AS568 O-Ring Sizes

Let’s start super basic with standard AS568 o-ring sizes before we get into the details of static o-ring groove design.

In the US, the most common o-ring standard is called Aerospace Size Standard for O-Rings (AS-568 ).  Each o-ring size is officially written as AS568-XXX, where the -XXX denoted a particular size of o-ring.  In practice, this gets shortened to simply “-XXX” and is commonly referred to as a “dash number”.  So if you are specifying an o-ring size, you might ask for a -015 or -314 o-ring.

as568 o-ring inner diameter cross section cs

The first digit of this dash number specifies the o-ring’s cross-sectional diameter, or “CS”.:

-0XX means 0.070″ CS diameter
-1XX means 0.103″ CS diameter
-2XX means 0.139″ CS diameter
-3XX means 0.210″ CS diameter
-4XX means 0.275″ CS diameter

 

The second two digits simply specify the inner diameter of the o-ring in sequential size order.  You need to refer to tables to know the actual size of the o-rings.  Fortunately, the tables are easy to find:

-001 thru -114 O-Rings
-115 thru -178 O-Rings
-201 thru -264 O-Rings
-265 thru -349 O-Rings
-350 thru -439 O-Rings

Make sense?  Now that we understand o-ring sizes, here’s a tool to help you size and design grooves for your static o-ring seals.

Static O-Ring Groove Design

If you don’t understand it already, start by reading standard AS568 O-Ring Sizing.   Once you understand o-ring sizes, let’s discuss how to use o-rings for low-pressure (0-200 psig) static sealing applications.  These guidelines will work for higher pressure applications but you’ll have to do some additional homework when you get into thousands of psi.

There are two design scenarios: face sealing (o-ring is sandwiched between two plates) and radial sealing (o-ring is sandwiched between two cylinders).

static o-ring groove face seal radial sealing

There three groove design factors:

O-Ring stretch (only applicable to radial sealing applications)
This says that the o-ring should be stretched between 2% and 5% when it is installed on the cylinder against its inner diameter.  An o-ring groove with a 10.0″ OD should be mated to an o-ring between 9.524″ (10″/1.05 => 5% stretch) and 9.756″ (10″/1.025 => 2% stretch).  O-ring stretch does not apply to face seal applications.  With a face seal, simply match the ID of the o-ring to the OD of the o-ring groove.

O-Ring Compression
This says how much interference this is before compressing the o-ring.  For static application, I recommend 30-40% compression, so let’s say 35%.  Since o-ring CS diameters are denoted by the first digit of their dash number, this is easy:
-0XX groove depth = 0.070 – 0.070 * 35% = 0.0455″ groove depth
-1XX groove depth = 0.103 – 0.103 * 35% = 0.0670″ groove depth
-2XX groove depth = 0.139 – 0.139 * 35% = 0.0904″ groove depth
-3XX groove depth = 0.210 – 0.210 * 35% = 0.1365″ groove depth
-4XX groove depth = 0.275 – 0.275 * 35% = 0.1788″ groove depth

Percent Fill
Since an o-ring is being compressed, it needs a volume to “squish” into.  This means the volume of the o-ring groove needs to be greater than the volume of the o-ring.  This should be obvious, but it tends to evade the logic of many engineers.  The volume of the o-ring itself should only occupy 65-95% of the volume of the o-ring gland.  This is an area of debate, but guess what we are going to do?  Yes, the middle, because it is easier.   Let’s go with 80% fill and call it a day.

O-Ring Groove Width
Since we already derived the groove depth from the o-ring compression, and we already said that we are going to target an 80 percent fill, all we have to do is simple match to derive the o-ring groove width.  (By the way, if you are a nerdy engineer, yes, I understand that the math we are using is not mathematically perfect based on the volume of a torus, but it is way more than close enough.)
Groove width * Groove Depth * 80% = PI * CS^2 / 4, so,
Groove Width = (PI * CS^2 / 4) / (Groove Depth * 0.8)
-0XX groove = (PI* 0.070^2/4) / (0.0455″ * 0.8) =  0.106″ groove width
-1XX groove  = (PI* 0.103^2/4) / (0.0670″ * 0.8) =  0.156″ groove width
-2XX groove  = (PI* 0.139^2/4) / (0.0904″ * 0.8) =  0.210″ groove width
-3XX groove  = (PI* 0.210^2/4) / ( 0.1365″ * 0.8) =  0.317″ groove width
-4XX groove  = (PI* 0.275^2/4) / ( 0.1788″ * 0.8) =  0.415″ groove width

That’s as simple as I can make it.  If you are still confused, please comment below or reach out.

