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Best tool to cut old thick rock lath plaster indoors with dust control

This topic contains 16 replies, has 6 voices, and was last updated by  Miamicuse 10 months ago.

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  • #707161

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    In your opinion what is the best tool to use to cut plaster up to 1.5″ thickness?

    The application is indoors, sometimes vertical (walls), sometimes horizontal (on ceiling standing on a ladder).

    The rock lath is a multi-ply surface, seems to be very popular in the 1950s to 1970s. First is a single ply of 5/8″ or 3/4″ gypsum, typically nailed to the wood framing. Next is a hand trowel layer of brown coat plaster again about 5/8″ to 3/4″ thick. This layer is hard like stucco. The final coat is a 1/8″ of eggshell or venetian plaster. Followed by multiple layers of paint. The total thickness of these wall/ceiling can be as thick as 1.5″ total.

    On all inside corners, there is either chicken wire or stiff metal lath.

    So far, I have tried different methods to cut a clean rectangular opening on these surfaces in order to gain access for repairs.

    (1) Sawzall with carbide blades – USELESS.
    (2) OMT tool fitted with diamond blades – limited success, very slow, dulls the blade very quickly, and limited dust control.
    (3) Angle grinder fitted with diamond blades – this is the fastest and most efficient, except for the dust control aspect.

    As far as using an angle grinder I have experimented with the following dust control methods.

    (A) Having someone holding a vac inlet nearby helps, but keep thinking that there has to be a better way.
    (B) Using different cutting shrouds. I have bought three in the last year alone. One was a “universal” clear dustless “Cut Buddie”, followed by a Milwaukee cutting shroud. Both of these were disappointments in terms of fit, lack of visibility, and increase of dust as the depth of cut increases. My latest one is a Bosch GA50DC, which was my very first redemption at BTP. I look forward to trying it out once I buy a Bosch grinder to pair with it.

    The problem with using this shroud, or any other shroud with a grinder or cutoff tool, is the shroud limits your cutting depth to about 5/8″ to 7/8″ depending on the shroud and grinder. It would be nice to be able to cut deeper to 1.5″.

    In addition, when I need to cut at an insider corner, where the combination of thick plaster and metal lath is present, the geometry of the corner makes it impossible to use a shroud with a depth gauge, so I go back to having a buddy holding a vac near by.

    Wet cutting is not possible because it’s indoors, and sometimes it overhead.

    Are there new tools out there that can perform this task – corded or cordless, able to cut on horizontal or overhead surfaces with dust control, as well as along inside corners?

    #707162

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    I have included a reply from CB in a related thread.

    The optimum thickness I am looking for is about 1.5″ thick. I run into having to cut open rock lath ceilings and walls a lot. Actually may be 80% of the time that’s what I bump into and the other 20% modern sheetrock. The rock lath is a layer of 5/8″ or 3/4″ gypsum nailed to the wood framing, followed by a hand troweled on layer of brown coat plaster that is 3/4″ thick, then usually another layer of smooth Venetian or eggshell plaster about 1/8″ thick, then of course over the years another 6-8 coats of paint. This makes a total thickness of slightly over 1.5″. There is no metal lath or chicken wire in them except at all inside corner joints.

    I have tried various tools to make cuts on these surfaces, carbide tipped blades on sawzalls don’t do anything, OMT with diamond blades do better, but real slow. The brown coat is hard as rock. The only effective tool that works is the old angle grinder fitted with a diamond blade, but dust control is a real issue, especially when I am standing under making cuts on a ceiling. My current tool is a 5″ angle grinder fitted with a cutting dust shroud, which helps some…but the dust shroud limits the cutting depth to a max of 7/8″, so first pass use the dust shroud, second pass remove the dust shroud, well…this cutoff tool with a built in DC would have been perfect, except the depth limitation.

    Also, at the inside corner, where wire mesh or stiff lath are used, I have to score a clean line. Then there is no place for a dust shroud there, no matter what depth, as I need to get the blade close.

    Can you start a separate thread with this issue?

    The reason for a new thread is not because this problem is tangential to Milwaukee tools, but rather because this problem is interesting enough to deserve it’s own thread that is irrespective of Milwaukee tools, and for that matter, any brand of tool.

    If a diamond blade has provided the most efficient cutting performance, apart from depth of cut and dust control, then there are a host of saws that have dust shrouds with vacuum port attachments from a variety of brands that might serve better than two passes with a grinder, where the second pass is without even a shroud.

