Saginaw Steering Gear’s Secret Weapon
By Charles Brown

Everybody had a “secret weapon” in WWII. The British had ASDIC (the U.S. Navy later called it SONAR) and RADAR, Germany the V1 and V2 rockets and very late in the war jet aircraft like the ME 262 and the U. S. had the Manhattan Project which produced the first atomic bombs.

Saginaw Steering Gear, the all time champion low cost, high quality producer of the M1919 air cooled Browning .30 caliber ground type machine guns had one too. It was the Malleable Iron Division of General Motors Corporation formed in 1917 to produce 100% interchangeable cast iron parts for America’s rapidly expanding automotive empire. Casting parts like axle and clutch housings and suspension parts speeded up production and more importantly reduced costs, which enabled the increased sales of anything automotive.

Saginaw Steering Gear started life in 1906 as Jacox, the Jackson, Church and Wilcox Company making automotive chassis parts for Buick, then an independent auto manufacturer. During World War I, Malleable Iron got into the arms business by manufacturing mortar shells and tank track parts. In 1919, General Motors bought the common stock for 1.1 million dollars acquiring three plants: Malleable Iron, Grey Iron Foundry, and Saginaw Steering Gear. GM called the acquisition Saginaw Products Division of General Motors Corporation.

Control of the Grey Iron Foundry eventually passed to the Chevrolet Division of GM and in 1928 Saginaw Products split into Saginaw Steering Gear and Malleable Iron, both full Divisions in GM’s business structure.

In 1936, Malleable Iron developed a pearlitic malleable iron formulation suitable for casting automotive parts trade named Armasteel (sometimes seen spelled ArmaSteel in GM documents). Pearlitic malleable iron is formed by controlled additions of minerals during the melting process and careful heat treating at 1,650 degrees F after which the cast part is removed from the mold and rapidly cooled. GM used this alloy to cast pistons, rocker arms and transmission parts. Casting of parts to near finished size greatly reduced costs for tooling, machine time, labor and wasted material and could produce parts nearly impossible to forge or machine that were 100% interchangeable.

Conventional wisdom has it that the U.S. was totally unprepared for WWII – which is not completely accurate. The Industrial Services Division of the Ordnance Department was shopping around for non-traditional producers of weapons as early as 1937 applying the lessons learned in WWI regarding the traditional commercial and government facility’s inability to mass produce firearms and everything else needed in wartime. Saginaw Steering Gear was approached about the manufacture of machine guns and agreed to undertake an engineering study contract and provide sample weapons, drawings, tooling and the production data necessary to set up a plant for air cooled Browning .30 caliber machine guns. There was only one problem: the War Department had no funds available to pay for these services.

An extremely isolationist and stingy public, and their congress ever paranoid about a large standing army, didn’t get very interested in funding anything connected with the military until Germany invaded Poland on September 1, 1939 dragging France and Britain into the conflict. It was the WWI alliance blowback all over again with all the usual suspects except that initially the aggrieved party was Poland instead of Belgium.

This event seemed to get everybody’s attention and by June 1940 money became available for the Saginaw pilot program and in September serious negations were underway for actually mass producing the now standard M1919A4 Browning air cooled machine gun.

Government arsenals and traditional firearms manufactures pooh-poohed the whole idea of a car parts maker mass producing machine guns. Apparently the fact that their cars started every morning didn’t enter into the thought process.

Saginaw took the position that “Parts is parts.” After nearly 35 years of the mass production of precision components with 100% interchangeability and carrying no baggage from previously manufacturing firearms they were very good at what they did and they knew it. The engineering and production management culture at Saginaw was to constantly ask, “Why are we doing this and why are we doing it this way.” This philosophy is an excellent way to run anything from a hot dog pushcart to a plant that makes machine guns.

Saginaw built, equipped and staffed a plant for the production of M1919A4’s in record time while at the same time producing some sample guns in an existing plant. The samples rolled off the production line seven months ahead of schedule and more importantly ahead of Rock Island Arsenal’s pilot models.

In November of 1941, due to some GM management shuffles, William Doerfner, generally credited with being the driving force behind the development of Armasteel and the General Manager of the Malleable Iron Division, became the General Manager of Saginaw Steering Gear. It wasn’t very long after Doerfner’s arrival when the subject of the possibility of casting some of the M1919A4’s parts surfaced. Saginaw’s engineers reasoned that if cast parts worked in high stress components of internal combustion engines they should work in firearms.

The biggest advantage of cast parts was the saving of the time and machine tools necessary to fabricate a part from a billet of ordnance grade steel. Castings also allowed what were previously assemblies of parts to be cast in one piece saving fabrication time and even more machine time and tooling. Casting of parts also reduced scrap and conserved steel, an important wartime consideration.

When Saginaw began working on cast parts an interesting situation developed. In the normal order of business, parts drawings were produced at Rock Island Arsenal (RIA) or some other ordnance facility and sent to the various manufacturers. Since RIA had no experience with cast small arms parts Saginaw produced the drawings and sketches in their own drafting room and sent them to RIA for review and approval. The Ordnance Department had no procedure for filing drawings received from contractors so they did the next best thing; they hand wrote the drawing number of the affected part and filed it away with their own drawings. Many of these Saginaw produced drawings were archived on 35mm film along with official Ordnance Department drawings and survived to this day.