Hardness and Tensile Strength of Steels: Brinell and Rockwell Scales

Following is an estimate of the relationship between various hardness scales and the tensile strength of standard steels.  It should be considered as a general comparison not applicable to all materials:

Hardness Conversion Table

Brinell Hardness Rockwell Hardness Scales
Tungsten Carbide Ball 3000 KG A Scale 60 kg B Scale 100 kg C Scale 150 kg Tensile Stength (approx.)
86 68
85 68
85 67
767 85 66
757 84 66
745 84 65
733 84 65
722 83 64
712 83 64
710 83 63
698 83 62
684 82 62
682 82 62
670 82 61
656 81 60
653 81 60
647 81 60
638 81 59 329,000
630 81 59 324,000
627 80 59 323,000
601 80 57 309,000
578 79 56 297,000
555 78 55 285,000
534 78 54 274,000
514 77 52 263,000
495 76 51 253,000
477 76 50 243,000
461 75 48 235,000
444 74 47 225,000
429 73 46 217,000
415 73 44 210,000
401 72 43 202,000
388 71 42 195,000
375 71 40 188,000
363 70 39 182,000
352 69 38 176,000
341 69 37 170,000
331 68 36 166,000
321 68 34 160,000
311 67 33 155,000
302 66 32 150,000
293 66 31 145,000
285 65 30 141,000
277 65 29 137,000
269 64 28 133,000
262 64 27 129,000
255 63 25 126,000
248 62 24 122,000
241 62 100 23 118,000
235 61 99 22 115,000
229 61 98 20 111,000
223 97 20
217 96 18 105,000
212 96 17 102,000
207 95 16 100,000
201 94 15 98,000
197 93 95,000
192 92 93,000
187 91 90,000
183 90 89,000
179 89 87,000
174 88 85,000
170 87 83,000
167 86 81,000
163 85 79,000
156 83 76,000
149 81 73,000
143 79 71,000
137 76 67,000
131 74 65,000
126 72 63,000
121 70 60,000
116 68 58,000
111 66 56,000

GD&T (ASTM Y14.5)

Geometric Dimensioning and Tolerances: Symbols (ASTM Y14.5-2009)

Angularity – The condition of a surface, centerplane or axis being exactly at a specified angle
Circularity – A condition where all points of a surface of revolution, at any section perpendicular to a common axis, are equidistant from that axis.
Concentricity – The condition where the median points of all diametrically opposed elements of a cylinder (or a surface of revolution) are congruent with the axis of a datum feature.
Cylindricity – A condition of a surface of revolution in which all points of the surface are equidistant from a common axis.

Flatness – The condition of a surface having all of its elements in one plane.

Parallelism – The condition that results when a surface, axis or centerplane is exactly parallel to a datum.
Perpendicularity – The condition that results when a surface, axis, or centerplane is exactly 90° to a datum.
PositionThe zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position.
Profile of a Line Control – A geometric tolerance that limits the amount of error for line elements relative to their true profile.
Profile of a Surface Control – A geometric tolerance that limits the amount of error a surface can have relative to its true profile.
Circular RunoutA composite control that affects the form, orientation, and location of circular elements of a part feature relative to a datum axis.
Straightness (Axis or Centerplane) – The condition where an axis is a straight line (or, in the case of a centerplane, each line element is a straight line).
Symmetry – The condition where the median points of all opposed elements of two or more feature surfaces are congruent with the axis or centerplane of a datum feature.
Total Runout – A composite control affecting the form, orientation, and location of all surface elements of a diameter (or surface) relative to a datum axis.

