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

The Hobson UNF hex bolt range has 73 items (Grade 8, plain): 1/4" to 7/8", in lengths of 3/4" to 11". 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

• Screwing into a tapped hole in a casting, plate or housing where there is no room for a nut
• Trailer, rack and frame builds where a replaceable bolted joint is preferred to welding
• Replacing worn or missing bolts of the same thread form, diameter and length
• Dry indoor machinery, tooling and equipment
• Heavy-duty assemblies and machine building where a high-strength fastener is wanted
• The 73 items cover diameters from 1/4" to 7/8" and lengths from 3/4" to 11", confirm the size against your drawing before ordering

Features

• 73 items: 1/4" to 7/8", 3/4" to 11" long
• UNF thread, hex head
• Grade 8, plain
• Minimum tensile strength for each size, shown for each size
• Plain (uncoated) steel for dry indoor and machinery use
• Heavy-duty Grade 8 alloy steel

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.

Plain steel carries no protective coating apart from a light oil film, which is why it rusts quickly if it gets wet. It suits dry indoor jobs, machinery, and assemblies that will be painted, oiled or enclosed. Where the job is outside or damp, move to hot dip galvanised or 316 stainless.

In the SAE J429 convention Grade 8 is alloy steel for heavy-duty use, shown by six radial lines on the head. UNF is the fine inch thread: the finer pitch gives more threads per inch and a finer adjustment. It only mates with UNF nuts and tapped holes of the same diameter. For load-critical, structural or lifting joints, confirm the fastener against the engineer's specification. Fasteners are not lifting rated unless marked.

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