# Tapered Edge Finder



## RJSakowski (Jun 29, 2020)

A recent thread brought this tapered edge finder to the surface. The tapered edge finder, used in conjunction with a standard edge finder allows the user to accurately locate the vertex of a tapered edge and a horizontal surface. It works on both acute and obtuse tapers and doesn't require a sharp vertex.

A few years ago, after an inspiration from Tom Lipton of OxTools, I made one for myself. I used a 1/4" x 1" dowel pin and a small piece of flat stock to fabricate the tool. The two piece were clamped together with a pair of Vise Grips and the ends tack welded. Excess material ground away to create the finished profile.
View attachment 329091
View attachment 329084


To use the tool to find the vertex of a tapered edge requires a bit of trigonometry. Finding the vertex requires knowing the angle of the taper as well as the diameter of the cylinder. The math is complicated but not impossible.

When I used the tool, I created a drawing in SolidWorks and let it do all the mathematical grunt work. However, since not everyone has a parametric CAD package at their disposal, I decided to create an Excel spreadsheet to spit out the numbers.

The process is simple. Enter in the diameter of your cylinder and the taper angle, expressed as the angle between the flat and the taper. An acute angle will be less than 90º and an obtuse angle will be more than 90º. With those two knowns, the distance from the outer surface of the cylinder will be determined. Use that value plus any offset from your edge finder for the total offset to the vertex of the taper.

Calculating a taper angle from the measured offset is more complicated and I find it easiest to let SolidWorks do the hard math. The spreadsheet can also be used to determine the taper angle by entering assumed a trial angle and viewing the resultant offset. An adjustment is made to the trial angle and the offset results are again viewed. by this trial and error method, the correct taper angle can quickly be determined. A more sophisticated approach is to use Excel's Solver tool which will quickly and accurately determine the taper angle.

Solver is selected from the Tools dropdown menu. Selecting the Offset cell will fill in the "Target Cell". On the next line, select the "Value Of" option. For the "by Changing Cells", click in the icon at the right and select the Taper Angle cell and click the right hand icon to enter it into Solver. Finally, click the "Solve" button in the upper right hand corner. The taper angle will now be entered into the Taper Angle cell.

 Note: this was done in Excel 97-2003. Newer versions of Excel and other compatible software may have slightly different formats.


----------

