Question about making a furniture assembly table.
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  1. #1
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    Default Question about making a furniture assembly table.

    I've been working on various framing and assembly tables for my furniture client. To be clear, they are on the "fast and cheap" side of the market so a good, sturdy and flat surface of up to 60" x 109" is needed to ensure that frames and assembly are done correctly so that the furniture sits "square" on your floor. Various layers of tops have been used, always at least 3/4" plywood with some form of steel on top. The support frame is made from 2" (0.12" wall thickness) square tubing.

    The latest issues have been with rust on carbon steel and it being too thin (16 GA over 1.5" plywood) so I was going to go with SS 304-2B which has a nice smooth finish and was going to go 12 GA. I was going to do a trial with using 3M spray adhesive(which is a dry contact cement) to hold the SS onto the plywood, using a "pull out" ramp fixture to ensure that the installation process didn't create any air bubbles (one end starts with contact and gradually lowers it as the shallow ramp fixture is slowly pulled out the other end).

    I talked with someone there yesterday and his concern is that temperature fluctuation will cause warping/blubbling since the only thing holding the SS down is the adhesive. One option would be to use flathead screws on countersunk holes but he is holping to go "solid steel" surface (no plywood). While I'm not against this, I'm concerned about three things: 1. What's the best design? 2. Will it be too expensive? and 3. Will there be other issues like it's too "loud and cold" (thick raw steel as opposed to thin steel over thick plywood).

    Just wondering if anyone out there has experience with this kind of table construction and has any recommendations. To be clear, I'm NOT trying to come up with reasons not to go the solid steel route, I just ideally want verification and recommendations on how to do it if we would. The main issue is how to fasten a stainless top to a carbon steel frame? I have several options:
    • Bolt thick rails and TIG weld the thin top onto the thick rails underneath (or maybe even on top using laser-cut small slots that we grind/sand smooth)
    • Use weld studs under the sheet that go through holes in the frame.
    • Have a thick and solid enough top frame so that a thin layer of stainless can be laid on top with just some light adhesive.



    If you have any recommendations, please net me know. We currently have two frames that would need new tops (replace the thin carbon steel and plywood). They have two or three (one table top is 40" wide, the other 60" wide) long 2" square tubing rails (about 106" long) with five cross rails so "openings" on the top are as big as about 24" x 32". We could of course make these smaller to support a thicker single sheet of steel.

    Thanks,
    The Dude

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    I would use 16 gauge EG.

    Stainless is shiny, but it sure isn't flat and it's expensive. EG will never rust and it's same price as plain mild steel.

    I've had my pick of hundreds of factory assembly tables and the ones I prefer are gray plastic top over wood (probably UHMW?, Looks like nylatron, but doubt the ones I have are made from that). 3/4 plywood is dropped inside a 1" angle iron top edge which leaves about 1/8" of lip on the angle iron to keep the plastic from sliding anywhere.

    For thinner steel, countersink holes and use brass screws into the 3/4" plywood. File off the screw head if necessary to get flush.

    What about fancy wood? You can buy form grade plywood that is super tough. I skinned 7000 sq ft of my shop roof with 13/16 and 7/8" thick form grade plywood. I bought units of blows from the mill in Roseburg for $8 a sheet. You can't tell there's a blow in plywood. Doesn't matter a bit for most things.

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    Quote Originally Posted by Garwood View Post
    I would use 16 gauge EG.

    Stainless is shiny, but it sure isn't flat and it's expensive. EG will never rust and it's same price as plain mild steel.

    I've had my pick of hundreds of factory assembly tables and the ones I prefer are gray plastic top over wood (probably UHMW?, Looks like nylatron, but doubt the ones I have are made from that). 3/4 plywood is dropped inside a 1" angle iron top edge which leaves about 1/8" of lip on the angle iron to keep the plastic from sliding anywhere.

    For thinner steel, countersink holes and use brass screws into the 3/4" plywood. File off the screw head if necessary to get flush.

    What about fancy wood? You can buy form grade plywood that is super tough. I skinned 7000 sq ft of my shop roof with 13/16 and 7/8" thick form grade plywood. I bought units of blows from the mill in Roseburg for $8 a sheet. You can't tell there's a blow in plywood. Doesn't matter a bit for most things.
    Hey thanks, never though about the EG, that's worth considering. UHMW won't work, if it gets scratched it can damage the fabric (that's unfortunately been verified). We do use that on some upstream framing processes and it works good for that.

