What does "billet" mean?

They are machined out of a solid block of material. They are usually nicer and can be customized. Standard lowers and uppers are cast, then they machine the casting.
 
its a block of Aluminum in this case, but can be other metals. Think of it as a large extruded piece of unfinished metal.
 
Lowers are either cast, forged, or billet.

Cast is when liquid metal is poured into a mold.

Forged is when metal is heated and then stamped into the desired shape.

Billet is metal in solid block form. In this case, a block of aluminum that is then CNC machined into an AR15 reciever. The benifits of billet is lower cost for short runs (no molds or stamping machines), more easily customized, and less likely to have issues related to casting impurities or voids.
 
Armedsask said:
Lowers are either cast, forged, or billet.

Cast is when liquid metal is poured into a mold.

Forged is when metal is heated and then stamped into the desired shape.

Billet is metal in solid block form. In this case, a block of aluminum that is then CNC machined into an AR15 reciever. The benifits of billet is lower cost for short runs (no molds or stamping machines), more easily customized, and less likely to have issues related to casting impurities or voids.
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Which is sort of funny, because "billet" is cast too. I think the word billet is way overused, and really has no meaning by itself. As you say, it may be a better quality casting, but I've seen lots of billet with extra stuff in it, and air pockets.

It's the fault of those damn hot rod builders. ;)

BB
 
Aluminum extrusions are aluminum heated until it is soft but not liquid and then forced through a die. Think of it like those Play-do spaghetti making things.

Most "billet" lowers would be machined from a rectangular bar cut into smaller pieces. Those rectangular bars would be extruded. I would think 99% of "billet" lowers are from an extruded bar.

Billet has become one of those words that people associate with being better. Like calling something "space age". Is billet better than cast? Not really. They might look nicer simply due to the nature of casting but with most things they are only as good as the builder.
 
beeperboy said:
Which is sort of funny, because "billet" is cast too. I think the word billet is way overused, and really has no meaning by itself. As you say, it may be a better quality casting, but I've seen lots of billet with extra stuff in it, and air pockets.

It's the fault of those damn hot rod builders. ;)

BB
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Billet isnt cast. Its rolled and shaped, one step short of a forging. There is no comparing billet to castings when it comes to the integrity of raw materials unless your using a high pressure or investment cast.

If you are seeing billet with quality issues i suggest you change material suppliers. There is a reason flight critical aircraft parts are made from billet or forgings and not castings.
 
Power Pill said:
so is billet better quality?
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Cosmetically? Yeah forsure. A machinist thats worth his weight can design and spec kick ass lowers. example, ATRS lowers, Spikes, LaRue etc.

Strength? perhaps that's splitting hairs, especially when said materials are used as an AR-15 lower. In other applications machined "billet" and forgings are typically more durable then castings.
 
Forging Industry Association

-well, of course they are biased to forging.

How FORGINGS compare to Castings

Forgings are stronger. Casting cannot obtain the strengthening effects of hot and cold working. Forging surpasses casting in predictable strength properties - producing superior strength that is assured, part to part.
Forging refines defects from cast ingots or continuous cast bar. A casting has neither grain flow nor directional strength and the process cannot prevent formation of certain metallurgical defects. Preworking forge stock produces a grain flow oriented in directions requiring maximum strength. Dendritic structures, alloy segregation's and like imperfections are refined in forging.
Forgings are more reliable, less costly. Casting defects occur in a variety of forms. Because hot working refines grain pattern and imparts high strength, ductility and resistance properties, forged products are more reliable. And they are manufactured without the added costs for tighter process controls and inspection that are required for casting.
Forgings offer better response to heat treatment. Castings require close control of melting and cooling processes because alloy segregation may occur. This results in non-uniform heat treatment response that can affect straightness of finished parts. Forgings respond more predictably to heat treatment and offer better dimensional stability.
Forgings' flexible, cost-effective production adapts to demand. Some castings, such as special performance castings, require expensive materials and process controls, and longer lead times. Open-die and ring rolling are examples of forging processes that adapt to various production run lengths and enable shortened lead times.
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How FORGINGS compare to Machined Bar/Plate

Forgings offer broader size range of desired material grades. Sizes and shapes of products made from steel bar and plate are limited to the dimensions in which these materials are supplied. Often, forging may be the only metalworking process available with certain grades in desired sizes. Forgings can be economically produced in a wide range of sizes from parts whose largest dimension is less than 1 in. to parts weighing more than 450,000 lbs.
Forgings have grain oriented to shape for greater strength. Machined bar and plate may be more susceptible to fatigue and stress corrosion because machining cuts material grain pattern. In most cases, forging yields a grain structure oriented to the part shape, resulting in optimum strength, ductility and resistance to impact and fatigue.
Forgings make better, more economical use of materials. Flame cutting plate is a wasteful process one of several fabricating steps that consumes more material than needed to make such parts as rings or hubs. Even more is lost in subsequent machining.
Forgings yield lower scrap; greater, more cost-effective production. Forgings, especially near-net shapes, make better use of material and generate little scrap. In high-volume production runs, forgings have the decisive cost advantage.
Forgings require fewer secondary operations. As supplied, some grades of bar and plate require additional operations such as turning, grinding and polishing to remove surface irregularities and achieve desired finish, dimensional accuracy, machine-ability and strength. Often, forgings can be put into service without expensive secondary operations.
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polskadude said:
They are machined out of a solid block of material. They are usually nicer and can be customized. Standard lowers and uppers are cast, then they machine the casting.
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I can't believe this thread went this far without anyone correcting the above.

Standard lowers and uppers are forged. There used to be some aftermarket cheapie lowers that were castings, but the process developed an internet black eye over the years, to the point that every maker I know of abandoned casting of lowers.

All aluminum forms start out by pouring liquid aluminum into a mould to make an ingot, that doesn't mean they can be considered to be castings. A casting uses the part as-solidified, this has important impacts on the structure of the alloy. Castings have porosity created by gas evolution as the melt cooled, they have the potential for shrinkage tearing, and they have segregation created as the alloying elements separated from each other during solidification.

Billets, plates, sheets, rods and bars are made by forging ingots down to rectangular or round shapes. The forging process closes the porosity, and more importantly homogenizes the chemistry and causes the structure to recrystallize into a wrought structure, rather than a cast/dendritic form. Note that this does not mean parts made from these shapes can be considered forgings, either. Again, to be a forging the part must leave the die in essentially finished shape. A billet, bar, etc. will require substantial machine cutting, which will result in a loss of directional grain flow which is a benefit of a true forging.

In terms of simple performance, the standard forged AR lower is almost certainly the best. The point of the billet lower is get a distinct appearance and a custom look. The manufacturer could also choose to make the part stronger by simply leaving more material in some areas. The practical performance of the billet material will be indistinguishable from the theoretically stronger forging.
 
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