Geometric Dimensionsing and Tolerances: Modifiers (ASTM Y14.5-2009)

All-Around Symbol – A circle placed on the bend of the leader line of a profile control.
Basic Dimension – A numerical value used to describe the theoretically exact size, true profile, orientation, or location of a feature or datum target.
Between Symbol – A double ended arrow that indicates the tolerance zone extends to include multiple surfaces.
Controlled Radius – A radius with no flats or reversals allowed. The symbol for a controlled radius is “CR.”
Datum Feature – A part feature that contacts a datum.
Datum Target – A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Feature Control Frame – A rectangular box that is divided into compartments within which the geometric characteristic symbol, tolerance value, modifiers, and datum references are placed.
Least Material Condition – The condition in which a feature of size contains the least amount of material everywhere within the stated limits of size.
Maximum Material Condition – The condition in which a feature of size contains the maximum amount of material everywhere within the stated limits of size.
Projected Tolerance Zone – A tolerance zone that is projected above the part surface.
Radius – A straight line extending from the center of an arc or circle to its surface.

Reference Specification for Geometric Dimensioning and Tolerances:
ASTM Y14.5-2009

Metric Hex Bolt Head Size

Do you ever struggle to remember the relationship between a metric hex bolt thread size and the related hex head size (between the flats, or ‘wrench’ size).

Or, do you have a design with limited clearance?  Use this table to see if you have room, but don’t forget to check that you have enough room for a socket or a wrench to get in there.  Otherwise, you might be better off using a Socket Head Cap Screw (SHCS) instead of a Hex Head fastener.

The first column (ANSI/ISO) is pertinent to ‘standard’ metric  hex bolts:

Bolt Diameter
(mm)
Head/Wrench Size
(mm)
ANSI/ISO DIN JIS DIN/ISO
Heavy Hex
4 7 7 7
5 8 8 8
6 10 10 10
7 11
8 13 13 12
10 16 17 14
12 18 19 17 22/21*
14 21 22 19
16 24 24 22 27
18 27
20 30 30 34/32*
ANSI – American National Standards Institute
ISO – International Organization for Standardisation
DIN – Deutsches Institut fur Normung
JIS – Japanese Industrial Standard
* Indicates ISO standard.

Learn more about threaded joints.

 

National Pipe Thread (NPT) Tap Drill Size

Below is the National Pipe Thread – NPT Tap Drill Size Chart.  It tells us what size hole must be drilled to begin tapping the tapered NPT thread.

Standard NPT Tap Drill Sizes

NPT Size
 Tap Drill Size (in.)
Decimal Equivalent (in.)
1/16 – 27
“C”
0.242
1/8 – 27
“Q”
0.332
1/4 – 18
7/16
0.438
3/8 – 18
9/16
0.562
1/2 – 14
45/64
0.703
3/4 – 14
29/32
0.906
1.0 – 11•1/2
1•9/64
1.141
1•1/4 – 11•1/2
1•31/64
1.484
1•1/2 – 11•1/2
1•23/32
1.719
2.0 – 11•1/2
2•3/16
2.188
2•1/2 – 8
2•39/64
2.609
3.0 – 8
3•15/64
3.234

Metric Tap Drill Sizes
Standard UNC Tap Drill Sizes
Standard UNF Tap Drill Sizes

Drill Size Chart – Standard Fractional, Letter, Gauge and Metric

Why do you need a Drill Size Chart?  Because what the hell is the diameter of a size “F” drill bit?

