When I opened the packaging, I was startled to find that the instruments required a 3.5" hole for installation--huge. Since I planned to install the instruments in the mahogany cockpit bulkhead, I was understandably nervous about boring such large holes in the varnished surface.
Eventually, I had no other choice but to just do it. I proceeded with great care to avoid damage; it doesn't take much for a large hole saw to bind and chew up the surrounding surface.
Here is the raised panel bulkhead before beginning the installation.
![Image](http://www.tritondaysailor.com/images/st60-1.jpg)
Next, I covered the whole area with masking tape for protection against chipout.
![Image](http://www.tritondaysailor.com/images/st60-2.jpg)
The instruments include drilling templates, which I taped to the bulkhead in the proposed configuration to see how things would fit. Fortunately, there was just enough room for all three instruments in the field of the raised panel.
![Image](http://www.tritondaysailor.com/images/st60-3.jpg)
Next, I marked the centers of the holes with an awl. Each instrument requires the large 3.5" hole for the main body, plus two smaller holes (3/16") for the studs that secure the instrument. Once I had marked the holes, I had no choice but to go ahead and drill.
I used a new 3.5" holesaw chucked into my big, slow-speed right angle drill. I began on the exterior, drilling very slowly and carefully until the hole saw bit well into the wood. Once I had the hole partially cut, I bored the center hole all the way through with a 1/4" bit, then brought the big drill inside the boat to start the hole cutting from inside as well; this would prevent the plug from chipping out the interior surface.
![Image](http://www.tritondaysailor.com/images/st60-4.jpg)
Finally, after some minutes, I managed to bore all three huge holes successfully. With the thick solid wood panel, the overall thickness of the bulkhead was over 2".
![Image](http://www.tritondaysailor.com/images/st60-5.jpg)
Of course, the studs supplied with the instruments were too short for my thick bulkhead, so I had to modify some longer screws to replace the studs. Since I couldn't find screws with a fine-enough thread (the studs were some thread count finer than 8-32), I used 8-32 screws that I managed to thread into the receptacles on the back of the instrument, thanks to the soft brass threads.
Here are the instruments completely installed, with covers on.
![Image](http://www.tritondaysailor.com/images/st60-6.jpg)
And here they are with the covers removed.
![Image](http://www.tritondaysailor.com/images/st60-7.jpg)