    Some of the solutions might be plug in. I’m going to mention Makita again, Makita model number 5057KB, a vacuum ported, transparently clear shrouded, 13 amp, side winding, blade right, fiber cement circular saw that accepts very common 7 1/4″ diamond blades that will give you more than 2″ depth of cut, that has a blade guard lever inboard, despite the fully enclosed shroud, so that plunge/pocket cutting in the middle of a ceiling could be accomplished:

    There are about 5 other similar types of saws made by Makita alone, in various blade sizes, power capacities, RPMs, blade orientation, including a blade left, dry cut, 5″ masonry circular saw that has a bag and a vacuum attachment as well as a clear shroud (Makita 4100KB)…

    I’m not advocating Makita tools, and I don’t have either of these tools above… I just so happened to be looking at Makita tool catalogs in the last couple of days due to my recent purchase of a dry wall saw. That isn’t to say that Milwaukee doesn’t have similar solutions. Or Bosch, for that matter. The new OSHA cement dust regs have motivated tool companies to FINALLY bring over to North America some of the dust control solutions that European regulations already required across the pond.

    Five years ago, when I first considered a 6 1/2″ battery powered circular saw, I looked at the Milwaukee M18 line up, and found where the exact same saw in Europe had a dust control shroud, whereas the same models sold in the United States did not. I briefly looked into “importing” the shroud parts for model sold in Europe, but I don’t have time for that nonsense.

    Dust control regulations (particularly with harmful substances that never dissolve) are REGULATIONS for a reason… that reason being that tool manufacturers have proven time and again that they will not voluntarily add content to their tools to make humans safer as long as they can get away with making their tools more profitable by thrifting out content in markets where there is no regulation.

    So now that the United States has some regulations, your options for overhead cutting of plaster with more effective dust control solutions have likely expanded dramatically within the last year. An exploration of those options across ALL brands of tools is warranted, and shouldn’t be limited to just Milwaukee.

    Hence, I suggest a new thread to resolve your specific problem, where this community can pitch in with their ideas from what they’ve stumbled across recently, and we can all learn more about what solutions promise to be effective, versus what solutions actually work.

    #707164

    roninohio
    Pro
    New Franklin, OH

    Sledge hammer or a pick works well . We use the sawzall with a bi metal blade if we need a clean cut in a corner with wire . The blades last a while . Wear a dust mask. Some of the old plaster has asbestos in it .

    #707173

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    Sledge hammer or a pick works well . We use the sawzall with a bi metal blade if we need a clean cut in a corner with wire . The blades last a while . Wear a dust mask. Some of the old plaster has asbestos in it .

    What kind of plaster do you have that you can cut with a bi-metal blade? There is no chance I can cut these with any sawzall blade. It is as hard as stucco.

    When I do this I wear a paint coverall, eye protection, silica dust respirator, gloves, and a full face shield. In south Florida, when it’s 90 degrees outside, and the air conditioner is always turned off when we do any sort of concrete cutting, I get totally soaked in less than 5 minutes and the eye piece fogs up totally LOL.

    #707211

    roninohio
    Pro
    New Franklin, OH

    Maybe plaster is different in Florida than Ohio?

    #707222

    kurt@welkerhomes.com
    Pro
    Owatonna, MN - Minnesota

    we have had the Kett saw for several years and swear by it for cutting drywall and plaster. It gets used on all our remodels. with a HEPA vac, it is virtually dustless. they have fine tooth blades for drywall and carbide blades for plaster.

    They are not cheap but well worth the price if you are worried about dust control and have occasion to use them very often

    https://www.toolfetch.com/kett-ksv-434-vacuum-saw.html?utm_source=bing&utm_medium=cse&utm_term=KSV-434&msclkid=2e83b71e505e1d2eb473eb0c1fac2ac1

    #707231

    RonW
    Pro
    Holladay, Tn

    Maybe plaster is different in Florida than Ohio?

    It must be.

    Ron

    A Working Pro since 1994!

    Member since March 26, 2014.

    #707245

    DirtyWhiteBoy
    Pro
    Honolulu,, Hi.

    There is no chance I can cut these with any sawzall blade. It is as hard as stucco.

    There are masonry sawsall blades that we cut CMU block with. That might work.

    Dirty

    A Working Pro since 1988!

    Member since January 26, 2013.

    #707282

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    Maybe plaster is different in Florida than Ohio?

    Don’t know. May be you have lime plaster and we have cement plaster?

    #707283

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    There is no chance I can cut these with any sawzall blade. It is as hard as stucco.

    There are masonry sawsall blades that we cut CMU block with. That might work.

    I would be interested to see what sawzall blade can cut CMU blocks, but the main issue here is to be able to do interior cut with dust control.

    #707284

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    we have had the Kett saw for several years and swear by it for cutting drywall and plaster. It gets used on all our remodels. with a HEPA vac, it is virtually dustless. they have fine tooth blades for drywall and carbide blades for plaster.

