> There is no need to "try again"
Then who is being arrogant?
and I appreciate your veiled
> Where are you having trouble with the math?
Your identifiers are poorly chosen making your "work" difficult to read.
From your words/diagram, it looks like delta1, delta2, and L are all
I don't see the 5-degrees you mentioned (in your diagram).
Doing math is like doing design: Do-over, and do-over, and do-over. One
get quite humble about the process!
On Thursday, January 3, 2013 8:43:05 PM UTC-5, Bill wrote:
Not at all. The red d2 is above the red line. d denotes distance.
The passage "take a reading at the bottom of the square (d2 in Figure 1)" should
have clued you in that d was a distance. We are, after all, discussing a dial
indicator method. Dial indicators measure distances.
" Tilt your miter gauge to approximately 5 degrees." You can't tell that the
miter gauge and square are tilted in Figure 1?
Point out what you think needs a do over. If you have other questions let me
Ummm.... Brian, you don't know Bill personally. I do.
He's not the sort of guy to toot his own horn, so without his consent, I'm not
going to say why I'm
so sure of it, but please trust me on this: the man *knows* math.
Doug, Thank you for your support. Brian, Thank you for your indulgence,
as I came into
this confused about the details of the procedure/algorithm that was
being proposed--and I apologize for any
fuss that I may have created as a result of that. I think I may need to
see a picture with a real dial
indicator in it, or a drawing of one, to understand the procedure. There
is so sense in me making any further comments, other than the
request for clarification I have already made, until I understand the
Brian, I know Doug well-enough to know that he has a lot to offer on
this problem. If he understands what you are trying to do, than
I'm sure that he can help you make it "first-rate" if that's your goal.
We're all here to help and support each other, right?
On Friday, January 4, 2013 12:43:52 AM UTC-5, Bill wrote:
The procedure really couldn't be any simpler, I can only conclude that you have not read the procedure carefully enough.
Procedure: As shown in Figure 1, position the dial indicator to the left of the square and miter gauge so that the stylus makes contact with the square to obtain reference distance d1. Push the square and miter gauge forward to obtain distance d2. If you zeroed the dial indicator at d1 then the Delta1 is determined directly (See equation 1). Flip the square over and repeat the same process with the dial indicator on the right side to obtain Delta2. Delta2 = abs(d3-d4).
L is the length of the square. Because we rotated the square and miter gauge (to make the calculations work) there will be some error introduced into the equation that is very small. See Reference 2. L actually gets a little smaller because of the rotation.
If you have access to CAD, draw an 8" square with an angle of 89.5 degrees (0.5 degree angle error). Create an isosceles trapezium to simulate the two squares coming together when flipped.
(With the 0.5 degree angle error, Figure1 creates an isosceles trapezoid)
Rotate your trapezoid by 5 degrees to give a representation of Figure 1 in CAD. Measure your d1 - d4 and calculate the angle error per equation 2. You should calculate an angle error of 0.498 degrees. The 0.002 degrees that the calculation is off is explained in reference 2.
I hope this helps.
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...
Make it as simple as possible, but not simpler. (Albert Einstein)
Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
As I understand his equations the L is not a variable in any given
situation as it is the length of the square. How ever it would be
different depending on whether one used the long or short arm of the square.
On 1/3/2013 7:32 PM, email@example.com wrote:
Appears to be a matter of resolution. I'm of the camp that if you don't
have perfection as a goal for every step of the process, you will never
scratch that itch some of us are cursed with.
At the same time, I'm just as guilty as anyone of occasionally settling
for less ... mainly due to time, circumstances, the medium
(woodworking), and the need to 'git r' done'. ;)
That said, you are only as accurate as your tools allow ...
Tools, and the material you are working. Context is a large part of it.
A couple of thousandths over two feet is out of context for woodworking
joints. The material is going to move more than that simply due to
I'd rather spend a few bucks on a quality square than putz around with
a dial indicator.
Outside of a dog, a book is man's best friend. Inside a dog, it's too dark to
read. - Groucho Marx
Here, let me put back in the part you conveniently left out:
"At the same time, I'm just as guilty as anyone of occasionally settling
for less ... mainly due to time, circumstances, the medium
(woodworking), and the need to 'git r' done'. "
Notice the mention of "woodworking"?
How does that not set the "context"?
Here, I'll say it again:
You are only as accurate as your tools allow.
I don't know why google groups double-spaces every one of your posts, but it is
Starrett is in business to supply precision tools to the metalworking and
industries, for which a much higher level of precision is required than for
furniture, where "within a 32nd" is usually more than sufficient.
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