*
i’m going to be installing about 1200′ of 5” mdf crown molding in a house i’m building. the last time i mitered all my inside and outside joints with a hitachi compound saw. i was wondering of the pros and cons of mitering or coping the inside corners. any advice would be appreciated
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
The RealTruck AMP Research Bedsteps give you easy access to your truck-bed storage.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
*
Robert,
Try running a few searches using various words to find previous discussions on this subject.
Since you've done this before, you're familiar with the tweaking sometimes required to get tight joints in crown. Coping inside joints allows the wall angles to be off somewhat (not pure 90 degrees) and still get a tight fit. It also helps hide seasonal wood movement, which may not be as prevalent with MDF.
Careful nailing MDF. It tends to "volcano", or protrude around the nail hole. Have a sharp wood chisel in your hip pocket to shave off the nubs after nailing. Predrill near the edges, thin sections can split when nailed.
MDF dust is like fine talc. Get it into your HVAC ducting and you're a dead man. Dust everywhere, for months. Close off your registers. Wear not just a good dust mask, but a great mask when sanding the stuff. Try one with HEPA filters.
After nailing it up you'll most likely have to putty, then sand, prime, then sand, paint, then scuff, then paint. Lots of sanding involved. Not heavy duty, but enough to knock the rough stuff down. More fine dust.
Have fun.
*Mongo is not an MDF moulding fan!
*Long time, andrew!MDF has its place. As for MDF molding...I've seen it, handled it, but have never used it. I'm still holding off. Maybe someday?I do like MDF for paint-grade raised panels in wainscoting. But, the dreaded dust...it will get you.
*Mongo,I just did my first whole house in mdf and the results were great. You have to learn where to shoot. The puckering was not as bad as expected. I have had that problem when using 3/4 mdf. The thinner moldings didnt do it as bad. Dont use it in the bath.Rick Tuk
*I almost forgot, Always cope moldings.Rick Tuk
*I 'm with Rich. I cope everything.The results look so much better, because I have never met a square corner, and who has time to screw with bastard angles? As for coping mdf, I've never had to do it.(thankfully)
*I cope almost all inside corners. It is possible to have crown molding that is not copeable according to an article in FHB #68 (July 1991). I've run into barely copeable crowns but never the uncopeable crowns that this article warns about.Joe
*Rick, how was it to cope? Do you cope using a coping saw/rasp or jigsaw? Any tendency for the "pointed ends" of the cope to snap off, either while coping or when installing?Did you glue as well? Type of glue?Where did you find the best place to nail?Was there even milling, in terms of the profile on one board matching with the profile on another?Thanks...always looking for new info.Mongo
*Hi fellas, I also have been sold on copeing the inside corners when installing crown moulding; however , recently I purchased an electronic angle/mitre finder manufactured by Bosch. After using it on the last crown installation I feel that I have greatly cut down my installation time by using this tool and mitering both the inside and out side corners. By measuring the spring angle of the moulding and measuring the angle of the corner, the digital protractor calculates the mitre and bevel settings for your saw giving you as good a fit as if the inside corners were coped.
*md, you're kidding?
*Calvin, I'm serious. I forgot to point out that this tool goes hand in hand with a CMS or SCMS. Just this week I was installing some baseboard and came to an outside corner that looked to be far from 90 degrees. I measured it with the mitre finder and found out that it was actually 94 degrees. Set my mitre to 43 degrees and came up with a perfect fit. It was also a time saver when I came to a angled wall going into a hallway. In the middle of the angled wall was a cased opening and by measuring the angle on each side of the opening I found one side to be 5 degrees different than the other side but once again you can set your saw to the exact angle and get a good fit.The mitre finder also has to vials to use it as a level for checking level and plumb.
*
Robert
I installed a few thousand feet of Mdf crown on a job a couple of years ago. I've always coped mouldings so that is what I did with the Mdf, the only problem I incurred was that Mdf becomes extremely fragile when coped leaving a paper thin edge so some broken edges are inevitable,to help combat this I blind caulked the piece during instalation to help give some strength while fitting the joint together.
Good Luck
*
Yeah, I was a lot happier too when I started using a protractor to take the actual angle. To do it right I need to rig up or buy a protractor with long arms because of the waviness of the plaster walls I'm dealing with.
On miter v. cope -- to get a proper reveal cut when coping, the angle is 1/2 of the corner angle, exactly as with bevel joints. Why? Because you have to make it around the corner in both cases, and want the slice of the profile on each piece to be identical, so you have to divide the corner angle equally between the two pieces. The difference with the cope is that you don't cut the second piece; instead you hollow out the backside of the first piece (backcut) to allow the profile of the second to pass right on by unmolested.
I'm not saying I'm any GOOD at doing these, just trying to establish for myself the correct geometrical perspective so I don't have those long agonizing periods of confusion in front of the CM, only to blow the cut anyway.
P.S. I like the cope cut better because it pins the uncut piece against the wall securely.
*noooooo.....
*House expands and contracts....MDF does not....butt joints will crack with the seasonal humidity changes, and biscuits won't stick....miter and caulk....Dap??? LOL"shaking head", waste of wood me thinks!OOps, forgive...what wood???...LMAOLSarcastically.L
*
i'm going to be installing about 1200' of 5'' mdf crown molding in a house i'm building. the last time i mitered all my inside and outside joints with a hitachi compound saw. i was wondering of the pros and cons of mitering or coping the inside corners. any advice would be appreciated