Collected Data Charts

Fraction to Decimal Equivalents

Fraction to Decimal Converter Enter the Fraction
Decimal Equivalent

Fraction <1/2"	Decimal	Fraction >1/2"	Decimal
1/64	0.01563	33/64	0.51563
1/32	0.03125	17/32	0.53125
3/64	0.04688	35/64	0.54688
1/16	0.06250	9/16	0.56250
5/64	0.07813	37/64	0.57813
3/32	0.09375	19/32	0.59375
7/64	0.10938	39/64	0.60938
1/8	0.12500	5/8	0.62500
9/64	0.14063	41/64	0.64063
5/32	0.15625	21/32	0.65625
11/64	0.17188	43/64	0.67188
3/16	0.18750	11/16	0.68750
13/64	0.20313	45/64	0.70313
7/32	0.21875	23/32	0.71875
15/64	0.23438	47/64	0.73438
1/4	0.25000	3/4	0.75000
17/64	0.26563	49/64	0.76563
9/32	0.28125	25/32	0.78125
19/64	0.29688	51/64	0.79688
5/16	0.31250	13/16	0.81250
21/64	0.32813	53/64	0.82813
11/32	0.34375	27/32	0.84375
23/64	0.35938	55/64	0.85938
3/8	0.13500	7/8	0.87500
25/64	0.39063	57/64	0.89063
13/32	0.40625	29/32	0.90625
27/64	0.42188	59/64	0.92188
7/16	0.43750	15/16	0.93750
29/64	0.45313	61/64	0.95313
15/32	0.46875	31/32	0.96875
31/64	0.48438	63/64	0.98438
1/2	0.50000	1/1	1.00000

Drill Bits: Fractional, Metric, Letter, Number, & Associated UNC/UNF Threads

Enter either Fraction/Metric/1-97/A-Z size or Thread Size/Pitch Enter the fraction or mm
Decimal Equivalent
or Enter the desired thread (size-pitch)

Thread Production

Thread	Major Dia.	Root Dia.	Tap Drill	Clearance Drill	Allowed Load (lb)
					(Brass)	(Steel)
0-80	0.0600	0.0438	3/64	#50	8	13
1-64	0.0730	0.0527	#53	#46	11	18
1-72	0.0730	0.0550	#53	#46	12	19
2-56	0.0860	0.0628	#50	#41	15	24
2-64	0.0860	0.0657	#50	#41	17	27
3-48	0.0990	0.0719	#47	#35	20	32
3-56	0.0990	0.0758	#45	#35	23	37
4-40	0.1120	0.0795	#43	#30	25	40
4-48	0.1120	0.0840	#42	#30	28	45
5-40	0.1250	0.0925	#38	#29	34	54
5-44	0.1250	0.0955	#37	#29	36	58
6-32	0.1380	0.0974	#36	#25	37	59
6-40	0.1380	0.1055	#34	#25	44	70
8-32	0.1640	0.1234	#29	#16	60	96
8-36	0.1640	0.1279	#29	#16	64	102
10-24	0.1900	0.1359	#25	#7	73	117
10-32	0.1900	0.1494	#21	#7	88	141
12-24	0.2160	0.1619	#16	I	103	165
12-28	0.2160	0.1696	#14	I	113	181

Threads in Depth

n = threads/inch

P = pitch (inches/thread)

H = thread depth — sharp crest to sharp root (compound at 90°)

d = thread depth — flat crest to flat root (compound at 90°)

D = thread depth — sharp crest to flat root (compound at 90°)

X = thread depth — flat crest to sharp root (compound at 90°)

