Workbench screw-up

[Marc Prudhomme]

hi fellow creekers,
What the hell did I do wrong.Tried to make a Nice flat workbench using a solid core door toped off with hardwood flooring.Table is 3x5.Its nice and straight the long way(5ft side)but the 3 ft way is bowed BEYOND belief.The mdf and plywood surface I had before was much flatter.What can I do to straighten it, if it is possible.I already mounted my vice and everything.It was pretty flat when I finished but I am guessing that the humidity got to it.I just did not think that it would bow that bad with the Hardwood flooring glued to the top.I am guessing that this will be a lost and I will have to start over.
Help
Marc

[Jamie Buxton]

Yep, the lumber expanded and the door didn't, so you get bowing. You might relieve the pressure by using a circular saw to cut kerfs lengthwise on the top. That is, everyplace you now see a seam between two pieces of flooring, you'll have a kerf. If that flattens out the top, you can then cover the kerfed flooring with plywood or some other sheet goods. Another approach would be to try to remove the flooring. Maybe you can split it off at the glue line. You probably won't get a smooth surface, so again you'll want to reface the top.

[Jim O'Dell]

Possibly the 2 different types of material glued together and reacting differently to the humidity? I was cautioned against using 2 different types of material (MDF and OSB) for torsion box skins because of that. Makes it warp because the materials react different to the moisture. Can you chisel/scrape the laminate flooring off? sand the door back smooth and see if it returns to normal? Then if you want the flooring on it, put it on but let it "float".
Beyond that, some big honkin' angle iron underneath to flatten it back out, but that may not work. Sorry you're running into trouble. Jim.

[Marc Prudhomme]

Possibly the 2 different types of material glued together and reacting differently to the humidity? I was cautioned against using 2 different types of material (MDF and OSB) for torsion box skins because of that. Makes it warp because the materials react different to the moisture. Can you chisel/scrape the laminate flooring off? sand the door back smooth and see if it returns to normal? Then if you want the flooring on it, put it on but let it "float".
Beyond that, some big honkin' angle iron underneath to flatten it back out, but that may not work. Sorry you're running into trouble. Jim.
Soppose I could try to remove the top from the base an apply some sort of stiffner underneath but I doubtt that it will work.Its really pretty bad,,if you layed out a strairhtedge on one side flat ,the other side would be about 2 inches or more from the table.I am seriously considering throwing it in the burn pile in the fall....

[Bill Wyko]

Does the table have room for a steel frame under it? I'd bolt it to a steel square stock sub frame.IMHO:)

[Marc Prudhomme]

Does the table have room for a steel frame under it? I'd bolt it to a steel square stock sub frame.IMHO:)
If you thing that mounting it to a steel fram would solve my problem then I will try.I havnt taken the top[ off yet but I think that the hardwood flooring on top is bowed more than the solid core door.At least thats what it looks like.I cant figure out why though because I used ceiling cauls to keep the harwood slats flat on the table when glueing>>>

[Bill Wyko]

I think it'll hold it solid. I'd use 1-1/2 square stock .125 wall thickness. The flooring instructions even say to leave room for expansion next to walls. That's most likely what has caused your problem.

[glenn bradley]

Ouch. I remember posts here about the dangers of glueing solid lumber to man-made materials. I think one suggestion was to build the outer frame such that it held the tongue and groove lumber in a sort of surround to let it expand and contract.

The problem is of course that even if you flatten the surface as it is now with a router sled or something, when the weather changes you'll have another problem.

These concerns are what led me to my 'next' bench of 4 layers of laminated 3/4" MDF.

http://www.sawmillcreek.org/attachment.php?attachmentid=65687&d=1180753948

If you can get the flooring off, perhaps you can replace it with a slab of MDF and still save the balance of your efforts on the top/vises/base/etc.

I wish you all the luck in recovering,

Glenn

P.s. This is probably lame but if the flooring doesn't strip off well, can you flip it over and add a slab top?

