Replies

1. 
   calvin | Apr 02, 2003 05:22am | #1

   Check out blodgetts article on mdf in the latest FHB. I think he does mention a fast feed rate and either there or someones' response was a mention of HSS bits instead of carbide.

   __________________________________________

   Remodeling Contractor just outside the Glass City.

   http://www.quittintime.com/

2. 
   migraine | Apr 02, 2003 06:02am | #2

   Ever seen a window leak or accidentally left open in a storm?  MDF  should not be used in these types of applications.  I have argued this with a friend of mine about a year ago when he decided to do a whole house with the stuff.  He spent an enormous amount of time in priming the material and caulking every thing.  About a month ago, he received the dreaded furious client phone call saying that the products he used was an  inferior product and expected him to fix it.  The designer specified the materials for the job because the homeowner wanted to reduce costs.  Unfortunately my friend had a contract directly with the homeowner.  I'm waiting to hear how this is going to end.  He'll probably end up replacing it all at his cost.  He says he will never use MDF for trim work again

1. 
   HeavyDuty | Apr 02, 2003 06:14am | #3

   >>The designer specified the materials for the job because the homeowner wanted to reduce costs. Unfortunately my friend had a contract directly with the homeowner.

   I thought he has the headache, but how do you get your migraine? Here is a lesson to be learned, I'll take more care from now on trying not to get into similar situations.

   Tom

2. 
   Piffin | Apr 02, 2003 06:16am | #4

   I don't care for it that much either but one reason he made this choice (it's on another job - not mine) is because we have such wood movement here on the coast.

   the Medex product is waterproof though. It's just the plain MDF that swwells and eventually falls apart. The GP Primetrim product is also waterproof..

   Excellence is its own reward!

1. 
   jonblakemore | Apr 02, 2003 07:31am | #7

   What is the cost of Medex?

   Do you find it to be any different to work with the regular MDF?

   Jon Blakemore

1. 
   migraine | Apr 02, 2003 08:15am | #9

   Medex(exterior) eats up carbide router bitsand saw blades.  Not the same as medite (mdf)

3. 
   SgianDubh | Apr 02, 2003 06:25am | #5

   Yeah, that's as maybe, migraine, but piffin's mate is using the stuff for interior trim. True, there can be water damage here too, such as around windows, but the stuff is not going to be exposed to exterior use.

   I can't recall the name, but somewhere out there I've heard that at least one manufacturer is  selling MDF which they claim is suitable for exterior or wet location suceptible usage. I find it hard to believe myself that MDF of any sort could ever be successfully used in such locations, but I couldn't say one way or the other. Maybe this wasn't the type of material your contact used? 

   Normal MDF, HDF, or the new lightweight stuff (name?) certainly has no external use, or wet susceptible location usage that I can think off, but that's a different kettle of fish, ha, ha. I still wonder if your friend used the 'waterproof' stuff? Slainte.

   Website    The poster formerly known as Sgian Dubh.

   Edited 4/1/2003 11:33:12 PM ET by Richard Jones

1. 
   Piffin | Apr 02, 2003 06:38am | #6

   I guess by now you've seen post #5 about the waterproof for exterior MedEx. It has less formaldehyde, I hear,too.

   I think it uses polyurethenes for the adhesive binder in it. I used it once for large plinths in a covered proch type room with a stonme floor that gets hosed down daily. No problems at all.

   I've also used it for a routered lettering sign - also exterior..

   Excellence is its own reward!

1. 
   SgianDubh | Apr 02, 2003 08:13am | #8

   MedEx? Medite? That Sounds familiar piffin. Yep, I have seen post 5. You're the first I've heard give a resounding thumbs up for usage of the stuff in wet locations. I just don't know anyone else that's used an MDF type product in such situations. In my line of work-- furniture of one type or another-- I'm not really looking to use water resistant MDF type products for anything, so it's never really entered my mind as a 'must investigate' material-- I'm pretty happy working with planks of wood that came from trees for the most part, ha, ha. Slainte.Website    The poster formerly known as Sgian Dubh.

1. 
   clampman2 | Apr 02, 2003 08:24am | #10

   I once threw a chunk of medex I was using to set my shaper height for raised panels out of the shop. It went through the winter and wet muddy spring before I got around to throwing it into the garbage.

