Sunday, April 20, 2014

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!

Sunday, April 13, 2014

Ancient Techniques of Rifling Machines - III

In our last post, we saw how a gunsmith from hundreds of years ago, could construct an indexing guide, a key part of a manual rifling machine. In today's post, we will study how they could make the indexing head, another key part of the machine. Like the indexing guide, the indexing head is also constructed as accurately as possible.

The purpose of the indexing head is for the indexing guide to pass through. This is the part that serves to rotate the indexing guide at a precise twist rate, which is in turn, used to move the cutting tool inside the barrel and cut the rifling grooves. Here's what the indexing head looks like:

Click on image to enlarge. Author places the image into the public domain. Some dimensions are not to scale.

The gunsmith starts with a flat plank of wood of suitable size. The gunsmith then bores a large hole B in the plank, to a diameter slightly larger than the indexing guide that we studied in the previous post. In the previous post, we had decided that the indexing guide had a diameter of 4 inches at its thickest part. Therefore, the diameter of the hole B is drilled to about 4.25 inches, so that the indexing guide can fit through this hole with a bit of clearance.

After that, the gunsmith chisels a hole at one edge of the hole B, so that he can screw in a small indexing pin A. The indexing pin A can be made of steel, brass or any hard wood such as oak, maple etc. The material is simply cut from a blank using a hacksaw blade and then filed into shape, and a hole is drilled in the middle to support a screw. The indexing pin is made long enough to fit in the groove that was cut in the indexing guide we saw in the previous post.

Building the indexing pin. Drawing is not to scale. Click on image to enlarge.
Author places the image in the public domain.

The indexing pin is inlaid into the indexing head, so that it cannot move at all.

The gunsmith also drills three or four holes C, at the bottom of the indexing head, so that the indexing head can be attached to the rifling machine bed via screws through these holes.

The indexing head mates with the indexing guide from our last post, as shown in the image below:

Drawing is not to scale. Click on image to enlarge.
Author places the image in the public domain.

The indexing head is fixed to the bed of the rifling machine and the indexing guide is pushed through it. The indexing pin fits into the groove of the indexing guide and causes the guide to rotate at a fixed rate, as it is being pushed or pulled through the head.

Of course, the curious reader might ask, how does a person drill such a large hole like B into a plank of wood. Luckily for us, the tools to do this were already invented and perfected several hundreds of years ago. Remember that mankind has been using the wheel for thousands of years and the wheel is attached to the axle with a relatively large hole. The first solid wheels and axles began to appear in Mesopotamia, Central Europe, Balkans and Northern Caucasus around 3500 BC. By about 3000 BC, the Indus valley civilization in Northern India shows evidence of having spoked wheels. By 1200 BC, chariots with spoke wheels were known to just about everyone in Europe and Asia and parts of Africa as well. Therefore, the technology for boring large holes into objects (e.g. for attaching an axle to a wheel and attaching spokes to wheels) was pretty well developed by this point in time. Tools such as the bow-drill and gimlets could be used to drill smaller holes and then the holes could be enlarged by using augers and reamers.

A Bow Drill

An Auger. Click on image to enlarge.

Several examples of Reamers. In particular, note the one from Roman times. Click on image to enlarge

A wheelwright using boring tools to fit an axle to a wheel. Click on image to enlarge,

While the images above show the tools used by a wheelwright to bore a hole into a wheel for an axle, the same tools and techniques were also used by ship builders, architects, carpenters etc. Therefore, it is a pretty safe bet to say that a gunsmith in 1500 AD had the tools and knowledge to easily bore a large hole into an indexing head.

The parts in this post and the previous one need to be built as accurately as possible, to produce good rifling. In the next few posts, we will study some of the other parts needed to build the manual rifling machine.

Tuesday, April 8, 2014

Ancient Techniques of Rifling Machines - II

In our last post, we started a series on studying how people used to cut rifling in their barrels manually, without the benefit of modern machinery. In our last post, we left off with the study of an important woodworking and metalworking tool, the lathe. As we saw in our last post, lathes were available to various cultures around the world, since the times of ancient Egypt, so it is pretty reasonable to assume that they were available to people around 1500 AD as well.

