## Introduction: How to Use the DRO (Digital Read-Out)

I made a glow engine crank case using the mill.  I made it at TechShop (http://www.techshop.ws/).  The DRO (Digital Read-Out) device played a significant role in insuring that the dimensions were correct and matched my schematic.  I decided to write up an Instructable that talks about the DRO.   It seems the time I spent understanding the functionality was well spent and it helped me accurately build the part.  After I was done, I was surprised to see how much functionality was available.  This Instructable discusses some of the more interesting functions of the DRO that I employed while building this part.   Note: this Instructable is not meant to be an exhaustive list, it simply details  some of the more useful functions that I've found thus far on the DRO Model W411 Readout.  If you don't have the same model, the functions and keys will probably be a little different but some of the concepts may nevertheless be useful despite having a different model.  You'll have to check your specific model for applicability.

## Step 1: Calculator

Did you know there is a calculator on the system.  I DIDN'T.  I kept running back to the desk and doing some quick calculations on paper or the calculator on a computer until I found this handy little function.

The calculator can be accessed pressing CALC on the keyboard.  AFTER hitting CALC select the softkey STANDARD/TRIG.  Then use the keyboard to input numbers and operators (e.g. addition, subtraction, etc.) like a normal calculator.

On this model, the trick is to remember to hit the "STANDARD/TRIG" button to access the calculator.  It is a time saver.

## Step 2: Cutting Speed

The DRO can also calculate the correct RPM speeds.  This can also be accomplished using the calculator button.  Select CALC button and then select the softkey RPM.
1) Enter the diameter of the mill your using.
2)  Enter the surface speed.  (If it is not known, select the help screen, and a list of common materials with the appropriate surface speeds are given).
3)  Press enter and the calculator will determine the appropriate RPM setting.

## Step 3: Table of Drill Index

To determine drill sizes, I used to carry a heavy reference book in the car. It is not needed.  There is a drill index contained within the help files on the DRO's.   It can be found by selecting the softkey "HELP".  Use the up/down arrows to select drill index listing.

## Step 4: Datum References - Set the Mill to Read 0,0 at the Center of Your Part.

Because it helps when you are milling a complicated part (see image above), setting up the datum references is very helpful and helps to minimize errors.  For example, having a rectangular section and needing to bore a hole in the center and drill holes near the edges at specific coordinates can be simplified by using the datum tool to superimpose the axis with the center of the part at 0,0.  Here are the steps that I used to set up the part:
1)  Place the part in the mill.
2)  Place the edge finder in the mill collet.
3)  Select the drill bit icon to bring up the tool menu.
4)  Select the correct tool from the tool menu by using the arrow keys to highlight the appropriate tool and push  the USE TOOL softkey.   Make sure it has the correct diameter.  This is an important point.   If the diameter of the edge finder is incorrect, the datum will be off.  If the correct edge finder tool is not listed, simply follow the prompts to add a new tool making sure to enter the appropriate diameter of the edge finder that your using.
5)  After selecting the tool, select the datum key.  It is the key with the axis icon.
6)  Select the PROBE soft key and select PROBE again.
7)  Select CENTER LINE soft key.
8)  Using the X-axis only, move to the edge then press teach.
9)  Move to the opposite side and press teach.
10)  Repeat the steps for the y-axis.

When complete you will now have a datum axis (0,0) at the part's center.
This is a VERY useful function when you have sketches or drawings that your using to make the part.

## Step 5: Conclusions

Using a few simple steps, it is possible to turn the DRO into much more.  It is possible to:
*  Do calculations using the "STANDARD/TRIG" calculator.
*  Determine turning speeds of a known material using the RPM on the calculator
*  Determine drill diameters using look up materiel in the reference section of HELP.
*  Easily  establish an intuitive datum axis that sets the center of the part at 0,0.

This DRO has functionality that I didn't know existed at first.  Using its embedded help files has allowed me to leave some of my heavier reference books at home and more importantly set up coordinates that are intuitive and help to reduce errors.