U = amount to undercut below nominal diameter for class 2A and 2B (female) threads

n	P	H	d	D	X	U	Z
160.0	0.00625	0.00541	0.00338	0.00406	0.00474	0.00135	0.00469
120.0	0.00833	0.00722	0.00451	0.00541	0.00631	0.00180	0.00625
96.0	0.01042	0.00902	0.00564	0.00677	0.00789	0.00226	0.00781
90.0	0.01111	0.00962	0.00601	0.00722	0.00842	0.00241	0.00833
80.0	0.01250	0.01083	0.00677	0.00812	0.00947	0.00271	0.00938
72.0	0.01389	0.01203	0.00752	0.00902	0.01052	0.00301	0.01042
64.0	0.01563	0.01353	0.00846	0.01015	0.01184	0.00338	0.01172
56.0	0.01786	0.01546	0.00967	0.01160	0.01353	0.00387	0.01339
48.0	0.02083	0.01804	0.01128	0.01353	0.01579	0.00451	0.01563
44.0	0.02273	0.01968	0.01230	0.01476	0.01722	0.00492	0.01705
40.0	0.02500	0.02165	0.01353	0.01624	0.01894	0.00541	0.01875
36.0	0.02778	0.02406	0.01504	0.01804	0.02105	0.00601	0.02083
32.0	0.03125	0.02706	0.01691	0.02030	0.02368	0.00677	0.02344
28.0	0.03571	0.03093	0.01933	0.02320	0.02706	0.00773	0.02679
27.0	0.03704	0.03208	0.02005	0.02406	0.02807	0.00802	0.02778
24.0	0.04167	0.03608	0.02255	0.02706	0.03157	0.00902	0.03125
20.0	0.05000	0.04330	0.02706	0.03248	0.03789	0.01083	0.03750
18.0	0.05556	0.04811	0.03007	0.03608	0.04210	0.01203	0.04167
16.0	0.06250	0.05413	0.03383	0.04059	0.04736	0.01353	0.04688
14.0	0.07143	0.06186	0.03866	0.04639	0.05413	0.01546	0.05357
13.0	0.07692	0.06662	0.04164	0.04996	0.05829	0.01665	0.05769
12.0	0.08333	0.07217	0.04511	0.05413	0.06315	0.01804	0.06250
11.5	0.08696	0.07531	0.04707	0.05648	0.06589	0.01883	0.06522
11.0	0.09091	0.07873	0.04921	0.05905	0.06889	0.01968	0.06818
10.0	0.10000	0.08660	0.05413	0.06495	0.07578	0.02165	0.07500
9.0	0.11111	0.09623	0.06014	0.07217	0.08420	0.02406	0.08333
8.0	0.12500	0.10825	0.06766	0.08119	0.09472	0.02706	0.09375
7.0	0.14286	0.12372	0.07732	0.09279	0.10825	0.03093	0.10714
6.0	0.16667	0.14434	0.09021	0.10825	0.12630	0.03608	0.12500
5.0	0.20000	0.17321	0.10825	0.12990	0.15155	0.04330	0.15000
4.5	0.22222	0.19245	0.12028	0.14434	0.16839	0.04811	0.16667
4.0	0.25000	0.21651	0.13532	0.16238	0.18944	0.05413	0.18750

Standard Metric Screws and Their Imperial Equivalents

dm = diameter (mm)

pm = pitch (mm)

di = diameter (in)

pi = pitch (in)

tdm =tap drill size (mm)

tdi = tap drill size (in)

