# Anchor Bolt Thickness



## jmc (Jun 25, 2012)

What is the exact thickness of a 1/2" anchor bolt? A concrete sub is using a bolt that measures 7/16". Does this equate to a 1/2" or 3/8"? Thanks!


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## David Henderson (Jun 25, 2012)

Did you use micrometer or a tape to measure? didn't think they made a 7/16" or a 3/8" AB.


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## jmc (Jun 25, 2012)

i used a tape measure. pulling against the tab it measures right at 7/16"...pushing against the tab it measures 1/2"...if that makes sense. your comment that you weren't aware of 3/8" anchor bolts is very helpful though.


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## ICE (Jun 25, 2012)

jmc said:
			
		

> i used a tape measure. pulling against the tab it measures right at 7/16"...pushing against the tab it measures 1/2"...if that makes sense. your comment that you weren't aware of 3/8" anchor bolts is very helpful though.


Measure it from one side of the 13" mark


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## Builder Bob (Jun 26, 2012)

how loose is the tab on the tape measure.......??


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## tmurray (Jun 26, 2012)

Like ICE said you should never use the first couple inches of a tape measure if you need it to be very accurate as the end tab has a tendency to move.


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## Doorman (Jun 26, 2012)

_"...as the end tab has a tendency to move."_

Yes, the hook of a steel rule moves the thickness of the hook.


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## Doorman (Jun 26, 2012)

A 1/2" anchor bolt has a major diameter of 1/2"

A quick and easy measuring aid is a 'Sharpie' marking pen.  These are (close enough for this exercise) 3/8 of an inch on the smaller end of the reservoir, and 1/2 inch diameter at the fattest part.


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## Big Mac (Jun 26, 2012)

If it is new, it should only move the thickness of the hook.  However, over time those holes elongate and the movement becomes larger making measurements inaccurate.  A better rule of thumb is to use a section of tape not affected by the movement of the end tab or hook.


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## jmc (Jun 26, 2012)

measured elsewhere on the tape measure, it's exactly 7/16".


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## mtlogcabin (Jun 26, 2012)

They do make 3/8" anchor bolts. The code does not allow them but I assume an engineer could spec them with his/her design

http://www.grainger.com/Grainger/WESTWARD-Anchor-Bolt-11K382?cm_mmc=PJX:3578-_-category_program-_-WESTWARD11K382AnchorBolt,lHook,3/8-16,6InL,pk2511K382-_-productfeed


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## mtlogcabin (Jun 26, 2012)

Is it a 7/16 nut or 1/2 inch is the easiest way to tell. You won't get a 1/2" thread on a 7/16" shaft without it being vary obvious.


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## mark handler (Jun 26, 2012)

You can get anchor bolts 1/4" to 4"

7/16 14X12 ANCHOR BOLT http://www.tristatefast.com/detail.aspx?item=AB07C192G&id=-271


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## High Desert (Jun 26, 2012)

The movement of the end tab compensates for when you measure butting your tape versus hooking your tape. When you hook it it moves the thickness of the tab and when you butt it, it moves back. That's why they slide. It has to compensate for the thickness of the tab.


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## Mark K (Jun 26, 2012)

Anchor bolts are measured using the diameter where there is no threads.  What can confuse the issue is that some bolts have the threads rolled while others have cut threads. With a rolled thread the diameter of the unthreaded portion is slightly less than the diameter of a bolt with cut threads.

My belief is that any code provisions were developed in the context of cut threads.  Thus would be inclined not to accept rolled threads unless bolt was up sized or the design professional determined that there was no problem.


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## Mule (Jun 27, 2012)

What's a 1/16 of an inch among friends? Hey.. close enough for government work... Always hated that saying!


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## Frank (Jun 27, 2012)

Mule said:
			
		

> What's a 1/16 of an inch among friends? Hey.. close enough for government work... Always hated that saying!


About a 24% reduction in cross section of the bolt


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## jmc (Jun 28, 2012)

so the contractor brought in a new box of bolts. measuring the nonthreaded area of the bolt with three separate tape measures, they all hit exactly on 7/16".


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## KZQuixote (Jun 28, 2012)

I've a box of 5/8" anchor bolts out in my shop. They've rolled 5/8" threads with a shank that measures .560". I've had them for ten or more years.

Bill


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