In today's post, we will look into the construction of an indexing guide. This is basically the part of the rifling machine that twists the cutting tool at a fixed rate, so that it cuts the required rifling grooves inside the barrel. This is the one part of an ancient rifling machine that needs to be as accurate as possible. Of course, we will first study how they built the most complicated part, so that the rest will appear a lot easier!

As we studied in our previous post, lathes can be used to make cylindrical shapes. The workman simply mounts a log of wood on his lathe and starts turning it and applies a sharp tool to the side of the rotating log to carve out a cylinder. So our ancient gunsmith would have used a lathe to carve a wooden cylinder made of oak or maple, about 4 inches in diameter and at least 50 inches long (assuming that he wants to make a rifled barrel with a twist rate of 1 turn in 48 inches, which is a typical twist rate of that era, so he makes the cylinder at least 48 inches long, with a little bit extra), with smaller protruding cylinders at either end of the log, such as the illustration below shows (please excuse the crudeness of the drawing :)):

Click on image to enlarge. Author places this image in the public domain,

The next thing to do is inscribe a groove on the thickest part of the cylinder (i.e. the part that is 50 inches long). The groove will help guide the cutting tool at the required twist rate.

The groove forms a helical path on the outside of the cylinder. So how did people build this in the middle ages. Luckily for us, there is a simple way to do this, which has been with us since ancient times. First, the gunsmith draws two sides of a right triangle ABC on a flat surface as follows:

Two sides of a right triangle. Clck on image to enlarge

Here, AB is 48 inches long (because we wanted a twist rate of 1 turn in 48 inches) and the length of side BC is equal to the circumference of the wooden log that was just shaped. The gunsmith can calculate the length of BC to be (pi * diameter of the cylinder), or the gunsmith can simply measure this out by wrapping a thin thread around the surface of the cylinder and marking it, then placing the thread on the line BC and measuring out the length of the markings. The only trick is ensuring that the angle ABC is a right angle (i.e. 90 degrees) and as we will see, measuring this out is a piece of cake as well.

Sidebar: How to measure a right angle

This might be a good time to talk about how people measured right angles back in the day, if only for the reason that such knowledge of geometry is gradually being lost today unfortunately. Today, any student can buy a protractor at any stationary shop for a couple of dollars (A 10 piece Staedtler mathematical instrument set cost me $3.99 and it contains a protractor, two set squares, a compass, pencil sharpener, pencil, a ruler etc.). However, a protractor wasn't in common use before the 19th century and such instruments were generally more expensive before the 19th century and weren't easily affordable to ordinary smiths. So let us only consider instruments that were cheap and widely available for that era.

As it turns out, ancient civilizations like the Egyptians and the Chinese had already developed set squares, way back in the day (Egyptians seem to have had them as far back as 1300 BC or so), so they were probably widely available to various people in the middle ages as well. While you can't measure any angle with a set square like you can with a protractor, they can be used to measure right angles very well.

Ancient Egyptian set square from 1300 BC.

The above instrument is from ancient Egypt and such instruments were known back in the time of the Pharoah Ramses and used by them to build pyramids, so they were definitely widely available in many countries by the middle ages. Using one of these instruments, a gunsmith could have easily drawn a right angle.

The other ancient mathematical instrument is the compass, which was also known to ancient civilizations like the Greeks, Chinese, Indians, Romans etc. For example, Euclid's classic mathematical work Elements from around 300 BC mentions compass and straight-edge problems in book II of the series, and a classic Chinese mathematical text, the Zhoubi Suanjing from around 100 BC, also mentions the use of set square and compass in geometry problems. Ancient compass instruments have been found intact in the ruins of Roman cities like Pompeii and ancient Indian mathematical texts also talk about usage of such instruments.

