# Quick and dirty sine bar setting



## Blogwitch (Feb 8, 2015)

This post isn't for those people who do everything by the book and only use the best equipment.

What I am about to show you is a relatively cheap method to get good levels of angle accuracy.

Whether you know or not, the sine bar is a method of producing very accurate angle measurement, if you know how to use one.

It  can also be a rather expensive way of doing it, due to the cost of a  top quality precision sine bars and the related slips gauges that are  normally used with them. But help is at hand.

These are what is  called 'value' sine bars, the 5" one cost me less than 20 pounds and the  small one, which I purchased recently was less than 6 pounds. You can  spend hundreds on buying one, but for general workshop use, one of these  would do just fine.

This shows you what they look like.

http://littlemachineshop.com/products/product_view.php?ProductID=3760

Sorry  that they are no longer available from that source, but it does give  you an idea of how much they cost and what to look for.

Even  though they are cheap, it doesn't mean you should throw them about, you  treat them as you would any other precision instrument. If it doesn't  come with a storage box, they should be stored by resting on one of the  sides, as shown by the small one. The top top face and the bottom of the  rolls are the critical bits.








This  is how they are normally used, either sitting on a parallel, or another  true flat face. One end is supported on a stack of slips that have been  built up to the required height to put the top face at the correct  angle.
Getting that required height can be rather daunting for the newcomer, because of the calculations involved.
I am going to show you a way where the calculations are done for you, and you should get acceptable accuracy on your angle.







You  first need a small engineering conversion program installed on your  computer, this shows the one I use the most. It must have a right angle  triangle calculator program within it's walls. I have gone through the  getting the bit you need stage in numerical order, so it should be very  easy to carry out.


You can obtain it from here, free of charge.

http://home.scarlet.be/mini-draaien-frezen/engels/program-01.html







How to use.

1) Select 'Right Angle Triangle', this main page appears.

2)  These bits are to do with what you are trying to achieve. The  Hypotenuse is the distance between centres of YOUR Sine bar, and the  angle is the one you want your bar to sit at. You need to find the  length of Side 2. So select 'Hypotenuse and Angle A'.

3) This is  where you select your input and output figures. Mine is set to Imperial  with Degrees, Minutes and Seconds (DMS). If you wanted Metric with  Decimal Input and Output, then just select those buttons.

4) This  is where you input your figures, the top figure is the distance between  centres on YOUR particular Sine bar, then you input the angle you  require, again, this shows what I entered in DMS, you could enter yours  in decimal if you had selected that option. Underneath the input, you  will see a button for selecting the accuracy of output. I have selected  3, which gives the output to 3 decimal places, in fact in thous (mils)  if you are in Imperial. If you are using metric, then I would suggest  #2. You could select 6 decimal places, to give you super accuracy, but I  think you would have trouble getting your spacer pack to the right  height.

5) That is the figure you require for your spacer pack  height, that you sit under one of the Sine bar rollers to give you the  angle that you require.

It does look rather complicated, but it  isn't. Just look at the ovals in order, input your figures, and once you  have done it once, you will never have trouble again.

Marv also  has a little program the he has written that will also do the same  function, I am sure if he reads this he will show you all about it.

There are many ways you can obtain that figure, even by the use of a normal scientific calculator.

The choice is all yours.

This is the controversial bit, what to use instead of those very expensive slip sets.

I  have two of the expensive ones, donated to me many years ago, but I  always use these little jobbies that a friend picked up for me when he  visited the US with his work.

http://littlemachineshop.com/products/product_view.php?ProductID=1757&category=988300808

So you still don't want to fork out any more cash?

Then  grab your trusty mic and go around your shop measuring the thickness of  things, and by holding the bits together, and using a set of feeler  gauges as fine tuning, you will soon find you can get to the height you  want.

If that is too much like hard work, then dive in on your  lathe and turn a piece of something down to the same diameter as the  height you need, and depending how the sine bar is situated, you can  either leave the turned down bit on the original bar, or just part it  off. But remember, don't try to put the round edges against each other,  they need to be at 90 degrees to stop things rolling about.

I  hope that this has helped to explain how easy a sine bar can be used,  and it is not in the domains of master machinists, as a lot of beginners  suspect.

John


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## Cogsy (Feb 8, 2015)

Although I haven't yet used them, I recenlty ordered the sine bar and the space blocks from that same source. All I was missing was the program, which I now have.

Thanks for the timely advice!


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## rodw (Feb 8, 2015)

You don't need software. Just a calculator. Just take the sine of the Angle you want and multiply it by the length of your sine bar. 
eg. 

H= sin(A)×L
where:
H is the height of the packers
L is the length of your sine bar
A is the angle you want. 

There's a reason why they call it a sine bar. 
If you have a DRO, it will calculate the sine of an angle in calculator mode. I use Realcalc on my Android phone. Such a good calculator, I bought the App!

