I need to cut a one-off round disc of 20mm MDF

Need it to be as perfectly true to round as possible, as will then run a
guided moulding cutter around it with router to make it slightly decorative.
My son has bought a house an there is a real naff plastic ceiling rose
... fitted to hide hole in plasterboard .. larger than teh light fitting
base.

My intents id to make a 175mm round 'decorative' MDF rose , screw it
though to a noggin fitted between joists.
Paint in white to match ceiling and then fit new light he has bought to
it (new light has a 115mm diam chrome base)

I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

I also have a Trend T11 and a router table for it ...

Just looking for suggestions for a simple quick & easily made circle jig.

Seen some great youtube videos but the jigs would takes many Hrs of use
.... and too much effort (and cost) of this one off.
Plus most of them are for larger circles.

I have a bandsaw .. also looked at options for this - great video he
https://www.youtube.com/watch?v=afGNbVrBiFE

Lots of waffle so skip the first 5 min

Nice idea but again too much work for this one off need.

Anybody got a simpler idea for using router for this ?

On 01/01/2017 22:23, rick wrote:


Anybody got a simpler idea for using router for this ?

Find someone with a lathe ...

rick wrote:

I need to cut a one-off round disc of 20mm MDF

screw an oversized square of MDF in the centre, with the router clamped
down to e.g. a workmate raised up by an offcut of 20mm MDF, then spin
the square to cut the disc.

On 01/01/2017 22:23, rick wrote:
I need to cut a one-off round disc of 20mm MDF

Need it to be as perfectly true to round as possible, as will then run a
guided moulding cutter around it with router to make it slightly
decorative.
My son has bought a house an there is a real naff plastic ceiling rose
.. fitted to hide hole in plasterboard .. larger than teh light fitting
base.

My intents id to make a 175mm round 'decorative' MDF rose , screw it
though to a noggin fitted between joists.
Paint in white to match ceiling and then fit new light he has bought to
it (new light has a 115mm diam chrome base)

I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

I also have a Trend T11 and a router table for it ...

Just looking for suggestions for a simple quick & easily made circle jig.

Seen some great youtube videos but the jigs would takes many Hrs of use
... and too much effort (and cost) of this one off.
Plus most of them are for larger circles.

I have a bandsaw .. also looked at options for this - great video he
https://www.youtube.com/watch?v=afGNbVrBiFE

Lots of waffle so skip the first 5 min

Nice idea but again too much work for this one off need.

Anybody got a simpler idea for using router for this ?
How about using a holesaw? For your purpose the central hole for the
drill bit should not be a problem

Malcolm

On 01/01/2017 22:23, rick wrote:
I need to cut a one-off round disc of 20mm MDF

Need it to be as perfectly true to round as possible, as will then run a
guided moulding cutter around it with router to make it slightly
decorative.
My son has bought a house an there is a real naff plastic ceiling rose
.. fitted to hide hole in plasterboard .. larger than teh light fitting
base.

My intents id to make a 175mm round 'decorative' MDF rose , screw it
though to a noggin fitted between joists.
Paint in white to match ceiling and then fit new light he has bought to
it (new light has a 115mm diam chrome base)

I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

I also have a Trend T11 and a router table for it ...

Just looking for suggestions for a simple quick & easily made circle jig.

Find a disk of something just under size (plate, biscuit tine lid etc).
Stick it to your MDF with hot melt of double sided tape. Then put a
guide bush in the router and use that to router around the periphery of
your template.

Alternatively use the router in the table. tape down a bit of 9mm MDF or
similar as a baseboard, and then roughly cut a circle a bit oversize
(jigsaw) in your material. Stick a nail though the centre, and then tap
it into the board on the table, so that its 175mm from the edge of a
straight fluted cutter. Now just rotate the material around on the pivot
nail, and raise the router up to make the cut.

--
Cheers,

John.

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Why not just fix the hole in the PB? If as you say there is a noggin there it makes it very simple to graft in a piece of PB and a bit of filler to finish.

Richard

On 01/01/2017 22:23, rick wrote:
I need to cut a one-off round disc of 20mm MDF

Need it to be as perfectly true to round as possible, as will then run a
guided moulding cutter around it with router to make it slightly
decorative.
My son has bought a house an there is a real naff plastic ceiling rose
.. fitted to hide hole in plasterboard .. larger than teh light fitting
base.

