Are hollow core doors really flat? (Use for assembly table)

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Forum topic by Bill Szydlo posted 03-11-2013 03:06 PM 4645 views 0 times favorited 9 replies Add to Favorites Watch
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Bill Szydlo

64 posts in 2593 days

03-11-2013 03:06 PM

I am planning on building an assembly table that is adjustable (height). Someone recently recommended I go the hollow core route rather than building a torsion box. I am planning on the width being 36” or 38”. I would use the hollow core door as the core with either 1/2” or 3/4” mdf glued on top and bottom. Before I go to my local big box and start checking each one for flatness I am curious if anyone on this forum has any advice on my planned build. Would it be better to just go the torsion box route?

9 replies so far

View RockyTopScott's profile


1186 posts in 3384 days

#1 posted 03-11-2013 03:07 PM

I thought the same thing, but plan someday to do the torsion box.

-- “When you want to help people, you tell them the truth. When you want to help yourself, you tell them what they want to hear.” ― Thomas Sowell

View a1Jim's profile


116906 posts in 3483 days

#2 posted 03-11-2013 03:17 PM

It’s not a matter of hollow core doors being flat,it’s that their not strong enough for an assembly table.Solid core doors will work fine.

sorry I missed the part about you wanting to glue mdf to the top and bottom. Why not just glue two sheets of 3/4” melamine together IMO this torsion box Idea is way over rated.

-- Custom furniture

View Bogeyguy's profile


548 posts in 1974 days

#3 posted 03-11-2013 03:32 PM

I would use a solid core door. Strong and solid. You can get one at your recycled construction material dealer. Here in Pgh. that is Construction Junction. Not sure if there is one in your area but I would check around. I have one that is 2” thick and I have been using it for at least 25 years.

-- Art, Pittsburgh.

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Bill Szydlo

64 posts in 2593 days

#4 posted 03-11-2013 03:43 PM

I don’t live in Pgh but I am an avid Steelers fan. I live in Mn and will check out the local recycled building material dealer. I assume a solid core door is laminated to stay flat and would be heavier. The reason for the laminated mdc was to add weight. I am going to be building a “jack bench” ( with an basic flat top for the top. This design, developed by a local woodworker, uses 2 car/motorcycle jacks to (1) lift the top and (2) lift the entire bench for portability. Since the top is resting on a jack I want to make sure it is very sturdy.

View Pdub's profile


923 posts in 3086 days

#5 posted 03-11-2013 04:31 PM

I have some hollow core doors in my house and they tend to twist or bow, depending on the time of year. I live in North Dakota. As stated above, I would look for a solid core.

-- Paul, North Dakota, USAF Ret.

View Loren's profile (online now)


9958 posts in 3553 days

#6 posted 03-11-2013 04:53 PM

Well, they tend to be flattish because they are really
built pretty light and inside honeycombed with
cardboard. This does help them stay pretty flat.

I’ve never built a permanent assembly table from
a door, but plenty of times I’ve used a door salvaged
from the trash as an assembly table. Just set up
a couple of sawhorses, put the door on them, then
shim up the low corner and check with winding sticks.

If your door is twisting, screw it to the sawhorses.

For a permanent table with a 3/4” skin on top, I’d consider
adding some sort of adjustment mechanism at the
corners and be aware that for the table to stay flat,
it needs to be evenly supported so at least one leg
should be adjustable.

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Bill Szydlo

64 posts in 2593 days

#7 posted 03-11-2013 05:13 PM

Thanks for all the help, it looks like a solid core door is the way to go. Next question, if I put a piece of mdf on one side only will it affect the tendency of the door to warp? I know if you veneer a panel you should do both sides for equilibrium, do you think it will affect a door the same way?

View woodbutcherbynight's profile (online now)


3957 posts in 2315 days

#8 posted 03-12-2013 05:02 AM

Bill Szydlo A friend tried that and it warped the first severe temp change. I have done as a1Jim posted, glued two mdf boards together and if you want a nice surface put laminate on it, thicker stuff though not the box store version it is way too thin. Currently have 3 workbenches with this type of top and they all have been around for 10 years or more and are still flat.

-- Live to tell the stories, they sound better that way.

View MrRon's profile


4632 posts in 3149 days

#9 posted 03-13-2013 05:08 PM

Torsion boxes are a pain to build. Their only advantage is light weight. Go with MDF. Solid core doors are made with a particle board core (similar to MDF), so don’t pay extra for a SC door when cheaper MDF will work as well.

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