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5/8 Threaded Rod in Compression

02/14/2021 8:55 PM

Hi Smart People! I'm Mike, and I'm not an engineer. But I am designing a project for my wood shop, and need some help. My design is a mobile tool cart, holding (2) 100 pound tools in the vertical, saving floor space. I want to build a wooden frame, around 30" x 30" x 36" tall. In the corners of the cart I want to place (4) 5/8" threaded rods, secured at the bottom in bushings. Moving up and down on these rods will be a bottom deck holding a 95 pound wood planer, and about 30" above that will be another top deck holding a 85 pound drill press. The (4) rods will be about 60" tall, and the two decks will be supported by rod couplers of 2" length, and another bushing. The rods are Home Depot junk, listed as Q195 low carbon steel. Given that this project is small in stature, and not too heavy, my Spidey Sense is telling me things will work fine. I just a little worried about the threaded rod in compression. I've never done it before, so have no real experience to back up my Spidey Sense. So, before I invest in hardware, wood, time, and expensive tools that may crash to the ground, I thought I'd run it by you guys here, and see what you have to say. I hope I've given enough information, but will gladly answer any questions you have. Thanks in advance...Mike.

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#1

Re: 5/8 threaded rod in compression

02/14/2021 10:32 PM

Trying to picture this. Would it be possible to include a sketch? Just wondering how you will rotate the rods or the nuts holding the platforms with your tools. What keeps the whole shebang from going kittywampus or off-kilter?

You might want to consider an acme thread. I have no financial or emotional interest in McMaster-Carr other than being a satisfied user of their products.

https://www.mcmaster.com/threaded-rods/thread-type~acme/

Good luck with your quest.

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#4
In reply to #1

Re: 5/8 threaded rod in compression

02/15/2021 6:57 AM

Good Morning Sir Robin. I'm inept at using Sketch Up, and pretty bad at drawing by hand as well. I design most things in my head. Hope this helps a little bit. I considered using acme threads, but trying to keep the cost down, as this is proof of concept, and if it works, I may or may not rebuild it.

The bushings at the bottom will keep the rods from moving. And passing through the 2 platforms with 2" rod connectors should keep things semi square. Since all 4 rods will be connected by a chain and sprockets at the bottom, they all should move evenly when the motor drives them.

I'm not sure if there is a way to attach the rods to the cart columns, and still allow the platforms to pass the attachment points. At least I can't see a way. I might consider adding some angled steel to the bottom of the cart top opening, to corral the platforms, and glide them into the opening, in case the whole thing goes "kittywampus". (I assume that's a proper engineering term)

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#16
In reply to #4

Re: 5/8 threaded rod in compression

02/15/2021 7:15 PM

That's a fine sketch. That is what I thought it might be, but I wasn't sure. The issue is the lack of triangulation that may result in the 'tower' being wobbly. There isn't much to keep the structure from parallelagramming. (Which isn't really a word.)

If the platforms were constrained by a rigid frame, then the threaded rods could simply act as lifting agents and not providing lateral stability.

I threw something quick together in PowerPoint to illustrate my thoughts. The four threaded rods would have bushings top and bottom and you could use sprockets and chain to hook all the rods together so they all turned as a unit.

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#17
In reply to #16

Re: 5/8 threaded rod in compression

02/15/2021 11:11 PM

Well, that's an even finer sketch! As my project evolves, I'm thinking of adding some expense by using acme screws, since the mating threads between the screw and the carriage will be more secure. I'm also thinking of shortening the rods to about 36", and building the two platforms attached to each other with 2x4's, and push the whole arrangement up and down from the bottom. That way, I can attach the top of the rods to the corners of the mobile cart, thus preventing them from swaying, and using those attachment points as stops, so the whole thing doesn't just rise up and fall off the jack screws. I'm sure eventually it'll be necessary to add limit switches, and a whole computer system that I know nothing about at this time. If I ever get around to actually building it, it should be pretty sweet! I just have to keep the overall height in mind, so I don't smash the top tool into the ceiling! lol

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#18
In reply to #17

Re: 5/8 threaded rod in compression

02/16/2021 7:10 AM

If you so decide to build your project, you may need to reconsider the actual dimensions of the wooden cart together with the size of casters you plan to use..

Considering some heavy tools will be placed on a moving platform, the concern is with the center of gravity which I think will be shifting up and down and make the cart very unstably dangerous.

Being on casters may make the cart to easily topple over while pushing and the casters hit some impediments like dirts on the floor.