A set of bronze compasses from the Roman era

Even if a person has no compass, he can still improvise with two sharp objects (e.g. two pencils) and a ribbon connecting the two sharp objects together at a given length. As we will see below, we can still draw a fairly accurate right angle with such a crude instrument, using the procedure below:

Say we have a line AB and we wish to draw a right angle at point B. Imagine that the only instruments that the gunsmith has available are a straight edge and a compass (and if he doesn't have a compass, he has improvised by tying two pencils, one on each end of a shoe lace!). The first thing to do is to mark the point B and then use the straight edge to extend the line AB beyond the point B, as shown in the illustration below:

Then, he opens his compass (or his crude shoe-lace and pencil contraption) to any convenient length and using B as the center, he draws two arcs on either side of B to mark out C and D as shown below:

Now, he opens the compass out a bit so that it measures out any arbitrary distance greater than BC (it can be greater than CD also, it doesn't matter). Then using point C as the center, he uses the compass to draw an arc above line AB as shown in the image below:

Then, using the compass set to the same length as the previous step and using D as the center, he draws another arc above line AB, that intersects the previous arc at point E, as shown below:

Now, he uses the straight edge to connect points B and E together in a straight line as shown in the figure below:
 Voila, angle ABE is a right angle and it has been drawn without any sophisticated (for that time) instruments at all.

Now back to topic...

Now that we know how to construct a right angle with simple tools, we go back to our original figure ABC, where line AB is 48 inches long and BC is the diameter of the wooden log that the gunsmith intends to use as an indexing guide. The gunsmith then uses a ribbon or a thread dipped in glue to connect points AC, such as in the figure shown below:

Then, the gunsmith places the indexing cylinder guide so that it is touching AB and rolls it up, so that the sticky thread on AC gets wound on the outside of the cylinder. Instead of using sticky thread, the gunsmith can also mark AC with a dark charcoal marker, so that the marking gets transferred to the indexing cylinder when the cylinder is rolled on it. The procedure is shown below:

Now that the cylinder is marked properly, the gunsmith can use a sharp chisel and mallet to cut a groove along the path marked by the sticky tape. Voila, the groove is produced at the desired twist rate and we have our indexing guide, as shown in the image below:

The indexing guide was actually one of the trickiest parts that the gunsmith needed to manufacture for his manual rifling machine. As you can see, even in the middle ages without access to any sophisticated modern tools, it was possible for a skilled workman to construct an indexing guide pretty accurately.

In the next post, we will look at the next part that needs to be constructed relatively accurately, the indexing head and pin. Then we will look at how the remaining parts were built and how the machine was assembled in subsequent posts.

Sunday, March 30, 2014

Ancient Techniques of Rifling Machines - I

In the last few posts, we studied some videos of rifling techniques and we had also studied the descriptions of these techniques in detail many months earlier. The thing to note though is that all these videos showed relatively modern machinery making the rifling. In fact, the oldest machine in those videos dates to some time in the early 1900s. However, as we have seen earlier, the history of rifling dates back to about 1520, well before such automated rifling machines were invented. So how did people historically cut rifling grooves into their barrels, without the aid of modern machinery? We will attempt to reconstruct their techniques in the next series of posts, only using technologies that would have existed in the 1500s and 1600s. As we are studying the techniques, it will become fairly obvious to the reader, that historical gunsmiths would have had some pretty good skills in both woodworking and metalworking, which is why they formed separate gunsmithing guilds, which were different from carpentry and blacksmith guilds.

The first tool that any gunsmith would have used would have been a lathe. This handy tool was known to the ancient Egyptians in 300 BC and later spread to the Greeks, Indians, Chinese, Assyrians, Romans etc. The first design simply had one person alternately pulling on two ends of a rope looped around a wooden work piece, to rotate the work piece around two centers, and the other person would apply a sharp edged tool to the rotating wooden piece, to cut it into a cylinder or a tapered cylinder or a similar shape.

The following image can be found in a bas-relief carving at the tomb of Petosiris, a high priest who lived in Hermopolis, Egypt, dated to about 300 BC.

