CP Wood Question, 1/2" or 5/8", MDF or Ply ?

[Squeeky]

Ok guys I apologize, but I'm headed back to the rents house for mother's day, and to use my fathers wood shop.  He is a master woodworker, but explaining things over the phone can be an issue.

1. Should one use MDF or Ply when constructing CP?

2. What thickness should be used 1/2" with 1/4" Plexi, or 5/8" with 1/8" Plexi?

Originally I assumed 1/2" with 1/4" plexi when using 3/4" T-molding.  However father asked if using 3/4" T-molding, the groove is cut in center roughly 3/8", this is bringing the groove extremely close to the top of the wood and may cause issues.  Any thought on this?

[ChadTower]

You could go 3/4" wood and no plexi.

[Squeeky]

I really like the plexi, as I intend on artowork and sandwhiching makes this easy. 

[ChadTower]

Since you are concerned about the T molding cut being close to the top of the wood, it would make sense to go with the thicker wood and thinner plexi.

I'd use Lexan for a CP, btw, not Plexi.  Plexi is too soft for a CP, IMO.

[Chris G]

Agree with the thickness comments.

In terms of materials, I went with plywood for a few reasons, mainly due to it being lighter.  Also, I've only seen MDF in 3/4" (although, admittedly, I haven't looked very hard).

[Dustin Mustangs]

I'm personally using 3/4" board with 1/8" lexan and 1" tmold on mine.  That way, with the tmold slot centered on the board, it will fit perfect on the top and overhang by 1/8" on the bottom.  That 1/8" is really easy to trim off with a sharp chisel or flat razor blade once it's installed on the board and you'd never know by looking at it if you do it right.  Most of my reasoning for going this route is because I am using 3/4" board for the rest of my project and I didn't want to get a whole sheet of 5/8" material for just one part.

 

[ChadTower]

What!  Use your flush trim bit!

 

[scotthh]

5/8" MDF and 1/8" Lexan gives you 3/4" total depth. Although the t-molding groove is not centered, it is further from the edge than with 1/2" wood. I got a 2' x 4' piece of 5/8" MDF at Home Depot. I haven't cut the groove for the t-molding yet.

[Dustin Mustangs]

What!  Use your flush trim bit!

 

Wanna race?  I'll be done before you even get your bit tight.

 

[ChadTower]

That's what she said.

[Rusty]

I used 3/4" MDF and 1/8" plexi with 3/4" T-molding.  Then I took a roundover bit (chamfer would work, too) in the router and hit the bottom of the control panel.

Worked great for me and I didn't have to buy an extra piece of MDF since I used 3/4" for the whole cab.

[bfauska]

What!  Use your flush trim bit!

 

Are you suggesting using the flush trim bit to trim the T-Molding flush with the bottom of the CP?  Seems like a bit of a risk to keep the router flat against the curved t-mold.  If you rock the router up toward the top of the CP you will cut into the bottom edge.  T-Molding cuts like butter with a fresh razor.  Mind you I am biased as I just spent the last week at work on a project that is 1-3/32" thick that is getting 1-1/8" t-molding and we are cutting with a razor, small project too, about 600' of T-molding. 

That's what she said.

That was pretty funny.

Back on topic, I would say either MDF or Plywood as long as the plywood is a smooth finish plywood.  AC, AB, Superply, Shop-Birch, Apple Ply, or any of the veneer plywoods would be my suggestions.  I haven't used T-Molding in plywood, but I suspect there is a chance of the groove being somewhat problematic depending where it lands in relation to the layers within the plywood.  MDF is nice and flat, smooth and you don't have to worry about grain or layers.  5/8" MDF + 1/8" Plexiglass (or other acrylic is much less likely to get scratched up than Lexan or other polycarbonate) = 3/4" t-molding and no trimming necessary (which beats either router or razor.)

[NiteWalker]

5/8" baltic birch plywood and 1/8" plexi. Chad are you sure about the plexi being softer? In my experience it was the polycarbonate that was softer and thus more prone to scratches. Acrylic is the harder stuff.

Here's a good place for small pieces of Baltic Birch Plywood. Perfect for building a control panel or 2. Great place.

[Joystick Jerk]

Isn't there such a thing as offset T-Molding, where the center bit that gets inserted isn't centered on the T-Molding strip? That way you can compensate for any Plexi you have on top.

[NiteWalker]

There is, but it only comes in black (I think).

[ChadTower]

5/8" baltic birch plywood and 1/8" plexi. Chad are you sure about the plexi being softer? In my experience it was the polycarbonate that was softer and thus more prone to scratches. Acrylic is the harder stuff.

I could be wrong but that's how I remember it.   Lexan being harder and more like glass than plexi.

[bfauska]

Lexan LOOKS more like glass, and is much more impact resistant than plexi or glass.  But that is because it is softer and more prone to scratches.

Hard=Brittle=Fewer scratches=Acrylic (Plexiglas)
Soft=Flexible=More scratches=Polycarbonate (Lexan)