Ply or MDF For MFT Top?

[squall_line]

[member=7266]jeffinsgf[/member] that's an unfortunate Menards story... [sad] ...the local Menards here has 9 sheets of MDO in stock and will ship to the house for $22 or ship to the store for free.

Wires crossed there. Festal and I were talking about Lowe's. His stocks it, mine used to offer it for special order, but I looked today and couldn't find it.  Menard's here in Cleveland still stocks both 1/2 and 3/4 4x8s and will order 4x10s.

That's how I interpreted it, but I can see how that could have gotten confusing.

I looked at MDO last time I went to Menards here.  Or, at least, I tried to look at it.  There were a bunch of people getting sheets of OSB and taking up space in the aisle, so I just kinda surfed on by.  I'm thinking of making a laundry tower for our basement and figured that MDO was a decent starting point for that environment, all things considered  (basement, laundry, sink).

 

[justin_248]

I recently made a top out of MDO, and it was quite an experience. 

If you go this route, I recommend you spec 3/4" MDO, smooth both sides, unprimed.  And, if possible, have somebody with a CNC cut it.

The only thing my local lumber yard had was 3/4" MDO, smooth and primed one side.  It was essentially ACX with a veneer.  This introduced a number of problems:

(1) The primer was thinly applied and produced a fine layer of dust every time something touched it.  I had to repaint it and then apply three coats of poly.  This added a significant amount of time.

(2) The MDO is very strong, and this combined with the knots in the material made it a real struggle for the bit included with the UJK Parf Guide System.  It probably took me two to three times as long to drill out the holes in the MDO as it would've taken with MDF.  I also think the bit ate away more of the material than it otherwise would have with MDF, probably partly because of the knots, and the tolerances on each of the holes are all over the place--some are kind of loose, some are tight.

(3) Because it was only smooth one side, the bottom was just like any other plywood.  I had a lot of blowout with the UJK Parf bit.  To remedy this, I used the included stop collar to only drill the holes about 9/10 of the way through, then flipped the piece over and finished boring out the holes from the other side.  This reduced much of the blowout but added a lot of time.

(4) Being smooth one side also meant the bottom was exposed, and everywhere there was a knot, a potential void formed.  Some chipped out with the included bit.

In all, it probably took me 5 or 6 hours to drill the entire top, not including the time it took to prepare, paint, and poly the piece.

If I had to do it all over again, I'd stick with MDF unless I could get MDO that was smooth on both sides, unprimed, and had access to a CNC.

 

[Packard]

MDO, with the overlay on both sides is a standard material for the sign making industry.

Google  “Sign makers’ supplies” for vendors of this material. I am under the impression that is is pretty pricey, but I have never shopped for it, so that is not necessarily an accurate statement.

 

[Peter Kelly]

MDF and laminate both faces with vertical-grade Formica or Wilsonart. I had to store my MFT table in the lower part of my house on summer and the mildew smell from the top never went away.

 

[Oldwood]

I made some MFT tops that were the exact size of the Festool top out of MDF. I had an OEM top sitting there, so just out of curiosity, I weighed both tops. The one made out of MDF was slightly heavier than the OEM top. I saw no difference in how they stood up to use.

FWIW

 

[Crazyraceguy]

I recently made a top out of MDO, and it was quite an experience. 

The only thing my local lumber yard had was 3/4" MDO, smooth and primed one side.  It was essentially ACX with a veneer.  This introduced a number of problems:

(1) The primer was thinly applied and produced a fine layer of dust every time something touched it.  I had to repaint it and then apply three coats of poly.  This added a significant amount of time.

(3) Because it was only smooth one side, the bottom was just like any other plywood.  I had a lot of blowout with the UJK Parf bit.  To remedy this, I used the included stop collar to only drill the holes about 9/10 of the way through, then flipped the piece over and finished boring out the holes from the other side.  This reduced much of the blowout but added a lot of time.

This seems quite odd to me. Finishing/sealing on only one side can cause warping and twisting. The overlay on one side would be bad enough, but priming it too?
Plus, I have never seen this "paper thin" stuff that some have referred too. The kind we get is very smooth on both sides and the overlay itself is at least 2mm thick. It's more like MDF than paper.
Having the skin on both sides still won't guarantee that it won't blow out on the back. It is best to drill these with a sacrificial layer underneath.
It's a great material to work with, but I still wouldn't make an MFT top with it. MDF (pre-oiled) would always be my first choice.

Even though it was a giant PITA, if I had it to do over, I would probably replicate my first big top.
It was 1 1/4" MDF, which increases the drilling/routing effort in the first place, but the real kicker is that the F style clamps will not fit through the holes. I got around that issue by turning the top over and routing a 45 degree chamfer bit around them, giant pain with over 300 holes.
I wouldn't go quite that thick again, but 1" would be good. It's considerably stiffer.

 

[Packard]

I topped my old workbench with a sheet of tempered Masonite as a wear surface.  It was held in place with carpet tape.

But I don’t think that would work well with dog holes in the bench.  It does make a disposable top surface though.

 

[justin_248]

This seems quite odd to me. Finishing/sealing on only one side can cause warping and twisting. The overlay on one side would be bad enough, but priming it too?
Plus, I have never seen this "paper thin" stuff that some have referred too. The kind we get is very smooth on both sides and the overlay itself is at least 2mm thick. It's more like MDF than paper.
Having the skin on both sides still won't guarantee that it won't blow out on the back. It is best to drill these with a sacrificial layer underneath.
It's a great material to work with, but I still wouldn't make an MFT top with it. MDF (pre-oiled) would always be my first choice.

I was surprised, too.

Hard lesson learned on my part, which is why I posted it.  Indeed, I am proof you can buy smooth one sided MDO.  And you're right, it isn't as flat as it should be.  I'm mounting it to steel Rockler Rock Steady stands, so those will do a good job flattening it out once I anchor it down.

It's hard to find good plywood near me, or even good lumber.  The closest large plywood supplier is 90 minutes away (not the one that sold me the crappy MDO) and Woodcraft and Rockler are the only local sources for quality plywood like Baltic Birch, although I can get some decent quality oak plywood more locally.  When it comes to hardwood, I rely almost entirely on Craigslist or Facebook Marketplace, and I'm having to learn how to mill rough stock acquired from sawmills.