Locating and Drilling Side Holes
While I can locate and cut side holes with the duplicator, the holes are not as clean as can be cut with drill and forstner bits, nor are they necessarily located exactly where the action ends up being happy in the inletting. It is much better for you to drill your own final holes if I don't have an action to do it from, or in the case for those that might be reading this article that carved your own stock or inletted a carved stock from Boyds or Richards on your own.
So here's how to achieve absolute perfection with bolt holes on the side of a stock, like forearm screw holes on spring guns.
Finish the inletting so the action is fit to the wood in it's final location.
Put masking tape on the side of the action (compression tube on a spring gun) above the hole location.
With the action in the wood, mark the top side of the forearm of the stock in pencil at the rear of the action or some similiar easily identified exact position, like a parting line in the machining of two parts. Don't use a moveable piece like the plastic end cap on a Diana rifle, but some steel feature of the action itself.
Draw a line on the masking tape with a sharp pencil exactly at the top of the forearm.
Remove action from wood.
Measure from the feature on the action you used to mark the spot on the stock in a line parallel to the action to the screw hole and transfer that dimension to the top of the forearm. To say this differently, measure from the back of the action to the screw hole. Don't measure at an angle to the screw hole if the angle is such that the dimension when measured along the straight line of the top of the forearm would then be too long. Measure from the mark you made on the top of the forearm to the point where the screw hole is along the top of the forearm. Mark this spot in pencil at the top of the forearm.
Measure from the line you drew on the masking tape perpendicular to the center of the threaded hole. Transfer this dimension to the stock. Use a square (a corner of a sheet of paper makes a conveniant accurate square) to measure down exactly perpendicular from your first mark.
Use a sharp tool like an awl, large needle, screw tip, or similar, to work a divot on your mark. Use a small benchtop drill press (or mill) and drill a small hole (~1/16" diameter) on both sides of the stock.
Put action back in the wood and shine a flashlight inside the action to illuminate the threaded hole and look through your drilled hole and see how close you are. As you step drill up to the final size, continue to check your progress to make sure you are staying centered on the threaded hole, and if not, work each subsequent drill bit around to stay centered. You can use a hand drill to 'hog' it out a bit in the direction it needs to go before moving up to the next size bit.
Step drill (go up one drill bit size in the box at a time) until you finish at the final hole size.
Several drill bits before arriving at the final size, transition to using an electric/battery drill and run the drill bit through the stock through both holes at once. Finish drilling to final size in this fashion. A size or two larger than the minimum perfect size is fine if needed to get the screws to fit the threaded holes. Don't cross thread the holes! If the screw doesn't go in easy, it must be touching the wood a little bit somewhere. Either 'hog' out the hole a little bit in that direction or drill the hole out a larger diameter to provide the necessary clearance.
Pillar bedding holes:
If your holes end up significantly off, have no fear. Or, if you wish to create hard points for your holes:
Strictly speaking pillar bedding involves gluing a piece of aluminum or steel tubing in to create the 'pillar', but here we will use epoxy resin to create a perfect fit hard point.
Drill hole over size, but under the size of the larger diameter hole that will be drill next to fit the screw head.
Acquire an allen screw and washer long enough to fit through the stock into the threaded hole. Allen screw will take some torque if necessary for removal. Allen will also typically tightly fit a washer to go over the epoxy slurry.
Wax threaded boss on action and the screw and washer and use laminating epoxy resin or bedding compound per instructions here. Fill hole with resin, bolt action in place with all bolts in final positions. Let cure. Remove action from wood. Drill bedded holes out to clearance diameter.
Drilling the recessed hole for the screw head
Clamp stock on it's side in a drill press or mill. Use a drill bit or center finder to align the hole in the stock. Change out the drill bit/center finder for a Forstner bit, typically 3/8" or 7/16". Drill the recessed hole for the screw head. A 7/16" Forstner is a rare find. They can be sourced on eBay. I like the one called Wave Cutter.
That's it. Don't forget to oil those holes when you finish the stock.