dm x pm	(di x pi)	tdm	(tdi)	easily confused with
1.6 x 0.35	(0.063 x 72.6)	1.25	(0.049)	[0-80 = 0.060 x 80]
1.8 x 0.35	(0.071 x 72.6)	1.45	(0.057)	[1-72 = 0.073 x 72]
2.0 x 0.40	(0.079 x 63.5)	1.60	(0.063)	[2-64 = 0.085 x 64]
2.2 x 0.45	(0.087 x 56.4)	1.75	(0.069)	[2-56 = 0.085 x 56]
2.5 x 0.45	(0.098 x 56.4)	2.05	(0.081)	[3-56 = 0.099 x 56]
3.0 x 0.50	(0.118 x 50.8)	2.50	(0.098)	[4-48 = 0.112 x 48]
3.5 x 0.60	(0.138 x 42.3)	2.90	(0.114)	[6-40 = 0.138 x 40]
4.0 x 0.70	(0.157 x 36.3)	3.30	(0.130)	[8-36 = 0.164 x 36]
4.5 x 0.75	(0.177 x 33.9)	3.75	(0.148)
5.0 x 0.80	(0.197 x 31.8)	4.20	(0.165)	[10-32 = 0.190 x 32]
6.0 x 1.00	(0.236 x 25.4)	5.00	(0.197)	[1/4-28 = 0.25 x 28]
7.0 x 1.00	(0.276 x 25.4)	6.00	(0.236)
8.0 x 1.25	(0.315 x 20.3)	6.75	(0.266)
8.0 x 1.00	(0.315 x 25.4)	7.00	(0.276)
10.0 x 1.50	(0.394 x 16.9)	8.50	(0.335)
10.0 x 1.25	(0.394 x 20.3)	8.75	(0.344)
12.0 x 1.75	(0.472 x 14.5)	10.25	(0.404)
12.0 x 1.25	(0.472 x 20.3)	10.75	(0.423)
14.0 x 2.00	(0.551 x 12.7)	12.00	(0.472)
14.0 x 1.50	(0.551 x 16.9)	12.50	(0.492)
16.0 x 2.00	(0.630 x 12.7)	14.00	(0.551)
16.0 x 1.50	(0.630 x 16.9)	14.50	(0.571)
18.0 x 2.50	(0.709 x 10.2)	15.50	(0.610)
18.0 x 1.50	(0.709 x 16.9)	16.50	(0.650)
20.0 x 2.50	(0.787 x 10.2)	17.50	(0.689)
20.0 x 1.50	(0.787 x 16.9)	18.50	(0.728)
22.0 x 2.50	(0.866 x 10.2)	19.50	(0.768)
22.0 x 1.50	(0.866 x 16.9)	20.50	(0.807)
24.0 x 3.00	(0.945 x 8.5)	21.00	(0.827)
24.0 x 2.00	(0.945 x 12.7)	22.00	(0.866)
27.0 x 3.00	(1.063 x 8.5)	24.00	(0.945)
27.0 x 2.00	(1.063 x 12.7)	25.00	(0.984)

Cutting Threads on the Lathe

threading dial

even numbered threads — use any line

odd numbered threads — use any numbered line

half threads — use any odd numbered line

lathe setup

A — Threading tool upright, point toward lathe back

B — Threading tool inverted, point toward lathe back

C — Threading tool upright, point toward lathe front

D — Threading tool inverted, point toward lathe front

L — Direction of feed = Left

R — Direction of feed = Right

f — Forward Spindle Rotation

r — Reverse Spindle Rotation

To Cut Right Hand External Threads: Lf(A/D) Rr(B/C)

To Cut Left Hand External Threads: Lr(B/C) Rf(A/D)

To Cut Right Hand Internal Threads: Lf(B/C) Rr(A/D)

To Cut Right Hand Internal Threads: Lr(A/D) Rf(B/C)

Pipe Threading Data

S = Nominal Pipe Size (in)

T = Threads per Inch

D = Diameter (in)

TD = Tap Drill

S	T	D	TD
American Standard Taper Pipe
1/16	27	0.3125	D
1/8	27	0.405	R
1/4	18	0.540	7/16
3/8	18	0.675	37/64
1/2	14	0.840	23/32
3/4	14	1.050	59/64
1	11.5	1.315	1-5/32
1-1/4	11.5	1.660	1-1/2
1-1/2	11.5	1.900	1-47/64
2	11.5	2.375	2-7/32
2-1/2	8	2.875	2-5/8
3	8	3.500	3-1/4
3-1/2	8	4.000	3-3/4
4	8	4.500	4-1/4
4-1/2	8	5.000	4-3/4
5	8	5.563	5-9/32
6	8	6.625	6-11/32
7	8	7.625
8	8	8.625
9	8	9.625
10	8	10.750
12	8	12.750
American Standard Straight Pipe
1/8	27	0.405	S
1/4	18	0.540	29/64
3/8	18	0.675	19/32
1/2	14	0.840	47/64
3/4	14	1.050	15/16
1	11.5	1.315	1-3/16
1-1/4	11.5	1.660	1-33/64
1-1/2	11.5	1.900	1-3/4
2	11.5	2.375	2-7/32
2-1/2	8	2.875	2-21/32
3	8	3.500	3-9/32
3-1/2	8	4.000	3-2/32
4	8	4.500	4-9/32
4-1/2	8	5.000	4-25/32
5	8	5.563	5-11/32
6	8	6.625	6-13/32

