# Sine bar



## Deny1950 (Apr 19, 2013)

Hi all was woundering if someone can explain how these sine bar work?  Thanks Denis


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## Daver (Apr 19, 2013)

http://en.wikipedia.org/wiki/Sine_bar

If no one answers this by tomorrow, I will attempt to.  I had a kidney stone removed today and I'm afraid I might not make sense with the drugs...

See if this helps


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## ESnel (Apr 20, 2013)

If a picture is worth a thousand words....

http://www.youtube.com/watch?v=ojjdRRXjK68

http://www.youtube.com/watch?v=ojjdRRXjK68


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## John120/240 (Apr 20, 2013)

Deny1950 said:


> Hi all was woundering if someone can explain how these sine bar work?  Thanks Denis



I hope this makes sense. Sine is one of the functions of a triangle. There is also secant, cosecant, cosine etc.  Find 45 degrees in your sine table
The sine is 0.7070.  Knowing the function of sine we know that a 45 degree angle one inch long will have a rise of 0.7070 thousandths of an inch.
So for a five inch sine bar multiply 0.7070 X 5". This result will tell you the exact height you need to raise your sine bar to achieve a 45 degree angle.


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## Tony Wells (Apr 20, 2013)

It's all about the relationship between the hypotenuse of a right triangle and one of the adjacent sides. On a sine bar (or sine plate) the two points of contact on the bottom, generally cylindrical pins sometimes called rolls, are a very closely controlled distance apart and represent a line that is the hypotenuse of the triangle. Generally, sine plates and bars are available in either a 5 or 10" distance between the rolls. One roll is set on the reference surface, and the other is elevated (or if used horizontally, rotated) a fixed distance according the the sin*5 (or 10) for the given angle. Note that the base side of the generated right triangle is of no real consequence here. It's probably easiest to understand if you think on the terms of setting this up on a surface plate. One end (sometimes if not most often) has a small plate attached to it to keep any work inclined to not slide off. So if you set the "fixed" roll on the plate, and want to create a 30° inline on the sine bar, calculate the sine value for 30° (which happens to be 0.5000) and multiply it by the distance between the rolls (5 or 10), and then we know what elevation we need to get the inclined angle to be 30°. So in our example, we have 5.000 inches, multiplied by 0.5000 and get 2.5000. Stack up gage blocks, or set an adjustable parallel to that and elevate the other roll, and the top of the bar will be exactly 30°.

You can use this concept in many ways, limited only by your imagination. You can set up work with it, as well as inspect work with it.


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## arvidj (Apr 20, 2013)

Yet another explanation that I like is here ... http://rick.sparber.org/rick/sbe.pdf.


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## Tony Wells (Apr 20, 2013)

That's a good writeup, and with pictures, describes pretty well my explanation. I didn't get into any of the error analysis, but for some applications, if should be examined. But he did make a case against using spacer blocks in lieu of a gage block set to me. I've never needed or used such a block set, as I always use gage blocks. It goes without saying that gage blocks, even the lowest grade that is supposedly more accurate than such space block sets, will give more accurate results. For one reason, you get to use fewer blocks to get the proper elevation dimension.

But his description is very good, and I thank you for the link.


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## Deny1950 (Apr 20, 2013)

Thanks all for the info guys, now I am one baby step closer to a machinist lol   Denis


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## cazclocker (Apr 24, 2013)

Daver said:


> http://en.wikipedia.org/wiki/Sine_bar
> 
> If no one answers this by tomorrow, I will attempt to.  I had a kidney stone removed today and I'm afraid I might not make sense with the drugs...
> 
> See if this helps



Looks like the original poster got some good answers re: his sine bar questions...but I gotta say, Daver, I certainly sympathize with you about the kidney stone. I just had my third one removed last week. The first one two years ago was the doozy, though... it was like pushing a Volkswagen through a soda straw, and trying not to damage the soda straw. Hallelujah for Oxycodone!


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## Kevin45 (Apr 28, 2013)

John120/240 said:


> I hope this makes sense. Sine is one of the functions of a triangle. There is also secant, cosecant, cosine etc.  Find 45 degrees in your sine table
> The sine is 0.7070.  Knowing the function of sine we know that a 45 degree angle one inch long will have a rise of 0.7070 thousandths of an inch.
> So for a five inch sine bar multiply 0.7070 X 5". This result will tell you the exact height you need to raise your sine bar to achieve a 45 degree angle.



Not to disagree with you, but to add to what you said, today there are more odd length sine bars out there than the standard 5" bar. So whoever has a sine bar but does not know how to use one, the first thing to do is measure from center of one roll to the center of the other roll. It may be 3", 4", 5". That dimension will be your multiplier as John120 states.


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