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#19
In reply to #18

Re: 5/8 threaded rod in compression

02/16/2021 7:28 AM

These are excellent points. Thank you. Of course the casters will be locked while the tools are in use, and the cart should never be moved once the platforms are elevated. The cart containing the platforms will be dimensioned 30” square, while the platforms will only be 24” square. The height of the cart will be approximately 40”-42” including the 4” casters. The movement of the platforms will likely be limited to 30”-36” in the vertical. So, while in the closed position the weight of the tools will be low enough the cart should not tip. Moving the cart with the tools elevated would likely be disastrous.

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#20
In reply to #19

Re: 5/8 threaded rod in compression

02/16/2021 8:51 AM

Using a 2 X 2 angle bars welded together as a dolly at the base to hold the casters and serve as the base for the wooden framing may lower and improve the location of the center of gravity, since the angle bars are much heavier than wooden based framing.

Using a smaller sized casters will also lower the CG although may make it harder to push.

Good luck!

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#21
In reply to #16

Re: 5/8 threaded rod in compression

02/16/2021 12:55 PM

Pretty impressive concept sketch for power point, Sir Robin. Seems a little flexible to me though.

I suggest first building a 2 level open box large enough and sturdy enough to hold the power tools you want and allow you to work with them. Try the tools on real work at both levels on anything solid you can throw together at the working height you want. Make sure you can safely work on both tools and get the results you want. If your platform is not sturdy enough the resulting work may not be what you want.

Then build a second open box around that to act as base and guide. Your elevator screw only has to lift the bottom of the moving box so your screws can be shorter. And make sure there is a secure locking mechanism for the up position, do not rely on the screws, they will wiggle as you work which will show up in the finish.

Good luck.

BTW - Check out Misumi for small parts like bushings and bearings.

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#22
In reply to #21

Re: 5/8 threaded rod in compression

02/16/2021 4:48 PM

Hi JRiversW, I’m Mike. I was just about an hour ahead of you. See post 17. I pretty much decided that with no way to support the rods above the main cart, the top would sway too much and probably buckle. So, shorter rods pushing the interior box seemed the way to go. The tool on bottom will be a drill press. I should be able to work within the 24” square area between the wooden uprights. Longer work pieces will pass through them, and I don’t see myself drilling holes in anything wider than 18”, as it’s only a 12” drill press. I will add some t-nuts to the side of the working platform and use star handle bolts to lock the platform in place through the outer cart frame. That should eliminate any wiggle as you mentioned.

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#2

Re: 5/8 threaded rod in compression

02/14/2021 10:36 PM

I have a wood shop that I have everything mounted on wheeled wooden carts that I built....Don't see any need for the threaded rod, I just built everything out of 2x4's and plywood, and mounted locking wheels...You will want the planer at working height, well you want everything at working height for that matter...

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#5
In reply to #2

Re: 5/8 threaded rod in compression

02/15/2021 7:07 AM

Good Morning SolarEagle,

I already made a flip top cart, for my drill press and my small band saw. I find the weight of the drill press makes it difficult for me to rotate the top. I'm constantly afraid I'm going to let go of the drill press shaft, and grab the top of the press, and the top will open, and my grip will come loose, and the whole thing will slip out of my hands.

Since I need a cart for my planer, because I'm tired of lifting it up onto the table, I need a solution for storing and using it that doesn't involve lifting. I saw a guy on youtube build a elevator cart using a car jack, but it looked pretty unstable. I hoped I could do better, and get my drill press in on the action as well. Hence the 2 level cart. The threaded rods are for the elevator action. See drawings I included in an answer to a previous reply above.

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#9
In reply to #5

Re: 5/8 threaded rod in compression

02/15/2021 1:00 PM

You could alleviate that problem with a geared setup...

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#10
In reply to #9

Re: 5/8 threaded rod in compression

02/15/2021 1:59 PM

I'm considering such a setup for the elevator mechanism. If I get that going, I'll use the current flip top cart for my small router table and my sanding station. A lot less weight on the tables, and easier to flip by hand. Also, since those two tools are a lot less tall, there will be room at the bottom of the cart for a drawer or two. As for the small band saw, it might be getting replaced with a floor standing 14" model. But for now, the small one can live on the end of the work bench.

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#11
In reply to #10

Re: 5/8 threaded rod in compression

02/15/2021 2:49 PM

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#3

Re: 5/8 threaded rod in compression

02/15/2021 2:40 AM

1.5" sq. timber, properly jointed, sounds a better bet than <...5/8 threaded rod in compression...>. After all, this is a <... wood shop...>.

