Thread: So... Who else has got one of these? (it's a 1600w Cornice-Saw...)

Dear Chaps,

Some of you might have read a Thread that I started in another Sub-Forum earlier this year regarding the search for a replacement for the burnt-out Power Switch on my 1600w 10" PowerMaster Compound Mitre Saw.

Now, as most of you would probably already know, many of these Chinese Powertools are just "clones" of name-brand units, but for the life of me I couldn't work out at the time whether or not this situation was also the case with my "Cheapie". As a result, I wasn't able to just race out and buy the replacement Switch as a name-brand spare-part. In addition, because the Saw's handle was fairly narrow, and the unit was running an Electric Safety Brake, I also wasn't able to initially track down a sufficiently slimline Double Pole, Double Throw Rocker Switch that could handle the current draw in question, in order to get the Saw back up and running...

As such, and in desperate need of a Mitre Saw at the time, I raced out and bought a 2nd-hand German-made Elu, which got me out of trouble on the wood-cutting front. Only other trouble was - not long after this, another Forumite suggested an Electronic Components supplier whom I hadn't initially thought of because they didn't have an outlet on this side of town, and I didn't have a Credit Card. But I nonetheless looked into what they carried in the way of Rockers, and Lo! - they had a nice, slim, 10A DPDT unit on offer, and - pending "clearance" - they were willing to take a Personal Cheque . Now although the Saw itself was a "cheapie" (I picked it up on "clearance" for only $57 at BigW back at the end of '05...), she was still surprisingly accurate and well-made. For example, the base was made of Cast Alloy - which you wont get in a new Ryobi or GMC for under $100. As for the accuracy - well, as I only recently discovered, the thing is a clone of everyone's "darling" CMS - the Makita LS1040 - and some of the Mak's virtues seemed to have rubbed off on the PowerMaster as a result. It was nice and light like the Mak too. In short, the thing seemed too good to either throw away or just allow to collect dust in a corner somewhere. But what then to do with it?...

Well the answer came in a flash one day in the midst of wasting a lot of time installing a little piece of Plaster Cornice less than a foot long that was "crossing the tee" of a particular wall, so as to form an "External Corner" at each of its two ends. I just couldn't get the thing "pat" because Angular Errors had been accumulating at all of the mitred "Internals" at each previous corner. And because the piece was only short, the resulting "wrongness" really stood out from back down on the floor. I could only get it to "mate" correctly with either one of the two longer Cornice pieces that it was joining to, or the other - not both. The source of these Angular Errors?: the "slop" of my Handsaw in the pre-cut slots of those plywood Mitre Boxes that you buy to cut your Cornices in. Other problems I'd had with the "Handsaw and Mitre Box" setup included damage to the front face of Cornice ends by movement towards it during half of the strokes by the Handsaw, as well as not being able to shorten over-measured pieces by only 1mm or so, because of the tendency for the Handsaw to just drop off the end of the Cornice in the Box. Thinking about all of these issues, the idea suddenly came to me - a 1600w 10" Cornice Saw... There would be no Angular Slop, the circular blade would have the advantage of moving in one direction only, and if I wanted to take another millimetre off a piece of Cornice, the Cornice wasn't going to argue with that spinning blade, was it?...

Now, the concept is not Rocket Science, so I'll let the attached photos do most of the talking. But a few small but critical details first need to be emphasized:

Firstly, if it weren't for the sudden and fortuitous re-appearance of the Jaycar 10A Speed Control Kit, I probably wouldn't have attempted the conversion, because the fineness of the Plaster Dust that would have resulted at full 4600rpm cutting speed would have likely rendered the project impractical, as well as quickly clogging up the mechanicals of the Saw. Secondly, although one's instincts naturally point towards using the amply-exposed front half of the saw's blade to do the cutting with, you quickly see upon reflection that the blade there is spinning in the wrong direction if the Cornice (which must be cut "upside down", so to speak...) is inserted back-to-front to match the curvature of the blade. Thus, the required locating-fences have to be positioned under the rear half of the blade - with the Cornice facing forwards - and this represented a true "packaging" challenge that was not to be sneezed at. Thirdly, as a result of this cutting orientation, and even with its 254mm blade, the Saw can truly only practically cut a 75mm Cornice (which is luckily all that I was wanting to cut...). For "90's", I think you're going to need a 12" Saw, unless you take your chances cutting the Cornices back to front. But anyway, on to the photos:

