Bar stock

Bar stock
Storage area containing assorted bar stock.

Bar stock, also colloquially known as billet,[1] is a common form of raw purified metal, used by industry to manufacture metal parts and products.

Most metal produced by a steel mill or aluminium plant is formed (via rolling or extrusion) into long continuous strips of various size and shape. These strips are cut at regular intervals and allowed to cool, each segment becoming a piece of bar stock. A good analogy is pasta-making, in which lumps of dough are extruded into various cross-sectional shapes (from simple bar or tube shapes, such as linguine or penne, to more elaborate extrusions, such as rotelle, fiori, or rotini); cut into lengths; and then dried in that form.

A machine shop typically has a storage area containing a large variety of bar stock. To create a metal component, a bar of sufficient volume is selected from storage and brought to the machining area. This piece may then be sawed, milled, drilled, turned, or ground to remove material and create the final shape. In turning, for large-diameter work (typically more than 100 millimetres (3.9 in), although there is no universal threshold), a piece of the bar is cut off using a horizontal bandsaw to create a blank for each part. The blanks are then fed into a chucking lathe (chucker) which chucks each one in turn. For smaller-diameter work, the entire length of bar stock is more often fed through the spindle of the lathe. The entire bar rotates with the spindle during the part-machining cycle. When the cycle ends and one part is done, the chuck opens, the bar is pulled or pushed forward ("fed") by any of various automatic means, the chuck closes, and the next cycle begins. The last step of the cycle is to cut off the machined part from the bar, which is called "parting it off" and is achieved with a "cutoff" or "part-off" tool, a tool bit that grooves the bar all the way down to the centreline, causing the part to fall off. Then the cycle repeats.

The not-yet-cut bar protruding from the back of the spindle, rotating quickly, can present a safety hazard if it is sticking out too far and unconstrained from bending. Thus sometimes long bars must be sawn into shorter bars before being fed as "bar work" (which is the term for such work).

CNC lathes and screw machines have accessories called "bar feeders", which hold, guide, and feed the bar as commanded by the CNC control. More advanced machines may have a "bar loader" which holds multiple bars and feeds them one at a time into the bar feeder. Bar loaders are like magazines for part blanks (or pallets for milling work) in that they allow lights-out machining. The bar loader is filled with bars (or the magazine or pallet with part blanks) during working hours, and then it runs during the night unattended. Given that there is no human around to detect if something went wrong and the machine should stop, there are various kinds of sensors that are used to detect this, such as load meters, infrared beams, and, in recent years, webcams, which are placed inside the machine tool's enclosure and allow remote viewing of the cutting action.


Standard sizes throughout a supply chain

To stock every possible size of bar stock (every possible fraction of a millimetre or inch in diameter or thickness) is impossible. Thus, bar stock is stocked by metals supply houses in various standard sizes, arrayed in discrete steps. For example, round bar with diameters of even millimetres (or in the USA, on the eighths of an inch) can usually be ordered from standing stock. Bar diameters of nonstandard sizes can also be obtained, but only as a separate mill run from the rolling mill. Thus they are much more expensive than the standard sizes, can take much longer delivery time, and are not desirable as inventory for the supply house or the machine shop (because the chance of selling or using any particular custom size is slim).

Sometimes it is necessary that the bar not be very much larger than the intended part, because the metallurgical properties of some metal alloys in some finishing processes may vary by how far inside the bar the metal lies. Thus an engineering drawing will specify a certain size (or a maximum size) that the bar may start out as. These specs face the aforementioned limitation of stocking sizes versus custom mill runs; standard sizes are used wherever possible to avoid wasted expense and needless delays.

Drill rod

Drill rod is tool steel round stock with a tight tolerance diameter; it is usually ±0.0005 in (±0.013 mm). Diameters range from 0.0135 to 1.5 in (0.34 to 38 mm); in the United States diameters smaller than 2764th of an inch are made in letter drill sizes and number drill sizes, in addition to fractional sizes. Lengths are usually one or three feet (0.3 or 0.9 m). It is commonly used to make drill bits, taps, reamers, punches, dowel pins, and shafts.[2] Note that the numbered sizes are different from the drill numbered sizes starting at 52. These sizes are:[citation needed]

gauge in
52 0.0630
51 0.0660
50 0.0690
49 0.0720
48 0.0750
47 0.0770
46 0.0790
45 0.0810
44 0.0850
43 0.0880
42 0.0920
41 0.0950
40 0.0970
39 0.0990
38 0.1010
37 0.1030
36 0.1060
35 0.1080
34 0.1100
33 0.1120
32 0.1150
31 0.1200
30 0.1270
29 0.1340
28 0.1390
27 0.1430
gauge in/mm
26 0.1460
25 0.1480
24 0.1510
23 0.1530
22 0.1550
21 0.1570
20 0.1610
19 0.1640
18 0.1680
17 0.1720
16 0.1750
15 0.1780
14 0.1800
13 0.1820
12 0.1850
11 0.1880
10 0.1910
9 0.1940
8 0.1970
7 0.1990
6 0.2010
5 0.2040
4 0.2070
3 0.2120
2 0.2190
1 0.2270

Drill blanks have an undersize tolerance of +0/-0.0002 in, while reamer blanks have an oversize tolerance of -0/+0.0002 in.