My intents id to make a 175mm round 'decorative' MDF rose , screw it
though to a noggin fitted between joists.
Paint in white to match ceiling and then fit new light he has bought to
it (new light has a 115mm diam chrome base)

I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

I also have a Trend T11 and a router table for it ...

Just looking for suggestions for a simple quick & easily made circle jig.

Seen some great youtube videos but the jigs would takes many Hrs of use
... and too much effort (and cost) of this one off.
Plus most of them are for larger circles.

I have a bandsaw .. also looked at options for this - great video he
https://www.youtube.com/watch?v=afGNbVrBiFE

Lots of waffle so skip the first 5 min

Nice idea but again too much work for this one off need.

Anybody got a simpler idea for using router for this ?

Hammer a panel pin part way in to a scrap board, cut the end off the pin
(leave 5-10mm) and file the pin to a point. Attach the scrap board to
the band saw or router tables so that the metal spike is the correct
distance from the blade or router cut point. Make a small indentation in
the centre of your MDF then introduce it to the band saw or router, get
the spike into the indent, turn MDF through 360 deg ... job done. Simples!

On 1/2/2017 8:48 AM, wrote:
On 01/01/2017 22:23, rick wrote:
I need to cut a one-off round disc of 20mm MDF

Need it to be as perfectly true to round as possible, as will then run a
guided moulding cutter around it with router to make it slightly
decorative.
My son has bought a house an there is a real naff plastic ceiling rose
.. fitted to hide hole in plasterboard .. larger than teh light fitting
base.

My intents id to make a 175mm round 'decorative' MDF rose , screw it
though to a noggin fitted between joists.
Paint in white to match ceiling and then fit new light he has bought to
it (new light has a 115mm diam chrome base)

I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

I also have a Trend T11 and a router table for it ...

Just looking for suggestions for a simple quick & easily made circle jig.

Seen some great youtube videos but the jigs would takes many Hrs of use
... and too much effort (and cost) of this one off.
Plus most of them are for larger circles.

I have a bandsaw .. also looked at options for this - great video he
https://www.youtube.com/watch?v=afGNbVrBiFE

Lots of waffle so skip the first 5 min

Nice idea but again too much work for this one off need.

Anybody got a simpler idea for using router for this ?

Hammer a panel pin part way in to a scrap board, cut the end off the pin
(leave 5-10mm) and file the pin to a point. Attach the scrap board to
the band saw or router tables so that the metal spike is the correct
distance from the blade or router cut point. Make a small indentation in
the centre of your MDF then introduce it to the band saw or router, get
the spike into the indent, turn MDF through 360 deg ... job done. Simples!

I like that one, but don't have a bandsaw. TBH I think I would just cut
slightly oversize by jigsaw, then dress by hand down to a pencil-drawn
circle with a sanding disk in an angle grinder. If you are putting a
moulding on it afterwards with a router it doesn't have to be that accurate.

I have a fixed disk/belt sander, with this you can do an even better job
using the disk.

In article ,
rick wrote:
I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

Glad I bought that oddball circle cutter tool from Lidl ages ago. Used for
speaker cutouts in baffles and will do 150mm. Think it may be Dremel based
by the very difficult to get imperial cutter.

But for a one off like this in MDF I'd just cut it out roughly with a saw
then file/sand to size.

--
*Gun Control: Use both hands.

Dave Plowman London SW
To e-mail, change noise into sound.

On 03/01/2017 13:19, Dave Plowman (News) wrote:
In article ,
rick wrote:
I have a router and suitable bits, but have no circle cutting jig for a
disc this small ... the trammel bar that came with the TREND T5 is not
really suitable for circles less than about 250mm diameter.

Glad I bought that oddball circle cutter tool from Lidl ages ago. Used for
speaker cutouts in baffles and will do 150mm. Think it may be Dremel based
by the very difficult to get imperial cutter.

But for a one off like this in MDF I'd just cut it out roughly with a saw
then file/sand to size.



I bough the TREND circle cutting jig in the end - did a great job and
easy to use.