I'm installing a suspended lighting track system in a concrete ceiling. The ceiling has some abnormalities and the anchors (seen here: https://www.grainger.com/product/DEWALT-ENGINEERED-BY-POWERS-Vertical-Rod-Hanger-Anchor-54PD63) I've installed are slightly off so that when I insert a 5 foot 1/4 20 threaded rod, they all hang un-level (there are about 16 of them in total). I know that I can bend the rods to appear level - but I thought a better solution would be to purchase these from mcmaster carr:


This pivot adapter can screw directly into those ceiling anchors.

The problem now is that the set screw cavity (which the threaded rods will go into) is 0.328 or 21/64"

I can't find a M 0.328 to F 0.25 adapter.

Any ideas on how to do this? Should I just use a hand-tap to make that hole 3/8 so that I could more easily find a 3/8 to 1/4 adapter? Is there some kind of sleeve I can insert to accept the 1/4" threaded rod.

Per the answers below, I just want to clarify that I am using the set screw threading to insert a 1/4" threaded rod. The hole is too big and I can't find an adapter suitable. Thanks!

enter image description here

****Ended up just ordering threaded rods @ 5/16 24 which fits perfectly in the coupling. The 15 degrees from center of movement is perfectly fine because the threaded rods are 5 feet long. Did a strength test too and the couplings are more than suitable to support the lighting track. Thanks everyone for your help in troubleshooting.


Let me take another swing at this.

This is a common issue when hanging pipe or conduit: your threaded rod goes up, but you need adjustability. Preferably without having to take it all apart.

I would use a basic pipe strap.

enter image description here

Cut it so there are an odd number of (major) holes. Make a loop. Then use a short 1/4-20 screw to go through first a washer, then both outer holes (creating a loop around the screw head), then on into the concrete fastener. Now a loop of pipe strap dangles from the fastener. Run the threaded rod up through the center (bottom) hole, then a washer, then a nut. It will stretch out vertically, but you can turn the nut to adjust height.

First, that binder isn't made for .328 rod. It is made for solid 1/4 to 5/16 rod, exactly like it says on the tin.

enter image description here

Now, using the setscrew hole is not a great plan. It's the wrong size and pitch (finethread), and you won't find an adapter from 1/4-20NC to 5/16-24NF (if it's even that), not even a helicoil.

Also, the fastener only pivots 15 degrees from straight, but even if that is acceptable, it's not made to have tension loads through the ball joint, it's designed for shear loads across the ball joint.

However I would also consider standoffs like these if you can find them in 1/4-20.

  • Thanks Harper. I updated my previous post with an image. I think I was unclear - I'm not going to insert a rod as intended, I'm going to use the threading for the set screw to hang the 1/4" threaded rods. – user89588 Aug 7 '18 at 15:30
  • @user89588 You can't. That swivel only gives you 15 degrees off center. It is also made for 90 degree force not endwise force.You want the other ones I linked, which are also half the price. – Harper Aug 7 '18 at 15:37
  • Thank you. The hinged m/f standoffs would be great except they don't make them in 1/4 20 (to attach to the ceiling anchor). – user89588 Aug 7 '18 at 15:46

The dimension 0.328 inches is approximately 8.3 mm which coincides with the hole size for a 5/16" helicoil insert.

Unfortunately, you then have a 5/16-18 thread into which you want to insert a 1/4" rod. There aren't any easy adapters for such configuration, but...

You could chop up some 1/2" aluminum rod, thread one end for 5/16" and the other for 1/4" and use them to join the short piece of 5/16" threaded rod in the fitting with your 1/4" rods, but only if you have the available vertical space for your installation.

You ask if you should tap the hole for 3/8 thread, but I was not able to find the thread pitch currently in place. Tapping to a different pitch reduces the strength of the threads by a substantial amount. The helicoil method will provide greater strength.

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