Cutting only plywood stuck on chipboard

[Invisible Man]

I am putting in a larger offset shower tray. Chipboard floor is in good condition and joists are in suitable positions to take weight.

Flooring up to edge of old shower tray is vinyl fake wood lathes stuck to fairly thin ply stuck to the chipboard.

I need to cut back the ply to the edge of the new tray without weakening the chipboard. Any idea how? Circular saw will not follow bend of offset. Jigsaw would need to go through chipboard to be accurate. Stanley knife is not tough enough.

I am reluctant to build the new tray higher and go on top because that would mean a lot more tiling and the tiles are old and no longer available.

TIA for any ideas.

[dom]

Hard to follow what the problem is without a piccy, but sounds like you need to attach a batten and either follow it with a smallish router set to the correct depth to just get through the ply but not the chip - or get hold of a fein multimaster (or bosch equivalent) and follow a similar procedure.

The multimaster is the tool that will get anywhere, though a router will giv you a better finish.

Or, with skill and patience, hand chisel it.

[Gib Bogle]

Angle-grinder?

[meow2222]

They will cut wood, not very well, but handy occasionally. They burn it a lot though, might not be too good for the vinyl. You need to keep a separate disc for wood cutting, it makes a mess of the disc.

NT

[Gib Bogle]

I just remembered I once bought a tool called a biscuit cutter, that cuts to a specified depth. It will go places a circular saw will not, but still has some limitations.

[fred]

In article , Invisible Man writes

A good sharp chisel (+ mallet) should sort this out in 2 mins flat.

[PeterC]

No fun using an angle grinder if it's actually going to do the job!

[Invisible Man]

Thanks to those who suggested a chisel. That is probably the way I will go.

2 minutes could be pushing it for the border of a 1000 x 800 offset shower tray.

[meow2222]

You just need a 1m x 0.8m chisel....

NT :)

[John Rumm]

You could do the straight bits with the circular saw...

[Invisible Man]

... with a 550mm radius bend

[Invisible Man]

Probably will but with a 550mm radius on the corner there is a lot of corner.

[fred]

I thought I'd set you a challenge ;-)

You could probably rough it out quite quickly, leaving a few mm which you could go back over to get it really tidy..