British Association Threads

closest american counterpart for ba threads

British Association Threads				Closest American Threads
BA Size	OD (in)	TPI (in)	Pitch (mm)	Thread	OD (in)
16	0.031	134.0	0.19
15	0.035	121.0	0.21
14	0.039	110.0	0.23
13	0.047	102.0	0.25
12	0.051	90.9	0.28	0-80	0.060
11	0.059	82.0	0.31
10	0.066	72.6	0.35	1-72	0.073
9	0.075	65.1	0.39
8	0.087	59.1	0.43	2-56	0.086
7	0.098	52.9	0.48	3-48	0.099
6	0.110	47.9	0.53	4-48	0.112
5	0.126	43.0	0.59	5-44	0.125
4	0.142	38.5	0.66	6-40	0.138
3	0.161	34.8	0.73	8-32	0.164
2	0.185	31.4	0.81	10-32	0.190
1	0.209	28.2	0.90	12-28	0.216
0	0.236	25.4	1.00	4-28	0.250

notes from me-05/05/95-529 post bag letter by Jim Nicholson

Full series runs from 0 to 22.

Thread angle = 47.5°.

Crest and root radii = 0.18p (p=pitch).

Pitches are calculated as $p (mm) = {0.9}^{n}$ (n=number of thread in BA series).

Diameters are calculated as $D (mm) = 6 p^{1.2}$ .

N	OD (in)	TPI	Pitch (mm)
22	0.015	257.9	0.098
21	0.017	232.1	0.109
20	0.019	208.9	0.122
19	0.021	188.0	0.135
18	0.024	169.2	0.150
17	0.028	152.3	0.167
16	0.031	137.1	0.185
15	0.035	123.4	0.206
14	0.040	111.0	0.229
13	0.046	99.9	0.254
12	0.052	89.9	0.282
11	0.059	80.9	0.314
10	0.067	72.8	0.349
9	0.076	65.6	0.387
8	0.086	59.0	0.430
7	0.097	53.1	0.478
6	0.111	47.8	0.531
5	0.126	43.0	0.590
4	0.142	38.7	0.656
3	0.162	34.8	0.729
2	0.183	31.4	0.810
1	0.208	28.2	0.900
0	0.236	25.4	1.000

tap drills for british standard whitworth and fine threads

	British Std Whitworth		British Standard Fine
Thread	TPI	Tap Drill	TPI	Tap Drill
9/32	40	2.55 mm
3/16	24	3.70 mm	32	5/32
7/32	28	4.65 mm
1/4	20	5.10 mm	26	5.30 mm
9/32	26
5/16	18	6.50 mm	22	6.75 mm
3/8	16	5/16	20	8.25 mm
7/16	14	9.25 mm	18	9.70 mm
1/2	12	10.5 mm	16	7/16
9/16	12	12.10 mm	16	1/2
5/8	11	13.50 mm	14	14.00 mm
11/16	11	14
3/4	10	41/64	12	16.75 mm
7/8	9	19.25 mm	11	25/32
1	8	22.00 mm	10	22.75 mm
1-1/8	7	24.75 mm	9	25.50 mm
1-1/4	7	1-3/32	9	28.75 mm
1-3/8	8	31.50 mm
1-1/2	6	33.50 mm	8	1-23/64
1-3/4	5	39.00 mm
2	4.5	44.50 mm

Minimum Thread Engagement

Ted Edwards, in Canada, published some minimum thread engagement data on the Usenet news group. I've reproduced his article below.

I added another column to Ted's original data. The factor 'F' is:

F = \frac{LE 3}{diam}

I've seen 'rules-of-thumb' that state that minimum thread engagement should be equal to the diameter of the bolt. From Ted's data, that would be adequate for the LE1 case where the nut and bolt are the same strength.

On the other hand, I've seen rules that say minimum thread engagement should be 1.5 times the diameter (or, equivalently, an 'F' factor of 1.5). Again, from Ted's data, that would appear to be a reasonable rule to use that would cover both the LE1 and LE3 cases.