1. The first photo shows the full 1600w Cornice-Sawing "System" (or "Solution" in modern Wank-speak...) in all it's glory, and consisting of:

a) The Saw itself, with the adjustable Jig in place.
You will doubtless note the new little black Rocker Switch sitting up towards the top of the handle; it's not quite as safe as a "Squeeze-Lever" when you're checking settings and alignments, but it is certainly more conducive to accurate cuts as a result of less "gripping force" being required on the handle during the cut. As you can also see, the positioning-Jig is arranged to present the visible face of the Cornice to the cutting-edge of the Blade. What you can't quite see is that the Jig consists of two parts; a rear Fence, and a front Toe.

b) The Jaycar 10A Speed Control Kit that is used to slow the Saw down to a more practical cutting speed.

c) The four little "Stands" that are used to support the otherwise dangling ends of the 4.8m-long Cornice sticks that I am cutting from. As some of you may have guessed, they were made from my now-obsolete plywood Mitre Boxes. Today I will cut off most of the vertical front-faces of these stands in order to make them much easier to "load" with Cornice...

2. This is the Jig in its elegant original format, before I sadly had to "butcher" it because it was just too high to enable a practical drop of the blade. For ease of installation and removal, it had a single base that supported both the rear Fence and the adjustable front Toe. Please note at this point that the little Fence "Buttresses" are straight triangles, and that the Fence's face is an unblemished Furniture-grade veneer...

3. This is the Jig in its final installed format. The front and rear parts no longer have a common Base, and you can just see the bolts that hold down the rear Fence using the holes that were provided for the Saw's original aluminium Fence. The holes through the base of the Fence are oversized so as to allow adjustability for precise angular-alignment to the Saw (because you can't alter the location of the "detents" for the Saw's 45deg mitre-cutting positions...). You can also see that the little Fence Buttresses have now become concave in shape, as a result of having to make room for the back of Cornice sticks, which effectively dropped down by the thickness of the now-removed Common Base (luckily my brother's stationary Belt Sander was in "port" at the time...). You can also see the damage to the Fence's previously-lovely front-face that I inflicted with the said Belt Sander... The little grooves and notches in the top of the rear Fence were made with a little 5" Circular Saw and a Reciprocating Saw, and were necessary to provide clearance to the Arm of the Saw during its drop.

4. Here is the Saw at "Full-Drop", showing the obvious reasons why it is important to locate the Toe in such a way as to position the front of the Cornice as close as possible to below the centre of the blade. Just by-the-by, I can confirm that the swing of the Guard as it opens just nicely clears both the top of the Fence, and the face of any Cornice stick that has been inserted.

5. The Jaycar 10A Speed Controller Kit: I'd have to say that for the $64.95 pricetag and the effort required to build it, it's a bit of a dissappointment . The Speed Reduction does not seem linear, nor wide-ranging, nor sufficiently low at its minimum setting, and just about every tool that I've tried on it has "Cogged" (ie. ran roughly). You can make out the destabilising effects of this Cogging in a later close-up photo of some mitred Cornice cuts that I did yesterday with the whole Shebang.

6. These are the little Stands that hold the otherwise very-floppy Cornice Sticks at the correct angle for the Saw. How satisfying it was to be able to make the legs for these little buggers out of a gnarly old lump of lumber that I never thought I'd ever find a use for (y'all know what I mean...). Anyway, the thickness of the legs was cut down so that the Cornice Sticks would end up sitting in the Stands at a height that perfectly matched the height at which they sit in the main Jig. The legs extend a little way out from the back of the Stands to provide stability against the Cornice Stick's natural tendency to twist back and fall over in this direction.

7. For some crazy reason, those Zany Funsters over in China must have thought that it would be a good joke to make a Mitre Saw where the central rotating part of the Table was slightly higher than the stationary parts on either side. It was therefore necessary to raise the ends of both the Fence and the Toe of the Jig with some little pieces of Silky Oak veneer...

8. This close-up of the Fence - taken from end-on - shows two important little details. Firstly, it was necessary to make a little notch into the side of the table at each end before removing the original aluminium Fence (after first perfectly aligning it with the blade, however...), so that I'd have something by which to align the new timber Fence before cutting through it (because you can't really align the Fence using the blade until you actually do cut through it...). Secondly, I trenched the Fence's Base ever so slightly so as to make the vertical alignment of the Fence very easy to achieve. In the upper-left corner of the photo, you can just make out the top of one of the screws that secure the Jig's front Toe. For the sake of practicality and convenience, instead of trying to reach under the Saw's Table with a little spanner each time I wanted to adjust the alignment of the Toe, these screws would instead have to screw-down into threaded holes in the table (that didn't yet exist...). So...

9. ...After measuring the Table's thickness as best I could (only about 2.5mm...), I picked out these little "nodes" in the casting, and drilled right up through them and into the temporarily-clamped wooden Toe from below, and then "Tapped" the aluminium Table down from above. The Toe could then be adjusted and then re-tightened easily from above the Table...

