Thread: Cutting big holes in ply

Depends on accuracy need I guess and if you want a clean centre or don't mind a hole in it. Are you after the remaining panels with a hole or the hole/circle cut.

As they are only 3mm you could put them together and cut them all at once with a jig saw or router done in one go.

hi wheelin around, I need the outsides that remain after the inner circles have been cut and removed.

The problem is that there is not much room to clamp all these pieces together and run a jigsaw or router around - it will be only 20mm from the outside edge of the square to the inner circle edge in places.

Pity I don't have a bandsaw or scrolling machine

A band saw can't actually do what you want, so you'll need to find another justification to buy one! Since you have several to do, I would use a router on a trammel. Quick and easy, and you'll get a cleaner result than a jig-saw.

Jillib

No need to clamp all together if you don't need the centre.......time to use your instinct here.
How can you secure 12 bits of wood with out using clamps .......screw them

Then use a plunge router off a tramel from centre

N-Compass Routing Jig for ¼" routers from M.POWER - Precision Engineered Tools

Another way to hold them in place while you use a router and tramel if you don't want to damage the ply by screwing and you don't want to use clamps, is to build a frame from some scrap pieces of timber 300X300mm and allow for router base so the pieces you want to cut fits snugly inside the frame. nail a sacrificial bottom to the frame and mark the centre point on it.
You can make your own tramel from a piece of thin timber and nail through one end to use as your pivot point marked on the board. It is a good idea to have the frame held securely bench dogs or clamps. you can just pop one piece in after the other and they will all turn out the same. The sacrificial bottom of the frame will avoid tear out when you make the cut through.

Have you got a lathe and if so how big is it?

But this is what I would use.
That is what I used to make this.


the centre hole-less version is here.

Might be a little snug, but I think this will go small enough: https://www.woodworkforums.com/f88/router-compass-50372/

And screw them together, in the waste interior portion, for gang-cutting. Probably need two or three sandwiches, for your thicknesses, each sandwich screwed to a waste panel below.

Cheers,
Joe

many thanks everyone. A trammel it is, with munruben's suggestions for a frame and sacrificial base! Will probably try and do 4 sheets at once - ie., cut through 12mm at a time, with 12mm ply cleats holding the sheets in place.

Will post pictures.

sorry I don't have a big lathe, BobL

Joe Griener's jig has given me an idea of using two rods through the base of the router to make a trammel.

This is my router circle cutter ,It's a design by Template Tom. Fits the the Makita 3600 series.But could be modified to suit any router with holes through the base to take a fence.
The two rods are 12mm stainless and slide into the holes in the base , the row of holes down the center at 50mm centers give adjustment plus the finer adjustment of the router on the rods.
Ive used it a fair bit and it's a gem to use.

Kev.

thanks Kev, this has solved a problem for me. I had previously made up a parallel bar arrangement for cutting large circular sections up to 450mm radius, but the minimum distance from the centre hole of my bar plate to the centre of the router was 125mm. With a 10mm router bit, I can just do a 260mm hole in a large board.

I did not know how to do a circle less than this size. With your base, I can use my parallel bars.

One question, what are the little gizmos in the 20mm centre holes that you have fitted. Do these determine the thickness of the perspex base?

Also, can you work the jig with the centre hole under the router edge ie., what do you use for fixing the centre swivel point of the jig on to the timber so that it does not interfere with the base of the router ?

Sorry for the questions but the details are of Tom's new Circle Cutting Jig are only available on his CD-ROM 2