Tech Tip: Anchor Bolt Size
How to measure anchor bolts.
Anchor bolts are commonly mis measured causing delays in installation or costly changes.
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3/4″ and 1″ are the common light pole anchor bolt sizes. Standard thread pitches are 3/4″-10 and 1″-8 (threads per inch). 3/8″, 5/8″, 7/8″, and 1-1/8″ do exist, they are highly uncommon in parking lot lighting. 1-1/4″ will occasional be used on larger and older poles.
When measuring anchor hardware, remember, the outside diameter of bolts and the inside diameter of nuts will measure smaller than the hardwares given size.
Wall thickness of a nut does not affect its size. Standard sizes are pictured. Thicker and thinner do exist.
These is a difference in the hardwares finish and this does affect the fitment. Anchor hardware should be galvanized.
Galvanized nuts are oversized to accommodate the thickness of the galvanizing. A zinc coated or raw nut will not
thread onto some thicker galvanized bolts depending on the thickness of the galvanizing.
Click on the picture to enlarge.
Steps to measure anchor bolts
- Clean any debris or rust from the bolt threads.
- Measure to the outside of the threads. Crest to Crest of the threads.
- Some bolts are tapered at the butt and will show significantly smaller that their nominal size.
- Take notes of bolt size in the field. Picture of tape measures and bolts are NOT a reliable source of information. This decision must be made in the field.
Steps to measure anchor nuts
- Remove any debris of the nut.
- If possible use a removed nut.
- We are looking for the Outside Dimension of the bolt that will thread into the nut. Root to Root of the nut threads.
- The root of most nuts can be seen on the top finish of the nut.
- Take notes of nut size in the field. Picture of tape measures and nuts are NOT a reliable source of information. This decision must be made in the field.