Works for metric and imperial. Whatever the units you measure your sine bar in is what you will get for the height.


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## Cogsy (Feb 8, 2015)

You're right of course Rod, and that's how I planned on doing it, but I have to admit just plugging the values into the program appeals to me more and eliminates the possibility of mis-keying the calculator. 

For stuff like this I like to do the calcs in advance before I head to the shed and make the appropriate notes to take with me, so having it on the computer is very handy.


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## Blogwitch (Feb 8, 2015)

The reason I showed that little prog was to help people who aren't really into maths etc. I used to be, but age is now taking it's toll, so now I prefer to use a little program rather than a bit of paper and working things out.

People, sorry, beginners to model engineering, are sometimes baffled by what people like ourselves get up to, and are scared of asking questions about such things. If they can be put into laymans terms and the methods explained, showing exactly how easy it can be, hopefully they will start to use a few more techniques that they didn't understand before, so making their building of something much easier.

BTW, that little prog has a lot more going for it than just trig or geometry. The little gear bit is great for working out all your diameters and tooth depths etc.

Here is another with a bit more to it, if you want to try it out.

http://www.colinusher.info/Software/Model%20Engineers%20Utilities.html


John


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## Geartooth (Feb 8, 2015)

I have a home built 3.5 inch sine bar that I use in my 4 inch milling vice. I made up this one page chart in Excel and keep it in the workshop. 

View attachment 3.5 INCH SINE BAR.xls


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## Geartooth (Feb 8, 2015)

Here is a photo. I made these 3.5 inch sine bars for use in my 4 inch milling vice. I cut the V-slots in the bar on 3.500 centers and used screws to assemble the round pivots. The sometimes handy thin one was welded. For the spacers, I use adjustable parallels, or for more range I&#8217;ve trued up the heads of short 3/8 bolts and mate them with inverted ny-loc nuts. I look up the spacer needed for an angle, adjust the spacer, and the angle comes out just right.


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## purpleknif (Feb 8, 2015)

I've been a machinist for 30 years now and i have never used a sine bar. To set the angle you merely need to travel a known distance and use some sort of gage set to the sine for that distance and slip it in between the part and your indicator.  This gives greater accuracy because you can go longer distances and your sine bar cant move.  On a knee mill for instance you would move the X or Y axis , NOT the Z ! If you need to move the Z to get your measurement then you multiply distance time tangent.


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## Blogwitch (Feb 8, 2015)

Very nice home made bars there Gear.
Just an aside, for working on and around my mill, I use one of the cheapo digital angle gauges, they are fine for 99.9% of what we do.
The sine bars I use mainly for layout work, as even though I have DRO on my mill, I also like to see if I am cutting correctly as well, it is called wearing both belt and braces machining.

John


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## Herbiev (Feb 8, 2015)

Looks great but program won't load on iPad


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## /// (Feb 8, 2015)

LittleMachineShop still have sine bars available, though slightly larger and slightly more expensive -- http://littlemachineshop.com/products/product_view.php?ProductID=3525

An alternative to the LMS Space Block set, and slightly cheaper, is the Gauge Block set from CTC Tools with a _claimed_ Grade AS-2. Accuracy +/-50 Millionth of an Inch (+/-0.00005") -- http://www.ctctools.biz/gauge-block-set-imperial-36pcs-l97/
I have the equivalent metric set on its way to me


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## RichD (Feb 9, 2015)

When I made my taper attachment for the lathe, I tossed around different lengths for the sine bar. I finally settled on 28.648" since every degree is 1/2" at that length. My original thought was to make a 20 TPI adjusting mechanism so I could divide the screw dial for easy setting.

After using it several times I never bothered with the adjuster since using purpose made spacers was so easy and accurate. Most often I just cut MT 2 or 3 so I have a single spacer with either end machined to the correct sizes for each. simple center punch marks on each end are my labels ** and ***.

The longer the sine bar, the more tolerance it has for slight errors in the spacer(s) dimensions and the thicker spacers are easier to produce. Although mine only has ~ 9 degree
range due to the long bar.
Rich


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## rodw (Feb 9, 2015)

On the subject of sine bars and quick and dirty, here is my sine bar based taper setter for the compound.
http://www.homemodelenginemachinist.com/showthread.php?t=23268
Might look crude but works very well. I wish I had a longer sine bar though.


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## gus (Feb 9, 2015)

I have nothing to contribute. Am busy reading this thread and busy picking brains. To early to say
I don't need sine bars.  Been going around buy tools that I may need some day. So far so good. These tools did come to the rescue. May buy a sine bar. In trade school, I came across the MachineShop Instructors struggling with sine bars and go nowhere. With my trigo knowhow,I did offer to help calculate angle but was tool to piss off. Good Bye Sine Bars---------1961.:rant:


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