Two images of lathes, as used in ancient Egypt

The basic two-person operated lathe concept was modified by other cultures, as shown in the example from India below:

Horizontal two person lathe used in Ancient India.

The Romans came up with a lathe design that used a bow to turn the wooden work-piece. With this type of lathe, there is no need for a second person, as a single person can move the bow with one hand and manipulate the cutting tool with the other hand. However, there is lesser power applied, since the person is turning the work piece with only one arm and hence it is suitable for smaller jobs only.

The bow lathe design stayed with us for quite a long time: small bow lathes were still used by clockmakers in the early 1800s.

In the middle ages, someone got the idea of tying one end of the rope to a thin springy pole or branch and the other end to a foot pedal and the rope would loop around the wooden work piece to be turned. The craftsman would use his foot to operate the pedal and use his two hands to hold various tools against the turning wood piece.

Spring pole lathes from the middle ages

The above illustrations show some spring pole lathes from the middle ages. The left side illustration is based on a Parisian manuscript from the 13th century. As with bow lathes, spring pole lathes do not need for a second person to turn the wood piece. Spring pole lathe designs were commonly used for hundreds of years, all the way to the early part of the 20th century!

Other lathe designs included using horses, flowing water, steam and electricity to power them and lathes evolved to cut both wood and metal pieces.

Wednesday, March 26, 2014

Videos: Flow Forming

In our last post, we looked at a few videos showing how hammer forging works. In today's post, we will revisit another technique to manufacture rifling that we studied several months ago: flow forming. To refresh your memory, here's a link to that original post describing flow forming.

This is a relatively new technique and therefore there don't appear to be any videos on youtube specifically showing this process being used to make gun barrels. However, there are videos showing how a flow forming machine is used to form tubes, which is close enough for our purposes to understand the principles behind this method.

Happy viewing.

Tuesday, March 25, 2014

Videos: Hammer Forged Rifling

In our last post, we looked at a couple of videos showing how button rifling works. This is a technique we had studied many months ago. In today's post, we will revisit another technique that we had studied back in May 2010, hammer forged rifling. To refresh your memory, here's a link to the original post, describing the process of hammer forged rifling.

Now that you've read that post, let us watch a couple of videos showing the process in action. First up, we have a short video from Daniel Defense, a well known manufacturer of firearms and firearm parts here in America. While many American manufacturers prefer to use button rifling to make their barrels, Daniel Defense uses hammer forging machines.

As we mentioned in the original post, hammer forged rifling is much more prevalent in Europe than America. Here's a couple more videos of the process, from European manufacturers. The next video is from Armalon UK:

And finally, we have another video about the process, as done by the Steyr Mannlicher factory in the town of Steyr, Austria. Incidentally, the leading manufacturer of hammer forging machines in the world is an Austrian company called GFM GmbH, which is also located in the town of Steyr! It is interesting to note that Steyr Mannlicher actually uses a slightly different process to make their barrels, than most other manufacturers of hammer forged barrels. The following video describes their process and also how they do some things differently than other companies.

Happy viewing!

Monday, March 24, 2014

Videos: Button Rifling

In our last post, we looked at a video showing broach rifling in action, a subject we had studied many months ago. In today's post, we will revisit the process of button rifling. We had studied this process many months ago, here on this forum. In order to refresh your memory, here's a link to that original post describing the process of button rifling.

Now that you've read about the process, let's look at a movie displaying the process in action:

The movie above shows the process of button rifling a barrel, using a button that is pulled through the barrel. Notice how the chuck on the left rotates the barrel, as the button is being pushed through.

In the original article about button rifling that we linked above, we mentioned that there are two different ways for the button to be used. The button can be either pulled through the barrel (like the video above shows), or it can be pushed through the barrel, as the following video shows:

Note that in the second video, the barrel is not rotated as the button is pushed through. Instead, the button rotates as it is being pushed through the barrel.

Happy viewing!