One of the industries that produced significant advances in machine tools was gunsmithing. Obviously, this is an industry critical to national security, so the government took great interest in promoting improvements in quality and output capacity.

Interchangeable Parts: 1841 Rifles

Here are two rifles from two armories made 14 years apart from each other. Since both rifles are the same 1841 model rifle, the parts are fully interchangeable. The idea of interchangeable parts depends critically on precision machined parts because you have to be confident that any part in the crate can go into the device and make it work (as opposed to hand crafted parts that needed to be filed and fitted specially for each individual device).

Looking close up at the trigger assembly, you can see that there are a lot of small metal parts. You can imagine the amount of time a professional gunsmith would need to fit them together for each rifle.

Standardized Output: Gunstocks

Normally, a gunsmith would measure the buyer's body and carve a gunstock designed to fit the user's arm length, shoulder, etc. One of the sacrifices you make with standardized gunstock output is that buyers no longer got guns fitted exactly to their body. Nowadays, professional rifle shooting associations and snipers get custom made rifles measured to their body. For everyone else, there's machined gunstocks.

This gunstock lathe was invented in 1819 by Thomas Blanchard at the Springfield Armory. Using this machine to produce a gunstock took only 22 minutes from start to finish instead of the hours it would take a professional gunsmith to carve one by hand. How does it work? The solid metal template in the back of the lathe would be traced by a wheel attached to the big frame assembly.

What's a lathe? It's a type of machine tool that spins an object (typically a long block of raw material) that gets chipped away by a blade. Most lathes involve a stationary blade and the spinning block or bar of material is mounted on something that can move forwards or backwards for the blade to cut away at different parts of the block. This one is a little different because the cutting device is also moving, and the machine isn't a straight linear lathe.

In the foreground, a block of wood is mounted on the frame, and instead of a smooth tracing wheel there is a teethed cutting wheel. When the lathe is powered up, the cutter wheel spins and cuts away chips from the wood block. Guided by the wheel tracing the template, the frame moves so the cutting wheel reproduces the template as it chips away.