Sawdust on the Floor

Today we’re going to make cove molding for our wall clock.   Cutting wide cove molding on your table saw is a time consuming and dusty project.  The concept is that you run your stock at an angle over the spinning blade of your table saw. You start with the blade just making contact with the wood, and then you raise the blade in very small increments for each successive pass.  If you raise the blade too much, you will either damage the blade, or burn the wood.  The wood also will try to raise up off the blade, if too large of a cut is attempted, and that can be dangerous, and can really ruin the piece. 

To keep the wood at the correct angle, you clamp two  parallel guides to the top of your table saw.  The stock is then ran between these two guides.  The trick to this process is to figure out the correct angle for your guides. I will freely admit that I did a lot of this by the old trial and error method, or in other words I used a lot of scrap lumber until I found the right combination of blade height and angle of the guides.  The blade height determines the maximum depth of the cove, and the angle of the guide determines the width of the cove. 

I used a couple of 48″ long pieces of  4/4 oak that I had dressed and then ripped to 2″ wide for my guide. The method I used at the time for calculating the angle was this, and I apologize in advance if I confuse you because I confused myself doing this.  Your guide has two parallel bars, we will only be adjusting the front bar. The second is set parallel to the front bar at a width that is equal to the width of your stock.  To start, please put the front bar of your guide along the right side of your saw blade, with the rear end of the guide bar just beyond the rear end of the blade. This point is now our zero reference line. 

Then, while keeping the guide bar in contact with the front edge of the blade, move the end of the guide bar that projects over the front of your saw, toward your left.  The angle formed by moving the guide bar equals the width of your cove. The closer the angle is to the 0° reference line the wider your cove, the closer it is to the 90° angle the narrower the cove.  The only angles that will not work are 0° and 90°. Those would result in a rip cut or a complete cutoff of the stock.  Any number in between the two values will work. So what angle is the perfect number, that was the issue. Like I said a lot of trial and error. 

 This method was to determine the angle for the guide bars.  If you were to leave the front bar, as it is now, with the guide and the front edge of the blade making contact then your cove would run all the way to the edge of your stock. However, if say you wanted a 3/8″ space from the front edge of your stock to the point that the cove starts, then you would simply move the front guide bar 3.8″ away from the front edge of the blade, and at the angle you found above. 

A long time has pasted since I built this clock, and a lot of new toys have been added to my tool collection.  One of those is a digital protractor.  If I were making this cove molding today, once I had found the desired angle, one that produced the perfect cove, I would record the angle settings that I determined using the digital protractor.  Those values would then go into my project book for future reference.

 If I were to built a clock like this today, or even if I just wanted to cut wide coves, there are two methods that work much better then my trial and error method.  Take a look at one of my earlier postings on cutting cove moldings.  In that post I reviewed the method I learned from David Marks on cutting cove moldings. 

David’s method works great, and it really makes sense.   I only wish that I had learned his method back when I built my clock. Oh well.  

David Marks talks about building an adjustable cove cutting jig, which will make this a much easier task.  If you would rather not go to that trouble, then there are commercially available cove cutting jigs, that help take the guess work out of cutting coves.  

If you will indulge me a bit, I think I mentioned that cutting cove  moldings are not only time consuming, but they are a very dusty process. Each time you pass the wood over the blade, you will produce a significant amount of very fine saw dust.  The kind of saw dust that is really not good for any of us. I have a good shop vacuum system and a shop air filtration system, both of which got a very good workout when I cut these coves. I don’t want to bore you, or repeat myself so if you’re interested, check out another early post on the importance of Air filtration. 

After all of the cove was cut, I took it back to my shaper table where I cut a dado into both edges of the underside of the stock.  These dados are the same size as the rails and stiles of both the inner and outer boxes of the case. Once I was happy with the fit of the dado’s over the front edges of the inner and outer cases, I cut miters into the cove for the four corners of the clock.  To attach the cove molding to the clock, I used glue and a combination of bar clamps and spring clamps. 

I have attached a sketch of the cove detail for reference .

After allowing the glue to totally cure, I cleaned up the coves by using a combination of sanding and cabinet scrapers.  I found that by pushing the curved cabinet scraper along the cove surface, I was able to remove all of the saw marks made when I was cutting the cove.  No matter how small the height adjustments you make for each of the passes are, you will end up with saw marks in the cove, so be prepared to do a lot of scraping and sanding.

The next time I have time to get into my shop I will finish this clock.  Please join me then.

Welcome back, today we’ll continue with our wall clock project, building the outer box for the clock. Grab a cup of coffee and let’s get started. 

Again using the same 4/4 lumber as before, I created the outer box.  It measures 14 1/4″ by 23 5/8″ and is 4 1/4″ deep.

The outer box is deeper then the inner box by 5/8 of an inch.  The reason is that I cut a 3/8″ deep rabbet along the inside of the outer box and installed a piece of 1/4″ oak plywood in the dado to form a back of the clock. When the inner box was later installed, the front edge of the inner and outer box would be  same point. 

One of the weakest woodworking joints is a butt  joint, because of the limited surface areas that glue can be applied to. If you are interested in more on the relative strength of various woodworking joints, see my post, How Strong Are Your Joints? So I cut 3/4″ wide 3/8″ deep rabbets along the ends of the side stiles, where the top and bottom rails would later be joined. Not only is this a stronger joint, but it really looks better.  With the work done to the outer rails and stiles, it was time for some assembly.  After applying glue to all the joints, the rails and stiles were connected together, then the plywood back was installed and secured with small nails from my nail gun.  After verifying that the case was really square, it was set aside to dry. 

The easy way to verify that the case is square is to measure across the diagonals. both measurements must be the same for the case to be square. I have always had problems with this because while I understand the concept, it leaves a lot of wiggle room.  To get an accurate reading, you must place the tape in exactly the same place each and every time.  And that is sometimes a difficult thing to do, particularly if you are working on a big piece. I have found an inexpensive little tool that helps me get better readings.  It is the Square check for tape measures, from Rockler.  You simply place your tape in the holder and stretch it to the opposite corner, record the value, and then repeat for the opposite corner. No more second guessing your self. 

Once this outer box assembly was dry, I installed the inner box within the of the outer box.  This was a simple matter of gluing the ends of the stiles of the inner box to the top and bottom rails of the outer box.  But before I did that, I took one more step,  which I almost forgot to do this and that would have been a real bummer.  I installed the remote speaker for the clock into the space formed between the lower ends of the  inner case stiles, the bottom rail of the inner case and the bottom rail of the outer case.  I also drilled a small hole in the side of the inner box, and ran wires from the speaker up to the yet to be installed clock mechanism. So that the sound could escape the case, I also drilled a 3/4″ diameter hole into the bottom rail of the outer case. 

There is a sketch in part 1 of this project that details the inner and outer boxes, that may help make this a little clearer. 

With the inner and outer boxes connected together, I also connected the plywood back to the rails and stiles of the inner box, with pin nails from my nail gun. So now I had the case built, and all that remained was to apply the trim, make the door and install the clock itself. 

The trim actually took more time to do then the rest of the clock did.  The problem was that I wanted really wide cove molding, which I found was not commercially available at  any place near me.  And if it had been, I suspect that it would have been cost prohibitive.  So I did what any woodworker would do, I made my own. We’ll leave that for tomorrow as it’s time for dinner.  See you tomorrow morning and we’ll make the cove molding from scratch.