Q: How to make a compound mitre cut for plaster cornice?
nos...@our.site
I am trying to put up plaster cornice that I have made ( I will post
notes on how to do this in the future if any one is interested, though
it is not a small job )
The dimensions of the cornice are 200mm by 160mm. To do the corners I
need to make a compound mitre cut for the ends. I havent seen a hand
mitre-saw that will accomodate
something this large. Is there one out there or is there any other way
of doing this?
A power mitre saw is way too expensive and I am not sure that this would
cut the depth I am after.
Cheers
Aengus
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Aengus Stewart aengus....@icrf.icnet.uk
Computational Genome Analysis Laboratory Tel: +44 (0)171 269 3679
Imperial Cancer Research Fund
Lincoln's Inn Fields, Holborn, London, WC2A 3PX, UK
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ian_c...@my-deja.com
Aengus Stewart wrote:
> I am trying to put up plaster cornice that I have made.
>
> The dimensions of the cornice are 200mm by 160mm. To do the corners I
> need to make a compound mitre cut for the ends. I havent seen a hand
> mitre-saw that will accomodate
> something this large. Is there one out there or is there any other way
> of doing this?
Hi Aengus
I made a terrible hash of cutting coving mitres until I worked out what
was really needed.
I made a mitre box to suit. I think the following is the best way, esp.
for such a large coving.
Build a 'rectangular tube' that is a pretty snug fit, but you can thread
the coving into without damaging it. Make the base out of something
pretty thick.
Now make a cut through the top of and down the sides of the box at
45deg. Use careful measuring and a steady hand with a large saw to do
this.
Now you should have a 'sleeve' that you can thread over the cornice, and
use the slot you cut to guide you through the plaster.
You'll probably want to cut 'both' 45deg slots, and may find the 90deg
slot useful as well.
One final option: Use a holesaw to cut an inspection hole in the top so
you can see whether you're cutting the cornice at the correct place.
Alternative is to work out the offset from where the cut takes place to
the end of the tube, and use this to get the cornice in the correct
place each time.
Plan view, with inspection holes: End view: 200x160
internal
+==============================+ +-------+
| \ | / | | |
| O O O | | |
| \ | / | | |
+==============================+ +-------+
Side view: double thickness base to help stop cutting
through!
+==============================+
| | | | |
| | | | |
| | | | |
+==============================+
+==============================+
And a final tip: If the cornice is strong enough to take it, use wedges
to hold it firmly against the 'reference' faces when cutting. You can
then concentrate on a nice steady, even cut rather than having to stop
the cornice wiggling about.
HTH
IanC
nos...@our.site
ian_c...@my-deja.com wrote:
>
> Aengus Stewart wrote:
> > I am trying to put up plaster cornice that I have made.
> >
> > The dimensions of the cornice are 200mm by 160mm. To do the corners I
> > need to make a compound mitre cut for the ends. I havent seen a hand
> > mitre-saw that will accomodate
> > something this large. Is there one out there or is there any other way
> > of doing this?
>
> Hi Aengus
>
> I made a terrible hash of cutting coving mitres until I worked out what
> was really needed.
Tell me about it......I didnt think it through properly and made 2
simple mitres in 2 lengths that I had made ......ugh.......
Considering it takes considerable time and effort to make the cornice
cocking up like this made me so angry with myself.
>
> I made a mitre box to suit. I think the following is the best way, esp.
> for such a large coving.
Yup we came to the same conclusion last night after looking at all the
available tools and realising that they were all too small.
>
> Build a 'rectangular tube' that is a pretty snug fit, but you can thread
> the coving into without damaging it. Make the base out of something
> pretty thick.
I was thinking of 3 sides but obviously a 'tube' would be better, good
point.
>
> Now make a cut through the top of and down the sides of the box at
> 45deg. Use careful measuring and a steady hand with a large saw to do
> this.
This worries me, are you suggesting doing this cut freehand with a
27-point saw?
I am quite good with a saw but will this be accurate enough?
They are so bloody heavy that they dont move :)
I also lost one which fell of the ceiling about a month after I stuck it
up. I suppose assuming that coving adhesive would hold 15kg was a bit
naive as well. Everything is getting screwed in now as well!
Thanks for the suggestion Ian.
ian_c...@my-deja.com
nos...@our.site wrote:
>
>
> ian_c...@my-deja.com wrote:
> >
> > Build a 'rectangular tube' that is a pretty snug fit, but you can thread
> > the coving into without damaging it. Make the base out of something
> > pretty thick.
>
> I was thinking of 3 sides but obviously a 'tube' would be better, good
> point.
I found the extra face compensated for me not going a 'full' joint where
the sides meet the base. If I'd finished the faces and dowel+glued I
probably wouldn't have bothered with the top, as it was I just screwd
through so it was a little wobbly! Just hardboard or thin ply is all
that's needed to stop the sides splaying under use.
> >
> > Now make a cut through the top of and down the sides of the box at
> > 45deg. Use careful measuring and a steady hand with a large saw to do
> > this.
>
> This worries me, are you suggesting doing this cut freehand with a
> 27-point saw?
> I am quite good with a saw but will this be accurate enough?
You should be able to get a decent line with a sharp free hand saw. Mark
the full vertical on both sides and make sure you follow it all the way
through. Someone watching the other side might come in handy.
Best of luck.
IanC