Hobson UNF Hex Bolt, 1/4" / 1 1/2"

The Hobson UNF hex bolt range has 11 items (Grade 5, zinc): 1/4", 5/16" and 3/8", in lengths of 1" to 3". A hex bolt has a hexagonal head and a threaded shank, and is fitted with a nut or screwed into a tapped hole. Grade 5 is high tensile, and corresponds to metric class 8.8.

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

• Bolting steel plate, angle and flat bar together through drilled clearance holes, with a nut and washer on the far side
• Fixing machinery feet, guards and mounting brackets where the bolt may need to come out again for servicing
• Trailer, rack and frame builds where a replaceable bolted joint is preferred to welding
• Dry, indoor and sheltered locations such as workshops, enclosed machinery and interior fit-out
• Medium-strength machinery and equipment work that needs more than Grade 2
• Choosing between the 11 items here: they cover diameters from 1/4" to 3/8" and lengths from 1" to 3"

Features

• 11 items: 1/4", 5/16" and 3/8", 1" to 3" long
• UNF thread, hex head
• Grade 5, zinc
• Minimum tensile strength for each size, shown for each size
• Pack quantity shown for each item
• Zinc plated finish, for indoor and sheltered locations
• Grade 5 medium-carbon steel, quenched and tempered

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). Keep zinc plated parts for the dry side of the job, and use hot dip galvanised or 316 stainless where moisture, weather or salt air are involved.

Grade 5 steel is medium-carbon and quenched and tempered. 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. Fasteners are not lifting rated unless marked.

Related bolts: Hobson UNF Hex Bolt, Grade 5, Plain, 1/4" to 7/16" x 1" to 4", Hobson UNF Hex Bolt, Grade 5, Plain, 1/4" to 7/8" x 1-1/4" to 6" and Hobson UNF Hex Bolt, Grade 5, Zinc Plated, 1/4" to 7/16" x 1/2" to 4-1/2".