routing roundover on convex/flat surface

[James Baker SD]

I have made a wooden collar to fit around the decorative vent brushed chrome metal cover for a kitchen island cook top hood vent in order to hide where the ceiling drywall opening is just a little too big. It matches the shape of the decorative cover in that it has two convex sides and two flat sides. (see photos) The cross section of the wood is 1-3/4 high by 1-1/8 deep.

collar1.jpgcollar2.jpg


I have two questions.

1. I want to use a roundover bit on the four outside edges visible in the first photo to give it a little more finished look. The straight edges have exposed endgrain as seen in the 2nd photo. Will there be any problem having the router bit transition from the convex edge to the flat edge and maintain a smooth looking curve? Any gotchas I should be aware of.

2. I will likely have to drill holes in two of the edges for screws to make sure the collar stays tight up against the ceiling (hate to glue it in place in case I have to move it some day). I would rather drill the holes through the surface that will get the roundover treatment in case of any tear out as the drill exits, but this probably means drilling the hole first, then applying the roundover, I don't know yet, but I suspect the hole will be at least partially in the roundover area and I am worried that the router bit may chip out a chunk of wood when it encounters the hole. Any advice here (either for drilling the holes or another method of keeping it tight to the ceiling)?

Thanks.

James

P.S. This is the last step in a 52 month kitchen remodel and I am really looking forward to calling it done.

[Dave Richards]

I would do the convex edges first and very carefully, in light passes, rout the end grain from corner in along the convex edge.

As for the holes, first try in a scrap to see if you'll have any trouble. My inclination would be to drill the holes with counterbores and plug them temporarily for routing.

[Jerry Miner]

Well.... there are some issues that could arise.

The general rule is to route the end grain first, so minor blow-out can be removed with the routing process on the adjoining edge. Usually, this is enough, but not always. Sometimes a "climb-cut" is helpful. This is a "reverse-feed" operation in which the operator routs the outside edge right-to-left instead of the usual left-to right direction. It's called a "climb-cut" because the router tends to "climb" or jump in the direction of travel. It can be scary and I don't usually recommend it for beginner router users. But a small round-over is a pretty light cut and if you are careful to control the router and not let it get away from you, it can be done safely. But it CAN be dangerous, so be careful. Maybe practice on a scrap piece.

For this piece, you could also have a little trouble with the convex sides, because if you rout in the "normal" way, you will be routing "uphill" on the grain in a couple of spots. Climb-cutting can be helpful here, too. But the curve is gentle enough, and it looks like you are using walnut, so you may not have a problem at all. Might be smart to rout in small stages---maybe two or three different depth settings to get to full depth---in order to avoid chip-out.

If you're only doing 1/8" round-over, you can probably just rout away without issue, but /pay attention and change your technique if you start to see chip-out or blow-out.

p.s. I don't think the holes will give you problems--should not interfere with routing whether done before or after.

[johnny means]

A little off topic, but... judging by what I see, a roundover might not be the best looking choice. Breaking the corner with a piece of sand paper preserves the crisp lines and architectural quality. A round over IMO would make it look 2x4ish .

[James Baker SD]

A little off topic, but... judging by what I see, a roundover might not be the best looking choice. Breaking the corner with a piece of sand paper preserves the crisp lines and architectural quality. A round over IMO would make it look 2x4ish .

I had in mind a major roundover 1/2" to 1" radius and significant wood removal. The hood itself is oval in shape, so I thought that the straight edges did not blend well with the hood. Maybe I am wrong, Do not want to ruin what I have as the curved pieces were a bear to make since they are both different and not symmetrical about the midpoint either, getting them to fit the metal cover took a lot of time.

[James Baker SD]

I ended up using a 1.5" round over bit in a shaper with router spindle at 15000 rpm. Much more stable than my hand held routers would have been. Took many light passes to protect the endgrain. Did a little work on the top as well, just a few passes for a slight curving bevel, but mainly on the bottom. Has a bit of an oval look now which is what I dreamed of to blend with the decorative glass shell of the hood. All in all very pleased how it turned out.

Decided against drilling the holes, will think of another way to attach it.