Sine Plates, Sine Bars, Sine Fixtures . . .

[widgitmaster]

A sine plate or sine bar is one of the most important tools in a machine shop, as either one can enable a machinist to set a part on a precise angle for milling, drilling, grinding, or turning!
Here is a little How-To information and pictures of various Sine Plates and fixtures.
A simple sine bar can be used in a vise to hold blocks on an angle, or a vise can be bolted to an angle plate and a sine bar can be used to set the angle of the vise! Also, A sine bar can be used to set the angle on a lathe's compound, for very accurate boring, turning or grinding.
A sine bar is a precision ground bar with two V-grooves that are precisely 5" apart. So if you know the angle you want, use a calculator to get the SINE of the angle and multiply that number by 5 or the distance between the rails. Then stack up precision gage blocks and place them under one of the rails. This lift's the bar to the specific angle. For general use, round Space Blocks or even a gage pin can be used to span the distance.




1. To set an angle on any sine device, whether it is a sine bar, sine plate, compound sine plate, or other sine tool, you must first determine the center distance of the device (C) and the angle you wish to set (A).
2. Next, you must look up the 'setting constant' in the appropriate table.
The sine tables provided in this booklet are the basic sizes needed to set an angle on most sine products. For center distances other than those sizes listed, use the appropriate multiple of the constant determined from the basic chart.
For example: to obtain the constant needed to set a 15 degree 12 minute angle on a 10" sine plate, look up the constant in the 5" chart and find 1.310946". Multiply this by 2 and the result is 2.621892"
3. After determining the appropriate constant, assemble a stack of gage blocks (G) equal in size to that constant.
4. Place these gage blocks under the gage block roll of the sine device, and the desired angle is set.
5. Tighten the locking mechanism on those devices that have one, and you're ready to go.





Compound Angle:
When setting compound angles, it is necessary to compensate for the first angle set in order to correctly set the second angle. To obtain this compensation, refer to the following drawings and procedures.
where:
Angle A = First desired angle
Angle B = Second desired angle
Angle C = True angle setting required to get angle B
VIEW OF PART
1. Set the first of the desired angles (Angle A) on the top section of your compound sine plate.
2. Calculate the tangent of the True Angle (Angle C) using the formula:
Tan (True Angle C) =Tan (Angle B) X Cos (Angle A)
3. Lookup the True Angle (Angle C) in a table of tangents (or use the inverse tangent function on your calculator).
4. Set the lower section of your compound sine plate, using the proper sine table and the True Angle (Angle C).
5. Results: The compound sine plate is now set to obtain the desired angles (Angles A & B) in their respective planes.
Links:
http://www.eod.gvsu.edu/eod/manufact/manufact-130.html
http://www.tec-ease.com/tips/february-00.htm
http://www.cartertools.com/fmsbmb.html
http://www.auto-met.com/subtool/stcat/st_137.html



I hope you find this info useful!

WidgitMaster

[BobWarfield]

Widgit, as always, you're the best mentor available. Thank you for giving so freely.

It would be great if you added any pix you may have on how to setup things at an angle with sine bars and plates. For example, suppose I had a piece of plate and wanted to mill one edge with a 45 degree face instead of having it be square to the other faces.

Cheers!

BW

[widgitmaster]

Originally Posted by BobWarfield Widgit, as always, you're the best mentor available. Thank you for giving so freely. It would be great if you added any pix you may have on how to setup things at an angle with sine bars and plates. For example, suppose I had a piece of plate and wanted to mill one edge with a 45 degree face instead of having it be square to the other faces. Cheers! BW

Hello Bob!

Actually, a large plate at 45° is too much for a standard sine plate!
In that setup I would use a Sine Plate to tram the mill's head at 45° and leave the plate flat on the table! Or use the Sine bar to measure the angle of a cutter. Or even hold the cutter at 45° for sharpening on a surface or cutter grinder.


When tramming the mill head at an angle, it's good practice to setup a large Sine Plate (6x6) on the mill, and after it's pivot axis is dialed in parallel to the table, tilt the head and use a dial indicator to sweep as large a 360° diameter on the Sine plate as possible. This way all axis of the mill's head will be perpendicular to the sine plate, giving you a true angle. If you were to use a narrow Sine Bar, then you would only get one axis trammed true and get a false angle.

Hope this helps!
Widgit

[toastydeath]

It's also worthy to note that the closer you get to 90 degrees, the larger the angular error in the plate. Past 45 degrees, the error increases substantially. It won't affect 98.5% of operations, but for high precision/long boring work and inspection the error can be detrimental. If it is possible to reconfigure the sine fixture to use the complementary angle, do so - especially for inspection, where you do not have a fixed or semi-fixed spindle dictating how you set something up.

[CPBRAUN]

Can anyone explain the mathematical principle that makes this angular compensation necessary? I am trying to explain it to a long-time toolmaker.
Thanks

[easymike29]

Do-it-yourself sine bar/sine plate.