A question for brains

[adaran01]

Hello
I noticed you said you have been in the building industry for 20 years, and I have a question that no-one seems to be able to answer.
My question is how do I cut a mitre that requires a 45 degree cut one way (very easy), but also requires an angled cut another way.
an example that I have trouble with is a house with an angled ceiling (cathedral).
a) The cornice requires the normal 45 degree cut.
b) It also needs an angled cut to take into account the pitch of the ceiling.

Is there an easy way to work out where to make the second cut?
Is there an easy way to gauge the angle of the ceiling (a tool)?

I love renovating, however this job hurts my brain trying to work it out, I loose my patience and the final result looks unproffesional, of course I can hide my mistakes, but id rather know how to do the job properly.
regards Adam

 

[Kevmeister]

What you are talking about is a compound angle.

And the best way to cut it is by using a compound mitre saw (if we're talking about wood).

Imagine a flat sheet of wood that acts as a cutting base. If you had a saw (eg. a simple mitre saw like picture framers might use) set up to cut 45 degrees and put your flat sheet of wood on the saw base, then put your cornice on the sheet and cut the cornice, you'd end up with a 45 degree cut.

Now imagine if, without adjusting the saw at all you tilted that flat board up 10 degrees, laid some cornice on that, and cut it at the original 45 degrees, you'd then have a compound cut. The cut would be 45 degrees and "leaning over" 10 degrees.

Compound angles commonly turn up when building roofs. If you imagine a hip rafter it usually is cut on one angle (the roof pitch), whilst the other angle is 45 degrees (since it meets the ridge beam at a 45 degree angle).

 

[duncan_m]

Adam,

You need a compound sliding mitre saw like the one below.. which I bought around a year ago.. lovely saw.. well worth the $900.

The saw head tilts and the table turns.. locks in at the common angles, slides to about 310mm or so.

[ EDIT: moved image to photo gallery and replaced with image link - Sim' ]

 

[XBenX]

im amazed to see that bunning sells cheapo versions of these now for just over $100 one project done and its paid for itself in time saved

 

[brains]

Adaran,

Not all tradesmen in the building industry are chippies.

I was going to suggest a compound saw, but the boys beat me to it, especially Kevmeisters answer.

If youre cutting the plaster cornice, you can do it by hand and dont stress too much. A lot of sins can be forgiven with plaster and a good setter.

 

[beech]

Not all tradesmen in the builing industry are chippies.


Iwould have to agree Brains.

In fact some of the chippies arent even chippies.

Darren

 

[brains]

What are some of the chippies, Beech?

 

[beech]

Shocking Brains, just Shocking.

Darren

 

[Kevin Hockey]

I just picked up a sliding compound saw from Woolworths for $190. It will only be a handyman's version but it will do us for cutting sign stakes etc. Didn't have this as an option back in my furniture business days though.

Kev

www.nundahrealestate.com.au

 

[adaran01]

Thanks for the information.
I knew there was a tool I was missing, it may be a bit overboard for gyprock cornicing, however I have weiged up the pros and cons, and believe I need one.

 

[steve]

Adaran01.
Your cornice comes down the wall and across the ceiling.With an offcut of cornice with a square end sit it in position on one wall with the square end touching the other wall,then draw a line along the ceiling and mark where the square end finishes.Do this to both walls. Measure the distance from where the lines disect back to the square mark and this is the cut for that piece of cornice,do the same for the other wall and that is the mitre for that piece (making sure cornice is sitting in the same way it would be in a normal mitre box.If someone understands this ,could they please explain it to me .
PS This is the same method used to work out acute or obtuse mitres.

steve

 

[Kevmeister]

Even if you could use a "trade quality" compound mitre saw (I have the Makita LS1212 12" blade 300mm slide) then I would *never* consider using it to cut anything but wood.

I'd do exactly the same - pick up a cheapo compound saw from Bunning or whereever for $100 and use it till it was trashed. It's almost not worth replacing the blade, even.

Plaster will dull the blade quickly in my opinion and plaster is also potentially more abrasive than sawdust, which I wouldn't want to subject an expensive saw to.

Also, plaster does not need as exact tolerance as woodworking since you can always patch up with plaster, as brains notes, so a top-quality super-accurate saw isn't all that necessary.

 

[Ace in the Hole]

The problem with putting cornices on pitched ceilings is that it doesn't work. No compound saw in the world will solve the problem.

The only way I can see to make the join work perfectly is to bring the bottom edge of the cornice away from the wall (level cornice) to match the cornice running down the wall with the fall.

This would require just the standard 45 degree cut.
I could be wrong though.

Regards

Adrian See

 

[gecho1]

Hey there Adaran.
to answere the second part of your Q

Is there an easy way to work out where to make the second cut?

Is there an easy way to gauge the angle of the ceiling (a tool)?

Yes there is.
the tool that you require is called a 'bevel".
You can pick up a cheap one at "Bunnings" for about $10.
it looks a bit like an adjustable square. If you go to the tool section someone will be able to help you out.

gecho