[Marc Prudhomme]

Ouch. I remember posts here about the dangers of glueing solid lumber to man-made materials. I think one suggestion was to build the outer frame such that it held the tongue and groove lumber in a sort of surround to let it expand and contract.

The problem is of course that even if you flatten the surface as it is now with a router sled or something, when the weather changes you'll have another problem.

These concerns are what led me to my 'next' bench of 4 layers of laminated 3/4" MDF.

http://www.sawmillcreek.org/attachment.php?attachmentid=65687&d=1180753948

If you can get the flooring off, perhaps you can replace it with a slab of MDF and still save the balance of your efforts on the top/vises/base/etc.

I wish you all the luck in recovering,

Glenn

P.s. This is probably lame but if the flooring doesn't strip off well, can you flip it over and add a slab top?seems alot easier to take the vice off and hurl the top in the fire

[Marc Prudhomme]

Ouch. I remember posts here about the dangers of glueing solid lumber to man-made materials. I think one suggestion was to build the outer frame such that it held the tongue and groove lumber in a sort of surround to let it expand and contract.

The problem is of course that even if you flatten the surface as it is now with a router sled or something, when the weather changes you'll have another problem.

These concerns are what led me to my 'next' bench of 4 layers of laminated 3/4" MDF.

http://www.sawmillcreek.org/attachment.php?attachmentid=65687&d=1180753948

If you can get the flooring off, perhaps you can replace it with a slab of MDF and still save the balance of your efforts on the top/vises/base/etc.

I wish you all the luck in recovering,

Glenn

P.s. This is probably lame but if the flooring doesn't strip off well, can you flip it over and add a slab top? Glen I like the mdf laminate but is there a way to make the top into something replaceable and hard???

[Clay Crocker]

Glen I like the mdf laminate but is there a way to make the top into something replaceable and hard???

I bet that bench of Glenn's has a 1/4" hardboard top screwed to it. Just a guess though.

Clay

[Bob Hoffmann]

If you can get the top straight -- put the flooring on both sides of the top -- that should equalize the top.

Now in order to get the top straight .... did you try to put it in the sun to drt it out? You could waight till winter. You could hang it over your grill. You could try heat lamps for hours. You still may have to apply preasure on the piece to get it straight. When straight, the wood to put on the other side has to be at the same moisture content as the original side -- good reason to get a moisture meter.

Or, just start over!

[glenn bradley]

Glen I like the mdf laminate but is there a way to make the top into something replaceable and hard???

You make the frame 1/4" taller than the 'bench top core' and lay a piece of 1/4 TEMPERED hardboard on it. I did this on a rolling work table that I have used and abused for everything for almost 3 years, I have yet to replace the first piece.

My bench does not have hardboard on it although I have made provisions for doing so if later required. The reason I didn't just add it from the git-go is that I also have an MDF topped table treated with BLO and paste wax. It has yet to show signs of much wear and I doubt the bench top will either. Just in case I'm wrong though . . . I planned ahead.

At least two others here made bench tops this way and I drilled them with questions prior to buying off on the idea. It has worked out very well. Love the dog holes and the dual vise setup.

[Greg Funk]

Marc,

Next time if you want to use hardwood flooring I would rip off the tongues and grooves and glue the boards together on edge to form a hardwood top. You could then screw this through the door in a few places using elongated holes in the door to allow for movement in the hardwood top.

The problem you had is that for a top that size made in flatsawn red oak the width will change by approximately .130" for each percentage of change in moisture content (MC) of the wood. The difference in MC between winter and summer can easily exceed 5% so the oak top will be changing in width by about 5/8" whereas the door will not change at all. You are guaranteed to have significant warping of the door one way or the other.

Greg

[Marc Prudhomme]

Burn baby burn

[Jason White]

Was the flooring pre-finished? I'm sure the humidity got to the "unfinished" underside and moved on ya.