The thinking is that the anchoring for the <...bushings...> is the weakest link, and that the <...5/8 threaded rod...> is not inherently stiff enough for <...60" tall...>.

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#6
In reply to #3

Re: 5/8 threaded rod in compression

02/15/2021 7:17 AM

Good Morning PWSlack,

The main cart will be built of wood, 2x4 and plywood. The rods are to make an elevator action, one tool at the bottom out of the way, and one on top to use. Then, elevate the inner parts to raise the top tool out of the way and use the bottom tool at proper height. I had concerns about the rods not being stiff enough, which is why I'm here. If I put the drill press on the bottom, and the planer on top, I could probably limit the travel to about 36" or a little less. I won't need the entire column of the drill press above the table.

The elevator action is to be provided by sprockets and chains and a motor turning the threaded rods in unison. I included some crude drawings in a reply above.

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#7
In reply to #6

Re: 5/8 threaded rod in compression

02/15/2021 7:38 AM

Rectangular-section screw threads are used in lifting and shifting devices, which shies away from a <...5/8 threaded rod...> that has a triangular-section thread.

Otherwise, no change to #3⇑.

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#8
In reply to #7

Re: 5/8 threaded rod in compression

02/15/2021 8:25 AM

I researched and understand the difference. Thanks for the input. I'll try to find some inexpensive acme screws. Also, perhaps I'll use shorter rods, include an attachment point at the top of the main cart columns, and then build up the height of the bottom moveable deck so that the movement can stop at the attachment point, leaving enough of the drill press exposed for use.

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#12

Re: 5/8 Threaded Rod in Compression

02/15/2021 3:30 PM

Your design might work but it might not.

Threaded rod is not designed for compression, but rather tension.

I might bet on short lengths of which I do not consider 60" short.

If you're going to Home Depot to get your materials, why not use one of these.

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#13
In reply to #12

Re: 5/8 Threaded Rod in Compression

02/15/2021 3:51 PM

Hi WJMFIRE. The rods aren’t just to hold up the tools. If that were true, 2x4’s would do. I’m trying to make an elevator cart. Move the top tool up and away, and move the bottom tool up to the work position. Then lower the assembly to switch back to the first tool. Changing elevation of the two tool platforms is the purpose for the threaded rods. Hooked up with chain and sprocket and a motor to turn them. Just not sure if they can support the weight pushing down on them rather than pulling down on them. Compression instead of tension.

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#14
In reply to #13

Re: 5/8 Threaded Rod in Compression

02/15/2021 4:01 PM

Got it!

Ok, then can some brackets be installed on a wall with the 4 rods hanging in tension with the bottom of each rod secured?

This would transfer the load to the wall with the rods properly in tension.

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#15
In reply to #14

Re: 5/8 Threaded Rod in Compression

02/15/2021 4:06 PM

Another object of the project is to be mobile. I think I might use acme screws instead, and shorten them. I’ll make the two platforms connect via 2x4’s, so the rods can be attached to the corner of the main cart for stability.

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#24
In reply to #14

Re: 5/8 Threaded Rod in Compression

02/18/2021 8:58 AM

Another object of the project is to be mobile. I think I might use acme screws instead, and shorten them. I’ll make the two platforms connect via 2x4’s, so the rods can be attached to the corner of the main cart for stability.

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#25
In reply to #24

Re: 5/8 Threaded Rod in Compression

02/19/2021 2:20 PM

Check out the "Surplus Center" catalog at www.surpluscenter.com. They have good prices on acme rod, bearings, gears, sprockets, chain, etc.

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#26
In reply to #25

Re: 5/8 Threaded Rod in Compression

02/19/2021 3:16 PM

Great tip Ronseto. Thanks! I’ll check them out for sure. Mike.

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#23
In reply to #12

Re: 5/8 Threaded Rod in Compression

02/18/2021 8:58 AM

Hi WJMFIRE. The rods aren’t just to hold up the tools. If that were true, 2x4’s would do. I’m trying to make an elevator cart. Move the top tool up and away, and move the bottom tool up to the work position. Then lower the assembly to switch back to the first tool. Changing elevation of the two tool platforms is the purpose for the threaded rods. Hooked up with chain and sprocket and a motor to turn them. Just not sure if they can support the weight pushing down on them rather than pulling down on them. Compression instead of tension.

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