Drill size Diameter (in) Diameter (mm)
#107 0.0019 0.0483
0.05 mm 0.0020 0.0500
#106 0.0023 0.0584
#105 0.0027 0.0686
#104 0.0031 0.0787
#103 0.0035 0.0889
#102 0.0039 0.0991
0.1 mm 0.0039 0.1000
#101 0.0043 0.1092
#100 0.0047 0.1194
#99 0.0051 0.1295
#98 0.0055 0.1397
#97 0.0059 0.1499
#96 0.0063 0.1600
#95 0.0067 0.1702
#94 0.0071 0.1803
#93 0.0075 0.1905
0.2 mm 0.0079 0.2000
#92 0.0079 0.2007
#91 0.0083 0.2108
#90 0.0087 0.2210
#89 0.0091 0.2311
#88 0.0095 0.2413
#87 0.0100 0.2540
#86 0.0105 0.2667
#85 0.0110 0.2794
#84 0.0115 0.2921
0.3 mm 0.0118 0.3000
#83 0.0120 0.3048
#82 0.0125 0.3175
#81 0.0130 0.3302
#80 0.0135 0.3429
#79 0.0145 0.3680
1/64 in 0.0156 0.3969
0.4 mm 0.0158 0.4000
#78 0.0160 0.4064
#77 0.0180 0.4572
0.5 mm 0.0197 0.5000
#76 0.0200 0.5080
#75 0.0210 0.5334
#74 0.0225 0.5715
0.6 mm 0.0236 0.6000
#73 0.0240 0.6096
#72 0.0250 0.6350
#71 0.0260 0.6604
0.7 mm 0.0276 0.7000
#70 0.0280 0.7112
#69 0.0292 0.7417
#68 0.0310 0.7874
1/32 in 0.0313 0.7938
0.8 mm 0.0315 0.8000
#67 0.0320 0.8128
#66 0.0330 0.8382
#65 0.0350 0.8890
0.9 mm 0.0354 0.9000
#64 0.0360 0.9144
#63 0.0370 0.9398
#62 0.0380 0.9652
#61 0.0390 0.9906
1 mm 0.0394 1.0000
#60 0.0400 1.0160
#59 0.0410 1.0414
#58 0.0420 1.0668
#57 0.0430 1.0922
1.1 mm 0.0433 1.1000
#56 0.0465 1.1811
3/64 in 0.0469 1.1906
1.2 mm 0.0472 1.2000
1.3 mm 0.0512 1.3000
#55 0.0520 1.3208
#54 0.0550 1.3970
1.4 mm 0.0551 1.4000
1.5 mm 0.0591 1.5000
#53 0.0595 1.5113
1/16 in 0.0625 1.5875
1.6 mm 0.0630 1.6000
#52 0.0635 1.6129
1.7 mm 0.0669 1.7000
#51 0.0670 1.7018
#50 0.0700 1.7780
1.8 mm 0.0709 1.8000
#49 0.0730 1.8542
1.9 mm 0.0748 1.9000
#48 0.0760 1.9304
5/64 in 0.0781 1.9844
#47 0.0785 1.9939
2 mm 0.0787 2.0000
#46 0.0810 2.0574
#45 0.0820 2.0828
2.1 mm 0.0827 2.1000
#44 0.0860 2.1844
2.2 mm 0.0866 2.2000
#43 0.0890 2.2606
2.3 mm 0.0906 2.3000
#42 0.0935 2.3749
3/32 in 0.0938 2.3813
2.4 mm 0.0945 2.4000
#41 0.0960 2.4384
#40 0.0980 2.4892
2.5 mm 0.0984 2.5000
#39 0.0995 2.5273
#38 0.1015 2.5781
2.6 mm 0.1024 2.6000
#37 0.1040 2.6416
2.7 mm 0.1063 2.7000
#36 0.1065 2.7051
7/64 in 0.1094 2.7781
#35 0.1100 2.7940
2.8 mm 0.1102 2.8000
#34 0.1110 2.8194
#33 0.1130 2.8702
2.9 mm 0.1142 2.9000
#32 0.1160 2.9464
3 mm 0.1181 3.0000
#31 0.1200 3.0480
3.1 mm 0.1221 3.1000
1/8 in 0.1250 3.1750
3.2 mm 0.1260 3.2000
#30 0.1285 3.2639
3.3 mm 0.1299 3.3000
3.4 mm 0.1339 3.4000
#29 0.1360 3.4544
3.5 mm 0.1378 3.5000
#28 0.1405 3.5687
9/64 in 0.1406 3.5719
3.6 mm 0.1417 3.6000
#27 0.1440 3.6576
3.7 mm 0.1457 3.7000
#26 0.1470 3.7338
#25 0.1495 3.7973
3.8 mm 0.1496 3.8000
#24 0.1520 3.8608
3.9 mm 0.1535 3.9000
#23 0.1540 3.9116
5/32 in 0.1563 3.9688
#22 0.1570 3.9878
4 mm 0.1575 4.0000
