small gaps between the two pencil lines (especially with a thick pencil lead). The most you might be able to detect is a 0.010" difference which equates to a minimum detection of 0.036 degrees with an 8" square.
perfectly flat, otherwise you will not get an accurate calculation of your square's angle error.
Then use a marking knife.
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.
Too complex for you I know. I'll dumb it down for you next time.
rn small gaps between the two pencil lines (especially with a thick pencil = lead). The most you might be able to detect is a 0.010" difference which eq= uates to a minimum detection of 0.036 degrees with an 8" square.
be perfectly flat, otherwise you will not get an accurate calculation of y= our square's angle error.
You're still left with not being able to quantitate the error. Are you fol= lowing along?
----------------------------------------------------------- A slow night in the Carolinas.
Lew
On 1/3/2013 6:45 PM, snipped-for-privacy@garagewoodworks.com wrote: ...
...
I'm sure you're clever enough to figure it out...
--
Then go out and get a drink Lew! Get off yer butt! :)
snipped-for-privacy@garagewoodworks.com wrote in news: snipped-for-privacy@googlegroups.com:
Yes, and I was using it in relative terms. Where's the problem?
Sure, why not? You can easily see if the gauge overlaps the lines or fits between them. BTW, the width of the pencil lines isn't really relevant -- use a marking knife instead of a pencil.
Of course.
I have a Starrett square that never leaves the wood shop. I also have a Craftsman combination square, and a Stanley framing square, that I use for carpentry projects. It never crossed my mind to use the Starrett when I built a shed in the back yard a few years ago, or when my son and I built a deck last summer -- that degree of precision simply isn't needed, and there's no point in risking an expensive precision tool on a construction site.
No it does not.
First of all, 0.016" is double the error, so the actual error is
0.008" over 8" or 0.001. The inverse tangent of 0.001 is 0.0573 degrees (rounded to 3 significant digits). If you want to be really picky, the 8" distance is actually the hypotenuse of the triangle, so we should use inverse sine instead, but the result is the same to at least the seventh decimal place.
I wouldn't either -- *if* your number was right. It's not, though, and I'm not sure why you seem to have a problem with using a square that's accurate to one part in a thousand for woodworking.
I can estimate much finer gaps than that by eye. The thinnest feeler gauge I own is 0.001"; anything less than that is too fragile for wood shop use, and is pointless anyway. In practice, a
0.002" gauge is quite sufficient for woodworking.
read the article.
A minor caveat to this method is that it can be difficult to discern small gaps between the two pencil lines (especially with a thick pencil lead). The most you might be able to detect is a 0.010" difference which equates to a minimum detection of 0.036 degrees with an 8" square. Another caveat is that the edge you place your square against must be perfectly flat, otherwise you will not get an accurate calculation of your square's angle error. ============================================================================================================================================================== Use a knife to mark and do it on a flat smooth surface. MDF or. better yet, a piece of metal covered in dykem blue. Make your line as light as possible. Use magnifier. A discrepancy of .001 is readily visible.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ The dial indicator method is 10X more accurate =========================================================================================== Got a metal lathe? If you do, it can be used to make a master square that is more accurate than anything you can buy for less than several hundred dollars. Not needed though. Use the flip and mark method.
---------------------------------------------
wrote:
------------------------------------------------------ You must be kidding, it's 50F and dropping tonight.
Time to throw another log on the fire and enjoy a toddy.
Lew
That's not how the math is done.
If your gap between the two lines (drawn from the same point) is 0.016" then half the distance is 0.008" which is your "Opposite Side". Now I understand the confusion here.
See:
And I once caught a fish ------This Big------.
snipped-for-privacy@garagewoodworks.com wrote in news: snipped-for-privacy@googlegroups.com:
I check it periodically, using both the Starrett and the Jevons squares. Don't you?
same answer
same answer
Why would you think that?
Just for giggles and grins, I just checked a corner of an end table that I made about 12 years ago -- put the head of the Starrett square against a corner of the tabletop, and tried to slip a 0.002" feeler gauge between the blade and the tabletop. It won't fit, anywhere within 7 1/2 inches of the corner.
I'm satisfied with 99.97%.
snipped-for-privacy@garagewoodworks.com wrote in news:ee116537-b047-4754-88e2-dfc87af63570 @googlegroups.com:
_Of course_ you can "quantitate" [sic] the error. What makes you think it can't be measured?
Crap, you're right. It is 0.057. I misread a decimal place. Apologies.
following along?
can't be measured?
Measure thousands of an inch between two lines. Sure it can be measured. Accurately? No.
snipped-for-privacy@garagewoodworks.com wrote in news:bccdd6ea-eb29-401f-8b92-b76c1cb38818 @googlegroups.com:
LMAO
distance is 0.008" which is your "Opposite Side". Now I understand the confusion here.
And tangent = opposite / adjacent = 0.008 / 8 = 0.001.
(As I noted previously, the 8" is actually the hypotenuse, not the adjacent side, but for angles this small, it doesn't matter.)
Anyway... arctan (0.001) IS NOT 0.5 degrees. You're off by an order of magnitude. [...]
If you *can't* tell the difference between a gap of sixteen thou and a gap of six thou without using precision equipment, then you need to visit an optometrist. Seriously.
I periodically check my jointer fence with a dial indicator (Powermatic) and it's always off by +/- 0.003". I shim the pos stop w/ paper when needed.
I wouldn't square anything against it as a reference.
Same goes for my Osborne EB3 that hangs on a wall. It needs periodic adjusting.
snipped-for-privacy@garagewoodworks.com wrote in news: snipped-for-privacy@googlegroups.com:
What makes you think that? Do you own a set of feeler gauges?
snipped-for-privacy@garagewoodworks.com wrote in news:c844cf2e-258c-4d91-bdd5- snipped-for-privacy@googlegroups.com:
Accepted. Thank you.
Man I wish we had a log fireplace. The fake gas log variety just doesn't cut it.
snipped-for-privacy@garagewoodworks.com wrote in news:6bb06987-59c5-4cc0-a902- snipped-for-privacy@googlegroups.com:
it's always off by
+/- 0.003". I shim the pos stop w/ paper when needed.It is at least close enough to tell you if you've damaged a precision square by dropping it on the floor...
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