The versatile threaded rod.

Engineering trades have bee using threaded rod long before us builder's got in on the act.  The air conditioner guys have been using it to hang their duct work from.

On my hurricane upgrade page I talk about using it as hold down bolts for upgrading houses to cyclonic coding.

The whole emphasis on structurally upgrading an existing house is improving the connections.   Nails replaced with bolts, rafters bolted to hold down rods passing through wall and into something solid.  In the drawing above I show a HD rod (5.) passing through a wall and into a new concrete footing.
  • As you can imagine the number and variety of bolts needed to upgrade a house was enormous and expensive.
  • Apart from standard sizes available at hardware stores we need heaps of odd bolt lengths in two main sizes, M12 and M16. (1/2" and 5/8")
  • In the example above we have say an M12 bolt cast into concrete, connected to an extension rod which would be bolted to roof members above.
Metal cut off saw
Threaded rod - the old metal cut off saw is ideal for cutting the bolts to length.

The humble threaded rods. AKA "all thread" are lengths of rod which have a thread formed all the way, no smooth section as in normal bolts.  These are available in Zinc plated, galvanised or even in stainless steel.  (I recall seeing a very simple but effective set of shelves suspended from stain lees steel rods.)
They come in lengths of 1000 and 3000. (a bit over 3 feet and around 10 feet long).

If you have a project where you require a lot of different lengths of bolts, then threaded rods may be just the thing.  They will be cheaper and if you get extra rods, you will always be able to make up any odd bolts that you need, instead of making a separate trip to the store.
We would buy the rods by the pack, the nuts and bolts in large bags.  Very cost effective.

You can of course saw the rods to length by hand with a hack saw, but my tool of choice for this job is the metal cut off saw on the right.
There is a simple trick to using this that will save heaps of time and frustration.
If you just cut through the rod in the normal way, then a burr is created at the bottom of the cut.
This burr is a pain the the butt to get rid of so that the nuts are able to be put on easily.  We tried lightly grinding the bur off afterwards, grinding the end with a slight chamfer etc.  All of these ways work, but quite often you still need to grip the rod with a vise grip, and turn the nut with a spanner.

cutting threaded rod on a chop saw
Threaded rod - cutting on a steel cut off saw to create no burr.

The trick to cutting clean ends, first time, so that the nuts are easy to run onto the rod by hand only is shown in the sketch above.

  1. Mount the rod in the saw's clamp, only just tight enough to to hold it in position, but loose enough to allow you to slowly rotate the rod as you are cutting.
  2. This way, the last bit to get cut though is at the center of the rod, well away from the threads.

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Joiner Nuts

Normal good practice for bolted connections is for the nut to be completely on the bolt with a minimum of two and a half threads extra sticking clear of the end of the nut.
This generates the required strength out of the connection.

Joiner nuts are nuts that are about three to three and a half times as long as ordinary nuts, and they allow us to join two lengths of bolt together and still retain the full strength of the joint.

  • You must make sure that the two bolts are joined at the center of the nut.
  • Quite often with a rough end on one of the nuts, the thing jams when it is only a couple of thread in.
  • My usual method in say a wall like in the above sketch is to hold the joiner nut alongside the end of the bolt in the right position, and then clamp a vise grip onto the bolt.  That is half the length of the nut down.
  • Run the nut onto the bolt up to the vise grip, and it should now be half way on.
  • Then run the next bolt on and tighten again with another vise grip.

Quite often before threaded rods and joiner nuts came on the scene, we had to get threads cut on the end of rebar steel.
Then when we had to join the bars we had to weld them.  Welding is fairly quick in itself, but when working in an existing house there is always a risk of fire, so with welding comes the need for maybe an extra guy to help the welder set up, and to keep an eye out for fire etc.
Using joiner nuts is so much easier.

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Quick Definitions
Chamfer: A small 45 degree flat, on what would otherwise be a 90 degree corner.  Used with joinery etc.
Arris: The simplest form of chamfer, just a shaving to take away the sharp edge.



Please Note! The information on this site is offered as a guide only!  When we are talking about areas where building regulations or safety regulations could exist,the information here could be wrong for your area.  It could be out of date!  Regulations breed faster than rabbits!
You must check your own local conditions.
Copyright © Bill Bradley 2007-2012. All rights reserved.
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