#21 0.1590 4.0386
#20 0.1610 4.0894
4.1 mm 0.1614 4.1000
4.2 mm 0.1654 4.2000
#19 0.1660 4.2164
4.3 mm 0.1693 4.3000
#18 0.1695 4.3053
11/64 in 0.1719 4.3656
#17 0.1730 4.3942
4.4 mm 0.1732 4.4000
#16 0.1770 4.4958
4.5 mm 0.1772 4.5000
#15 0.1800 4.5720
4.6 mm 0.1811 4.6000
#14 0.1820 4.6228
#13 0.1850 4.6990
4.7 mm 0.1850 4.7000
3/16 in 0.1875 4.7625
4.8 mm 0.1890 4.8000
#12 0.1890 4.8006
#11 0.1910 4.8514
4.9 mm 0.1929 4.9000
#10 0.1935 4.9149
#9 0.1960 4.9784
5 mm 0.1969 5.0000
#8 0.1990 5.0546
5.1 mm 0.2008 5.1000
#7 0.2010 5.1054
13/64 in 0.2031 5.1594
#6 0.2040 5.1816
5.2 mm 0.2047 5.2000
#5 0.2055 5.2197
5.3 mm 0.2087 5.3000
#4 0.2090 5.3086
5.4 mm 0.2126 5.4000
#3 0.2130 5.4102
5.5 mm 0.2165 5.5000
7/32 in 0.2188 5.5563
5.6 mm 0.2205 5.6000
#2 0.2210 5.6134
5.7 mm 0.2244 5.7000
#1 0.2280 5.7912
5.8 mm 0.2284 5.8000
5.9 mm 0.2323 5.9000
A 0.2340 5.9436
15/64 in 0.2344 5.9531
6 mm 0.2362 6.0000
B 0.2380 6.0452
6.1 mm 0.2402 6.1000
C 0.2420 6.1468
6.2 mm 0.2441 6.2000
D 0.2460 6.2484
6.3 mm 0.2480 6.3000
1/4 in 0.2500 6.3500
E 0.2500 6.3500
6.4 mm 0.2520 6.4000
6.5 mm 0.2559 6.5000
F 0.2570 6.5278
6.6 mm 0.2598 6.6000
G 0.2610 6.6294
6.7 mm 0.2638 6.7000
17/64 in 0.2656 6.7469
H 0.2660 6.7564
6.8 mm 0.2677 6.8000
6.9 mm 0.2717 6.9000
I 0.2720 6.9088
7 mm 0.2756 7.0000
J 0.2770 7.0358
7.1 mm 0.2795 7.1000
K 0.2810 7.1374
9/32 in 0.2813 7.1438
7.2 mm 0.2835 7.2000
7.3 mm 0.2874 7.3000
L 0.2900 7.3660
7.4 mm 0.2913 7.4000
M 0.2950 7.4930
7.5 mm 0.2953 7.5000
19/64 in 0.2969 7.5406
7.6 mm 0.2992 7.6000
N 0.3020 7.6708
7.7 mm 0.3032 7.7000
7.8 mm 0.3071 7.8000
7.9 mm 0.3110 7.9000
5/16 in 0.3125 7.9375
8 mm 0.3150 8.0000
O 0.3160 8.0264
8.1 mm 0.3189 8.1000
8.2 mm 0.3228 8.2000
P 0.3230 8.2042
8.3 mm 0.3268 8.3000
21/64 in 0.3281 8.3344
8.4 mm 0.3307 8.4000
Q 0.3320 8.4328
8.5 mm 0.3347 8.5000
8.6 mm 0.3386 8.6000
R 0.3390 8.6106
8.7 mm 0.3425 8.7000
11/32 in 0.3438 8.7313
8.8 mm 0.3465 8.8000
S 0.3480 8.8392
8.9 mm 0.3504 8.9000
9 mm 0.3543 9.0000
T 0.3580 9.0932
9.1 mm 0.3583 9.1000
23/64 in 0.3594 9.1281
9.2 mm 0.3622 9.2000
9.3 mm 0.3661 9.3000
U 0.3680 9.3472
9.4 mm 0.3701 9.4000
9.5 mm 0.3740 9.5000
3/8 in 0.3750 9.5250
V 0.3770 9.5758
9.6 mm 0.3780 9.6000
9.7 mm 0.3819 9.7000
9.8 mm 0.3858 9.8000
W 0.3860 9.8044
9.9 mm 0.3898 9.9000
25/64 in 0.3906 9.9219
10 mm 0.3937 10.0000
X 0.3970 10.0838
Y 0.4040 10.2616
13/32 in 0.4063 10.3188
Z 0.4130 10.4902
10.5 mm 0.4134 10.5000
27/64 in 0.4219 10.7156
11 mm 0.4331 11.0000
7/16 in 0.4375 11.1125
11.5 mm 0.4528 11.5000
29/64 in 0.4531 11.5094
15/32 in 0.4688 11.9063
12 mm 0.4724 12.0000
31/64 in 0.4844 12.3031
12.5 mm 0.4921 12.5000
1/2 in 0.5000 12.7000
13 mm 0.5118 13.0000
