Trim – Finish or Cut, Which Comes First?
Truejoint
| Posted in General Discussion on
I’m going to be replacing a bunch of painted MDF baseboard and door trim with clear finished maple (shellac & waterbased acrylic). A bunch of mitres will have to be glued together as the trim is installed.
I could either cut the mitres ahead of time using the MDF trim I’m pulling off to get the final lengths right, then tape the mitres, then finish the trim and install and glue. Or I could finish the trim and cut and glue the mitres as I’m installing it.
I think the second option would be much easier to get right, however, I’ve never tried sawing a finished board before. Will the table saw cut mitres chip out the edges of the finish? Is there a way to prevent this? What type of saw blade will work best?
Replies
Finish, cut, install then touch up as needed.
Gluing your miters is easier if you cut after finish. You have a fresh glue surface, and any glue ooz out will be easy to clean because it will not stain the unprotected wood.
I have found that some finishes actually help minimize chips/splinters when cutting because they hold the wood fibers together. The saw tooth needs to cut into the finished surface. For extra protection, you can tape your cut line with masking tape. A sharp fine tooth blade or cross-cut will do.
Great! Thanks.
I finished our doug fir baseboard first w/ shellac and then with 2 coats of Minwax Polycrylic. The boards sat until the next weekend, then I cut to install. You'll notice that the very end of the baseboards get "beaded up" with finish, but since they get trimmed, it's not a problem.
The Polycrylic is clear, but the finish is soft.
FWW or FHB recently did a review on clear water based finishes I believe.
To finish before or after installing trim depends on the situation. In your case, I'd finish first because the finish floors are installed and painting is done.
Here's a question though. What miters are you talking about gluing? Casing corners around doors and windows or corners of base board? The reason I ask is that seasonal changes will change the width of the trim but not the length in any appreciable amount. Seasonal changes will change the angles cut on casing around doors and windows. Because you're dealing with two pieces at right angles, the angle change in the joint is doubled. These joints are open at the toe slightly in humid times and open at the heel during drier times. Mitered glue joints aren't strong enough to overcome this and the joints will fail. These failed joints are ragged and more easily seen than straight cuts slightly open.
When these joints fail, they tend to pull wood from mated pieces. It can be difficult or impossible to realign and adjust troublesome joints later if they have been glued. If you fit the joints well in the first place and let the wood be wood, you'll be happier with the work in the long run.
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