    They are not cheap but well worth the price if you are worried about dust control and have occasion to use them very often

    https://www.toolfetch.com/kett-ksv-434-vacuum-saw.html?utm_source=bing&utm_medium=cse&utm_term=KSV-434&msclkid=2e83b71e505e1d2eb473eb0c1fac2ac1

    <figure class=”oe-video-container”><iframe src=”https://www.youtube.com/embed/mFJtHHKWYHE?feature=oembed&wmode=opaque” allow=”accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture” allowfullscreen=”” width=”770″ height=”433″ frameborder=”0″></iframe></figure>

    This is very interesting. I had no clue such a tool existed. I need to look into this, like CB suggested may be a fresh look at all the product offerings would be in order. I have been stuck on finding the perfect grinder cutting shroud for a while now.

    #707318

    I have had some success in my own house (circa 1895) which has lathe and plaster with embedded horsehair with the Bosch or Dremel carbide blades on my Fein OMT, these are the same blades I use to cut nails with.

    Will

    #707335

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    I have had some success in my own house (circa 1895) which has lathe and plaster with embedded horsehair with the Bosch or Dremel carbide blades on my Fein OMT, these are the same blades I use to cut nails with.

    How do you deal with dust control with an OMT tool? One of my OMT tool is a corded Rockwell it does come with a DC connection but it collects may be 30% of the dust which makes it not practical. I have used an OMT with a diamond blade to do electrical cutouts on plaster walls, it works but very slow. Carbide, bimetal or other blades would do nothing on the rock lath I run into.

    #707338

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    we have had the Kett saw for several years and swear by it for cutting drywall and plaster. It gets used on all our remodels. with a HEPA vac, it is virtually dustless. they have fine tooth blades for drywall and carbide blades for plaster.

    Kurt, I was looking at various videos and reviews and a bit confused by the cutting depths. The depth I am looking to cut is 1.5″. With an angle grinder fitted with a 4.5″ or 5″ diamond blade with a cutting shroud I can cut up to 7/8″ and no more. The benefit of doing it that way is I can use cordless grinders (less weight and no cords for overhead cutting), and it’s for the most part a one handed operation with my other hand free to hold the vac hose or whatever.

    With this Kett saw it is a two handed operation but still better than kicking up all the dust if it can cut to the depth I need.

    In the video you linked it says it can cut up to 1.5″, but then it showed a plunge cut on plywood and it says it can cut up to 5/8″. May be different size saw blades? Not sure.

    On this Toolfetch site, the manufacturer’s specs stated:

    “Now you can cut heavy 5/8″ drywall, fiberglass, plastic sheet and other construction panels and automatically vacuum up the dust as you cut. The Kett Vacuum Panel Saw features a cast aluminum vac saw head to connect to your shop vac or in-plant collection system. It features a spring-loaded blade guard and cuts up to 1-1/16″ deep using a 3-1/2″ carbide abrasive or high-speed steel saw blade. It also accepts 2-1/2″ blades for cutting laminate panels or C.R. mild steel up to 16 gauge.”

    here it suggested 1-1/16″ deep with a 3.5″ blade.

    However, on this youtube video of the Kett saw, the reviewer at the 3:33 minutes in, said the max depth of cut is 1″.

    Is your Kett saw able to cut 1.5″ deep?

    The other issue is inside corner cutting where 1.5″ thick hard plaster with embedded wire is. I haven’t found anything that will do a clean cut except an angle grinder with no shroud. Using hammer or chisel with manual tin snip is a less dust alternative, but often times you end up transferring cracks and damages to the other side of the corner.

    #707429

    kurt@welkerhomes.com
    Pro
    Owatonna, MN - Minnesota

    here is a link to the Kett website. I think 1 1/16″ is the deepest.

    They used to hake a bigger saw with a dedicated motor, instead of using a drill motor, but I do not see it on their website any more.

    https://www.kett-tool.com/

    #707464

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    here is a link to the Kett website. I think 1 1/16″ is the deepest.

    They used to hake a bigger saw with a dedicated motor, instead of using a drill motor, but I do not see it on their website any more.

    https://www.kett-tool.com/

    Thanks Kurt! 1-1/16″ is still deeper than the 7/8″ I get with a grinder shroud. I will keep this in mind.

    #708169

    Miamicuse
    Pro
    Fort Lauderdale, Florida

    Here is a youtube video of someone using a Bosch angle grinder fitted with a cutting dust shroud. Don’t know why he was scoring a concrete floor with a 4.5″ grinder but it showed pretty good dust collection if he is getting the depth he needs.

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