JW


hi fellow creekers,
What the hell did I do wrong.Tried to make a Nice flat workbench using a solid core door toped off with hardwood flooring.Table is 3x5.Its nice and straight the long way(5ft side)but the 3 ft way is bowed BEYOND belief.The mdf and plywood surface I had before was much flatter.What can I do to straighten it, if it is possible.I already mounted my vice and everything.It was pretty flat when I finished but I am guessing that the humidity got to it.I just did not think that it would bow that bad with the Hardwood flooring glued to the top.I am guessing that this will be a lost and I will have to start over.
Help
Marc

[Dewayne Reding]

Burn baby burn

Good job Marc. Punting is not always such a bad strategy. :)

[Jim Heffner]

Mark , I'm trying to get it clear in my mind as to why you installed hardwood flooring on top of a solid core door for the workbench top?
If I'm thinking about in the right sense here, it was to make a thicker, heavier top more solid is that right? One of the previous posters gave the right advice if you are going to use this set up, strip off that top, cut off the tongue and grooved sides glue the boards face to face ( like a cutting board) and then reatttach it to the solid core door, it would be a more solid and stable application for what you are trying to do. I have been using a solid core door as my workbench top for a couple of years as it is,
and never had any problems so far, that thing is really tough and takes a beating and still is no worse for wear! Jim Heffner

[Howard Acheson]

>> seems alot easier to take the vice off and hurl the top in the fire

Marc,

Hate to say this but you have provided your own best solution to the problem. There is no way you can salvage a situation like you have created. Putting a steel frame underneath will only lead to other problems--most likely, splitting. Something has to "give" as the seasonal relative humidity changes. If it can't warp, it splits. Applying the flooring to both sides would not have prevented problem. Both sides will still want to move and with a non-moving center, splitting or delaminating is going to result.

I would rebuild it using a different approach.

[Marc Prudhomme]

I think I will go with 3 MDF 3/4 thick .I will laminate them together using glue and screws(contersunk on both sides to prevent blowout).When the glue sets I will remove the screws so I can drill 3/4 holes for dogs.I will top it off with 1/4 hardboard.Itsucks having to do this all over again but live and learn.I actually got the Idea for the worktable from hell on this forum.I did lots of research and posted many questions before I started the project.Oh well,what are you gonna do.
Marc

[Howard Acheson]

>> will laminate them together using glue and screws(contersunk on both sides to prevent blowout

I wouldl recommend solvent based contact cement. No need for screws, lots faster and just as strong. In fact, some have had trouble laminating MDF with water based adhesives like yellow glue. It will sometimes not fully dry because it is restricted in oxygen. Because it doesn't dry, it can cause the MDF to swell.

In the shop I was involved with we laminated particleboard or MDF in either two or three thickness for kitchen counters and bank teller stations. It was the fastest and most cost effective approach.

Cut the first panel to size, cut the other two about 1" larger. Apply contact cement (have to do two coats on MDF) to one side of the "to size" panel and one side of one of the oversized. Use 1/2" dowels to keep them apart as you align them. Be sure you have an overhand along each edge. Remove the dowels starting at one end and let the top panel gradually come in contact with the under panel. When they are in contact, use a J-roller of a block of 2x4 and a heavy hammer to apply pressure. Use your router with a flush trimming bit to trim the oversized panel the the exact size of the smaller panel. Now do the same to the other oversized panel. The whole thing should take you 3-5 hours and you will have a perfectly aligned--and very, very heavy--benchtop. As a final step, use the contact cement to attach your 1/4" hardboard panel.

[Marc Prudhomme]

>> will laminate them together using glue and screws(contersunk on both sides to prevent blowout

I wouldl recommend solvent based contact cement. No need for screws, lots faster and just as strong. In fact, some have had trouble laminating MDF with water based adhesives like yellow glue. It will sometimes not fully dry because it is restricted in oxygen. Because it doesn't dry, it can cause the MDF to swell.

