Hobson UNF Hex Bolt, 1/2" / 1 1/2"

The Hobson UNF hex bolt range has 67 items (Grade 8, zinc): 1/4" to 7/8", in lengths of 3/4" to 8". A hex bolt has a hexagonal head and a threaded shank, and is fitted with a nut or screwed into a tapped hole. Grade 8 is high tensile, and corresponds to metric class 10.9.

UNF means Unified National Fine Thread and TPI means threads per inch. Spanner sizes are the width across flats (A/F), using its grade 5 and 8 column. Pack quantity is shown for each item.

Where this product is used

• Fixing machinery feet, guards and mounting brackets where the bolt may need to come out again for servicing
• Securing timber to steel brackets or flitch plates, with a flat washer under the head to protect the timber
• Trailer, rack and frame builds where a replaceable bolted joint is preferred to welding
• Dry-environment assemblies where a zinc plated finish is enough protection
• Heavy-duty assemblies and machine building where a high-strength fastener is wanted

Features

• 67 items: 1/4" to 7/8", 3/4" to 8" long
• UNF thread, hex head
• Grade 8, zinc
• Minimum tensile strength for each size, shown for each size
• Electroplated zinc finish: indoor and under-cover use
• Grade 8 alloy steel for heavy-duty work

Key specifications

Choosing the right option

Choose the thread form first: the bolt and its nut must match in thread form, diameter and pitch. Sizes are nominal diameters in inches; compare the threads per inch shown for each item with your nut. Length is measured from under the head to the end of the bolt, so choose size and length together. Spanner size is the width across flats of the head and nut.

Zinc plating suits workshops, enclosed machinery and interior fit-out. Because the electroplated coating is thin, it is generally unsuitable for outdoor exposure and does not meet treated-timber requirements (not suitable for treated pine). For weather-exposed work, look at a hot dip galvanised version instead; within about 1 km of the sea, 316 stainless is generally the safer choice.

Grade 8 is alloy steel for heavy-duty work and is marked with six radial lines on the bolt head (SAE J429 convention). Minimum tensile strength is shown against each size. UNF has more threads per inch than UNC for the same diameter, giving a finer adjustment. It does not mate with UNC parts. For load-critical, structural or lifting joints, confirm the fastener against the engineer's specification.

Related bolts: Hobson UNF Hex Bolt, Grade 8, Plain, 1/4" to 7/8" x 3/4" to 11", Hobson UNF Hex Bolt, Grade 8, Plain, 1"-14 x 2" to 9" and Hobson UNF Hex Bolt, Grade 8, Plain, 1/4" to 1-1/2" x 1/2" to 16".