How Square is Your Square: A dial indicator method

[Father Haskell]

curate. =A0I had no way of checking before and I do now. =A0The Draw-A-Line= and flip method will never tell you how far out of wack your square is - o= nly that it might be out of wack. =A0There is no way to quantitate the angl= e error unless you can measure the distance betwene the lines/knife marks w= ith a caliper (good luck). =A0How much of a gap in between the marks is con= sidered unacceptable? =A0You can't easily answer that question so why bothe= r checking in the first place?

4x dollar store reading glasses.

[Father Haskell]

just measure our square references from our existing furniture. Right? =A0:= )

patternmaking

Which is as good as a foot for a luthier, who works to within 0.004" or better.

[Father Haskell]

and I feel confident making that claim.

3 x 5 index card =3D 0.004. Playing card =3D 0.012". Beer can stock =3D 0.015". Rolling paper (Job brand) =3D 0.001". and so on...

[Leon]

measure our square references from our existing furniture. Right? :)

LOL... Is this why you never post any of your work? I don't find 32's of an inch tolerances acceptable in woodworking. If you want multiple width and length pieces to fit precisely within a given constraint you have to do a lot better than 32's. A whole lot better.

[brian]

measure our square references from our existing furniture. Right? :)

patternmaking

Tight fitting half lap joints are sloppy with a 1/32" gap.

to mention the need for higher standards w/ regard to inlay and banding.

[Swingman]

Reminds me of a job we participated in last year where the inset door/drawer reveal was 3/32", or else.

Thank gawd for those poly shims ....

[knuttle]

square using a dial indicator. The method works in theory. I've tried it and it seems to work in practice. A caveat is that the square needs a thick edge to support a stylus.

Seriously it sound like Brian has a good method to check your master square if you are doing that much in the shop you need at least one master square of that accuracy.

Personally I don't own a gauge of that precision, as in my amateur work I would not know what to do with it if I did.

[Leon]

measure our square references from our existing furniture. Right? :)

patternmaking

This stack of 8 muntins were made with the aid of my kerfmaker. And each is 5/32" thick total after drum sanding. The joints are 5/64" deep.

[Larry W]

A commonly overlooked factor when using dial indicators that often interferes with obtaining accurate absolute measurements is accounting for the angle that the plunger makes with the surface it contacts. I'm a little rusty on trig & geometry, so I'll leave the calculation of that effect on this method as an exercise for some other reader...

[Larry W]

Better watch out, next yhing you know Steve Strickland will be back explaining how to cut a board to 1/1000 of an inch on his tablesaw... :)

[Doug Miller]

[e-mail] (Larry W) wrote in news:kc7ovb$2t8$1 @speranza.aioe.org:

Oh, my. I'm surprised anyone remembers that. IIRC, though, Steve was claiming

+/- 0.0001, not 0.001, wasn't he?

[Larry W]

You're right, after I hit the "send" key I realized I should have written

1/10000.

[Father Haskell]

Notes on the UKP-03 Concert Ukulele Plan, Scott E. Antes 2006/2012: "The concert ukulele, in general, does not require particularly close tolerances. The major exception to this statement is the fret spacing. The careful builder will hold fret spacing closer than

0.004 in., or .10 mm."

Overall instrument size doesn't much matter -- what does, is how well parts are fit together. Musical instruments are machines. Last banjo I did a major rebuild on went from sounding tinny and noisy to loud and punchy simply by reseating the parts for a closer fit.

[Father Haskell]

Norris smoother.