10. This photo shows how a Stick sits in the Jig, and how clean a cut is produced on the front face by the Saw. The little bit of paper fluff seen on the upper-pointing edge - which is the installed-bottom of the Cornice - only seems to occur on the outer side of the two 45deg Mitres, which are the sides of the cuts used for External Corners, which are few and far between anyway...

11. A close-up of some fair-dinkum mitre-cuts showing three points of particular interest: Firstly, once again how cleanly cut the front paper-face of each stick is (like shaving with a Gilette Blue II...), and secondly - the slight "furriness" of the faces of the sticks that were pointing away from the blade (ie. on the exit side of the cut). This is why I installed the Jig under the rear half of the Saw's blade. Thirdly, the circular "scoring" that you can see has been left in the plaster by the blade-teeth is a direct result of the previously-mentioned rough "Cogging" when running the Saw at at low speed via the Speed Control Kit. I certainly don't get those score-marks with the same Saw and the same Blade when cutting softwood at the Saw's full-bore unreduced 4600rpm.

12. The Plaster Dust produced by the reduced-speed cutting is pleasantly coarse - as you can see in this photo. About the size of fine sand (well, at least the stuff that settled, anyway...) I still blew out the Saw's motor with the Compressor at the end of the day, though...

13. Here is a photo of three installed sticks that were cut with the Beast, showing how accurate the resulting Mitres are. The yellow discoloration on part of the Cornice is caused by the sunlight falling each morning on my stockpile, and the generally messy appearance of the upper and lower edges is actually due to the removal of paint that came off both the wall and ceiling when the original 90mm Cornices were removed. Now, just in case you're thinking that the right-hand corner is oh-so-wide...

14. ...here is a close-up of that very same corner. As you can see, it's like a Lexus panel-shut-line in terms of fit; Sweet As.... The Saw is absolutely spot-on, and so much quicker than a Hand Saw in a Mitre Box. Just by the by, the pencil lines you see on the wall and ceiling in this photo give you something to aim at; you draw them by running a pencil along the edge of a moving little timber Float-like Thingy with a handle that you make to just the right width to let you draw the lines at just the right distance down or out from the ceiling or wall. Don't draw them exactly at where your Cornice's legs will touch down, because the squeeze-out of the cement will obliterate the lines from view if you do.

It might be propitious at this juncture to make clear the fact that no matter how accurate is the mitre-cutting of your Cornice ends, a ceiling or wall that is not sufficiently straight or flat can cause mismatch at the mitred corners of the Cornices. The Cornice sticks themselves have an inherent tendency to twist in conformity with the angle and deviations of the ceiling-to-wall intersection, but such twisting occurs only gradually, and also "unravels" only gradually. A corner between two sticks of Cornice at the edge of a Ceiling, can therefore be affected by the "legacy" of any out-of-trueness in the rest of the Ceiling or the two Walls in question as a whole. Just thought I'd better mention this to avoid any heartbreak in someone who went to the trouble of knocking one of these Babies up, only to still end-up getting dodgy mitred corners...

Now, the drawbacks to the System: In all practicality, it looks like you can only really cut up to a 75mm-thick Cornice with a 254mm Saw. Trying to cater for a 90mm Cornice would require not only an exponentially greater degree of notching into the rear Fence, but a notching out of the underside of the Saw's Dropping-Arm - a'la a Belt-Drive Dewalt. And who's going to buy a Belt-Drive DeWalt for this type of thing?... So you'd really need a 12" Saw, and that's going to weigh more like about 19 or 20kg, instead of just 13 or 14. This size and weight increase really adds cost and "hernia-factor" to the exercise. I was just lucky that I was going from 90mm Cornices (they seemed to be "overpowering" the place...) down to 75's...

The other drawback? - Plaster Dust getting into the machine, and your eyes and lungs. Because the Jig is now in two parts (ie. a front Toe and a rear Fence) Plaster Dust is able to fall down the very narrow gap between the parts, and because it is coarsish, it quickly wants to jam the Table when you want to swing the Saw around from one side to the other. I'm going to have to shove some kind of flexible strip down into that gap today. But even with that gap covered, I myself would be a fool to not always wear my Dust Mask when using the thing (which you don't have to do when cutting Cornices using just a Handsaw and a Mitre Box...)

I could go on for some time regarding the frustrations and little hitches that I encountered in the building of the thing - especially in the areas of the Depth Stop, and the positioning of the rear Fence, but I wont labour you any further beyond saying that it's not as much for the light-hearted as it might mistakenly appear to be from the photos. But anyway regardless, there you have it! Gentlemen, presenting the "1600w 10in. Cornice-Saw" - Another giant leap sideways from BMC (the Batpig Machinery Company...)

Best Wishes all,
Batpig.