By September of 1942, cast M1919 part such as the back plate, cover latch, top cover, lock frame and a complete receiver (casing) were being produced for a durability test which took place in November of 1942. The cast parts passed with flying colors and went on to production, however, the cast receiver was not produced in quantity even though the drawing for this part in the status of an alternate method of manufacture was maintained at RIA until 1954.

Saginaw then took a close look at the bottom plate of the M1919s that required much machining and developed a cast version and at the same time began working on a back plate casting that satisfied the Ordnance Department’s requirement for the cut-out at the bottom of the pistol grip that housed the spring used to latch up the stem of the T&E when the weapon was moved off the tripod.

The original M1919A4 Flexible back plate with pistol grip consisted of the back plate, the grip, the pin that locked the grip to the back plate, the aluminum one piece stock (pistol grip), two escutcheons, the stock screw and the top cover latch stop screw with its tapped hole. Saginaw’s cast version was a single part. Not only did the one piece casting eliminate making and assembling the other parts, it eliminated the labor and tooling associated with drilling the top cover latch stop screw and tolerances problems that ever bedevil mechanical and industrial engineers working with assemblies of parts.

The great axiom that these engineers live and die by is: “The greater the number of parts in an assembly the greater the chance of “stacking tolerance” problems. All manufactured parts have tolerances. Occasionally these tolerances accumulate or stack in a particular set of parts to produce an assembly that does not work or fails prematurely. Obviously, with a single part, it is much easier to control this problem and since you do not have to manufacture all the other parts separately, each with their own tolerances, there is a great saving of material, machine time, tooling and labor costs for both manufacture and assembly.

The top cover is another example; the forged/machined top cover had 8 parts made into an assembly that consisted of the cover itself, the cover extractor cam and two different rivets, the latch plate and two rivets and the top cover extractor spring stud. Next all these parts had to be assembled. The cast version had two parts the cast cover and the top cover extractor spring stud.

Some M1919 parts castings like the trunnion block didn’t cut down on the number of parts (generally there were only two although some cast trunnions omitted the cartridge bunter plate and “flame hardened” the vertical area of the feed way) as much as it simplified fabrication.

While Saginaw was busy designing and implementing the cast parts, it was also making parts by the traditional forge/machining method as nothing was allowed to interfere with wartime production quotas.

The top cover latch design of the M1919, which performed the dual function of keeping the top cover locked closed and the back plate from being dismounted, was and is roundly and justifiably criticized as being overly difficult to operate mostly because of the adoption of the M1919A4 rear sight base riveted to the left side plate which required a retracting handle with a small grasping area to be riveted to the top of the latch. Saginaw solved the manufacturing problem first by casting the latch with an integral handle eliminating the separate handle and the two attaching rivets.

At least as early as August 1943 Saginaw was working on a better top cover latch which was adopted in October of 1943. The new latch had a spring loaded plunger at the rear that when pushed forward allowed the back plate to be removed. This “pushbutton” style latch went on to be the preferred latch for all the M1919’s. This design eliminated the flat spring on the original latch and replaced it with a spring loaded plunger that engaged the front V notch detent in the top plate. This is likely the one and only case when the new and improved part had more components than the original. The new top cover latch seems to be closely associated with the adoption of the M1919A6 and is often referred to as the “A6 latch.”

Eventually the idea of casting parts caused the Ordnance Department to issue specifications for several different alloys of pearlitic malleable iron Class A and Class B each used for slightly different purposes. Saginaw is the only known WWII user of cast parts for the M1919’s. One reason for this is that about the time that castings started to be used in mass production about the last quarter of 1943, Saginaw was the only manufacturer in regular production of the .30 caliber ground type air cooled Brownings.

Eventually bottom plates, back plates, top plates, top covers, top cover latches, lock frame, front barrel bearing, trunnion block, rear sight base, the A6 bipod head, trigger, flash hider, and short round stops were being produced by casting. Cast M1918A2 BAR receivers and trigger guard assemblies also were produced.

Post WWII, RIA and its sub-contractors continued to cast parts for maintenance spares, overhaul and production of new weapons. The cast parts are fairly easy to spot because in unfinished areas they exhibit a pebbly or grained surface.

The introduction and refinement of this technology enabled Saginaw Steering Gear and their secret weapon, the Malleable Iron Division, to increase production, conserve material and improve the weapon while lowering the cost to the government all at the same time – something unheard of today.

While Saginaw ceased production of machine guns in mid 1945, The Malleable Iron Division, later known as the Central Foundry Division, continued to use Armasteel principally to cast crankshafts for Pontiac and Buick. Armasteel cranks are thought by some gear heads to be stronger than drop forged crankshafts. GM stopped using the name Armasteel in 1966 when the lawyers at GM thought the term misleading because Armasteel is not actually steel. The Armasteel trademark expired in 2002 and was not renewed.

This article first appeared in Small Arms Review SAW (December 2012)
and was posted online on November 2, 2012


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