Recessed cans in plaster

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Electromatic

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
Anyone have suggestions on cutting in 6" cans in a plaster and lath ceiling? I've cut in plenty of devices and a few cans before, but I need to do a couple dozen in a historical renovation.

I know a regular hole saw will get eaten up after a couple. A few brands have a continuous carbide grit version, but I'm doubtful how well it will actually go through the plaster or lath. There are also some that only have a few heavy carbide teeth (eg. Milwaukee Big Hawg) that seem like they'd do well with the plaster but I can see them being too rough on the lath and/or getting caught in the gaps between the lath strips. Our shop doesn't have a heavy-duty rotozip, and all I have is a little Dremel. Maybe it's time to get one since a 6" Big Hawg is about $90 anyway.

Thanks for any suggestions!
 
I have used every thing. I've found scoring it then chipping it works just as well. Also you get very little dust this way.

I would let the customer know their will be some broken pieces around some of the lights. They will require patching.
 
I have a few large carbide hole saws and they do go through plaster and lath. Cutting a 6" hole with one of them can be downright dangerous. :)
 
MAC702 said:
I've heard it said that getting knocked off your ladder kills more electricians than any other cause.
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We have used a Milwaukee 90° angle drill with a 1/2" chuck. If that gets caught you might fly across the room.
 
Carbide grit hole saw chucked in a variable speed cordless drill, one that you can adjust the torque. Go real slow and don't cock it so it grabs! You should have the torque adjusted so that if it does it stops turning. Make sure you use the side handle! It will chew right through plaster and lath, believe me. Try using one of those salad bowl dust catchers but I don't like them.

You may want to use a Baker scaffold instead of a ladder so you won't have far to go if you lose it. :eek:hmy:

We have used a Milwaukee 90° angle drill with a 1/2" chuck. If that gets caught you might fly across the room.
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Yup. Been there, done that and wont do it again!

-Hal
 
Yes, I'd have to choose the drill as well--something with more speed and less torque than a hole hawg!

The job is an old house that's now a museum. The plaster is all torn up in a lot of places anyway, and they're putting drywall over the plaster in some places. (Taking it down to the studs would've made my life a lot easier.) I'm not too concerned with some mess or damage, but looking to be somewhat neat so the cans will sit right and somewhat quick since there are a lot.

The carbide grit does work? Then switch to a regular hole saw for the lath?

Thanks everyone!
 
Electromatic said:
Yes, I'd have to choose the drill as well--something with more speed and less torque than a hole hawg!

The job is an old house that's now a museum. The plaster is all torn up in a lot of places anyway, and they're putting drywall over the plaster in some places. (Taking it down to the studs would've made my life a lot easier.) I'm not too concerned with some mess or damage, but looking to be somewhat neat so the cans will sit right and somewhat quick since there are a lot.

The carbide grit does work? Then switch to a regular hole saw for the lath?

Thanks everyone!
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Many cut in cans will have a hard time with the thickness of Wood lath and plaster.
There are can cutters with a carbide blade and have a catch housing, I have used before. You stop at the wood and change to regular teeth blade.
 
The carbide grit does work? Then switch to a regular hole saw for the lath?
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Noooo. Just keep on cutting. A regular hole saw will tend to break the lath lose from the plaster possibly causing chips and cracks.

ETA- You don't say whether wire lath or wood lath. Certainly keep going if it's wire lath. With wood, maybe a little faster if you change saws but I would just keep going. The carbide will have no problem with that 3/8" of wood lath and again, it's smoother cutting and won't disturb the plaster bond.

-Hal
 
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Drill hole with 1/4" masonry bit - no hammer... (bent snake up and in to check for ceiling joist).

Drill holes with 1/4" masonry bit around drawn circle through plaster - no hammer- connect holes by chiselling with screw driver (which becomes a chisel :D) carefully using finger/channel locks to steady wood from bouncing use wall board saw to cut wood lathe.

Caution.. careful not to disturb plaster squeezed through wood lathe about the existing ceiling.

Before starting, check for plaster cracks and plaster separating from lathe as if the ceiling plaster comes down you may be blamed or if it starts cracking or dropping it may need to get sheet rocked before it comes down..
 
At the supply house I saw a variety of Lenox grit edge hole saws made in the exact sizes for various recessed light types. That seems to be the ticket for the different types of plaster we have here (lath and plaster, structo-lite and blueboard).
 
It seems to me if you can cut the holes you are still going to have serious work to level the surface on which the can light will sit. In addition, the hole is going cut several laths; if any of the cut laths end on the neighboring joists, they will likely come loose. The easiest out might be to replace a square of the ceiling with drywall where ever you need to put a light. I am sure the owner will be pleased with that suggestion.:)
 
Buck Parrish said:
I have used every thing. I've found scoring it then chipping it works just as well. Also you get very little dust this way.

I would let the customer know their will be some broken pieces around some of the lights. They will require patching.
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Same here.Has worked well for me. Determine diameter, score with drywall blade [tip won't break] than start in center with hammer working towards edge.
If wood lath, cut with roto zip, if wire lath,nip out with diagonal pliers. Saves money on hole saws.
 
I use a rotozip, use a tile blade on the plaster then a wood blade on the wood. Very rarely do I have any chips that the trim doesn’t cover.
If it’s metal lathe I use the tile bit to go through all of it, same deal not many chips that don’t cover.
You have to use a vac to catch all the dust though. I’d use the grit hole saw but most times I’m using the thin water lights and can’t find a 4-1/8 one.
 
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