Wood Balls, Mallet & Overlapping Circles - #7 Overlapping Circles Completing Turning & Finishing

As I said in the last post the concentric circle pencil layout was really just to keep me on track.  The actual layout is done using a couple of dividers to score the blank.  The photos for these next steps are done after I had already scored the circles.  I was concentrating so much on getting them done right that taking photos of the process was not a priority.

First step is to set the divider at 7/16” for the inner circle. Then with the lathe running and one divider point at the center I used the other point to make a shallow cut in the oak.  With the inner circle scored I reset the divider to 9/16” and scored the outer circle of the first ring.  This gives me a 1/8” wide ring.

With the first ring done I set one divider to 5/8” and the second divider to ¾”.  By using these two dividers I can accurately mark the rest of the rings.  This photo shows the setup for making the scribing cuts.

The top photo below shows a different view of the divider set at 5/8” making the scribe line for the inner edge of the second ring.  The bottom photo shows the second divider set at ¾” scribing the line for the outer edge of the second ring.  Note that right hand leg of both dividers are working off the same inner circle reference scribe.

Scribing the edges of the third ring follows the same process as making the second ring.  Using the 5/8” divider to scribe the inner edge and the ¾” divider to make the outer ring.  Having two dividers set up to make each cut referenced off the same place removes any inconsistency in ring spacing or size.  If you look close the scribed lines do not exactly align with the pencil layout and that’s due to the slight differences in measuring when using a compass and center point.  Here you can see the setup for scribing the outer edge of the third ring.

Once the layout was done I could start cutting away the waste between the rings.  I start in the center and work out.  The depth of the cuts are quite critical.  I need to cut them half way through the blank.  However, it is more important that they are all the same depth.  That’s because when I make the intersecting cuts from the other side they need to align perfectly.  Here is the center cut to its finished depth.  I measure the depth the same way as I did earlier when setting the depth of the dished-out area by using a dial caliper and a 6” steel rule.

After making all the cuts to this face you end up with three offset concentric rings.  The last step on this side is to carefully sand the cut faces of the rings.  Here is the first side finished and ready to be removed from the MDF mounting board.

With the first side finished I can flip the blank and go through the same process on the other side starting with centering the blank on the MDF mounting board and screwing it in place.  That’s followed by dishing out this side then remounting off center for the ring layout.  The only difference in the ring layout is that it is offset the opposite direction as the first face.  The cutting between rings proceeds the same way as before except as you get close to the halfway depth point it is critical to use sharp tools and a very light touch.  If your measurements for the cut depth on the first side are dead on then when the cut reaches half way through the blank it will break through to the other side.  Here you can see after I broke through and quit.  At this point the bits and pieces that need to be removed are just barely holding on.  I could try cutting a little deeper to try and remove them but at this point it’s a bit nerve wracking and a pretty high-risk gamble.  There is not a lot of support for the wood remaining and it’s really easy for a little catch to turn this piece into designer firewood.

Removed from the lathe and set against a black background you can see what needs to be cleaned up. 

To do that I use a razor knife like a box cutter or an X-Acto knife followed by some light sanding.  It almost goes without saying that a very delicate touch is required here.  The rings are only 3/16” thick by 1/8” wide with not a lot of support and frequently cross grain so there is very little strength here.

The last woodworking step is to cut a quarter circle at the corners where the mounting screws were located then sand the edges to soften and do any other final sanding ending up with a piece ready to finish.

I chose to spray a satin lacquer on this piece since by spraying I could easily get finish in all the nooks and crannies that are in this piece.  This is my usual material and setup for applying lacquer to small pieces using an air brush.  In this case the piece is set on a lazy-susan so it can be easily rotated while spraying.  I always, always use gloves and a respirator in a well-ventilated area when working with lacquer and lacquer thinner.

I thin the out-of-the can lacquer by about 50% then apply three coats, let cure for a few days then wet sand with 6,000 grit and it’s finished.

I have to say that most of the work on the piece was not too hard.  It did require careful measuring and a fair amount of me talking to myself.  The final bit of turning on the rings required to break through to the first side was a was a little tense and could go wrong very easy, very quickly.  If I ever make another one then I will use a finer grain wood like maple or cherry.  I think the edges will be a little more crisp than with the open grain red oak.

Next Up - A Seam Ripper