Sunday, 20 April 2014

When to Push Your Limits

On March 22nd and 23rd I attended the 10th Annual Matisho Memorial Woodturning Cancer Benefit at Waldhiem.  This was my 4th trip there, and I enjoyed it as much as ever.  Because there are always a lot of very experienced turners there I see this event as a chance to bite off a little more than I normally chew.  There is a certain amount of comfort in knowing there is a lot of good help around if you get into trouble.

For my project this year I picked a piece of birch that I had picked up at a garage sale a few years ago.  It was about 4" thick and had been bandsawn into a blank about 10" in diameter.  I laid out a square on the top with a diagonal a little larger than the diameter of the circle.  This meant that the corners were rounded off, which would make them a little stronger.  I then sawed off the parts of the blank that fell outside the sides of the square.  I did all this before I went to Waldhiem and in my enthusiasm I forgot to take any pictures.

For the second year the event was being held at Menno Industries.  The people there were kind enough to donate their shop space and all-important lunch room to the cause.  Here is a shot of my set up.

This next shot may give you a better idea of what I was talking about up above.

Here you can see that the blank is a square with the corners chopped off.  The rough shaping of the bottom is done and I have left a tenon in the middle for the chuck to grab when I turn it around to work the top.

Now the top is shaped and sanded with 80 grit sandpaper, and the opening is defined.  In the picture below you get a good idea of the profile.

Time in the shop is usually time alone, but I think that people that come to this event enjoy the social aspect.  I know I do.  I think it is telling that, of the five turners in the picture, only two of them appear to be doing anything.

At this point I have hollowed it out enough to bring out the big gun, my Scorpion hollowing tool.  I was starting to lean a long way over the lathe , trying to look back along the tool to see what I was doing.  It got so bad that I went over to the other side of the lathe to see if it would be easier to turn from there.  It didn't work, but it did show me that the point of the cutter was getting to be a long way from the tool rest.  I switched to a scraper platform, stuck inside the mouth of the bowl, for additional support.

I continued working my way out to the edges and finally, toward the end of the day, I got to this point.

There are a couple of advantages to having holes in the side of a hollow bowl.  First, the bowl doesn't fill up with shavings anymore.  Second, you can stop leaning over the lathe and peering into the mouth of the bowl to see what you are doing.  You can stand up and see the point of the tool as it is cutting.

Thanks, Cal, For taking the picture.  I continued hollowing and this is where I wound up at the end of day one.

On day two I forgot to take my camera.  Don't worry, you didn't miss much.  I kept going until I was happy with the openings and the top and bottom were pretty close in thickness.  Then I sanded the corners of the openings until they all sort of matched.  This was necessary because I wasn't able to get the blank perfectly centred.  Like that ever happens.  Anyway, this is what it looked like when I got it home.

My next step was to get rid of the tenon on the bottom.  I used a chunk of scrap attached to a faceplate and turned a short stub that matched the diameter of the opening in the top.  Then I drilled out the centre and stuck a bolt through it from the back.

What's the bolt for you ask?  That's another advantage of  the open sides.  Once the bowl was on the stub I was able to put a thin piece of plywood over the bolt and snug it tight with a nut.  The wrench just fit inside the bowl.  This held the bowl in place so I could round off the bottom.

Once the bowl itself was done I started on the legs that support it.  While the bowl had stayed pretty much the same from the original concept to the finished product, the legs went through several changes in my head and on paper before I settled on the final shape.  Originally I was going to make them round in cross section, then changed that to curved sides with flats on the inside and the outside.  In both cases I was going to turn them on the lathe so they would be curved around the corners of the bowl.  There were a lot of technical challenges in doing it this way and, although I felt I had worked them all out in my head, I still wasn't 100% sold on either shape.  Eventually I settled on flat-sided legs to contrast with the curves of the bowl.  This meant that I could have different curvature on the inside and outside of the legs and when I drew it out that way I knew I had made the right choice.

I built a jig so that I could shape the inside and outside curves on my oscillating spindle sander.  Here I have done the inside curve.  To tie the legs visually to the bowl the radius of the curve is the  same as the outside of the bowl.

The radius of the outside curve is about half the length of the side of the bowl.

I feel that echoing the proportions of the bowl in the legs helps to give it an overall unity, even while the legs are in contrast to the bowl.  I know that it sounds pretty artsy-fartsy, but using that idea was a big help in figuring out how the legs would look, and in the end I think I got it right.

After sanding the curves I used a block plane to taper the legs from front to back.  This lightens the look of the legs, and makes the top and bottom of the leg look thicker than the middle.  It's cool the way the intersection of two simple forms, the curve and the flat surface, can produce such a complex looking shape.

With the bowl completed and the legs done all that was left was a way to hook them together.  I had decided early on that I was going to do this with dowels.  Drilling the holes straight required another jig to hold the bowl perpendicular as the holes were drilled.

My failure to get the blank perfectly centred reared its ugly head again at this point.  Getting one corner centerd  under the drill bit did not mean that any of the other corners would be centred side to side.  That is the reason for the two blocks clamped to the table in front of the jig.  They act as a reference to keep the drill bit lined up front to back as I slide it side to side.  I didn't have to move it very much.  You can't tell that the holes are not perfectly diagonal to each other, but you certainly would have noticed if they weren't centred on the corner.

I gave the bowl a couple of coats of Danish oil to darken the wood and give it a golden color.  The birch was too light to match the picture I had in my head.  The legs I painted with black semi-gloss acrylic.

The bowl went back out to the shop and was buffed with Hutt Perfect Pen Polish to give it a nice sheen.

The last design decision I made was the offset of the legs.  My original intent was to have them right up tight to the corners of the bowl but while I was sketching out the legs the idea of having them offset popped up.  When it came time to attach the legs I decided I liked it.  I feel it increases the sense of suspension.

This bowl was a challenge, both physically and mentally.  There were all kinds of places where it could have gone wrong, but in the end it turned out to be one of the most satisfying projects I have ever done.  It matches the vision I had in my head, and that's not easy to do.

Evil Alien Face

Feed Me!

I have decided to name this one 'Calling Occupants' after that old Klaatu song.  It has sort of a space ship-y kind of feel to it, and the open sides seem to invite you to fill it.

No comments:

Post a Comment