YOur question seems to be addressing the side plate, which I take it to mean the plate Opposite the lockplate. NO? On a right handed gun, the side plate is on the left side the gun, and acts like an overlarge washer to protect the wood from being crushed by folks with overactive glands who take their testosterone levels down by using a screwdriver to tighten the lock bolts an extra half turn every time they put the lock back in the gunstock. Sideplates are traditional on many Pennsylvania style rifles from the late 18th through the golden age of rifle building in the first quarter of the 19th century.
First, do as has been suggested, and mark where you want the lockplate bolts to go in the lock plate. Here, clearance of the mainspring for the front bolt, and avoiding the bridle and tumbler for the top bolt is the order of the day. The front bolt also has to fit between the bottom of hte barrel, and the ramrod channel so that it does not interfere with the ramrod going all the way to the back of the barrel in its own channel.
Drill pilot holes, using a smaller drill bit than the tap drill size, so that you can locate where the holes come out on the left side of the stock. Now, use a template, or, I guess, the sideplate itself, to locate where you want to position the holes through which the lock bolts will finally go. Holding the sideplate against the stock, use that pilot hole drill beit to score and mark the back side of the side plate for the two holes. Drill those pilot hole in the sideplate. Now, its appropriate to remove wood to inlay the sideplate into the stock, if that is the style of architecture you are wanting. Some just put the sideplate on the top of the wood. ( I don't like this approach, and prefer to inlet the plate at least half its thickness, and in some guns, its appropriate to inlet it the full thickness of the side plate.)
Now, you can use the pilot hole to help center and guild the bit for the tap size you are going to use. Measure twice, and drill once!
Now use those tap holes to guide the drill, through the stock only, for the diameter of the bolt you are going to use to hold the lockplate. I have one gun where the smith used a 6-28 treaded bolt to provide the clearance for the ramrod in the front lock bolt; but then use a 8-32 bolt for the Top bolt. Use the largest bolts that you can make fit, as holding that plate correctly in relationship to the barrel and trigger is very important for good lock function.
Once you have the final holes drilled through the stock for the bolt, you can use those holes as a guide to begin to tap the lock plate holes, cut with the tap size hole previously, without having to thread the entire width of the stock! Lock plates are pretty thin, and you are not likely to get more than 3 threads in the plate before you are through it, no matter how fine a thread size you choose to use. I like to begin the taps using the stock holes as a guild, to insure that the threaded lock plate holes are not canted one way or another. However, once you begin the hole, and get a full turn or a turn and a hald, you can remove the tap from the stock, put the stock aside, and finish tapping the lock plate for the bolts by locking the plate in a vise, and doing the turnings by hand. Use plenty of oil, and take it slow until the tapered nose of the tap is well out of the other side of the plate. Only then, when you feel less resistance, can you go ahead and run the tap through the hole, and back again, to insure a clean cut to the threads. Wipe off the chips from the flutes in the tap before backing the tap out of the plate. There is no sense to putting chips back into your thread, only to do damage to the threads the first time you put the lock bolts into the new holes. I now flood the new threads with a spray can of oil to flush out the chips that might remain. The first pass through with the bolt, however, is done slowly so I can feel if there are chips, burrs, or tears to the threads. I can't remember putting a bolt into a new cut hole that didn't produce some few chips that just didn't flush out with all the other methods I tried.
Take your time, and do it right.
Best wishes. :thumbsup:
