coupling nut for threaded rod mechanism

[Rob Marshall]

Hi,

I'm trying to set up an adjustable (height) platform for a table saw. My thought had been to do something similar to the router lift mechanism from shopnotes issue #121. Essentially using a threaded rod that runs through a coupling nut and raises/lowers whatever when the rod is turned.

The problem that I ran into is that I ordered 4 3/4"-10 threaded rods (one for each corner of the platform) and coupling nuts but I can only screw the coupling nuts on half-way. That makes sense since the idea behind a "coupling nut" is to extend rods by coupling them.

In the shopnotes issue #121 router lift the rod (in their case a 3/4"-16) is able to run all the way through the coupling nut. For those familiar with the router lift (Steve Ramsey also built one and has a video on youtube about the build) the coupling nut is epoxied into the pieced that holds the router. The router can then be raised/lowered as the rod is turned.

So my question is: Is there a "special" coupling nut that would allow me to run the rod all the way through? I don't want to order 4 more and run into the same problem.

Thanks,

Rob

[George Bokros]

I would try to buy locally or call the on-line vendor to make sure what you are ordering meets your need. Didn't Shop Notes list sources at the back like Wo0odsmith does?

[Jim Barstow]

McMaster Carr has coupling nuts with sight holes. I’ll bet these are through-threaded.

[Frank Pratt]

That's odd. I've never seen a rod coupler that wasn't threaded all the way through. We use lots of them at work. Maybe you just got a bad batch.

Related, I once bought a bunch of 3/8" threaded rod, and 3 lengths were not actually threaded, but had a series of ridges that looked for all the world like threads. One of my guys came to me very frustrated because he couldn't get a nut to go on. And I couldn't either. Then I used my fingernail to trace the 'threads' & saw that they were not threads at all.

[Lisa Starr]

I've purchased coupling nuts from McMaster-Carr and used them basically as you're describing. 3 of them work great and 1 has a "tight spot", but is very usable. I've found that McMaster-Carr tends to be more expensive than some other sources, but also usually supplies a higher quality product. In this case, what you're experiencing is that the threads are at the high end of the pitch tolerance and thus don't mesh properly with full engagement. That is a sign of poorer quality machining.

[Jamie Buxton]

I too bought 3/4” couplings. They were 5” long. I built a whole piece of furniture presuming that threads ran straight through. But when I attempted the final assembly, I found that the threads aren’t continuous. The manufacturer tapped 2 1/2” from one end, and tapped 2 1/2” from the other end! I had the coupling nut already epoxied in place. My fix was to buy a 5”-long tap to rethread the nut. That’s a $70 tap to fix a $5 nut.

[Bill Dufour]

The Simpson coupling nuts have cross holes drilled near the middle so the inspector can verify the rods have enough engagement. It is possible they would not be threaded clear through for safety so both ends have to be in deep enough.
If they are threaded from both ends it is unlikely the threads are timed together to allow the threads to be made full length with a longer tap.
Bill D

[David Buchhauser]

Hi,

I'm trying to set up an adjustable (height) platform for a table saw. My thought had been to do something similar to the router lift mechanism from shopnotes issue #121. Essentially using a threaded rod that runs through a coupling nut and raises/lowers whatever when the rod is turned.


Hi Rob,
This is the coupling nut called out in the shopnotes issue #121 plans. The plans did specify McMaster-Carr part number 90977A220 (this is the 3/4-16 version). Although not specifically called out, the drawing implies that the threads are continuous all the way thru the nut. I buy lots of hardware from McMaster-Carr for my various products, and I have never been disappointed with the quality of their parts. The 3/4-10 version lists for $8.13 each. You could give them a call to make sure that the threads are continuous from end to end.

Sales and Customer Service
(562) 692-5911
(562) 641-2800

David


https://www.mcmaster.com/90977a215

412857

[Jamie Buxton]

I bought my 3/4" non-continuous coupling nut from McMaster Carr. However, what I bought was an extra-long version which is 5" long. Now that I look at the product detail, the threading is described as "partially threaded".

[Rob Marshall]

Hi,

Actually I bought the 3/4"-10 coupling nuts (well, everything, rod, washers, nuts and drill bushings) from McMaster Carr. Checking the description of the extra long version, as Jamie points out, it clearly shows that the coupling nut is partially threaded and, even though the nut is 5" long, the thread is only 2-1/2". The part I purchased from them was: 90977A215 (https://www.mcmaster.com/90977a215). The description and details are identical to the 3/4"-16 coupling nuts, part number: 90977A220 with the exception of the thread type/spacing which says UNF/Fine for the 3/4"-16 nut and UNC/Coarse for the 3/4"-10.

The reason I went with the 3/4"-10 instead of the 3/4"-16 was because I didn't need much length. I settled on an 8" long threaded rod since the platform shouldn't have to move more than an inch. For the 3/4"-16 my choice was either 6", which I felt was a little short, or 1' which I felt was too long. I wanted the coupling nut to add extra stability to the rod. I would have preferred something even longer, but...

Perhaps I just need to change my approach. The original idea had been to place the drill bushing in the platform and secure the rod on either side with a nut and a washer (I would probably need to apply silicon or something to ensure they turn with the rod rather than turning, and perhaps even some epoxy to the nuts to lock them in place). The coupling nut was to be in the base and be used to lower/raise the platform. It may be easier to put multiple drill bushings in the base to allow the rod to float freely, but still straight, (it will have to bottom out in the base so that the rod doesn't move up and down) in the base and use the nut/washer at the bottom of the platform to raise/lower it. It's not as good of a solution as I had originally planned, but it would, in theory, work.

Another approach would be to use multiple nuts in the base in place of the coupling nuts. I'd have to experiment to make sure the epoxying several nuts in the base would line up properly. I'd most likely have to thread them onto a rod and shove them into the hole in the base and wait for the epoxy to setup before removing the rod. Would that work?

Thanks,

Rob

[David Buchhauser]

Hi Rob,
Is the adjustable height platform for you table saw the actual table around the blade, or an out-feed table? Perhaps if you could show a drawing (or photos) of what you are trying to accomplish - that would help me to gain a better understanding of your project. (Disregard the attached photo)
Thanks,
David

(Mechanical Engineer)

[Rob Marshall]

Hi,

What I have is a job-site table saw. The idea is to attach the entire table saw to a piece of plywood, i.e. the "platform", instead of the foldable stand that comes with the saw. I'm going to be placing a shop-vac on one side and a cyclone on the other (under where the table saw top extends out to the "right". There will be a flat service over the shop vac (on the left of the saw) and the idea behind the platform (this is all a little bit of over-engineering) is so that I can adjust all four corners of the "platform" so that the top of the table saw is in line with the top over the shop vac. If that makes sense. I don't really have a drawing, yet.

Thanks,

Rob

[David Buchhauser]

So the table saw rests on the adjustable platform? Doe it only need to be adjusted one time?

[Lee Schierer]

I have a picture frame clamp that uses 3/8 threaded rod for the clamping. I have several pieces that I use for extensions that connect with joiner nuts. All of the joiner nuts I have are threaded all the way through including one that is 2" long. They were purchased from a local hardware store.

My advice it to go to several local stores, including the big box stores and check out what they have on hand. From a manufacturing point of view it makes more sense to tap all the way through rather than have two operations to tap part way from each end.

[Rob Marshall]

Essentially, yes. Since I can adjust it if it should ever get out of whack I'll be able to easily re-adjust it. But the idea should be that I only need to do it once. I had tried using a platform that was not adjustable but getting it just right was problematic.

Thanks,

Rob

[Rob Marshall]

Hi,

I tried shopping locally and that was a complete bust. What little supply I found had the same problem, i.e. the coupling nut would only thread on half-way and then stop.

So I decided to get a 3/4"-16 rod (I found one that was 8" long - not sure how I missed it the first time) and a 3/4"-16 coupling nut (the identical part number as the one in the Shop Notes router lift article). The rod and nut arrived today and it works as expected, i.e. I can thread the coupling nut completely onto the rod. So I've ordered more from McMaster Carr and I'll use them.

Perhaps it's because the threading is "coarse" that it doesn't thread all the way through...but who knows. Certainly not me.

Thanks for all the help,

Rob

[David Buchhauser]

Hi Rob,
Glad to hear it finally worked out for you!
David