Do I need acme thread?

[koenbro]

I have a general purpose workbench, with a pine 6' x 2' x 1.5" top. Frame is welded angle, legs are 1.5" tube with casters. I would like to make the height adjustable, telescoping the legs with an inner tube (1.5") inside an external tube (1-3/4"). Was thinking of driving a threaded rod from the top inside the leg, weld a nut the top and screw into a captive nut inside the leg so i can lift or lower individually the legs.

Do I need an acme thread or will a regular 3/8" - 1/2" allthread work? Thank you all.

 

[dr_clyde]

Acme threads are designed for moving loads on a screw thread, so that would be an appropriate use. Depending on load, regular all-thread would probably work just fine.

 

[Kenstone1]

I think you'd be fine with all-thread and suggest you use coupling nuts that have three times + longer thread engagement for the internal captive nuts.

 

[lis2323]

What everyone above said[emoji106]


I would just use all thread but 5/8” minimum.



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[ClappedOutBport]

Acme threads are designed for moving loads on a screw thread, so that would be an appropriate use. Depending on load, regular all-thread would probably work just fine.

It would be appropriate. But if Kurt thinks that 60 degree is good enough for a vise, I think it would do fine here as well.

 

[fiftyv8]

Worst case scenario, find a couple of old trailer drop down jockey wheel mechanisms and utilise the thread and rod from them...

 

[matt_i]

Not trying to shoot down your idea but its tough to get a square tube-square tube setup to have a tight tolerance so that it won't rock. Sometimes the internal weld seam is what's messing you up. I've had good luck with a band-file (really a 1/2" wide belt sander by Milwaukee) for removing it but it only goes so deep.

Like any fastener you are using for moving loads, lubrication is going to be quite important. I would use Gr5 hardware and B7 threaded rods for a little more than your average zinc plated Grade 2.

 

[koenbro]

Not trying to shoot down your idea but its tough to get a square tube-square tube setup to have a tight tolerance so that it won't rock. [...]

Like any fastener you are using for moving loads, lubrication is going to be quite important. I would use Gr5 hardware and B7 threaded rods for a little more than your average zinc plated Grade 2.

My table already has this 1-3/4 outside and 1-1/2 inside telescoping cold-rolled 1/16" tube and it seems to fit OK.

Yeah I was worried about lubrication and have no idea how to do it, other than a hole above the retained nut, cap it off with some rubber to prevent dust, but open it up periodically and drop some lube into it.

Also thought about sprocket and chain to sync all four but would need 5 sprockets so that I can add a tensioner. I am putting the idea on a temporary hold because of cost. At McMaster, a sprocket is $18 x 5 = $90 plus 20 ft of chain at $5 = $100.

 

[Kenstone1]

My table already has this 1-3/4 outside and 1-1/2 inside telescoping cold-rolled 1/16" tube and it seems to fit OK.

Yeah I was worried about lubrication and have no idea how to do it, other than a hole above the retained nut, cap it off with some rubber to prevent dust, but open it up periodically and drop some lube into it.

I'm guessing the internal nut is in a fixed location...
I would just put a grease fitting in each nut and drill holes thru both tubes that can be lined up to grease the nuts.

 

[koenbro]

I'm guessing the internal nut is in a fixed location...

I would just put a grease fitting in each nut and drill holes thru both tubes that can be lined up to grease the nuts.

Great idea thanks that’s how I’ll do it.



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[yhprum]

For the chains and sprockets you could reuse bicycle parts if you have any available at the local dump.

 

[Bretny]

Try surplus center. I got acme thread, nuts and chain sprocket for a decent price from them before.

 

[Kenstone1]

Not to burst your bubble here...
But have you considered putting a scissor jack on a post/riser under the center of the table top?
The post could be mounted on a lower shelf and would of a length that would place the jack just under the table top at it's lowest position.
Raising the jack would raise the table top at or near level, and cross pins could pushed thru appropriate holes drill thru both the inner and outer tube of each leg to lock the table at any height.
A jack like this could be raised/lowered with a socket and a cordless drill:
https://www.harborfreight.com/2-1-2-half-ton-trailer-stabilizer-jack-96406.html
That's a lot less mechanism than a jack screw at each corner, and would raise/lower from one point.
just sayin'

Edit: the jack could be on the lower shelf and the "post" on top of it, the jack would be more accessible that way.

 

[torched]

Been there done that. I did a test with standard all thread and it wore out very fast, ACME is the way to go. As far as eliminating the side to side movement or slop in the legs I made a jamb bolt to lock the legs when I have the table at its desired height.

 

[Joemctag]

Yeah, jam-bolt’s what everybody uses because the fit’s loose. Haven’t tried it yet, but you can use an angle grinder to make a groove in the smaller tube that matches the inside weld seam on that leg’s larger tube. Still need SOME clearance but you could always grind a thirty-second to a sixteenth off 2 adjacent sides of the smaller tube to get that if , say, the one’s o.d. and the other’s I.d. were the same.

 

[kbs2244]

I like the adopting of a trailer hitch jack idea.
It is the same need solved by professional engineers.

 

[Kenstone1]

Do I need acme thread? NO!

I stole this pic off HF reviews of that stabilizer jack I mentioned in post #13.
Adjustable table height but it's made of wood.
More pics here, in the reviews:
https://www.harborfreight.com/2-1-2-half-ton-trailer-stabilizer-jack-96406.html

 

[Earp69]

Subscribing to this one. I'll be building something simalar in a couple of months

 

[C_F]

Lots of ideas flying here in this thread...I'm bringing in the popcorn & kicking back for the ride.

 

[Kenstone1]

There are these adjustable height bench/tables at Home Depot

https://www.homedepot.com/s/adjustable%20height%20workbench?NCNI-5

They get good reviews over there,

 

[83VillageRepair]

There are these adjustable height bench/tables at Home Depot

https://www.homedepot.com/s/adjustable%20height%20workbench?NCNI-5

They get good reviews over there,

I bought the white 2 drawer husky in the link to use for a desk in the house. Way too light duty to use as a work bench, except maybe for electronics repair. But it is a really cool desk.

Wade