Rounding over plywood edges (new to me)

[LinuxRandal]

As I am still in the "house project" side of woodworking , I am having to build a plywood access panel, to replace one at work.
There used to be a small frame, with a board screwed into it (with 3+" screws), as emergency access to the water shutoff, for the shopping center. The pressure regulator went bad, and a larger opening had to be cut to facilitate the replacement. Now, since I have the tools (and the landlord is in NO hurry to cover the opening), they asked me to get and stain a piece of plywood for the opening. As I have always trimed edges with a solid piece, when working with it, I have a stupid question.
Since plywood is wood, going opposite directions, do I need a backer piece when rounding over the edges, with a router?
Since this is both down low, and in an area accessible to little ones, I want to round off the edges and over the corners (believe me I am used to Murphy and his older brother Murdock and their laws).
Thanks all

[LCHIEN]

As I am still in the "house project" side of woodworking , I am having to build a plywood access panel, to replace one at work.
There used to be a small frame, with a board screwed into it (with 3+" screws), as emergency access to the water shutoff, for the shopping center. The pressure regulator went bad, and a larger opening had to be cut to facilitate the replacement. Now, since I have the tools (and the landlord is in NO hurry to cover the opening), they asked me to get and stain a piece of plywood for the opening. As I have always trimed edges with a solid piece, when working with it, I have a stupid question.
Since plywood is wood, going opposite directions, do I need a backer piece when rounding over the edges, with a router?
Since this is both down low, and in an area accessible to little ones, I want to round off the edges and over the corners (believe me I am used to Murphy and his older brother Murdock and their laws).
Thanks all

I think the grain on the top veneer edge will still tear out.

Wouldn't take a lot to make a 1x2 mitered frame grooved to accept plywood and round over the edges - will look a lot better - unless its not a critical viewing door, in whihc case why are you worrying about tearout on the edges/corners?

[RodKirby]

Treat the roundover just like a regular piece of wood. Imagine the top veneer is the only grain direction If the roundover is "large" take 2 passes.

ALWAYS do the end grain first, then the long grain pass will take off the tear out.

"Brisk" feed rate to minimize burning the end grain veneers.

PS: I have done this many times with complete success

[Pappy]

Success depends a lot on the plywood, too. Baltic birch accepts machining well and looks good when done. The worse the grade of plywood, the more trouble you are going to have with it.

[LarryG]

+1 on what's already been said. You'll want to use a REALLY sharp bit, too ... a brand new one, if available.

[Deadhead]

Wouldn't take a lot to make a 1x2 mitered frame grooved to accept plywood and round over the edges - will look a lot better - unless its not a critical viewing door, in whihc case why are you worrying about tearout on the edges/corners?

I was thinking a grooved frame too. Unless there isn't clearance above the hole to slide the plywood into the frame. And if you do frame it, attach the top horizontal piece to the plywood to use as a handle.

Not sure I'd want it screwed into place if it's an emergency cutoff. "Where's my drill??!!!"

[JimD]

If you are not using real good plywood (baltic birch or equivalent), you might consider doing the round-over on a router table with a fence. I have rounded the edge of a bunch of plywood and agree with Rod's suggestions but I would also observe that there is a tendency of a hand-held router to follow a flaw in the edge of the plywood and it looks pretty bad when this happens. With the edge against a fence, you can avoid this.

Jim

[RodKirby]

If you are not using real good plywood (baltic birch or equivalent), you might consider doing the round-over on a router table with a fence. I have rounded the edge of a bunch of plywood and agree with Rod's suggestions but I would also observe that there is a tendency of a hand-held router to follow a flaw in the edge of the plywood and it looks pretty bad when this happens. With the edge against a fence, you can avoid this.

Jim

Absolutely, Jim. Never occurred to me it would NOT be done on a router table. (Assumptions!)