33/64 in 0.5156 13.0969
17/32 in 0.5313 13.4938
13.5 mm 0.5315 13.5000
35/64 in 0.5469 13.8906
14 mm 0.5512 14.0000
9/16 in 0.5625 14.2875
14.5 mm 0.5709 14.5000
37/64 in 0.5781 14.6844
15 mm 0.5906 15.0000
19/32 in 0.5938 15.0813
39/64 in 0.6094 15.4781
15.5 mm 0.6102 15.5000
5/8 in 0.6250 15.8750
16 mm 0.6299 16.0000
41/64 in 0.6406 16.2719
16.5 mm 0.6496 16.5000
17 mm 0.6693 17.0000
43/64 in 0.6719 17.0656
11/16 in 0.6875 17.4625
17.5 mm 0.6890 17.5000
45/64 in 0.7031 17.8594
18 mm 0.7087 18.0000
23/32 in 0.7188 18.2563
18.5 mm 0.7284 18.5000
47/64 in 0.7344 18.6531
19 mm 0.7480 19.0000
3/4 in 0.7500 19.0500
49/64 in 0.7656 19.4469
19.5 mm 0.7677 19.5000
25/32 in 0.7813 19.8438
20 mm 0.7874 20.0000
51/64 in 0.7969 20.2406
20.5 mm 0.8071 20.5000
13/16 in 0.8125 20.6375
21 mm 0.8268 21.0000
53/64 in 0.8281 21.0344
27/32 in 0.8438 21.4313
21.5 mm 0.8465 21.5000
55/64 in 0.8594 21.8281
22 mm 0.8661 22.0000
7/8 in 0.8750 22.2250
22.5 mm 0.8858 22.5000
57/64 in 0.8906 22.6219
23 mm 0.9055 23.0000
29/32 in 0.9063 23.0188
21/23 in 0.9130 23.1913
59/64 in 0.9219 23.4156
23.5 mm 0.9252 23.5000
15/16 in 0.9375 23.8125
24 mm 0.9449 24.0000
61/64 in 0.9531 24.2094
24.5 mm 0.9646 24.5000
31/32 in 0.9688 24.6063
25 mm 0.9843 25.0000
63/64 in 0.9844 25.0031
1 in 1.0000 25.4000
25.5 mm 1.0039 25.5000
1 1/64 in 1.0156 25.7969
26 mm 1.0236 26.0000
1 1/32 in 1.0313 26.1938
26.5 mm 1.0433 26.5000
1 3/64 in 1.0469 26.5906
1 1/16 in 1.0625 26.9875
27 mm 1.0630 27.0000
1 5/64 in 1.0781 27.3844
27.5 mm 1.0827 27.5000
1 3/32 in 1.0938 27.7813
28 mm 1.1024 28.0000
1 7/64 in 1.1094 28.1781
28.5 mm 1.1221 28.5000
1 1/8 in 1.1250 28.5750
1 9/64 in 1.1406 28.9719
29 mm 1.1417 29.0000
1 5/32 in 1.1563 29.3688
29.5 mm 1.1614 29.5000
1 11/64 in 1.1719 29.7656
30 mm 1.1811 30.0000
1 3/16 in 1.1875 30.1625
30.5 mm 1.2008 30.5000
1 13/64 in 1.2031 30.5594
1 7/32 in 1.2188 30.9563
31 mm 1.2205 31.0000
1 15/64 in 1.2344 31.3531
31.5 mm 1.2402 31.5000
1 1/4 in 1.2500 31.7500
32 mm 1.2598 32.0000
1 17/64 in 1.2656 32.1469
32.5 mm 1.2795 32.5000
1 9/32 in 1.2813 32.5438
1 19/64 in 1.2969 32.9406
33 mm 1.2992 33.0000
1 5/16 in 1.3125 33.3375
33.5 mm 1.3189 33.5000
1 21/64 in 1.3281 33.7344
34 mm 1.3386 34.0000
1 11/32 in 1.3438 34.1313
34.5 mm 1.3583 34.5000
1 23/64 in 1.3594 34.5281
1 3/8 in 1.3750 34.9250
35 mm 1.3780 35.0000
1 25/64 in 1.3906 35.3219
35.5 mm 1.3976 35.5000
1 13/32 in 1.4063 35.7188
36 mm 1.4173 36.0000
1 27/64 in 1.4219 36.1156
36.5 mm 1.4370 36.5000
1 7/16 in 1.4375 36.5125
1 29/64 in 1.4531 36.9094
37 mm 1.4567 37.0000
1 15/32 in 1.4688 37.3063
37.5 mm 1.4764 37.5000
1 31/64 in 1.4844 37.7031
38 mm 1.4961 38.0000
1 1/2 in 1.5000 38.1000

