Author Topic: Long table, how to support  (Read 2101 times)

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Offline Rick Herrick

  • Posts: 526
Long table, how to support
« on: April 10, 2021, 02:31 PM »
I am trying to put together another sewing table for my wife.  She wants it open enough in the center to put and use 2 machines at the same time.  The end supports will be a couple of small cabinets for drawers.  I am mocking up a demo now and I am looking for some suggestions on some 'under table' support.  The boxes are ~ 425mm wide and I have ~ 1400mm of an opening.  I will be adding an ~ 150mm rear vanity skirt which should help.  Also thought about another, 50mm or so, stringer (on edge) in the middle to give more support.  She just doesn't want anything in front.  If I put something on the front, it doesn't give her the right height and clearance.  Some of these machines have a knee controller so overall height and overall clearance is tight.  The middle support won't be in the way.

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Offline Alex

  • Posts: 7481
Re: Long table, how to support
« Reply #1 on: April 10, 2021, 02:46 PM »
Over here we can get these in serious sizes like 50 x 50 cm long, about 1,5 foot.

2 or 3 of these under your table and you have all the support you need in the middle.

If your supplier doesn't have them, any metal company can easily make them.
 


Offline DynaGlide

  • Posts: 1057
Re: Long table, how to support
« Reply #2 on: April 10, 2021, 03:15 PM »
You could probably rout in some metal supports the length of the unsupported section. That's what my friend did with an overhanging countertop.
Instagram @matts.garage

Offline Mike35x95x1

  • Posts: 67
Long table, how to support
« Reply #3 on: April 10, 2021, 03:30 PM »
Hi,

I finished similar table week ago and used silicon antislip stoppers:

https://r.tapatalk.com/shareLink/topic?share_fid=11638&share_tid=66027

you can also place one extra vertical wooden board at the back to support the table top. Something like this:



Mike


Sent from my iPhone using Tapatalk
« Last Edit: April 10, 2021, 03:33 PM by Mike35x95x1 »

Offline guybo

  • Posts: 76
Re: Long table, how to support
« Reply #4 on: April 10, 2021, 04:07 PM »
Hi, maybe if you have left over ply,make a couple of wooden I beams front and back to the size you need,attach with the flange and fill the webs to attach the end cabs.looks nice,guy

Offline Peter_C

  • Posts: 1094
Re: Long table, how to support
« Reply #5 on: April 10, 2021, 04:27 PM »
For my industrial sewing machine the supports are all steel underneath the 2" thick top. The machine is very heavy and since it is flush mounted the top has a BIG hole cut out of it.

Knee lifts are awesome! So is auto-cut.

Offline mike_aa

  • Posts: 1229
Re: Long table, how to support
« Reply #6 on: April 10, 2021, 05:46 PM »
They make "L" supports for granite and stone countertops.  Maybe something like this would be sturdy enough for you.

https://www.bbindustriesllc.com/i-brace-countertop-supports.html

Mike A.

Offline Sparktrician

  • Posts: 4162
Re: Long table, how to support
« Reply #7 on: April 10, 2021, 06:29 PM »
You could also use some low-profile strut channel end-to-end.   [smile]
- Willy -

  "Show us a man who never makes a mistake and we will show a man who never makes anything. 
  The capacity for occasional blundering is inseparable from the capacity to bring things to pass."

 - Herman Lincoln Wayland (1830-1898)

Offline Crazyraceguy

  • Posts: 505
Re: Long table, how to support
« Reply #8 on: April 10, 2021, 08:04 PM »
You mentioned the height in the knee space being important, but what about overall height? If you could build the countertop as a torsion box, it will be much stiffer. This will span the gap with much less potential for sagging between the cabinets. The top will have to be thinker to accommodate it. It can be made with thinner material because the strength/stiffness comes from the glue line of the outer skins.
Even if it could only be two layers of 1/2" material glued together, it would be stiffer than a single sheet of 3/4" and only gain 1/4" overall.
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Offline Bob D.

  • Posts: 2132
Re: Long table, how to support
« Reply #9 on: April 10, 2021, 10:59 PM »
What is the maximum allowable thickness for the top?
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It's a table saw, do you know where your fingers are?

