Clearance holes for Metric Screws

Ref:- http://www.draughtsman.co.uk/information_images/mechanical/clearance_holes.htm

THREAD	CLEARANCE HOLE
	CLOSE FIT	MEDIUM FIT	FREE FIT
M1.6	1.7	1.8	2.0
M2	2.2	2.4	2.6
M2.5	2.7	2.9	3.1
M3	3.2	3.4	3.6
M4	4.3	4.5	4.8
M5	5.3	5.5	5.8
M6	6.4	6.6	7.0
M7	7.4	7.6	8.0
M8	8.4	9.0	10.0
M10	10.5	11.0	12.0
M12	13.0	14.0	15.0
M14	15.0	16.0	17.0
M16	17.0	18.0	19.0
M18	19.0	20.0	21.0
M20	21.0	22.0	24.0
M22	23.0	24.0	26.0
M24	25.0	26.0	28.0
M27	28.0	30.0	32.0
M30	31.0	33.0	35.0
M33	34.0	36.0	38.0
M36	37.0	39.0	42.0
M39	40.0	42.0	45.0
M42	43.0	45.0	48.0
M45	46.0	48.0	50.0
M48	50.0	52.0	54.0
M52	54.0	56.0	58.0

Note:- Tolerance Stack up is needed after apply the Clearacne hole dimension.

Ref : -http://www.brook-tech.fsnet.co.uk/Clearance%20Holes%20+%20Tolerance.pdf

Metric Conversion for threads to UNC & UNF

Ref :- http://www.elginfasteners.com/metric.htm

Diameter/Decimal/Metric Chart for Small Diameter Fasteners
Gauge or Diameter	Decimal (in)	mm
No. 0000	0.021	.53
No. 000	0.034	.86
No. 00	0.047	1.19
No. 0	0.060	1.524
No. 1	0.073	1.854
No. 2	0.086	2.184
No. 3	0.099	2.515
No. 4	0.112	2.845
No. 5	0.125	3.175
No. 6	0.138	3.505
No. 8	0.164	4.166
No. 10	0.190	4.826
No. 12	0.216	5.484
Fastener Conversion Chart
Inch Equivalent		Metric Size-Pitch ISO and IFI Rec.
UNC	UNF
1 - 64	1 - 72	M2 x 0.4
3 - 48	3 - 56	M2.5 x 0.45
4 - 40	4 - 48	M3 x .05
6 - 32	6 - 40	M3.5 x .06
8 - 32	8 - 36	M4 x .07
10 - 24	10 - 32	M5 x .08
1/4 - 20	1/4 - 28	M6 x 1
5/16 -18	5/16 - 24	M8 x 1.25
3/8 -16	3/8 - 24	M10 x 1.5
7/16 -14	7/16 - 20	M12 x 1.75
1/2 - 13	1/2 - 20	M14 x 2
5/8 - 11	5/8 - 18	M18 x 2
3/4 - 10	3/4 - 16	M20 x 2.5
1 - 8	1-12	M24 x 3
1-1/4 - 7	1-1/8 - 12	M30 x 3.5
1-1/2 - 6	1-1/4 - 12	M36 x 4
Approximate Equivalency Chart Metric/US Roughly Equivalent US Bolt Materials
Metric Nut Class	SAE J429 Normally Used	Grades	ASTM Grades
4.6	4 or 5	1	A307, Grade A
4.8	4 or 5	2	.
5.8	5	2	.
8.8	8	5	A325, A449
9.8	9	5+	A193, B7 and B16
10.9	10 or 12	8	A490, A354, Grade 8D
12.9	10 or 12	.	A540; B21 through B24
Common DIN Numbers for Metric Fasteners
DIN	Hex Capscrews
931	Coarse thread pitch partially threaded (specify grade)
933	Coarse thread pitch fully threaded (specify grade)
930	Fine thread pitch partially threaded (specify grade)
961	Fine thread pitch fully threaded (specify grade)
DIN	Nuts
934	Hex nuts (specify pitch and class)
985	Nylon insert locknuts (specify pitch and class)
980V	All metal locknuts (specify pitch and class)
DIN	Washers
125	Flatwashers
127	Lockwashers
DIN	Socket Products
912	Socket head capscrews (normally GR 12.9 and coarse thread)
7991	Flat head socket capscrews (normally GR 12.9 and coarse thread)
916	Socket setscrews (normally GR 12.9 and coarse thread)
DIN	Machine Screws
7985	Pan head Phillips drive zinc plated
965	Flat head Phillips drive zinc plated
DIN	Threaded Rod
975	All threaded rod (normally 1 meter lengths, specify grade and pitch)