The Drill Size Chart is necessary because imperial sizing, much like the English language, if full of bastard sizing and nomenclature.

Surface Finish of Machined Parts

When it comes to the surface finish of machined parts, most people are typically concerned only with average roughness of a part, Ra; however, there are many more roughness parameters which can be specified.



Surface Finish usually takes on the lay of its manufacturing process.  For example, if a part is saw-cut, it will have a linear lay following

the travel of the saw teeth.  On the other hand, if a part is rotary-ground it’s finish will have a circular lay.

There are several specification guiding the detailing of surface finish.  The Europeans use BS EN ISO 1302:2002 Geometrical product specifications (GPS).  In the US, ASME Y14.36M is commonly used.  The symbols in each standard are quite similar:

The metric-to-inch conversion is:

a-μm – 0.025 0.05 0.1 0.2 0.4 0.8 1.6 3.2 6.3 12.5 25 50
a– μinch 1 2 4 8 16 32 63 125 250 500 1000 2000

Various machining operations have different typical surface finishes inherent to their respective manufacturing process, as indicated in the table below:

National Pipe Thread (NPT) Sizes / Dimensions

What is the outer diameter of a pipe thread?  Pipes are odd in that their size is based roughly on the inner diameter of the pipe.  So when you have a National Pipe Thead – NPT fitting, the thread size is actually much larger than the name implies.


