What size bar should I buy for a turned part?

The next stock size above the largest finished diameter, with enough left to clean up. For cold-drawn bar a 1/16 in step up is often enough on small parts; for hot-rolled bar allow more, because the scale and the decarburized skin have to come off all around.

How is hex bar measured?

Across the flats, the same way a wrench is sized. The across-corners dimension is about 1.155 times the across-flats size, which matters when you check whether hex stock fits a collet or a spindle bore.

Why does cold-drawn bar move when I machine it?

Drawing through a die leaves residual stress in the skin. Cutting a keyway, a flat or a deep slot on one side releases it and the bar bows. Stress-relieved cold-drawn bar, or turned and ground shafting, moves less.

Is 12L14 a good substitute for 1018?

For screw-machine parts that are not welded, carburized for heavy loads or used where lead is restricted, it machines much faster. Do not substitute it on welded parts or where the drawing or the customer bans leaded steel.

Which aluminum bar temper should I call out?

6061-T651 or 7075-T651 for rolled or cold-finished bar and 6061-T6511 for extruded bar. Both are stress relieved by stretching and machine with less movement than plain T6.

Standard Bar Stock Sizes

The size steps distributors stock in round, square, hex and flat bar, in fractional inch and metric, and what each common machining material is sold as. Designing to a stock size saves a turning pass or a special mill order.

Inch size increments

Commonly stocked inch bar size increments by shape
Shape	From	To	Step	mm range	Note
Round	1/8 in	1-1/2 in	1/16 in	3.2 to 38.1
Round	1-5/8 in	3 in	1/8 in	41.3 to 76.2
Round	3-1/4 in	6 in	1/4 in	82.6 to 152.4
Round	6-1/2 in	10 in	1/2 in	165.1 to 254.0	Mostly hot rolled, turned or peeled bar
Square	1/4 in	1/2 in	1/16 in	6.4 to 12.7
Square	5/8 in	1-1/2 in	1/8 in	15.9 to 38.1
Square	1-3/4 in	2-1/2 in	1/4 in	44.4 to 63.5
Square	3 in	4 in	1/2 in	76.2 to 101.6
Hex (across flats)	1/4 in	1-1/8 in	1/16 in	6.4 to 28.6	Across the flats; follows wrench sizes
Hex (across flats)	1-1/4 in	2 in	1/8 in	31.8 to 50.8
Hex (across flats)	2-1/4 in	3 in	1/4 in	57.2 to 76.2
Flat	Thickness 1/8, 3/16, 1/4, 5/16, 3/8, 1/2, 5/8, 3/4, 1, 1-1/4, 1-1/2, 2 in; widths 1/2, 3/4, 1, 1-1/4, 1-1/2, 1-3/4, 2, 2-1/2, 3, 3-1/2, 4, 4-1/2, 5, 5-1/2, 6, 7, 8, 9, 10, 11, 12 in

Typical of large distributors for cold-finished bar. Many stock every 1/16 in only up to about 1-1/2 in; sizes in between the steps are often a mill order outside 1018 and 6061.

Round bar, inch sizes

1/80.1250 in · 3.18 mm
3/160.1875 in · 4.76 mm
1/40.2500 in · 6.35 mm
5/160.3125 in · 7.94 mm
3/80.3750 in · 9.52 mm
7/160.4375 in · 11.11 mm
1/20.5000 in · 12.70 mm
9/160.5625 in · 14.29 mm
5/80.6250 in · 15.88 mm
11/160.6875 in · 17.46 mm
3/40.7500 in · 19.05 mm
13/160.8125 in · 20.64 mm
7/80.8750 in · 22.22 mm
15/160.9375 in · 23.81 mm
11.0000 in · 25.40 mm
1-1/161.0625 in · 26.99 mm
1-1/81.1250 in · 28.58 mm
1-3/161.1875 in · 30.16 mm
1-1/41.2500 in · 31.75 mm
1-5/161.3125 in · 33.34 mm
1-3/81.3750 in · 34.93 mm
1-7/161.4375 in · 36.51 mm
1-1/21.5000 in · 38.10 mm
1-5/81.6250 in · 41.28 mm
1-3/41.7500 in · 44.45 mm
1-7/81.8750 in · 47.63 mm
22.0000 in · 50.80 mm
2-1/82.1250 in · 53.97 mm
2-1/42.2500 in · 57.15 mm
2-3/82.3750 in · 60.32 mm
2-1/22.5000 in · 63.50 mm
2-5/82.6250 in · 66.68 mm
2-3/42.7500 in · 69.85 mm
2-7/82.8750 in · 73.02 mm
33.0000 in · 76.20 mm
3-1/43.2500 in · 82.55 mm
3-1/23.5000 in · 88.90 mm
3-3/43.7500 in · 95.25 mm
44.0000 in · 101.60 mm
4-1/44.2500 in · 107.95 mm
4-1/24.5000 in · 114.30 mm
4-3/44.7500 in · 120.65 mm
55.0000 in · 127.00 mm
5-1/45.2500 in · 133.35 mm
5-1/25.5000 in · 139.70 mm
5-3/45.7500 in · 146.05 mm
66.0000 in · 152.40 mm
6-1/26.5000 in · 165.10 mm
77.0000 in · 177.80 mm
7-1/27.5000 in · 190.50 mm
88.0000 in · 203.20 mm
8-1/28.5000 in · 215.90 mm
99.0000 in · 228.60 mm
9-1/29.5000 in · 241.30 mm
1010.0000 in · 254.00 mm