   It was the same dimension, even raised portion that the knife had cut had not puffed up. Medex, made by Medite Corp, costs about 3x what regular MDF costs.

   My supplier informed me in the last year or so that Medex is no longer recommended for exterior applications. He didn't know if they had changed it or if it was just some liability manuvering.

   Clampman

2. 
   SgianDubh | Apr 02, 2003 08:43am | #11

   Thanks, clampman. There's some memory of the stuff coming over the horizon now. Slainte.  Website    The poster formerly known as Sgian Dubh.

3. 
   clampman2 | Apr 02, 2003 09:16am | #12

   Your welcome. I actually rarely use any MDF anymmore.The dust is both horrible to breathe, get rid of, and very slipery on the floor, ALL MDF even Trupan eats carbide and everything else, all of it stinks, and all of it itches. It soaks all but thick vinyl sealers up like magic, and the edges cut your fingers up.

   Aside from that, it's great stuff.

   Clampman

4. 
   jimblodgett | Apr 02, 2003 04:35pm | #13

   About the dulling of W+H moulding knives - you know how the edge of MDF looks and feels different than the face?  More porous, a little softer?  I've never tried machining the face of MDF, only the edge. I'm wondering if the problems Piffin described are because of this difference?

5. 
   Mongo | Apr 02, 2003 08:03pm | #14

   Here's something that I have encountered with MDF...it may or may not be related to the topic at hand...

   I've found that I get different results depending on how the bit meets the MDF. And, the results are either 'acceptable' or 'totally unacceptable'.

   If, for example, I have a beading bit in the router table and I'm trying to bead the edge of a 3/4" by 5" piece of MDF. I get great results if I feed the board through the bit wiith the face of the board riding on the table of the router table and the 3/4" edge of the MDF running through the bit (3/4" edge running against the router table's fence).

   Now, if I flip the board up 90º and run it throgh the router bit with the 3/4" edge of the board against the table of the router table and the face of the board riding against the router table's fence, I sometimes get a lot of chpping and tearout in the cut.

   As jb wrote, MDF has a soft-ish inside sammiched between two fairly hard surfaces, or skins. When the bits try to mill this skin with the cutting portion of the bit coming rotating from the interior of the MDF through the exterior or surface skin, it sometimes flakes this skin off, resulting in the chipping/tearout. If I reverse the feed of the board to a climbing cut, the tearout does not occur. But I dislkie climbing cuts, so I don't do that.

   This tearing out has happened with new router bits as well as old (1/2" shank Amana and Freud) and with various routers...PC and Bosch...1.5hp - 2hp...at varying feed rates.

   The only constant is me...so maybe operator error?<g>

   The tearout is a minor point in that it I can always work around it, but I have had it happen and the first time it happened I was pretty suprised...and peeved.

   Again, it doesn't happen with all bits. It just depends on the profile of the bit and what the cutting edge is cuttiing when it exits the MDF. Both MDF and Trupan.

   I dont think I'd ever want to run MDF through a molding machine to make something like a crown profile. The amount of material to remove is excessive, and yes, it'll kill the knife's cutting edge in a heartbeat.

6. 
   jimblodgett | Apr 02, 2003 08:51pm | #15

   Yeah, it almost stands to reason that if the cutting edge is (mostly) perpendicular to the face of the sheet it would cut cleaner and save wear and tear on the edge.  Might make an interesting test. 

   My sheet goods supplier stocks MDF in thicker panels, too.  I've bought 6/4, I think they might even have 8/4...dare I say 12/4?  So if what we're tossing around about milling an edge instead of a face turns out to be accurate, anyone interested in milling taller profiles, like crown, might be well served with thicker stock and ripping strips out of that.

   Have to have a fork lift to move it around the shop, though. Geez, can you imagine what that stuff must weigh?

7. 
   CAGIV | Apr 02, 2003 09:31pm | #16

   I glanced over the mag, and havent read it yet, says a sheet ways 95 lbs

   so thats what?

   roughly 200 lbs for the 6/4,  260 for the 8/4 and a whopping 400 lbs for the 12/4, not exact but damn heavy!View ImageGo Jayhawks