In the shop I was involved with we laminated particleboard or MDF in either two or three thickness for kitchen counters and bank teller stations. It was the fastest and most cost effective approach.

Cut the first panel to size, cut the other two about 1" larger. Apply contact cement (have to do two coats on MDF) to one side of the "to size" panel and one side of one of the oversized. Use 1/2" dowels to keep them apart as you align them. Be sure you have an overhand along each edge. Remove the dowels starting at one end and let the top panel gradually come in contact with the under panel. When they are in contact, use a J-roller of a block of 2x4 and a heavy hammer to apply pressure. Use your router with a flush trimming bit to trim the oversized panel the the exact size of the smaller panel. Now do the same to the other oversized panel. The whole thing should take you 3-5 hours and you will have a perfectly aligned--and very, very heavy--benchtop. As a final step, use the contact cement to attach your 1/4" hardboard panel.was thinkin about not glueing the hardboard.just a few screws so it can be replaced if damaged

[Marc Prudhomme]

does anyone else here concur with the contact cement idea.I was worried about getting it flat.I was going to drill a grid pattern in the 5x3 panel and screw it down nice and flat to each other.Is there another adhesive that would work well with MDF.I am not really that comforatable with contact cement for such a big panel.gotta work fast and I am not good under pressure.Any thoughts???

[Marc Prudhomme]

again, any thoughts?

[Randy Denby]

Marc,I'm not sure where you get the "pressure" of working with contact cement? All that I've worked with has alot of open time.Seems like 30min to an hour? Just roll it on with a small sponge type roller (cheap one) and put 2 coats on MDF ,as it will usually take it, and then let the cement tack up/dry good before joining.

BTW...just in case your not aware....you put the contact cement on "both "pieces to be joined together .
And IMHO, contact cement is the only way to join MDF, face to face.

[Michael O'Sullivan]

Why do you need to laminate the MDF panels to one another? One of the reasons I used MDF for my benchtop was that it would be cheap and easy to replace the top if it got dinged up too much. If it is all laminated togetther, it will not be easy to dispose of.

[Howard Acheson]

Marc, I agree using contact cement is not a pressure thing. You have more working time than you would with PVA adhesive. Driving all those screws will take you longer than the open time of the PVA adhesive..

To coat the MDF surface, you just pour it on and spread it around evenly. I generally use a piece of formica but will also use a roller on larger panels. In the shop I was involved with we sprayed it on.

Sure you can screw attach the 1/4 hardboard to make it easier to replace.

[joe greiner]

was thinkin about not glueing the hardboard.just a few screws so it can be replaced if damaged

Not "if", WHEN. Some years ago, Nawm (Abrams, New Yankee Workshop) used tiny box nails to secure the tempered hardboard. Removal of the nails substantially destroys the hardboard, but so what? if it wasn't already partly destroyed you wouldn't be replacing it.

Joe

[Brian Kent]

Marc, I agree with either contact cement or screws. Whichever is easier.

As for the 1/4" surface, I would want to either screw it on or glue the same surface to both sides. That way the top and bottom surfaces would match each other if there is a difference in slight movement of MDF an hardboard.

[Marc Prudhomme]

Why do you need to laminate the MDF panels to one another? One of the reasons I used MDF for my benchtop was that it would be cheap and easy to replace the top if it got dinged up too much. If it is all laminated togetther, it will not be easy to dispose of.laminating the panels together will assure a flat surface

[Jim Becker]

Mixing hardwood (solid stock) with manufactured material (solid core door) using glue will pretty much guarantee movement problems. The wood moves and the door doesn't. And in a dryer season the movement may be in the other direction...

[glenn bradley]

was thinkin about not glueing the hardboard.just a few screws so it can be replaced if damaged

Mine just sets in the frame tightly, no screws, no glue, just gravity.