Logic: there is a thin web of wood between the bottom of the barrel channel and the bottom of the ramrod channel. Since the barrel tenons and the thimble tabs are located within this web, it should be possible to accurately locate the retaining pins so they are in a straight line. Problems occur when the density of the wood causes the flimsy drill bit to wander on its journey thru the wood. This is my method for a straight sided barrel. Tapered or swamped barrels have their own inherent problems, but the method can be adapted to them by simple observation and deduction on your part by making the obvious modifications before beginning. It will, however, require some study and planning on your part.
The tool is designed for use with a 5/64ths drill bit. Your pins can be made from either 5/64ths drill rod, or wire nails of the size included. If you desire larger pins, the holes can be enlarged after initial drilling.
Here is how to do a straight barrel. Your barrel tenons should be flush with the bottom of the ramrod channel, and your thimble tabs flush with the bottom of the barrel channel. File both until they are so. Inlet the barrel and thimbles in the normal manner. Place the tool on the top flat of the barrel at the muzzle and using the locating pin, determine the hole that most closely lines up with the center of the web of wood between the two channels. Obviously this is done BEFORE the muzzle cap is installed.
Next, find the centers of your barrel tenons and mark them on the side flats of the barrel with pencil or a thin tip marker. Place the barrel in the stock and run a piece of tape around it lining up both your marks.
Extend your line on to the stock. Now, using your pre-determined hole, locate it over the center of your line. You will be able to see the line centered in the hole. Insert the wire nail back into the hole and press it with your thumb to make a small indentation. Do this on BOTH sides.
Then take a sharp pointed scribe, ice pick, or other sharp tool and deepen your indentations, making sure you hold it at 90 degrees to the barrel. This gives your drill bit a predetermined hole to follow without running out.
I prefer to drill my holes using a pin drill at this stage, rather than an electric drill, as I find it gives me more control. Clamp the tool to the barrel, so your drill bit is in the hole you made with the scribe. You may put a piece of dowel rod into the ramrod channel as a clamping surface. Using the tool as a drill guide, drill only until you hit your barrel tenon. Do not drill thru it at this point, but do try to leave an indentation on the tenon. Repeat on the other side of the barrel. Now repeat the operation with your other tenons.
Doing it this way minimizes two common problems. Often when you drill thru, you will get wood breakout when the bit comes into the tenon mortise. Since it is backed by the tenon, this should be minimized. The other common problem, especially when drilling brass, it that you get a ragged edge on the opposite side of the hole. This is usually true when doing your thimbles. Sometimes this prevents removal of them without tearing wood out.
* A note on using the tool as a drill guide. The plastic part of the tool is very sensitive to heat. If you use an electric drill to drill your holes, make sure it’s turning slowly and withdraw frequently to clear chips. If they build up in the hole, the friction will melt the plastic and bind your bit. It will stick to the bit like cotton candy and when you withdraw it, your tool hole will be way oversized. That’s why these things are so hard to make.*OK, now we have holes drilled from each side of the stock. Remove the tool and the barrel and re-drill the holes from both sides. As you come in from the first side, ensure that the bit goes thru the tenon mortise and enters the hole coming in from the other side. Anytime you drill holes that must meet, it is always better to have them meet in the center, because if there was any drill runout at all, the bit will follow the original hole and come out somewhere else on the opposite side. (This tip also applies when drilling the hole for your tang to trigger plate bolt, especially if it has a slight angle.
Now you have pin holes for each tenon that meet in the center of the stock. Your tenons have small indentations from the previous operation that mark where the hole should be. Drill these holes now, again trying to make sure the holes are 90 degrees to the barrel. Fit the barrel back into the channel and redrill from each side, only going in 2/3rds of the way. This will ream your hole even with your wood so that the retaining pin will enter on one side and exit in the same hole on the other side. You will also not have chips embedded in the wood like normally happens when you try to do the whole operation at one crack.
Now that the barrel is done, repeat the operation with your thimbles. I like to retain the thimbles with two pins rather than one. Sometimes when using only one pin, the thimbles wobble in the inlet. Using two pins securely locks them in place. They can be a little trickier because if they are not inlet parallel with the barrel, you might not get a solid hole. This is especially true with the rear thimble. It is often canted because you failed to inlet the tang deep enough into the forestock, resulting in a canted thimble.
Finally, I use drill rod for pins because you can harden them and also fire blue them. You can buy drill rod from
www.use-enco.com in 3 or 6 foot lengths for a couple of bucks. While building a gun, it is necessary to remove and install pins a number of times which is a PITA. Make yourself a set of try pins which are easily installed and removed when necessary.