Offline Rick Herrick

  • Posts: 526
Re: Long table, how to support
« Reply #10 on: April 10, 2021, 11:58 PM »
What is the maximum allowable thickness for the top?

I think 1-1/2" total.  I built her 2 smaller tables about 30 years ago, with only the 3/4" top, and she says they are perfect.  But those only had about 28" left to right opening where this one needs 5'.  The issue is having the knee clearance just right, so that the operating height doesn't put her arms at a weird position.

I like Alex's idea of the L brackets but I haven't been able to find (easily) bigger ones, still looking.  Willy's suggestion of that strut channel looks very interesting and simple to use. 

Offline Svar

  • Posts: 2402
Re: Long table, how to support
« Reply #11 on: April 11, 2021, 12:53 AM »
Looking at your constraints square or rectangular steel tube will be the most rigid (since they don't make I-beams this small).
For example, 1" x 3" x 0.125" wall steel tube placed flat, over a span of 5 ft will deflect less than 1/8" under 100 lb load.
U-channel/strut would be my second choice, angle - third. Although angle is most easily available.
Whichever beam you choose, securely attaching it to the top along entire length will further increase stiffness.
« Last Edit: April 11, 2021, 12:38 PM by Svar »

Offline Bob D.

  • Posts: 2132
Re: Long table, how to support
« Reply #12 on: April 11, 2021, 05:08 AM »
Easy to find.

https://www.homedepot.com/p/THE-ORIGINAL-GRANITE-BRACKET-26-in-L-Bracket-Countertop-Support-Bracket-LB-26/311400497

Do a Google search and you will find many choices in multiple sizes.

Now that we have a depth you could embed a couple of 1-1/4 x 1/8 steel angle (or 1-1/4 x 1-1/4 x 1/8 T bar) front and back using epoxy and screws. To hide the front angle cut a slot just wide enough for the vertical leg and epoxy it in. Doing this will not increase the thickness of the top more than the 1/8" of the steel. I don't know if aluminum would be strong enough but it might work.

If you wanted to go crazy drill some 1/4 or 5/16 holes in from the front edge through the angle and insert a rod to cross pin the angle and lock it in place. Cap the edges with a veneer to hide the holes.

« Last Edit: April 11, 2021, 05:19 AM by Bob D. »
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It's a table saw, do you know where your fingers are?

Offline Steve1

  • Posts: 91
Re: Long table, how to support
« Reply #13 on: April 11, 2021, 07:09 AM »
When you need high stiffness with short height, the answer is steel.
I would use angle iron, probably something like 2 x 2 x 3/16.   Ideally, running the entire length - if its fully supported on the end boxes, mounting screws are seeing very little load.
But I rather like Spartrician's idea of using Unistrut - looks a little better than steel angle and has nice rounded edges at the bottom. (but not the low profile aluminum stuff, you need the standard full height steel stuff to get good stiffness)
« Last Edit: April 11, 2021, 07:17 AM by Steve1 »

Offline morts10n

  • Posts: 292
Re: Long table, how to support
« Reply #14 on: April 11, 2021, 10:24 AM »
A 2" thick plywood top made from two 1" sheets glued together is a "solid" choice

Offline Bob D.

  • Posts: 2132
Re: Long table, how to support
« Reply #15 on: April 11, 2021, 01:44 PM »
This is what I was thinking of.

Adds nothing to your desired depth of 1.5 inches.

Cut a slot on the underside of the top then slide the angle in which has been buttered up with epoxy.
You can either recess the horizontal leg as shown in a groove or leave it below the underside of the tabletop.

If you don't think that is strong enough drill some 1/4 inch holes in from the front edge and insert some pins. Then cover the front edge with veneer or a cap of hardwood.
-----
It's a table saw, do you know where your fingers are?

Offline Peter_C

  • Posts: 1094
Re: Long table, how to support
« Reply #16 on: April 11, 2021, 03:13 PM »
No one has asked so...Do these sewing machines mount down in the table requiring a large hole cut into the top surface for flush mounting? Are the motors mounted under the table? What is the weight of the machines? Pictures of said machines?

