THREAD TAPPING GUIDE - UNC & UNF THREADS

The following tables are a guideline to selecting the correct drill bit sizes for tapping imperial threads.
Care should be exercised depending on the material to be tapped. For example cast iron is very soft
and easy to tap and in this instance a slightly smaller bit can be used.
Thread taps generally come in a set, however for cleaning threads ask you supplier for a 'machine tap'
THREAD SIZE
DRILL SIZE MM
METRIC SIZE
SPANNER SIZE
TORQUE VALUE
1/4"
5.10mm
6.35mm
7/16" (11mm)
N/A
5/16"
6.90mm
7.94mm
1/2" (13mm)
N/A
3/8"
8.00mm
9.525mm
9/16" (14mm)
60NM
7/16"
9.40mm
11.11mm
11/16" (18mm)
100NM
1/2"
10.80mm
12.70mm
3/4" (19mm)
120NM
5/8"
13.50mm
15.88
15/16" (24mm)
140NM
UNC - UNIFIED NATIONAL COURSE THREAD
UNF - UNIFIED NATIONAL FINE THREAD
THREAD SIZE
DRILL SIZE MM
METRIC SIZE
SPANNER SIZE
TORQUE VALUE
1/4"
5.50mm
6.35mm
7/16" (11mm)
N/A
5/16"
6.90mm
7.94mm
1/2" (13mm)
N/A
3/8"
8.50mm
9.525mm
9/16" (14mm)
60NM
7/16"
9.90mm
11.11mm
11/16" (18mm)
100NM
1/2"
11.50mm
12.70mm
3/4" (19mm)
120NM
5/8"
14.50mm
15.88
15/16" (24mm)
140NM
Agriline Diesel cc is a registered company in South Africa : Reg no CK 2010/044705/23 | Registered Office: Shop 4 Kenmare Mall, Kenmare Krugersdorp 1739. Original equipment manufacturers names and parts numbers are quoted for reference purposes only and are not intended to suggest that our replacement parts are made by the original equipment manufacturer.
VAT REG NO: 4400274579
All website prices displayed exclude VAT@14%
Agriline admin login
HOME
ACCESSORIES
CONTACT
SHIPPING
PRODUCTS
TECHNICAL ARTICLES
Technical articles
Engine specifications
Agriline Diesel Tractor Parts
FARM TRACTOR PARTS
CATALOGUES
Technical articles
011 955 3301
011 664 6303
SALES :
Ford New Holland tractor parts
ALL WEBSITE PRICES DISPLAYED EXCLUDE VAT@14%