Cutting small diam discs

[Argonaut]

Looking for a bit of advice.
I need to cut out a 170mm disc from 20mm mdf.

I have used the standard trammel arm which came with my router to do larger diameters .. don’t think it suitable for small diameters.
I have a Trend T11 which I can also fit into my router table, and a Trend T5.
Anybody any suggestions for a simple jig for doing this …. Don’t want to spend a lot of effort for this one off disc.

 

[CHJ]

If you have them:- Bandsaw/jigsaw and sanding disc machine

Make simple rotary platform/plate to clamp to sanding disc table out of hardboard and a scrap of MDF/Chipboard.
Rough cut your disc slightly oversize on bandsaw,
Stick MDF disc to rotary table with DS tape.
Clamp platform to disc table and adjust radius spacing of rotary disc until MDF disc is precisely the diameter you need.

 

[Argonaut]

I have a bandsaw .. but no disc sander. So your method is not an option.

Father Xmas didn't bring me a disc sander

 

[NazNomad]

https://www.youtube.com/watch?v=afGNbVrBiFE

 

[Argonaut]

https://www.youtube.com/watch?v=afGNbVrBiFE

I looked at the updated link (video has been superseded)
https://youtu.be/HAq7_nBpUrY

It's a good jig, and if I had a need for multiple round cutting it would be worthwhile - this is a one-off, so will need to find something simpler.

 

[NazNomad]

Can you draw a 170mm circle?

Rough it out with anything that cuts and sand it to the line, great for a one-off?

 

[ola c]

To rout small circles you need the rotation point under the router base. Instead uf running the router directly on the work surface there should be one layer in between.

My jig looks something like this and can handle diameters from 20 to 800mm. Pin is 6mm and threaded into a threaded insert in the jig. Diameter is adjusted using the fence rods (single rod would also work I guess if that's what you are using now).

https://www.byggahus.se/forum/attachmen ... 1422609682

https://mobil.byggahus.se/forum/attachm ... 1422609702

 

[Argonaut]

I decided to invest in a TREND CRB7

https://youtu.be/gdGQi22kUC8

Often thought of getting one ... found one at less than 1/2 price from one seller.
So treated myself to a post Xmas present.
The other functions will be useful.

Sent from my SM-G930F using Tapatalk

 

[sploo]

Looking for a bit of advice.
I need to cut out a 170mm disc from 20mm mdf.

I have used the standard trammel arm which came with my router to do larger diameters .. don’t think it suitable for small diameters.
I have a Trend T11 which I can also fit into my router table, and a Trend T5.
Anybody any suggestions for a simple jig for doing this …. Don’t want to spend a lot of effort for this one off disc.

No pictures (sorry) but it's relatively easy to create a small circle cutting jig:

1. Get a sheet of thin material (best 6-12mm thick) that's the width of your router's base, and probably 2-3x as long
2. Route two rebated slots along the length of the jig, through which you can use flat headed bolts to screw the jig onto your router's base - the slots mean you can slide the jig on the base before tightening
3. You'll also need another slot along the length but in the middle - probably 12mm wide (this is for router bits)
4. Drill a small hole (3-4mm) somewhere near the end of the jig, on the centre line (i.e. near one short edge, and equal in distance from each long side).
5. Countersink that hole and drive in a small bolt or machine screw (3-4mm dia, maybe 12-19mm longer than the jig's thickness)
6. The only thing protruding from either face of the jig should be the small bolt thread - no heads from the bolts on either side

That jig should now allow you to get the centre point for a circle (the small bolt) really close to the router bit - i.e. the rotation point can be underneath the router's base; meaning a 170mm dia circle should be easy. Obviously you will need to drill a small hole in the stock though.

 

[BertD]

You could consider making a full size circle template that would fit the OD of the router base + the radius of the desired circle. Place you work piece on cutting foam and clamp your router template on top. Simply plunge into work with edge of router against the template inner circle, gomround and voila a routed circle with no center hole. Repeatable and accurate although not adjustable.
Cheers,
Bert