I started on the butt today. I wrestled a bit with how to get the angle of the hole in the butt for the screw “just right”, when it dawned on me that there really is no need for that. Just drill the hole straight through the blank and shape the blank around the hole. It’s still not trivial, but it’s easier to do it that way than trying get the angle right. Here’s a picture of the factory butt with a cleaning rod through the bolt hole.
1) The comb of the stock is perpendicular to the horizontal.
2) The lower part of the stock is 12 degrees from vertical.
3) The through hole is 6 degrees from vertical.
Too much ‘fiddling’. Straight ‘works’, then shape stock around hole.
Turns out, the angle of the butt is parallel to the angle of the mortise of the stock with the receiver. In other words, the ‘front’ and ‘back’ of the stock are parallel. At least on the factory stock. We’ll see if that ‘works’ when I fit the stock to me.
Because the blank is 17.5″ long and the hole essentially had to be drilled through and through, I needed two “things”: 1) A long drill, and 2) a way to USE that drill. Fortunately, I have a set of drills that are at least 24″ long, and maybe 30″. That takes care of #1. #2 wasn’t going tobe so easy. However, J0e_bl0ggs suggested that I use my lathe headstock to hold the drill bit, and attach the blank to the lathe’s carriage. Excellent idea, and that is what I did. Still, drilling “deep” holes (technically in the machining world, anything deeper than the diameter of the bit is called “deep hole drilling”) is a challenge. Even though I ‘pecked’ at the hole in 0.2″ increments, the bit wandered a little. More on that later.
I decided that before I ruined the persimmon blank, I would practice on something else. Rummaging around in my shop, I came upon all of the birch I had milled a couple of years ago from a tree that came from my friend Jim’s yard. Perfect! Here is a picture of the two blanks sidexside.
As I said, I ‘pecked’ at it in 0.2″ increments and even still, it came ‘out’ about half the diameter of the bit ‘low’. That’s not a big deal, as one end of the hole is 7/8ths of an inch in diameter in order to fit a socket for tightening the bolt. Nevertheless, that was a ‘lesson learned’.
It’s common when drilling deep holes in wood, to drill from each end toward the middle. Given the outcome on the birch blank, I decided to drill from each end to the middle on the persimmon blank. That way I would only be drilling with a max of 9″ instead of 18″ of drill sticking out of the lathe chuck. It worked “ok”, but the holes did not meet perfectly. Again, not an issue because I will drill the ‘big’ hole, and that will allow me to choose ‘fix’ the middle to fit correctly.
It took about 4 hours to do all of that work, so I decided to call it a day once both holes were drilled. Tomorrow, I’ll drill the “big” holes, and cut out the forms.
Oh yeah. I was going to mention that I since I made the two blanks to identical dimensions, I measured the density of each. I’ll report it in units that most of us can relate to, but also the standard units of grams/cubic centimeter.
The persimmon blank weighed 6 pounds 4 ounces. The birch, 5 pounds 2 ounces.
The dimensions of the blanks in inches were: 17.5 x 6.8125 x 1.8125 = 216.08 cubic inches.
Therefore, the density of the persimmon is 100 ounces divided by 216.08 cubic inches for a value of 0.46oz/cubic inch.
The density of the birch is 84 ounces divided by 216.08 cubic inches, for a value of 0.388oz/cubic inch.
Therefore, the persimmon is 19% denser than the birch. (100 ounces divided by 84 ounces. No need to take volume into account since both blocks have identical volumes.)
To get pounds per cubic foot (a common unit of density for wood), the persimmon is 0.46 * (12*12*12) = 49.68 lb/ft^3.
The density of the birch in pounds per cubic foot is 42.00.
The standard unit for density is grams per cubic centimeter. The density of the persimmon in grams per cubic cm is 0.800. The density of the birch is 0.673g/cc.
While the standard units of density (g/cc) are not particularly easy for those of us that don’t use the metric system for weight, to ‘figure’, there is a physical characteristic of water that allows us to use the g/cc density value to know something about the object whose density we have. The density of water is 1.000. Therefore, if the density of the object you are interested in is LESS THAN 1g/cc, IT FLOATS. Note that both the persimmon and birch have densities less than 1g/cc. While “wood floating” is no big surprise, what IS interesting, at least to some of us, is that SOME woods have densities GREATER than 1.0g/cc. Therefore, when I am looking up a new wood, and the density is given, I can tell immediately if it floats, and generally speaking, how “hard” it is relative to other woods for which I have the density measurement.
How about pounds per cubic yard, or tonnes per cubic meter?
Persimmon – 1,341lb 6 ounces per cubic yard. (0.6708 tons/cubic yard)
Birch – 1,131lb 6.5 ounce per cubic yard. (0.5657 tons/cubic yard)
Persimmon – 800kg/cubic meter. (0.3636 tonnes/cubic meter)
Birch – 637kg/cubicmeter. (0.3059 tonnes/cubic meter)
After you take the initial measurements, it’s all ‘just math’. It is important though, in my opinion, to represent physical characteristics of ‘things’ in terms that people can relate to. I have always felt that way, and as a result, I didn’t get along with my “scientific” peers, the majority of whom LIKE to make things as confusing AS POSSIBLE. That way, they can maintain their “priesthood”. For me, science, TRUE SCIENCE, has ALWAYS been about COMMUNICATION and transfer of knowledge. Otherwise, ‘science’ is just another religion. And nowadays, THAT IS EXACTLY WHAT IT IS.
Anyway, climbing down from that hobbyhorse…
Just some info about birch and persimmon I thought SOMEONE here might be interested in. It does have a practical application to my project. The final weight of my rifle MATTERS to me. I might “like” the birch stock a little more than I do the persimmon when they get finished. If so, the final weight (which is a function of density) will be a determining factor on which butt gets used.