Ancient Techniques of Rifling Machines - IV

In our last post, we saw how an ancient gunsmith could have built an indexing head and in the post before that, we saw how they could build an indexing guide. In todays post, we will look into how they would mount the indexing guide and indexing head together, along with the head piece and tail piece.

As we noticed in the post for the indexing guide, the cylinder is mostly about 4" in diameter, except at the ends, where the diameter is 2" or 3" on either end.

The ends are where we will mount the head piece and tail piece. First, we look at the head piece.

The Head Piece. Click on image to enlarge. Not to scale.

Author places the image in the public domain.

It consists of a rectangular board of wood in which a few holes are drilled or chiselled out. Holes A and C are rectangular holes which are identical in dimensions. Hole B is a circular hole which is drilled to the diameter 3" (i.e.) the diameter of the cylinder at the right end of the indexing guide. It must be noted that the distance between the holes A and C must be greater than the width of the indexing head that we studied in the previous post. We will see why shortly. Finally, the gunsmith attaches handles on either side of the head piece.

Next, we look at the tail piece.

The Tail Piece. Click on image to enlarge. Not to scale.

Author places the image in the public domain.

In this piece, there are two notches A and C, which are to identical dimensions of A and C in the head piece above. The distance between A and C is also exactly the same as between A and C in the head piece above. The hole B is drilled to a diameter of 2", or exactly the diameter of the cylinder at the left end of the indexing guide. Finally, we have a large section D, which is the width of the bed of the indexing machine. We will see how this all fits in the next few images.

The gunsmith takes two long pieces of pine wood which are 1 inch x 2 inch in cross-section and about 50 inches long and attaches them to holes A and C on the head piece and tail pieces, using glue and nails. These long pine pieces act as braces and connect the head piece and tail piece together He also slips in the indexing piece into holes B on the head piece and tail piece. The figure below shows how the tail piece attaches to the indexing guide:

Tail piece assembly. Click on image to enlarge. Not to scale.

Author places the image in the public domain.

The next image shows how the head piece, tail piece, indexing head and indexing guide are all attached to the bed. First, the gunsmith selects a long plank of wood as the bed of the machine. Then he attaches the indexing head to one end, using nails or screws to secure it. Then he screws in the indexing pin  to the indexing head and passes the indexing guide through the hole. Then he attaches the head piece and tail piece to either end of the indexing guide and then connects the wooden braces to the head piece and tail piece. Note that the section D on the tail piece is wide enough to slide on top of the bed of the machine. The assembly so far looks something like this:

Assembly of the manual rifling machine. Click on image to enlarge. Not to scale.

Author places the image in the public domain.

The gunsmith can now grab the two handles on either side of the head piece and slide it back and forth along the bed. As the head piece and tail piece slide along the bed, the indexing guide also moves along with them. Due to the groove in the indexing guide meshing with the indexing pin on the indexing head (which is fixed to the bed and does not move), the indexing guide rotates at a fixed rate, equal to the groove's twist rate (which we saw how to machine, two posts earlier).

In the next few posts, we will see how our ancient gunsmith could have fashioned a cutting tool and attached it to the indexing guide and also see how the rest of the machine is built. Happy reading!