I found an article that says the cleanest and quickest way to make straight cuts on fibercement clapboard, is to score it with a knife on the backside, then snap it over a block. Touch up as required with a rasp.
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I think I'd disagree with that. IMHO the quickest way is with fiber cement shears (Kett, Snapper, Porter Cable, etc) and the cleanest cut is with a fiber cement blade on a circular saw (Makita or Hitachi)
I bought the carbide scoring tool. I score either side just like drywall, snap and use the street or sidewalk as my rasp. It cleans it up and knocks off most of those loose particles that like to scratch things. I do like to use my wet tools to cut holes and interior 90's and such.
Does that give you a clean/accurate enough cut to butt up against molding and caulk, or are you using something to cover the rough edge?
Check that. Thought the post was refering to cement board. Apply my findings when using Durock or Wonderboard. As you were.
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From what I hear, the Hardie reps carry lots of these in their trucks, to give out as needed.
I've got plenty of time to check this out. I'm going to get a knife like this, some sample sections of 1/2" clap board, and try it.
Failing that, I've got a Kett KD-200 shear for sheet metal, and Kett says the drill motor base is the same as for the FC siding shear, so I'll see about getting their 92-20 shear head to swap out for my 60-20 head.
A diamond blade on an angle grinder is a great tool to have and makes some cuts very easy. I think you could score and snap if the end was covered by casing or cornerboards, otherwise you'd have to clean it up quite a bit. Most cuts are probably by circular saw. The guys across the road have been cutting that stuff with a little screamer sidewinder for a few weeks now.
I trashed my Porter Cable sidewinder with Hardiplank siding. If you have more than one house to do, get a saw designed for cutting this stuff (Hitachi or Makita makes them). Or at least hook up a shop vac that turns on/off automatically. Nothing worse for saw bearings & guts than cement dust.
I thought the same thing, but i am up to eleven houses now with a ten year old Makita and no hassles yet.
My Porter Cable framer had trouble with the blade guard jamming in the up position from the cement dust. Then I'd set it down, not realizing the guard was up, and it would tear across the pile of Hardi siding on the saw horses and leap into the mud. Just a little scary/messy/dectructive.
I did that on a small addition. You'll need to clean up the cut (I used a piece of cinderblock for a rasp).
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How about a carborundum block from a masonry supply place? The kind of tool you use to "stone" a wall.
You might try using a steel staightedge like the carpet and vinyl flooring installers use. Much easier than using a level or board for a straight edge (as in the drawing). I clamp the straight edge on, score several times and snap. With the stiff steel straightedge clamped on, the siding breaks cleaner.
You've seen the fibercement clapboards, right? Mine to be cut are 5-1/4" and 7-1/4" width, 1/2" thick at their heavy edge, beveling off to maybe 3/16" thickness at their thin edge.
What I'll try when I get my carbide scoring knife and clap samples, is using regular and large-size speed squares to guide the knife, then a scrap of 2x lumber for my break-on block, and a mason's rub block to smooth up the snapped edge.
I know all about the dust, and what it can do to you, your tools, and your jobsite. I want to avoid that however I can.
The shears are possible, in that I can adapt my Kett with a new front end for fibercement ($100 for the part), but this score-and-snap sounds worth exploring.
What brand are those? The descriptions I've seen of the Hardie siding say it's 5/16" from top to bottom, not tapered.
By Jove, you are right! I just looked at the color sample package I got a couple days ago. I presumed the pieces were segments of either some kind of trim, or their soffit panel, but it probably is siding.
And when I just downloaded some installation instructions, I saw no taper at all.
I had a concern about the ability to get a clean snap across a section with a thickness taper across it, but that concern is gone now.
GeneMy use of the steel straightedge was for scoring and snaping lengthwise as was shown in your drawing. If I have to notch for a window I make the short cross cuts with a diamond blade in the circ. saw, then score and snap the long rip cut. For scoring and snaping claps to length clamp on a large speed square (clamping the stiff metal on helps with both scoring accurately and producing a clean break, score multiple times, snap and touch up with a diamond blade on a right angle grinder.One more thought. They would sell more breath mints and dust masks if they were right next to each other on the store shelves <g>.
the hardie literature says the cleanest way is score and snap but i can't find the tool to do it. when the hardie rep came out to us he gave us 2 $50 hitatchi blades. they work with 4 teeth unlike the dewalt ones @ HD with 6 teeth so the hitatchi blades produce less dust. but they still dust. i came home last week from a long day of siding and felt like i had started smoking again.
RTC
gene, that's my technique.
At first I used saw but that was major dusty. then I treated it just like sheet rock and it works fine. simple easy and dust free. the only time I need to create dust now is when I need a perfectly round hole. Often I can just punch thru with a center punch and then take an old pair of nibblers and chunk off stuff untill the hole is the right size..