    I just talked to the fabricator quoting it, we may go with about a 3/16" mild steel top that is welded on as part of the frame, and then go with a thin coat of EG or stainless on top.

    Thanks again,
    The Dude

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    SS sheet with contact cement will work, forget about trapping bubbles. There is no way you are going to get a 100% bond to trap air. That is not how contact cement works. Contact cement is flexible and will allow some movement, but frame needs to hold plywood substrate flat.
    The biggest issue with contact cement is getting the SS sheet indexed to the substrate without accidental bonding in wrong location. I have done maybe thousands of laminate tops using strips of Venetian blinds to keep the sheets from touching. But once a touch happens, that is where the top sheet ends up. SS is a lot heavier. Blinds need to be closer together. Count them and make sure you pull out as many as you place.

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    I agree that the stainless 12 ga will be good. Just be sure the wood subsurface is mounted to a frame that is flat with plenty of cross supports. Screws up from the bottom so no screws are hidden under the glued top.
    If you ever do want to use a solid steel top then it HAS to be screwed or bolted to the frame. Any welding at all will warp it and it will no longer be flat.

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    Depending upon what you're doing with this a standard kitchen counter top could be considered. I use them for tear-down and assembly of mechanical components and/or furniture assembly in woodworking projects. Cleans up nicely,doesn't absorb grease, solvent, aliphatic glue doesn't stick very well, fairly stable/flat, and can be cut to whatever shape/size needed. Holes can be drilled through for fixture mounting and/or clamping hold-downs. If you know someone that's remodeling a kitchen (or talk to a crew that installs them) one can often be had for free. I prefer them over my 3" oak top workbench for some operations. Just a suggestion.

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    Or a stone top
    Look at garden tables with stone top

    Peter

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    Thick phenolic is another option. Trespa, Wilsonart, Pionite. Up to 1" thick.

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    Quote Originally Posted by Scruffy887 View Post
    SS sheet with contact cement will work, forget about trapping bubbles. There is no way you are going to get a 100% bond to trap air. That is not how contact cement works. Contact cement is flexible and will allow some movement, but frame needs to hold plywood substrate flat.
    The biggest issue with contact cement is getting the SS sheet indexed to the substrate without accidental bonding in wrong location. I have done maybe thousands of laminate tops using strips of Venetian blinds to keep the sheets from touching. But once a touch happens, that is where the top sheet ends up. SS is a lot heavier. Blinds need to be closer together. Count them and make sure you pull out as many as you place.
    If we went this route, as mentioned, I was going to have a laser-cut ramp fixture with crossmembers that would index off one end and create a stable pull-out. It would be 3 ramps of 1/4" steel that raise from 0" to about 2", would pull out evenly so that the top layed in a continuous manner in only one direction.

    Quote Originally Posted by Rob F. View Post
    I agree that the stainless 12 ga will be good. Just be sure the wood subsurface is mounted to a frame that is flat with plenty of cross supports. Screws up from the bottom so no screws are hidden under the glued top.
    If you ever do want to use a solid steel top then it HAS to be screwed or bolted to the frame. Any welding at all will warp it and it will no longer be flat.
    That's basically the orginal direction I was headed, until the "other guy" said he wanted a solid steel top. The fab shop I'm working with said they did make a 4 x 8 table recently with an 1/8" steel top, similar support structure to mine and it stayed flat (just tack welds).

    All of the synthetic laminate material won't work, not strong enough. They assemble about 75 pieces per day on each table and it's pretty "rough". Any scratching/gouging of the material would affect the fabric. Not my preferred assembly process but what I have to deal with.

    Thanks,
    The Dude

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    Quote Originally Posted by The Dude View Post
    That's basically the orginal direction I was headed, until the "other guy" said he wanted a solid steel top. The fab shop I'm working with said they did make a 4 x 8 table recently with an 1/8" steel top, similar support structure to mine and it stayed flat (just tack welds).
    I could see that working, I would bend the edges all down 90º to have a nice radius on the edge, then tack weld the bottom edge of the bend. If the support frame is 2x2x120 tube then bend the edges down 1 3/4"

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    MDF torsion box with the stainless sheet adhered to the top. I have made this connection with good results using 3m 90 spray adhesive. That is how I would do it at least.


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