Sun Wall Clock
Friday 29 January 2010
Michael Forster's bright idea for a weekend project
This is a simple weekend, or perhaps evening, project for anyone with a bandsaw and bobbin sander (for the latter, you could substitute a sanding drum in a drill press). It lends itself to fairly streamlined production methods (glue up a batch of blanks, mark them all out, cut them, sand them, etc) which helped me get well ahead with my Christmas presents and could also serve to stock up for a craft fair.
I originally planned it as a routing project. However, with the outline constantly changing in relation to the grain, I knew there would be a serious issue about managing the breakout, but thought I could find a way to do that. Only after I'd spent a stressful day in the workshop did I realise that, in fact, routing just complicated the issue.
When I skipped that stage and went straight from bandsaw to bobbin sander, everything went smoothly. Anyway, let's start at the beginning.
The drawing was a trial-and-error business, using concentric circles with intersecting centrelines, and having marked the hour positions for the twelve flames which were sketched in freehand. I deliberately didn't align each flame tip precisely with the hour as I wanted a fairly natural look.
Once satisfied, I got some photocopies done so that I could preserve the original.
Step 1 Having come up with my design, I stuck a copy onto some 10mm MDF, using spray mount adhesive. I then bandsawed it out with the intention of forming a template for the bearing-guided router cutter to follow. When I abandoned the routing idea, I found the rigid template still useful for marking out, and it would considerably speed production if making these in volume for craft fairs. However, if you want to skip this stage, you could simply use a paper template, stuck onto the workpiece with spray mount adhesive.
To be candid, though, I'm not keen on the stuff because it always seems to leave a residue and increases the clean-up work later, so I'd draw round the template, but it's your choice.
Step 2 Sand the template's curves smooth at the bobbin sander or drill press. The best way to check for a fair curve is by removing the piece from the machine and running fingers over the edge. I must emphasise that no one should be cutting and sanding MDF (or quite a few hardwoods, come to that) without proper lung and face protection. Over the years, I've accumulated a Trend Airshield respirator, a dust extractor and an ambient air filter, all of which were in use during this operation, along with ear defenders.
Step 3 It's a good idea to joint up two or three slim boards to make the blank, reversing the end grain to reduce the effects of movement. I do this with a hand plane to remove the ripples left by the electric planer. Once happy with the joints, glue up and leave in the cramps for a couple of hours before cleaning up the front and back faces with a hand-plane.
Step 4 Mark a centreline along the grain and another one at right angles. As well as helping find the centre, these will be a useful reference when aligning the jig to cut the movement recess. I screwed my MDF template down through the centre hole to make sure it didn't move while I marked round it. Removing the template left me with the outline and the centre clearly marked.
If using a paper template, simply push an awl through the centre and then align it with the centre of the board and stick down. A single screw holds the template down and marks the centre for the spindle hole.
Step 5 At the bandsaw, I roughly cut a circle round the perimeter simply to make the workpiece easier to handle, but it's not really necessary. Next, I worked round the flames using the 1/8in 20 tpi blade I'd already installed for a previous project. With such a fine blade, there's no need to cut shy of the line as very little sanding is actually needed to smooth the flames, and the precise shape isn't critical anyway.
Step 6 I used the largest sanding spindle that would fit into the gullies, with the table set at 90 degrees. I then re-set the table to 45 degrees and lightly eased the front edge.
This doesn't need to be precise; just soften the sharp corner and then finish off with hand-held sandpaper to round the edge. If it doesn't come out clinically even, that's all part of the charm of the piece.
Step 7 Next, I went to the drill press and drilled out the spindle hole to 8mm, and then turned to routing the square movement recess using a straight cutter and a guide bush. You can just form a template with scrap strips but if you're making several clocks, it's easiest to cut a template from a single piece of MDF. Double-sided tape secures it well enough.
I gave the edge a final light sanding with progressively finer sleeves on the bobbin sander, finally cleaned up the front and it was time for the finish. One gloss and two satin coats of General Finishes' water-based acrylic varnish, as advised by their rep during a visit to Westonbirt's Festival of the Tree. It sounds an odd sequence, but does get a lovely finish.