Coping baseboard

I'm currently doing a small project that involves coping some made wooden baseboard to preexisting marble baseboard. Fortunately the homeowner had a piece of the marble leftover so that I could get cutters made to match. Here in lay my problem.

The base that I made and the marble have almost exactly matching profiles, however, there is some variation due to the ability of wood to hold a sharper edge. I'm not sure if this variation is the culprit but no matter how closely I cope to the line, I can not get a clean joint. Of primary concern is the persistent gap that appears between the lower non-coped (but back cut at 45) part of the wooden molding and the lower non-profiled flat face of the marble. Make sense?

Initially I thought my problem might be my material so I remade the molding and didn't cut the profile as deeper on the shaper. When butted end to end (marble to wood) all surfaces/planes are flush. Still no luck. Have double checked accuracy of machines and all are on. I'm at a loss with regards to how to fix this. Or do I accept the gap as the end result of slight variations in the profiles?

I'm sure there is some trick I'm missing here but finish carpentry isn't in my tool chest.

Thanks all!

Chris

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When you do the cope, are you back beveling the cope? (holding the saw at a few degrees off vertical)
If there is a flat area on top, you don't cope that, just cut it straight down and start coping at the first curve.

The most common issues are out of square corners and out of plumb walls. If the corners aren't square or the walls aren't plumb, the cope will have to be adjusted. Nothing you can do about the marble, but if the wood side wall isn't plumb, you can compensate. If the top is tilted out, you can install a screw into the bottom plate behind the molding and adjust it out so the molding is plumb. If the top is tilted in, you can plane a little off the back of the bottom to compensate.

If you only have a few to do, an assortment of files can cure a lot of ills.

Some pics might help us spot the issue.

I don't back cut the flat face, or at least not to a 45-ever so slightly, if anything. If you do, it leaves only a hair of wood that meets the other part. Even the coped molding profile doesn't get back cut hardly any. It doesn't do, as you found out, any good at all to back cut more than you have to.

Best of all is marking the cut with a preacher, so it doesn't matter if the piece you're joining to is out of plumb.

Tom, what is a preacher (tool-wise)?

It's not something you buy. You make them for a particular job. Carpenters used to use them all the time, but the young ones don't even know what they are these days. They use the piece you're fitting something against to register off of, and it doesn't matter if that part if square, plumb, or anything.

I had some pictures stored here of some I use for siding. The siding in the picture was marked by a preacher, with a sharp no. 4 pencil, and cut with a handsaw.

The preacher doesn't have to fit over the piece, but might need a cutout to fit over the piece you're marking so it fits close to what you need to mark, but doesn't necessarily need to go behind the piece. These for siding are easier to use with one hand if it fits all the way over the board, and registers off the corner board. The ones we make for baseboard are usually just a piece of 3/4" scrap.

I think I got a couple pictures attached....

Tom, thank you. As always, you are a gentleman. Patrick