awhile…good to hear from you again….. now for your question: I have a couple of Starrett combo squares that I like real good. They are pretty well on the money as far as being square. But…. most of the time when I draw lines and make marks, I usually use a marking knife instead of a pencil…. more accurate… But here’s a trick I learned in college when taking drafting and drawing house plans and mechanical drawing….. Once you decide where you want to start drawing the lines put your pencil down FIRST, and move the square TO the pencil (pencil being sharp, that is). But I wouldn’t use a square that’s out of will cause you more fustrations…Invest in a good combo square….I suggest the Starretts…..They are the best as far as I can see…....

-- " At my age, happy hour is a crap and a nap".....

View ChunkyC's profile


856 posts in 3249 days

#2 posted 08-29-2010 06:05 PM

I’ve looked and dreamed at the Starret’s and they are salty. I just can’t pull the trigger on that kind of money for a combo square and will it stay accurate over time?

I have Starret’s tools in my collection that I cherish, ie guard with my life. If I have guests in the shop, the Starret’s stay hidden. I love them to death. I think that they are about the best tools out-of-the-box that money can buy. The only down side is that you may need to win the lottery before buying them though. lol

-- Chunk's Workshop pictures:

View Dennisgrosen's profile


10880 posts in 3110 days

#3 posted 08-29-2010 06:18 PM

if you think teoretically then will a combo never bee square nomatter how precise it has been made
and it will only bee worse over time of use
but I agree its a niice tool to use,you will bee more satisfired with using a dead on trysquare

just my 2 cents

View Bothus's profile


441 posts in 3171 days

#4 posted 08-29-2010 06:19 PM

Hi Chuck,

I always had trouble transferring lines around a board with my combo square so I bought a saddle square:

Oh, I just reread what you wrote, never mind. LOL


-- Jerry Boshear, Professional Kitchen Designer, amature woodworker.

View vicrider's profile


179 posts in 2893 days

#5 posted 08-29-2010 06:22 PM

In the interest of accuracy, I only use an adjustable combination square for framing or ‘gross’ measurements. When in the shop, I use a machinist’s solid square.

Here is Grizzly’s set.

-- vicrider

View Steven H's profile

Steven H

1117 posts in 3055 days

#6 posted 08-29-2010 07:10 PM

Go with Empire combination square and use that for a while.
I suggest you tuned it up before any project you do.

View FWBGBS's profile


21 posts in 3234 days

#7 posted 08-29-2010 07:22 PM

Chunky, I was in the same boat as you not too long ago. I was using a “rarely dropped” combo square by Empire.
I went Starrett square hunting on Ebay for about two weeks. I acquired both a forged and hardened head, two 12’ blades, and one hook rule I just couldn’t live without.I got all five pieces for less than what a new forged head set would cost. I like the hardened (smooth finish) model better. Though, both are VERY accurate.
Lastly, in the almost two years of owning these I have NEVER dropped them!


-- No sane man will dance ~ Cicero

View ChunkyC's profile


856 posts in 3249 days

#8 posted 08-29-2010 07:22 PM

BoiseJoe – Dropping it… Well I’ve dropped mine more that I know. Another reason why a Starret may not fit me.

Anyone ever tried to tune a Combo square? Lots of thoughts about the accuracy of combo squares…

-- Chunk's Workshop pictures:

View Steven H's profile

Steven H

1117 posts in 3055 days

#9 posted 08-29-2010 09:38 PM

The cheap ones can be accurate if you can tune it up properly. I bought a Johnson $6 combination square. took me at least 1 hour. I still have to tune it up before I even use it.

When you drop a $80 combination square it will go out of square.

View Dan Lyke's profile

Dan Lyke

1520 posts in 4120 days

#10 posted 08-30-2010 06:38 PM

I have an aluminum 12” speed square that I use more than the combination square, and if I could buy a more accurate one machined out of something like stainless steel I would. The speed square is fine, but the head is so short that a piece of sawdust can seriously throw out the notion of 90°, let alone whatever may be happening inside the head and locking cam.

I really mostly use my speed square as a story stick. Although once I build my shop and have room to hang all my tools, I’m gonna have to spring for the Starrett.

-- Dan Lyke, Petaluma California,

View ChunkyC's profile


856 posts in 3249 days

#11 posted 08-31-2010 12:59 AM

The Starrett’s scare me because I know for a fact that the combo would be dropped on the floor. I knock mine on the floor constantly. So much so that the tips of the blades are rounded over quite nicely. ():

I personally don’t like a try square and I think it has to do with the fact that I use a combo so much, a try square seems like a waist of apron space to me. For example, if I need a mark at 1-1/16 from the edge, I set the combo at 1-1/16 and make mark at the end of the rule. You just can’t do that with a try square. I know that this is not idea for measuring accurately but it has served me well enough over the years.

CessnaPilotBarry: That’s a nice article. I scanned it, the pdf version, rather quickly and I didn’t see any mention of bringing the square back into square, only how to check it. This is the method that I use and how I know that my square is out of square. Oh yeah, and the new one that I got Friday. – I wish I had taken some scrap paper and a pencil w/ me…

-- Chunk's Workshop pictures:

View Steve Peterson's profile

Steve Peterson

375 posts in 3077 days

#12 posted 08-31-2010 01:06 AM

I am impressed with the quality of the “Pro” version of the Empire square. The local Orchard Supply Hardware has 3 versions with prices ranging from around $7 to $11. The cheap one is made overseas. The $11 is made in the USA with obviously better quality standards.

The slot is milled using a straight cut. There are no nibs to file off to make it square. I haven’t checked mine for 100% square yet, but I would guess that it would be easiest to grind a few thousands off the handle portion than the inside of the slot. If it is too far off to make it square that way, then it is probably not worth saving.

I am sure that a Starrett is another step up in quality. However, is it 6X better quality?

-- Steve

View ChunkyC's profile


856 posts in 3249 days

#13 posted 08-31-2010 01:21 AM

>>I am sure that a Starrett is another step up in quality. However, is it 6X better quality?

If they are anything like the other Starrett’s that I’ve used and owned, then absolutely. The other Starrett’s that I have get used and put away as soon as I’m done. Rarely if ever do they ever touch the work bench. A combo square is always out, in my apron pocket, laying on the bench or falling to the

-- Chunk's Workshop pictures:

View RandyinFlorida's profile


248 posts in 2063 days

#14 posted 08-30-2016 07:26 PM

I know this is an old thread but I wanted to comment on a couple things.

A lot of people mention tuning a combo square. But I wonder how many people would try to adjust using another square as a reference.

This is not good practice. The best way to confirm any given square is square is to put the “iron square” (that’s what that thingy with the 90 and 45 degree angles is called) against a reference, draw a line, then flip the iron square over, use the same reference, put the rule against the line drawn earlier. They should be parallel. If not, it ain’t square. Do this to both the inside and outside edges of the rule.

-- Randy in Crestview Florida, Wood Rocks!

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