From Ted_E@telus.net Thu Feb 27 10:31:08 2003

Newsgroups: rec.crafts.metalworking

Subject: Re: Thread engagement

From: Ted Edwards [Ted_E@telus.net]

Date: Thu, 27 Feb 2003 18:31:08 GMT

data for calculating thread strength


		UNC					UNF
nom.	diam.	tpi	ETA	LE1	LE3	F	tpi	ETA	LE1	LE3	F
#4	0.112	40	0.006	0.07	0.123	1.098	48	0.007	0.076	0.135	1.205
#6	0.138	32	0.009	0.085	0.149	1.080	40	0.01	0.093	0.168	1.217
#8	0.164	32	0.014	0.106	0.194	1.183	36	0.015	0.111	0.205	1.250
#10	0.19	24	0.018	0.116	0.209	1.100	32	0.02	0.128	0.239	1.258
1/4	0.25	20	0.032	0.155	0.287	1.148	28	0.036	0.172	0.331	1.324
5/16	0.3125	18	0.052	0.198	0.378	1.210	24	0.058	0.215	0.421	1.347
3/8	0.375	16	0.077	0.24	0.465	1.240	24	0.088	0.266	0.532	1.419
7/16	0.4375	14	0.106	0.279	0.546	1.248	20	0.119	0.305	0.614	1.403
1/2	0.5	13	0.142	0.322	0.637	1.274	20	0.16	0.356	0.725	1.450
5/8	0.625	11	0.226	0.403	0.81	1.296	18	0.256	0.448	0.927	1.483
3/4	0.75	10	0.334	0.489	0.999	1.332	16	0.373	0.538	1.125	1.500
7/8	0.875	9	0.462	0.572	1.18	1.349	14	0.50	0.622	1.313	1.501
1	1	8	0.606	0.652	1.354	1.354	12	0.663	0.703	1.492	1.492

Wood Screw Data

N = Nominal Size

T = Threads per Inch

D = Diameter of Unthreaded Root

B = Body Drill Size (in)

S = Pilot Drill Size in Soft Wood (in)

H = Pilot Drill Size in Hard Wood (in)

N	T	D	B	S	H	B	S	H
0	32	.060	52	75	66
1	28	.073	47	71	57
2	26	.086	42	65	54
3	24	.099	37	58	53
4	22	.112	32	55	51	1/8	1/16	5/64
5	20	.125	30	53	47	9/64	5/64	3/32
6	18	.138	27	52	44	9/64	5/64	3/32
7	16	.151	22	51	39	5/32	3/32	7/64
8	15	.164	18	48	35	1/64	3/32	7/64
9	14	.177	14	45	33	3/16	7/64	1/8
10	13	.190	10	43	31	3/16	7/64	1/8
11		.203	4	40	29
12	11	.216	2	38	25	7/32	1/8	5/32
14	10	.242	D	32	14
16	9	.268	I	29	10
18	8	.294	N	26	6
20	8	.320	P	19	3
24	7	.372	V	15	D

Recommended Drill Sizes for Self-Tapping Screws (Sheet Metal)

N = Number

T = Threads per Inch

OD = Outside Diameter

A = Drill for heavy metals

B = Drill for Light metals

N	T	OD	A	B
2	32	.086	49	49
4	24	.112	41	41
5	20	.125	36	36
6	20	.138	32	32
7	19	.151	30	30
8	18	.164	28	29
10	16	.190	20	21
12	14	.216	13	14
1/4	14	.250	3	4
5/16	12	.313	I	H
3/8	12	.375	R	Q

Tap Shank Diameter vs. Thread Minor Diameter

hsm 1/1/97 - pg. 23

Tap Size	Major Diameter	Shank Diameter	Minor Thread Diameter
0	.060	.141	.0465
1	.073	.141	.0561
2	.086	.141	.0580
4	.112	.141	.0764
5	.125	.141	.0979
6	.138	.141	.1040
8	.164	.168	.1300
10	.190	.194	.1450
12	.216	.220	.1710
1/4	.250	.255	.1960
5/16	.312	.318	.2520
3/8	.375	.381	.3070

Taps 7/16" diameter and larger have shanks that are smaller than the thread minor diameter.