Threading Tables

Chart No 8 - Model Engineer's and Admiralty Fine Threads

Model Engineer's Standard Threads (Whitworth Form) Dimensions in Inches except where stated
Thread Form Data
Diameter	O/Diameter	Core	Radius	Depth	Pitch	Effective Dia	T.P.I	Tapping Drill
1/8"	0.125	0.0930	--	0.0160	0.0250	0.1090	40	No 40
5/32"	0.1563	0.1242	--	0.0160	0.0250	0.1403	40	No 30
3/16"	0.1875	0.1555	--	0.0160	0.0250	0.1715	40	5/32"
7/32"	0.2188	0.1867	--	0.0160	0.0250	0.2028	40	3/16"
1/4"	0.2500	0.2187	--	0.0160	0.0250	0.2340	40	7/32"
9/32"	0.2813	0.2412	--	0.0200	0.03125	0.2613	32	Letter C
5/16"	0.3125	0.2725	--	0.0200	0.03125	0.2925	32	Letter J
3/8"	0.375	0.3350	--	0.0200	0.03125	0.3550	32	Letter R
7/16"	0.4375	0.3833	--	0.0246	0.03846	0.4129	26	10mm
1/2"	0.5000	0.4508	--	0.0246	0.03846	0.4754	26	29/64"

Admiralty Fine Threads (Whitworth Form) Dimensions in Inches except where stated
Thread Form Data
Component Diameter	O/Diameter	Core	Radius	Depth	Pitch	Effective Dia	T.P.I	Tapping Drill
Under 1/2"	N/A	N/A	N/A	0.0267	0.04166	N/A	24	N/A
1/2" & under 3/4"	N/A	N/A	N/A	0.0320	0.05000	N/A	20	N/A
3/4" & under 1"	N/A	N/A	N/A	0.0457	0.07143	N/A	14	N/A
1" & under 2"	N/A	N/A	N/A	0.0533	0.08333	N/A	12	N/A
2" & under 4"	N/A	N/A	N/A	0.0800	0.12500	N/A	8	N/A
4" & over	N/A	N/A	N/A	0.1067	0.16666	N/A	6	N/A

Used on pressure gauges and screwed glands on engines etc.

---

• Main • Mechanical Menu •