Some mills also sell square stock that is held to the same tolerances under the name "drill rod".[2]

Commonly available material grades in the U.S. are A2, D2, M2, M42, O1, S7, W1, and high speed steel (including M2/M7).[3]

Ground flat stock

Ground flat stock is annealed steel that has been ground to close tolerances (compare to drill rod). There are four types of materials available: O-1 tool steel, A-2 tool steel, A-6 tool steel, and 1018 steel (low-carbon or low-carb steel). Lengths are either 18 or 36 in (457 or 914 mm) long, various widths up to 16 in (406 mm) are available, and thicknesses range from 164 to 2.875 in (0.40 to 73.0 mm).[4][5][6]

Some geometrical sizes are known as gauge plate.[7]


  1. ^ Brafield, Evans (February 2009), What's Billet?, archived from the original on 03-05-2010,, retrieved 03-05-2010. 
  2. ^ a b Brady, George S.; Clauser, Henry R.; Vaccari, John A. (2002). Materials Handbook (15th ed.). McGraw-Hill. p. 322. ISBN 9780071360760. 
  3. ^ McMaster-Carr catalog (115th ed.), McMaster-Carr, pp. 3641–3653,, retrieved 2010-12-19. 
  4. ^ Burroughs, John (March 1968), "What You Should Know About Ground Flat Stock", Popular Mechanics 129 (3): 182–185, ISSN 0032-4558, 
  5. ^ Starrett catalog 32, p. 624, archived from the original on 12-22-2010,, retrieved 12-22-2010. 
  6. ^ Starrett catalog 32, p. 634, archived from the original on 12-22-2010,, retrieved 12-22-2010. 
  7. ^ Nesbitt, Brian (2007). Handbook of Valves and Actuators. Butterworth-Heinemann. p. 17. ISBN 9781856174947. 

Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • bar stock — noun The raw stock used in various machining operations. It comes in standard cross sections and certain lengths, such as six and eight feet …   Wiktionary

  • BAR MITZVAH, BAT MITZVAH — (Heb. masc. בַּר מִצְוָה, fem. בַּת מִצְוָה; lit. son/daughter of the commandment, i.e., a person under obligation, responsible), term denoting both the attainment of religious and legal maturity as well as the occasion at which this status is… …   Encyclopedia of Judaism

  • bar code — ► NOUN ▪ a code in the form of a set of stripes of varying widths that can be read by a computer, printed on a product and identifying it for stock control …   English terms dictionary

  • Stock market bottom — A stock market bottom is a trend reversal that marks the end of a market downturn and the beginning of an upward moving trend. A bottom may occur because of the presence of a cycle, or because of panic selling as a reaction to an adverse… …   Wikipedia

  • BAR — 1. n., v., & prep. n. 1 a long rod or piece of rigid wood, metal, etc., esp. used as an obstruction, confinement, fastening, weapon, etc. 2 a something resembling a bar in being (thought of as) straight, narrow, and rigid (bar of soap; bar of… …   Useful english dictionary

  • bar — 1. n., v., & prep. n. 1 a long rod or piece of rigid wood, metal, etc., esp. used as an obstruction, confinement, fastening, weapon, etc. 2 a something resembling a bar in being (thought of as) straight, narrow, and rigid (bar of soap; bar of… …   Useful english dictionary

  • Bar — A graphical representation of a stock s movement that usually contains the open, high, low and closing prices for a set period of time. For example, if a technical trader is working with daily data, one bar is the set of quotes for one day. In… …   Investment dictionary

  • Stock Car — Das Logo der NASCAR Serie. NASCAR Rennen auf dem Texas Motor Speedway 2008 Die NASCAR (National Association for Stock Car Auto Racing) ist ein großer …   Deutsch Wikipedia

  • Stock Keeping Unit - SKU — A store s or catalog s product and service identification code, often portrayed as a machine readable bar code that helps the item to be tracked for inventory. A stock keeping unit (SKU) does not need to be assigned to physical products in… …   Investment dictionary

  • bar code — universal product code; UPC A code, consisting of an array of parallel rectangular bars and spaces, printed on a package for sale in a retail outlet. When an optical scanner (bar code reader) reads the bar code at the checkout till (see… …   Big dictionary of business and management

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”