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Coping MDF Crown

13366 Views 24 Replies 16 Participants Last post by  Smithanator
Well that was a waste of my time. Never doing that again.

Is there any way to nicely cope this crap? I got average results with a fine blade on a coping saw and a file, but was really bummed about constant chipping when I tried to fine tune with a knife.
Very frustrating day.
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Angle Grinder and file to fine tune
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Funny you said that. I was thinking angle grinder. Also thought a palm router could work too.
Just try not to breathe the dust, the stuff sucks!
I have done it sucsesfally with a jig saw and a good lenox blade though it does take some practice.Not near as easy as wood of any kind.It's cheaper and eai\seir to just buy chaeap\\\\\\\\\\\\\\\\\\\





I have done it with cheaper mdf and a good Lenox blade on crown but in the long run it's quicker and easier to just buy some poplar crown.
The MDF purchase wasn't my choice. hah

I was working alone yesterday and I find coping easier than mitering when by myself, especially on longer runs.
I like to use the coping saw to get the majority of it out. I don't go right to the line with the saw. Leave like a 1/16" or even an 1/8" . Then like others suggested finish it off with a grinder and sanding wheel. This is where that cordless Makita really comes in handy.

I put a couple fingers with my left hand on the trim ( out of harms way of course) while the rest of the fingers to help the right hand steady the grinder.
Ugh. So much sneezing. Also, MDF dust on hardwood is like a sheet of ice.
Just try not to breathe the dust, the stuff sucks!
I sugjseted using a Bosch jigsaw with a good Lenox blade and that does work well for the initial cope but does take some practice and fine tuning.The bosch I have is probably 20 or so years old and very smooth cutting.With the right blade you can get very close.I use some self adhesive sandpaper on a dowel after that to fine tune.Or maybe a drum on a Dremel but it does not take much.I usually don't have to go that far.
dont cope mdf, its more stable just mitre it.. i used to cope it but its far too brittle and makes for a ugly joint. the only time i cope mdf is on remodels where existing trim wasnt removed so ill cope into it
I ran into the same thing on a whole house paint and remodel job I did last year. The homeowner chose the crown from a local millwork company and ordered 250 ft of 5 1/2" MDF crown without me knowing what they were getting until it was delivered. I learned pretty fast in the first room how to deal with the stuff. I dont really like the way it cuts and installs, but one thing I have to say .........its really nice and smooth after its painted. I ended up coping the inside corners after trying miters. It was more time consuming to keep adjusting the corners to get the miters tight than to cut the copes. I made my initial cuts with a fine toothed coping saw. The fine tuned with smooth files(flat, rat tail, and half round) then back cut with a Makita die grinder with Kutzall carbide grit bit. After the first room I got the hang of doing the corners. My only problem was putting up 16 footers alone. The stuff is really flexible. I ended up putting in a few 8 penny finish nails along the chalk line to hold the piece up while I nailed it in. Not sure if i want to ever use MDF again>:rolleyes: I have to say also that it is pretty stable stuff too. I was back to do some more work last week and I could only see 2 or 3 inside corners that opened up a tiny bit from the dry winter air in the whole house.
I find MDF LESS stable. Unlike wood, it will shrink along its length because the fibers aren't all parallel to the length. Now maybe this is my own ineptitude, but I find it much more difficult to miter vs cope a tight corner without having to cut twice or more to dial in the length.
dont cope mdf, its more stable just mitre it.. i used to cope it but its far too brittle and makes for a ugly joint. the only time i cope mdf is on remodels where existing trim wasnt removed so ill cope into it
I do not like mdf crown it is a pain start to finish with it.
I don't like it at all but some customers insist on it for paint grade and budgets.I don't paint but it does look nice after a good painter is finished with it.
I've found MDF to be fairly stable if back-primed. I don't usually cope MDF crown.
I always cope MDF, or anything. It makes a big difference in the finished product.

I use the easy coper jigs, and a bosch jig saw with a very small blade. You can get exactly up to the line, even me and I have the shakes. (essential tremors)

Ya it takes a little longer, but the results are amazing. you do have to be careful not to bump into stuff with the coped end(s) but other than that I guess it's like anything else you get good at it after a short while.

As for holding up the 16' lengths I use the Lee Valley crown hangers.

You put a screw up near the ceiling about 1" down, then this hanger "hangs" on that screw. It's sorta like a large fish hook with a movable barb.

Hang your crown on that, then adjust the "barb" part up a little bit so the crown is up against the ceiling, then nail off. When you get to the hanger, just lift it up a bit and slide it down out of the way. The screw will not interfere with the crown.

Lee Valley coping jig: 03J75.80

Lee Valley Crown hangers: 03K18.05
I always cope too. As a remodeler, I'm doing the finish so it always looks good when I'm done.
As a mater of fact, crown is the only place I will use MDF. Once it's installed, there is no chance for abuse. I go into homes that are 2-3 years old with MDF base and casings beat to he!! from the vacuum, pets, movers, whatever.

I just put my glasses on and use a simple coping saw. cuts way easier than solid wood. Just don't bump the cope end when handling..
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I keep swearing that I'm going to get a copemaster, but on those rare times that I see one on CL, I don't have the money or it's hundreds of miles away. or both.
I agree it does cut alot easier than most finger jointed pine moldings. And I found out the hard way several times about bumping into door frames when trying to flip a 16 footer around in a 12' x 16' room:no: Sometimes I had some trouble with the nails mushrooming the MDF. Usually after I fill the nail holes and sand the filler the mushrooms go away. I tried plastic crown hangers from Woodcraft and didnt like them, so I usually just put a few 8 penny finish nails in the wall along my chalk line. The resulting holes are filled with the caulking at the bottom of the crown. Works well for me.
I always cope too. As a remodeler, I'm doing the finish so it always looks good when I'm done.
As a mater of fact, crown is the only place I will use MDF. Once it's installed, there is no chance for abuse. I go into homes that are 2-3 years old with MDF base and casings beat to he!! from the vacuum, pets, movers, whatever.

I just put my glasses on and use a simple coping saw. cuts way easier than solid wood. Just don't bump the cope end when handling..
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