I have struggled with coping detailed MDF crown moulding joints. Unlike wood, the material is much thicker and creates interferences on the backplane of the moulding at detailed contours. If you file or sand down the profile backcut, the material becomes too thin and crumbles. I have seen other carpenters successfully mitre and glue with poly-urethane glue, however, it required two men to set, cut and fit the trim. I typically work alone and after several years of perfect wood joints, I am perplexed. Any advice?
Thank you.
Edited 9/14/2007 12:34 pm ET by kfisch
Replies
use something else
seriously though, mdf crown behaves like a wet noodle. too much for a solo artist.
if you insist enlist the help of a dremel for coping
Thank you all for the insights. Funny you should mention the Dremmel. I use a Rotozip to shape and make the fine radius cuts. (kind of like a dentist) I think I will just have to try a mitre joint for this application (90% of the project has this crown profile) I prefer wood, however, the cost of the larger and more detailed profiles is prohibitive and custom millwork is out of the question and budget. "Designing on a dime"
Some crown is simply "uncopable" If any portion of the molding goes past the horizontal line, then that crown is "uncopable"
I too typically work alone and I gave up using MDF crown - wet noodle is a good analogy. The minimal extra cost for primed pine is worth the expense in time saved. The joints are tighter, coping is easier/cleaner, and the nails hold better.
The "third hand" tool is a god send when working with this stuff. Also make sure your cutting stand offers good support along the length of the molding.
That's what I was about to suggest.
Miter the joints and use a "third hand"....maybe even a 4th with MDF.
J. D. ReynoldsHome Improvements
One of my mail order catalogs (I think it was McFeely's) has an item that might help you with your problems hanging this stuff. It's a molding hanger. It has a horizontally oriented slot for a screw with one large end to drop over the screw head. The bottom end of the hanger is a hook that you can rest the bottom edge of the molding in.
The way it works is that you drive sheet rock screws into the wall close to the ceiling. Slide one of these things over each screw, and place the molding on the hangers. The angled hook will keep the molding at about the correct angle. Start at one corner and nail off your molding. As you move along the strip, slide the next hanger sideways and pull it away from the wall. Leave the screw in the wall; the molding will hide it.
If I had seen this last December, I would be able to tell you how well it works, but .....