Method to cut a shallow detail

[VenomBottle]

Hello.

I plan to make a 5mm thick, 36mm diameter plywood disc with a detail removed to a depth of 5mm as indicated by the red filled section in the attached image. So 5mm thickness on the disc, 4.5mm thickness in the red filled section.

I'm looking for tips of a clever method to do this.

Current ideas include:
1. Removing most of the material with a router using a 1/8 inch bit then finishing with knife and chisel.
2. Cutting the perimeter using a knife with some tape on to act as a depth stop, adding a grid of cuts to the inside of the detail and then finishing with a chisel.

I think in reality; either of these methods will be tricky to do in reality. Any tips or advice is greatly appreciated!

Thanks.

 

[bjm]

I'd go with the router and clean-up. Is this a one-off though?

 

[Ollie78]

I agree with bjm, router the detail when its still part of a larger sheet, then cut the perimeter out.

Ollie

 

[VenomBottle]

Yeah it's a one off. Hadn't thought of doing it before cutting the D36 disc though, that should help.
Thanks

 

[pe2dave]

Route a chunk out of your ply (test piece). The resultant surface is unlikely to be a 'decent' finish IMHO?
Layers of ply are seldom truly linear.
How could you use marquetry / parquetry to make the inset look a bit special?
(Or even a resin poured - in red?).

 

[marcros]

Are the dimensions critical? I think that I would probably do the cut out with a coping saw/fret saw and stick a piece of veneer to the underneath. Glue the centre block to it.

Is 5mm ply available, I don't buy much but it doesn't sound familiar. Probably something near though.
I may even be tempted to use MDF, make the cutout. Lip the edges of you want.
stick a veneer to the top,
use the cutout as a template and a scalpel to cut through the veneer
Stick a veneer on the back
Glue in central block

 

[J-G]

That's a job for a small CNC router or something like Roland MX-20 but if - as seems likely - if the [Image] is just the 'Face' does it need to be 4.5mm deep ? At 1 or 2mm deep it will look just the same.

 

[MorrisWoodman12]

Just an idea that may solve your quandary. Can you make it in two layers? First layer has your home design cut all the way through (coping saw?), the second is solid. Then simply glue the two together. I suggest you cut the outer 36mm shape after gluing.
How important is the 5mm thickness? Ply is available in 3mm, 3.6mm, 4mm but also model making ply comes in 0.4, 0.8 & 1.5mm thicknesses.

 

[xy mosian]

A tricky bit, at that size, will be marking out the edges, either to cut directly, or for some router guiding template. How about using a punch, of the sort used by folk putting name stamps on tools. Control could be better than a lump hammer by using some sort of clamp, possible even a vice. The edges are not likely to be 'crisp' , but that may not be an issue. If edges being non too sharp are a problem then at least you have an accurate template around which to mark with some ease.
xy

 

[Droogs]

If you are going to do this often then a Veritas mini plunge router base and a dremel would be what you want along with some micro bits