Adjustable Squares shootout..Starrett VS B&S, Mitutoyo and Chineseum

[Timberwolf]

https://www.youtube.com/watch?v=0vNt5h2sNO8

[hbmcc]

https://www.youtube.com/watch?v=0vNt5h2sNO8

Butting one combo against another only points out the difference and similarity in the two. Do the standard square test over a straight edge and the tool will reveal its own accuracy. We can usually afford a straight edge. I even find a straight shelf or edge at the Borg to test what is being sold. Lines front-and-back work for me. 

Don't use a combo square for carpentry work. An eighteen inch line on a framing square is far more accurate than the 4.5 inches of the combo.

[Timberwolf]

Butting one combo against another only points out the difference and similarity in the two. Do the standard square test over a straight edge and the tool will reveal its own accuracy. We can usually afford a straight edge. I even find a straight shelf or edge at the Borg to test what is being sold. Lines front-and-back work for me. 

Don't use a combo square for carpentry work. An eighteen inch line on a framing square is far more accurate than the 4.5 inches of the combo.

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Do the standard square test over a straight edge and the tool will reveal its own accuracy.

Starrett at one time used a "cylinder square" like in this test, to check the accuracy of all the precision squares they manufactured. I remember Fine Woodworking ran an excellent article about how the were made and checked for accuracy...IIRC this was back in the nineties.

[daddo]

Great- now I'll be watching Pete again till 2 am.  

[EricU]

He has precision squares and it took him 3/4 of the way through to measure the Starrett against a precision square. At least do the back to back test by flipping the square, that's a known metrology method. And I don't know if I believe that the Chinese square was better over the first 6" than the Starrett.  But I do believe that the Starrett isn't that great.  My first Chinese square is horrible, I just bought it because I was broke and didn't need much accuracy.  It also has an 18" blade, which is very useful.  I regret buying it a little though.  Ended up with a fairly nice Chinese combo square I bought from MSC, it seems to be fine. And I also have a Starrett combo square.

His stuff probably needs to be stoned to do this right. If you have a really flat stone, it doesn't affect the flatness.  Learned that in a metrology lab.  Granted, we weren't really going for NIST traceable flatness, but it really doesn't matter if you are.  Surfaces get dings on them

I was looking for precision squares on ebay a while back.  I didn't see any cylindrical or square squares, but I'll have to look again.  The high-end Chinese stuff is really good.  In the afore-mentioned metrology lab, we used Chinese thickness gauges.  They do know how to use a grinder if they want.  Now that they have gotten serious about holding tolerance, so Western companies should pay attention.

[daddo]

Place it on a known straight edge and scribe a fine line- flip it over and scribe another line on the first. If it's off, you'll see it.

Same as a testing level.

[pprobus]

https://www.youtube.com/watch?v=0vNt5h2sNO8

Well, I'm throwing out all my Starretts and getting Chinese no-name ones.

[Phil Thien]

For the greatest accuracy, skip the drawn or scribed lines.

Instead use another blade or straight edge, align it to the square and clamp it to the bench so it won’t move.

Now flip the square and use feeler gauges to check between the blade and the clamped straight edge.

[daddo]

To be honest, you won't see a machinist using a square like this to build anything that requires any expected machining tolerances. It wasn't designed for such work.

They need to be used for other things such as woodworking and construction. In fact, I don't even have one or use one anymore.

[Phil Thien]

To be honest, you won't see a machinist using a square like this to build anything that requires any expected machining tolerances. It wasn't designed for such work.

They need to be used for other things such as woodworking and construction. In fact, I don't even have one or use one anymore.

That sure is true, they'd beat you with it if they saw you using one.

One thing that caused me grief when I got serious about woodworking, was the compounding nature of inaccuracy/errors.

Parts slightly off from 90-degrees could snowball into assemblies that wouldn't assemble or looked terrible/gappy.

And I struggled with the "draw a line and reverse."  Parallax would engage and I was never sure how close I was.

But the clamped straight edge (I actually use a spare blade) works wonders.