Square bar, inch sizes

1/40.2500 in · 6.35 mm
5/160.3125 in · 7.94 mm
3/80.3750 in · 9.52 mm
7/160.4375 in · 11.11 mm
1/20.5000 in · 12.70 mm
5/80.6250 in · 15.88 mm
3/40.7500 in · 19.05 mm
7/80.8750 in · 22.22 mm
11.0000 in · 25.40 mm
1-1/81.1250 in · 28.58 mm
1-1/41.2500 in · 31.75 mm
1-3/81.3750 in · 34.93 mm
1-1/21.5000 in · 38.10 mm
1-3/41.7500 in · 44.45 mm
22.0000 in · 50.80 mm
2-1/42.2500 in · 57.15 mm
2-1/22.5000 in · 63.50 mm
33.0000 in · 76.20 mm
3-1/23.5000 in · 88.90 mm
44.0000 in · 101.60 mm

Hex (across flats) bar, inch sizes

1/40.2500 in · 6.35 mm
5/160.3125 in · 7.94 mm
3/80.3750 in · 9.52 mm
7/160.4375 in · 11.11 mm
1/20.5000 in · 12.70 mm
9/160.5625 in · 14.29 mm
5/80.6250 in · 15.88 mm
11/160.6875 in · 17.46 mm
3/40.7500 in · 19.05 mm
13/160.8125 in · 20.64 mm
7/80.8750 in · 22.22 mm
15/160.9375 in · 23.81 mm
11.0000 in · 25.40 mm
1-1/161.0625 in · 26.99 mm
1-1/81.1250 in · 28.58 mm
1-1/41.2500 in · 31.75 mm
1-3/81.3750 in · 34.93 mm
1-1/21.5000 in · 38.10 mm
1-5/81.6250 in · 41.28 mm
1-3/41.7500 in · 44.45 mm
1-7/81.8750 in · 47.63 mm
22.0000 in · 50.80 mm
2-1/42.2500 in · 57.15 mm
2-1/22.5000 in · 63.50 mm
2-3/42.7500 in · 69.85 mm
33.0000 in · 76.20 mm

Metric bar sizes

Commonly stocked metric bar sizes in millimeters
Shape	Common sizes (mm)
Round	3, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 25, 28, 30, 32, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 100, 110, 120, 130, 140, 150, 160, 180, 200
Square	5, 6, 8, 10, 12, 14, 15, 16, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 100
Hex (across flats)	6, 8, 10, 12, 13, 14, 17, 19, 22, 24, 27, 30, 32, 36, 41, 46, 50, 55, 60
Flat	Thickness 3, 4, 5, 6, 8, 10, 12, 15, 20, 25, 30, 40, 50; widths 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 150, 200

Metric hex follows the ISO and DIN wrench sizes (10, 13, 17, 19, 22, 24 mm and so on).

