Scribe-Cutting a Ceiling Edge

Here's a challenge: cut 1/4 inch off the edge of a ceiling panel that's mounted flush to the wall. The pros can think of several ways. December 14, 2005

Has anyone ever had to saw a kerf in a ceiling, parallel to the wall, and within 1/4 of the wall? The design calls for plywood panels on the ceiling. The trim guy installed the panels, and scribed them nicely to the wall. However, he wasn't told that the panels had to be set back from the wall 3/16 or so - there are negative reveals everywhere in this ultra-modern house. The panels are glued or screwed or nailed to the metal or wood framing. The contractor called me this evening to see if I had any ideas on how to cut this reveal without removing the panels. Other than taking a couple of days playing Michelangelo with a chisel, mallet, and offset handsaw, Im at a loss.

Ive read about offset trim router bases, but have never used them. Perhaps a jamb saw turned upside down and on its side? A wood-cutting wheel in a pneumatic cutoff saw? Does anybody have any ideas?

Forum Responses
(Architectural Woodworking Forum)
From contributor A:
An offset base wont get close enough. I myself have only used a Fein Multimaster once and I was not impressed, but it would work

From contributor B:
I pity the contractor who didn't spec the job properly. How many feet of wall need to be done? I'd consider making a throw-away tool based on a battery powered circular saw. A line powered tool would be too heavy and powerful for long periods of overhead work. I'd start by stripping the motor housing off the frame, mounting a good carbide blade (you'll not be able to remove and replace it easily), and then drilling through the blade and backing flange to accept spring pins, epoxy the blade in place, and drive spring pins to take some of the load. This might allow you to then remove the outside flange plate and mounting bolt and, thus, get close enough to the wall. You could then make an MDF or ply carriage and cover - in case the blade comes off. That might let you get the long runs and up to a foot of the corners. I'd try climb cutting a shallow first pass to limit chipping. I'd include a powered dust-hood face mask in the bill. If you could get the architect to approve about a 1/2-3/4 reveal, you could retain the bolt and flange washer. This would be safer and easier.

The opportunity costs are high enough that the contractor should be responsible for a fair amount of testing to see if the idea would work. You could get a good feel by trying a sheet of the plywood on the bench top before you modified the saw. I sure hope the wall surfaces are not high value. The contractor would need to buy off on the risk that the blade would come off and damage the wall. Even with the larger reveal, he'd need to accept the risk of contact.

From contributor C:

I believe you can use an offset router to cut this. About 10 years ago I had a situation where I forgot to make a rabbet cut. I had my local machine shop make a custom router shank out of 1/2" drill rod that allowed me to mount a guide bearing between the cutter and the router collet so that I could attach a slot cutter on the end of the shank with a flathead screw. This allowed the cutter, in effect, to flush cut at the end. You will need to build up the base of the router at the outside to the thickness of the cut. The offset would allow you to then get into the corner with the base of the router on the wall and travel around the room to make your cut. You will have to do some hand work at the corners because the router won't go all the way in and you may have to make some minor repairs to the surface to the drywall if you contact it with a spinning cutter. I will say that it may make more sense to just paint a flat black line around the room instead!

From contributor D:
If you can go over 1/4" a biscuit jointer may work. With some modifications to the base (the blade would be exposed) my DeWalt would cut within 5/16 or so of the wall.

From contributor E:
I would look into the saw that the hardwood floor guys use to trim the jambs up off the floor - it can go flush to a surface.

From contributor F:
You can use a Crain Jamb Saw to do this. They can be adjusted to cut flush with the base, which you would need to run against the ceiling. You can get carbide blades for them and they cut very clean. As already suggested, you could also modify an offset base router with a wing cutter to kerf the wall. The jamb saw will give you an 1/8" kerf. If you need more you will need to adjust the base and trim more material away. Jamb saws can sometimes be rented from flooring suppliers.

From the original questioner:
Interestingly enough, the architect decided on his own - a flat black line.