I actually found the thread. But the funny thing is I have one of these dewalt already. Id like to attach a Lowell full pole n clamp to railings or chair arm.
Do yourself (and the audience below) a big favor and get a real
Super Clamp. They're only $30, are made to hold 5/8" studs to attach all kinds of lighting accessories like the Lowell pole you want to use, and will grip tighter than you would imagine on any flat or rounded fixed object. Once you use one, you'll see that they're well worth the money and are the best tool for the job.
You also need a steel safety cable if clamping to railings - you don't want your stuff letting go and falling on people below. Check the extensive threads on clamps
bookmarked here for tons more info on this.
In contrast, the type of clamp you want to use might work OK on something flat, but will not be any good on a railing, nor will it be strong enough to support anything cantilevered out. With a pole on it, especially mounted to a 1/4"-20 bolt through that hole, you're asking for trouble, IMO. I have a few of those clamps and I would never use them for something like this.