Offline MikeGE

  • Posts: 245
Re: Long table, how to support
« Reply #17 on: April 11, 2021, 03:43 PM »
A 2" thick plywood top made from two 1" sheets glued together is a "solid" choice

Along that theme, here's a video of a guy making a wide bookshelf that doesn't sag under the load of books.  He used two layers of plywood with steel strips sandwiched between the layers in a dado along the length of each shelf.



Offline Sparktrician

  • Posts: 4162
Re: Long table, how to support
« Reply #18 on: April 11, 2021, 04:41 PM »
A 2" thick plywood top made from two 1" sheets glued together is a "solid" choice

And ridiculously heavy to move!   [eek]
- Willy -

  "Show us a man who never makes a mistake and we will show a man who never makes anything. 
  The capacity for occasional blundering is inseparable from the capacity to bring things to pass."

 - Herman Lincoln Wayland (1830-1898)

Offline Sparktrician

  • Posts: 4162
Re: Long table, how to support
« Reply #19 on: April 11, 2021, 04:51 PM »
No one has asked so...Do these sewing machines mount down in the table requiring a large hole cut into the top surface for flush mounting? Are the motors mounted under the table? What is the weight of the machines? Pictures of said machines?

Although unstated, this is what I was considering when I suggested Unistrut.  That stuff is quite rigid and can withstand considerable weight without bowing.  If concealment is desired, set the Unistrut into a 1/2" deep dado with epoxy.  If the appearance of thickness is desired, double up the front and back 3" (as we often do with solid surface material) or so and band it with solid wood to cover the plies. 
- Willy -

  "Show us a man who never makes a mistake and we will show a man who never makes anything. 
  The capacity for occasional blundering is inseparable from the capacity to bring things to pass."

 - Herman Lincoln Wayland (1830-1898)

Offline Rick Herrick

  • Posts: 526
Re: Long table, how to support
« Reply #20 on: April 11, 2021, 11:37 PM »
No one has asked so...Do these sewing machines mount down in the table requiring a large hole cut into the top surface for flush mounting? Are the motors mounted under the table? What is the weight of the machines? Pictures of said machines?
This table is beyond simple.  A desk to hold a sewing machine, nothing fancy.  Today I wrapped the front and both sides with 3/4" oak, 1-1/2" wide.  She wanted something akin to a back splash so I made one 3-1/2" wide from the same 3/4" oak and secured it to the back of the top with pocket holes, about 5" apart.  Those two things alone have made a big difference and she will spend this coming week testing it.  I am still looking at @Sparktrician Willy's idea on that strut option.  Closet Maid has some shelf standards that are very tough.  I will see how much those are before going to McMaster to get the low profile ones that Willy suggested.

Offline Bob D.

  • Posts: 2132
Re: Long table, how to support
« Reply #21 on: April 12, 2021, 08:16 AM »
You can get the narrow strut at the big box stores, no need to order online. Look in the electrical section, usually near the EMT and rigid conduit.
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It's a table saw, do you know where your fingers are?

Offline Rick Herrick

  • Posts: 526
Re: Long table, how to support
« Reply #22 on: April 12, 2021, 08:37 AM »
You can get the narrow strut at the big box stores, no need to order online. Look in the electrical section, usually near the EMT and rigid conduit.

Thanks Bob, as an electrical supply it may even be cheaper than the Closet Maid stuff.

Offline Sparktrician

  • Posts: 4162
Re: Long table, how to support
« Reply #23 on: April 12, 2021, 08:48 AM »
You can get the narrow strut at the big box stores, no need to order online. Look in the electrical section, usually near the EMT and rigid conduit.

Thanks Bob, as an electrical supply it may even be cheaper than the Closet Maid stuff.

One thing to note is that the strut I suggested is aluminum, while the more commonly available strut is steel. 
- Willy -

  "Show us a man who never makes a mistake and we will show a man who never makes anything. 
  The capacity for occasional blundering is inseparable from the capacity to bring things to pass."

 - Herman Lincoln Wayland (1830-1898)

Offline Bob D.

  • Posts: 2132
Re: Long table, how to support
« Reply #24 on: April 12, 2021, 09:00 AM »
Didn't notice that you had proposed AL strut. Yes, that would weight less.

Either I think would be much stronger than the shelf standard channel as
it has a much larger cross section than the ClosetMaid stuff.
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It's a table saw, do you know where your fingers are?