And a few more: "angle setting/measuring":
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DIY 5" sine bar
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Originally posted by oldtiffie View Post(snip)
One of these days I will start a thread about "limits and fits" and "tolerances" and "surface finish" all of which are interrelated/dependent/reliant to some degree  and how to take advantage of them for the optimum result.
But the forum brings interesting response and experience.
In my no doubt limited definition of "Home shop machinist" a true grasp of tolerance seems lacking. An individual who can produce flawless parts on their own can be at a complete loss if having to spec' for a jobber whereas the jobber can likely move decimals to the left and produce functional cost efficient parts.
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Thanks Gerrit  appreciated.
A very obvious and practical and useful "angle setter/measurer" is the common shop rotary table. I got rid of my very good 8" rotary table as my 6" rotary tables do all that I need  the 8" table was far too heavy and awkward for me and it was just an accident waiting to happen  so "Zip"  it got "binned" to/for scrap as it had no value to me and it just took up space that could be better used for other "stuff".
Stand it vertical (on its end), bolt an angle plate to the face of it with the vernier setting to zero and the "flat" (face) of the angle plate set to zero (horizontal)  and there you have an ability to measure and/or set up to an angle of 20 arc minutes which is more than accurate enough for may purposes.
The angles do not need to be calculated and they can be read off and be set or read directly from the handwheel and table vernier.
A magnetic angle table is a great help too  especially on a surface grinder or tool and cutter grinder. There may be no need to bold the rotary table to a machine table either as both work quite well enough on any reasonably flat surface (including but not necessarily needed  a surface plate).
The rotary table is not as "stiff/rigid" as I'd like when it is stood vertically on a machine table so I used a bit of hot rolled 1" x 1" x 1/8" angle  seen here  works a treat and was made from stuff I had in the shop and cost no money or very little time.
Last edited by oldtiffie; 10062016, 10:22 PM.
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Yes, for small angles there is very little difference between the sine and the tangent functions. But as the angle gets larger, the difference increases at an accelerating rate. The sine of 45 degrees is 0.7071 while the tangent is 1.000. And when you get to 90 degrees the sine is 1.000 while the tangent is infinite. You just can't get a bigger difference than that.
So don't try to expand that trick as you will quickly get into trouble.
I took similar liberties in the case of small angles in my article that I posted a link to above.
Originally posted by oldtiffie View PostFor what its worth:
sin 5 degrees = 0.0872
and similarly is:
Tan 5 degrees = 0.0875
The difference over 5 units is (0.0875  0.08720) = 0.0003 units over 5" length so the difference is minute (very small) and nothing to get hung up about.
A good scientific/mathematical calculator will do the conversion from decimal degrees to degrees:minutes:seconds  and reverse  with just one or perhaps two keystrokes.
The difference over either the sin or tan of an angle is very close to being linear over a distance 5 degrees
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OldTiffie THANK YOU. I have never been able to understand why some individuals on these various forums need to slag others off for presenting ideas, esp ones that seem to be well documented.
So, I appreciate greatly that you and the others above took the time to find the information for me/us and share it. I enjoy making tools to use for my various projects. I promise not to use over specified dimensions, I am happy when two parts fit closeenough for the purpose :)
Gerrit
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For what its worth:
sin 5 degrees = 0.0872
and similarly is:
Tan 5 degrees = 0.0875
The difference over 5 units is (0.0875  0.08720) = 0.0003 units over 5" length so the difference is minute (very small) and nothing to get hung up about.
A good scientific/mathematical calculator will do the conversion from decimal degrees to degrees:minutes:seconds  and reverse  with just one or perhaps two keystrokes.
The difference over either the sin or tan of an angle is very close to being linear over a distance 5 degrees
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A couple of decades ago, when we were still measuring angular errors in degrees, arcminutes, and arcseconds  then using custommachined wedge shims to reduce them to less than one arcminute  I designed a shim machining fixture using three balls (arranged as in Les A W Harris's picture in Posting 7, above) to generate the required compound of angles. To simplify the calculation of the required underball spacing shims, the distances between the ball centers was set to 3.441 inch along the balltriangle base and height, squarerootof2 times 3.441 inch = 4.866 inch along the triangle hypotenuse, so that each 0.001 inch of underball spacer tilted the plate 1 arcminute.
The 0.001 inch per arcminute is, of course, a linear approximation of a nonlinear function . . . but for angles of five degrees or less (and we hardly ever needed to correct more than a half degree of angle error), the error of the approximation is less than arcseconds magnitude.
Worked really well, but updating our measurement equipment resulted in angularmeasurement units expressed in decimallysubdivided degrees. I revised the fixture design, enlarging it so that two of the ballcenter distances were 5.735 inch, with the third being squarerootoftwo x 5.735 inch = 8.111 inch. This reduced tilt angle generated by 0.001 inch of underball spacer to 0.01 degree, with very nearly the same maximum error over a range of 0 +/ 5 degree.
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Originally posted by George Bulliss View PostDon't know for certain, but I'd guess it's one of those "stair step" looking blocks, with the step heights equaling the height required for setting standard angles on a 5" sine bar. I've seen them before, along with shop made versions.
https://www.google.com/search?q=sine...lE1lQgKfkLM%3A
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I shudder when some one wants "Jo Block" and "True Sine Bar" measurement  and "tolerance" where all to often they are neither wanted nor needed within what ever the real tolerance/limits needed for a job really is in fact.
Same applies to "surface finish".
If they really are justified  then by all means use them  otherwise don't.
I rarely use some quite accurate and sophisticated tools that I have as I always start at "basics" and "fundamentals".
They have stood me in very good stead over any years and are often "on show" (used) where as the "better/precision" stuff rarely gets used or sees the light of day  but they are there for when they really are needed.
Same applies to choosing which machines to use.
One of these days I will start a thread about "limits and fits" and "tolerances" and "surface finish" all of which are interrelated/dependent/reliant to some degree  and how to take advantage of them for the optimum result.Last edited by oldtiffie; 10062016, 03:01 AM.
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Back in the JanFeb 2009 issue of Home Shop Machinist I had an article on an inexpensive method of generating accurate angles. It describes a method for using a set of angle gauges, which are less expensive than Jo blocks, and combining them with the sine method but without an actual sine bar, so that any in between angles could be accurately generated.
It also discusses sine bar theory.
I have placed it in my LockBox folder so it can be downloaded.
Caution: It contains math but only addition and subtraction is needed to actually use the method in the shop.
https://www.dropbox.com/s/6hx2gq491h...Gauge.doc?dl=0
If you have any questions just post them here.Last edited by Paul Alciatore; 10062016, 02:35 AM.
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The reason the pics of mine referred to as regards the "shop made" sine bar are no longer here  or in existence so far as I am aware  is that there was so much adverse comment regarding some/most/many pics that I posted that I just "called it quits" and removed them from PhotoBucket and my computer.
Too many of the adverse comments were directed to/at me personally and I wanted to remove that post and pics and some others so as to avoid the "pile on" and to get things "back to topic".
I thought that some one else may have stored those "sine bar" pics away  but it seems not thus far.
Sorry.
(Edit).
I had another (better) "close(er?) look"  and lo and behold:
Last edited by oldtiffie; 10062016, 01:55 AM.
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Originally posted by tony ennis View PostThis is a great thread.
...lew...
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