The Museum's machine tool collection is one of the most extensive collections in the world. Included are single and multiple spindle lathes, shapers, planers, milling machines, single and multi spindle drills and grinding machines. The highlight of the machine tool collection is the machines developed in this building by Robbins and Lawrence to mass produce firearms with interchangeable parts. The remainder of the collection spans over two hundred years, representing the major advances in precision manufacturing from the earliest uses of the slide rest up to the introduction of CNC (computerized numerical controls) control, powered by foot, water and electricity.
An Inletting Machine
This inletting machine was designed by Cyrus Buckland, the Superintendent of Springfield Armory MA, in 1842. It is currently on display at the American Precision Museum.
What is an inletting machine?
This inletting machine, also known as a routing machine and lock bedding machine, cuts a recessed pocket into the gunstock in just the right shape to receive the lock plate. The iron pattern on the right guides the cutting tool on the left. This inletting machine could cut out a lock bed in as little time as 45 seconds.
How does this inletting machine work?
It has a five-sided turret set up above the gunstock; each side has a cutting tool and a stylus that are the same diameter. Next to where the gunstock lies, there is a pattern. Each stylus follows a different portion of the pattern and the cutting tool cuts that pattern into the gunstock. The machine is powered by a leather belt driven by the overhead line shaft. Since the line shaft rotates horizontally, there is a group of pulleys on the rear of the machine to change the motion through a right angle to drive the cutter spindles, which rotate on a vertical axis
There is a belt that attaches to the top of the cutter spindle. To turn the turret a lever is flipped that pops the belt off the cutter spindle and onto an idler pulley, thus freeing the turret to turn. Then the belt gets popped back down onto the new cutter spindle using the same lever that was used to push it off. Because of the complexity of the machine, an average unskilled worker could not run it; the cost would be too high if something were to go wrong.
Why is the inletting machine important?
This inletting machine was accurate in a way that was not achievable by hand in the same amount of time. It also could produce recessed gunstocks a lot faster than could have been done so earlier. It not only made interchangeable parts but it made interchangeable parts quickly.
This is a quite sophisticated machine. It had two nozzles which blew air into the recess being cut into the wood and the pattern to prevent saw dust from building up. It was not a big problem for the gun recess but if too much sawdust got into the pattern it would become distorted. This was a very early use of low pressure compressed air.
There were not many machines at the time that could rival it in its forward thinking technology. Machines of this complexity take a lot of time and money to design and develop. This successful machine proved that it was worth the time and money to invest in such a specialized machine it increased production immensely.
Inletting Machine by Anna Grallert, Collections Intern 2015