Pipe thread sizes

Nominal
NPT Size
Outer
Diameter
inch (mm)
Threads
per inch
Pitch
of Thread
inch (mm)
1/16 0.3125 in (7.94 mm) 27 0.03704 in (0.94082 mm)
⅛” 0.405 in (10.29 mm) 27 0.03704 in (0.94082 mm)
¼” 0.540 in (13.72 mm) 18 0.05556 in (1.41122 mm)
3/8″ 0.675 in (17.15 mm) 18 0.05556 in (1.41122 mm)
½” 0.840 in (21.34 mm) 14 0.07143 in (1.81432 mm)
¾” 1.050 in (26.67 mm) 14 0.07143 in (1.81432 mm)
1″ 1.315 in (33.40 mm) 11½ 0.08696 in (2.20878 mm)
1¼” 1.660 in (42.16 mm) 11½ 0.08696 in (2.20878 mm)
1½” 1.900 in (48.26 mm) 11½ 0.08696 in (2.20878 mm)
2″ 2.375 in (60.33 mm) 11½ 0.08696 in (2.20878 mm)
2½” 2.875 in (73.02 mm) 8 0.12500 in (3.175 mm)
3″ 3.500 in (88.90 mm) 8 0.12500 in (3.175 mm)
4″ 4.500 in (114.30 mm) 8 0.12500 in (3.175 mm)
5″ 5.563 in (141.30 mm) 8 0.12500 in (3.175 mm)
6″ 6.625 in (168.27 mm) 8 0.12500 in (3.175 mm)
10″ 10.750 in (273.05 mm) 8 0.12500 in (3.175 mm)
12″ 12.750 in (323.85 mm) 8 0.12500 in (3.175 mm)
14″ OD 14 in (355.60 mm) 8 0.12500 in (3.175 mm)
16″ OD 16 in (406.40 mm) 8 0.12500 in (3.175 mm)
18″ OD 18 in (457.20 mm) 8 0.12500 in (3.175 mm)
20″ OD 20 in (508.00 mm) 8 0.12500 in (3.175 mm)
24″ OD 24 in (609.60 mm) 8 0.12500 in (3.175 mm)
Definition of pipe thread acronyms
NPT National Pipe Thread
FPT Female Pipe Thread
MPT Male Pipe Thread
PTF SAE short taper pipe thread – dryseal
NPTF American National taper pipe thread for dryseal pressure-tight joints
NPSM American National straight pipe thread for mechanical joints
NPSI American National straight intermediate pipe thread
GHT Garden Hose Thread
NST Fire Hose Thread
BSPT British Standard taper pipe thread (metric dimensions)

Hex Nut Grade Identification and Mechanical Properties

How strong are these nuts?  That’s what she said.  Seriously, what do those marks mean?  Should I order a hex nut with one dot or three dashes?  Here’s a cheat sheet with nut identifying marks, material grade and mechanical properties.


Grade
Identification
Marking
Specification Material Nominal Size
In.
Proof
Load
Stress
ksi
Hardness
Rockwell
See
Note
Min Max

No Mark
ASTM A563 – Grade 0 Carbon Steel 1/4 thru 1-1/2 69 B55 C32 3,4
ASTM A563 – Grade A Carbon Steel 1/4 thru 1-1/2 90 B68 C32 3,4
ASTM A563 – Grade B Carbon Steel 1/4 thru 1 120 B69 C32 3,4
over 1 thru 1-1/2 105
ASTM A563 – Grade C Carbon Steel
May be Quenched
and Tampered
1/4 thru 4 144 B78 C38 5
ASTM A563 – Grade C3 Atmospheric
Corrosion
Resistant Steel
May be Quenched
and Tampered
1/4 thru 4 144 B78 C38 5,9
ASTM A563 – Grade D Carbon Steel
May be Quenched
and Tampered
1/4 thru 4 150 B84 C38 6
ASTM A563 – Grade DH Carbon Steel
Quenched
and Tampered
1/4 thru 4 175 C24 C38 6
ASTM A563 – Grade DH3 Atmospheric
Corrosion
Resistant Steel,
Quenched
and Tampered
1/4 thru 4 175 C24 C38 5,9
ASTM A194 – Grade 1 Carbon Steel 1/4 thru 4 130 B70 7
ASTM A194 – Grade 2 Medium Carbon
Steel
1/4 thru 4 150 159 352 7,8
ASTM A194 – Grade 2H Medium Carbon
Steel, Quenched
and Tempered
1/4 thru 4 175 C24 C38 7
ASTM A194 – Grade 2HM Medium Carbon
Steel, Quenched
and Tempered
1/4 thru 4 150 159 237 7,8
ASTM A194 – Grade 4 Medium Carbon
Alloy Steel,
Quenched
and Tempered
1/4 thru 4 175 C24 C38 7
ASTM A194 – Grade 7 Medium Carbon
Alloy Steel,
Quenched
and Tempered
1/4 thru 4 175 C24 C38 7
ASTM A194 – Grade 7M Medium Carbon
Alloy Steel,
Quenched
and Tempered
1/4 thru 4 150 159 237 7
See Note 1,2 10