Character LCD modules based on the HD44780 display controller, and its equivalents, are popular for DIY projects and are available for low cost at eBay and other places.
Here are the cutouts I’ve been using for the 16 character LCD modules I buy from eBay.
I’ve created a PDF document that provides these templates scaled 1:1.
You can download it here:
Mounting Templates for 16 Column LCD Displays
Cut out the template you want to use, align and tape it to your panel. Use the center-marks to locate the center-punch for the hole centers.
I’ve used these templates successfully with both 16×1 and 16×2 LCD modules. Your display may or may not work with them so beware.
It’s important that you set your printer’s scaling to 100% before you print the PDF. If your printer is set to “fit to page” or some other setting then the hole locations on the printout will be wrong and you will ruin your panel or enclosure. Use the dimensions provided on the PDF to check the scaling.
Make sure the dimensions of your display match these templates before you start drilling and cutting.
I find template -B- to be easier to fabricate. Figure 2 shows the front of the frequency counter I use with my OHR100A. It uses the cutout with the rounded ends (template B).
After center-punching all the holes I used a step drill to cut the 12.7mm (1/2-inch) holes at either end and cut across with a nibbler tool. I then used a mill cut file to clean up the top and bottom of the opening and make them tangent with the 12.7mm holes.
The filing operation is the most time consuming. Take your time. Remember that a mill file cuts only on the forward stroke. Don’t drag it back and forth like a saw. Keep the file clean with a wire brush.
Filing metal is an art and can be a zen like experience. To be successful, be the file.
One last thing – be aware of the conductors on the back of the LCD module you are using. You may need to use nylon washers under the nuts.
Here is a collection of 16 column LCD modules I gathered to show the issue:
As you can see there is no standard layout for these inexpensive LCDs. Don’t rely on the soldermask to act as an insulator. If you do you are going to have a bad time.