Replies

1. 
   forestgirl | Apr 19, 2005 12:45am | #1

   The big disadvantage to use MDF for the whole thing is the weight.  I don't know how big you're going to make the base of the DD table but if it's pretty big, you can build doors or drawers into it and use it for storage, separated from the blower of course.  That's gonna be easier with ply.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
   Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

1. 
   mvac | Apr 19, 2005 04:01pm | #4

   Jamie,

   Thanks. In addition to weight, did you mention the added convenience of ply with doors because of an advantage with screw/hinge holding?

   Regards,Mitch

   "I'm always humbled by how much I DON'T know..."

2. 
   nikkiwood | Apr 19, 2005 12:50am | #2

   No reason not to use MDF for the top. As long as it is adequately supported (underneath, with ribs), it will perform as well as apple ply, for much less cost.

   Stuff is heavy, but that shouldn't be a problem with a bench.

   I build most of my shop cabs from birch ply with an MDF core, and it costs about $10 a sheet more than plain MDF. I varnish my cabs, but if you're going to paint, plain MDF will work just fine. Again, there is no structural advantage to building the carcase from apple ply.

   "I would never die for my beliefs because I might be wrong."
   -- Bertrand Russell

1. 
   mvac | Apr 19, 2005 04:07pm | #5

   Nikmeister,

   "No reason not to use MDF for the top. As long as it is adequately supported (underneath, with ribs), it will perform as well as apple ply, for much less cost."

   I'm assuming you're referring to the assembly top for the ribs - makes sense.

   "I build most of my shop cabs from birch ply with an MDF core, and it costs about $10 a sheet more than plain MDF. I varnish my cabs, but if you're going to paint, plain MDF will work just fine. Again, there is no structural advantage to building the carcase from apple ply."

   Is this the typical Baltic Birch ply one would by from the HI stores, and if not would that work just as well?

   As always, thanks for the advice.

   Regards,

    Mitch

   "I'm always humbled by how much I DON'T know..."

1. 
   nikkiwood | Apr 19, 2005 07:10pm | #8

   Perhaps you are confused re: the different types of brich ply available."Baltic" birch (sometimes called Finnish", as in Finland) is the stuff always imported from the Baltic states. Most of what I can get around here comes from Russia. It has many plys, and is generally void free, and is available in 5' X 5' sheets. "Apple Ply" (which is a brand name) is I believe, an American (or maybe Canadian) made equivalent, but can be bought in 4 X 8 sheets. Around here, at least, you need to buy any of this stuff from a wholesaler; I have never seen it in any of the home centers. "Regular" birch plywood comes with two types of core: Veneer core, or fibre core (MDF). This is the stuff most commonly used, and is sold by wholesalers and most home centers. If you look at the listings from a wholesale house, the ply will be designated either "FC or "VC".It is the birch ply (FC) that I am talking about. Yes, it is quite a lot heavier than VC, but it stays flatter and is generally easier to work with. If you're making a carcase, for instance, and the sides are slightly bowed (which is often the case with VC), fitting doors/drawers can be a challenge. Screw holding capability (with FC) is just okay. I have never had a problem with drawer glides. Hinges could be more problematic, but not if you use the European cup hinges (which are really designed for this type of material."I would never die for my beliefs because I might be wrong."
   -- Bertrand Russell

1. 
   forestgirl | Apr 19, 2005 08:38pm | #10

   Baltic Birch and Finnish Birch are not exactly the same animal.  Finnish birch is made with an exterior glue, and the plys are a higher quality, with a clear face on both sides.  Baltic Birch is made with an interior glue, will have lower quality plys (no biggie if it's going to be painted or not seen, or in a shop jig), and much less expensive than BB ply.  Aircraft ply is the best Finnish birch ply.

   Unfortunately, many of the suppliers are not good about using the terms correctly, so they get interchanged inappropriately.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

1. 
   nikkiwood | Apr 19, 2005 11:04pm | #12

   Around here, Baltic, Russian, and sometimes Finnish are terms used pretty much interchangeaby. And as far as I know, the glues are all interior. If you want something with exterior glues, then you specify "marine grade" -- which is a whole different (and more expensive) animal."I would never die for my beliefs because I might be wrong."
   -- Bertrand Russell

2. 
   forestgirl | Apr 19, 2005 11:32pm | #13

   "Baltic, Russian, and sometimes Finnish are terms used pretty much interchangeaby."  My point exactly.  They shouldn't be used interchangeably.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

2. 
   mvac | Apr 19, 2005 08:38pm | #11

   Thanks for the education. I'm not sure which ply I'll go with, although the VC seems to have the weight advantage, and with interior compartments and shelving holding the sides together, I think degree of flatness won't be an issue. I'd be singing a wholly diferent tune if this were a piece of fine furniture vs. a shop workhorse with multiple uses and likely to be rolled around a lot.

   Again, thanks for your help - it's made the project much more straightforward for me.

   Regards,Mitch

   "I'm always humbled by how much I DON'T know..."

3. 
   migraine | Apr 19, 2005 04:23am | #3

   There is ultra light MDF on the market where it weighs about 67lbs per sheet for 3/4" (18mm).  About the same as 3/4" plywood.   Runs around $25 per sheet(maybe more depending on where you buy).  The stuff coming from Chile and made with Radiata pine is my favorite.

   I would recommend applying a verticle grade laminate to the front and back to reduce warping from uneven moisture. 

1. 
   mvac | Apr 19, 2005 04:16pm | #6

   Migraine (Great name, btw),

   I'd never heard of the ultra-light MDF - good to know. But doesn't the warping issue kind of defeat the purpose a bit? It's cheaper, but sounds like it's lessdimensionally stable than the ply.

   Regards,Mitch

   "I'm always humbled by how much I DON'T know..."

4. 
   jackplane | Apr 19, 2005 04:27pm | #7

   Mdf is no more dimensionally stable than plywood.It'll move like any sheet good. It is up to you, the builder, to make it stable and strong.

   Yes, ply holds screws in edges far better than mdf, but cup hinges can overcome this. The strength of this project again comes from your design. As forest girl said, the major consideration is weight.

    

   
   

   ---

   Edited 4/19/2005 9:32 am ET by jackplane

1. 
   mvac | Apr 19, 2005 08:33pm | #9

   Wow. I thought MDF was both flatter and more dimensionally stable. Thanks for setting me straight on that.  And, since ply holds screws better and is lighter, I'll certainly use that for all but he perforated top, since I don't want to get a hernia moving this thing from one part of the shop to the other.

   Thanks again,Mitch

   "I'm always humbled by how much I DON'T know..."

5. 
   Pondfish | Apr 20, 2005 01:26am | #14

   MDF may be dimensionally stable, but it will flex and bend.  Don't expect a dead flat surface unless you've built a supporting structure that is dead flat.

   One thing I've noticed with jigs that I make from 1/2" MDF is that when I have hold-down clamps on them, it takes only a little too much clamp pressure to warp the MDF jig base.