By material

Bar stock by material: condition, shapes, typical round diameter range and notes
Grade	Sold as	Shapes	Typical rounds (in)	Notes
1018Carbon and alloy steel	Cold drawn	Round, Square, Hex, Flat	1/8 to 4	General-purpose low carbon. Welds well, case hardens. Larger sizes come hot rolled or turned.
12L14Carbon and alloy steel	Cold drawn	Round, Square, Hex	1/8 to 4	Leaded free-machining screw machine stock. Poor choice for welded or highly stressed parts.
1045Carbon and alloy steel	Cold drawn, or turned, ground and polished (TG&P) shafting	Round, Square, Flat	1/4 to 6	Medium carbon for shafts and pins. Induction hardens.
4140Carbon and alloy steel	Annealed, or pre-hardened (about 28 to 32 HRC)	Round, Square, Flat	1/4 to 10	Chromoly alloy. Pre-hard bar skips heat treat for tooling and shafts.
303Stainless steel	Cold drawn, annealed (condition A)	Round, Square, Hex	1/8 to 4	Free-machining austenitic. Less corrosion resistant and less weldable than 304.
304 / 304LStainless steel	Cold drawn, annealed	Round, Square, Hex, Flat	1/8 to 6	The default austenitic stainless. Gummy to machine compared with 303.
316 / 316LStainless steel	Cold drawn, annealed	Round, Square, Hex, Flat	1/8 to 6	Molybdenum grade for chlorides and marine service.
17-4 PHStainless steel	Condition A (solution treated) or H1150	Round, Hex, Flat	1/4 to 8	Precipitation hardening. Machine in A or H1150, then age to the H condition on the print.
6061Aluminum	T6 / T651 (drawn or rolled), T6511 (extruded)	Round, Square, Hex, Flat	1/8 to 8	The default machining aluminum. Every shape, widest size range.
7075Aluminum	T651 (rolled or drawn), T6511 (extruded)	Round, Square, Flat	1/4 to 8	High strength. Fewer shapes and sizes than 6061; flats are often sawn from plate.
2011Aluminum	T3	Round, Hex	1/8 to 3	Free-machining screw machine alloy. Poor corrosion resistance; not for welding or anodized cosmetics.
360 brass (C36000)Brass	Half hard (H02)	Round, Square, Hex	1/8 to 4	Free-cutting brass, the machinability benchmark (rated 100).

Approximate ranges; availability varies by distributor, especially above 4 in and in 7075, 17-4 and 316.

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Cold drawn vs hot rolled: what the tolerance means for you

Hot-rolled bar is finished at rolling temperature. It carries mill scale, a thin decarburized skin, and plus-and-minus size tolerances several times larger than cold-finished bar (on the order of ten thousandths around 1 in diameter), plus some out-of-roundness. Treat it as raw stock: plan to turn or mill every surface and allow roughly 1/16 to 1/8 in on the diameter for cleanup.

Cold-drawn (cold-finished) bar is hot-rolled bar that has been descaled and pulled through a die. It is bright, straighter and held to a couple of thousandths on small rounds, and the tolerance is minus-only, so the bar is never over its nominal size. The tolerance opens up as the size grows, and squares, hexes and flats get more than rounds. Drawing also work-hardens the skin and leaves residual stress that can bow the bar when one side is machined.

Turned, ground and polished (TG&P) shafting and precision-ground stock are tighter and straighter again, and are meant to be used as-is for shafts and pins. Stainless and aluminum cold-finished bar are held to similar small tolerances; extruded aluminum bar (T6511) is looser than rolled or drawn bar (T651). The exact limits are in the product specs (ASTM A108 and A29 for carbon and alloy, A484 for stainless, B211 and B221 for aluminum). If a surface on the drawing matches a stock size, check its tolerance against the spec before you leave it as-supplied.

Related charts, tools and guides

Tube and pipe sizes Standard plate thickness Aluminum temper chart Hardness conversion chart Metal weight calculator CNC turning Swiss machining Screw machining

Frequently asked questions

What size bar should I buy for a turned part?: The next stock size above the largest finished diameter, with enough left to clean up. For cold-drawn bar a 1/16 in step up is often enough on small parts; for hot-rolled bar allow more, because the scale and the decarburized skin have to come off all around.
How is hex bar measured?: Across the flats, the same way a wrench is sized. The across-corners dimension is about 1.155 times the across-flats size, which matters when you check whether hex stock fits a collet or a spindle bore.
Why does cold-drawn bar move when I machine it?: Drawing through a die leaves residual stress in the skin. Cutting a keyway, a flat or a deep slot on one side releases it and the bar bows. Stress-relieved cold-drawn bar, or turned and ground shafting, moves less.
Is 12L14 a good substitute for 1018?: For screw-machine parts that are not welded, carburized for heavy loads or used where lead is restricted, it machines much faster. Do not substitute it on welded parts or where the drawing or the customer bans leaded steel.
Which aluminum bar temper should I call out?: 6061-T651 or 7075-T651 for rolled or cold-finished bar and 6061-T6511 for extruded bar. Both are stress relieved by stretching and machine with less movement than plain T6.