Thick Walled Two Piece Hollow Forms

 by Brian McEvoy

Back in July 2010 we published our third newsletter featuring one of my trade mark projects, the 'thin walled two piece hollow form'. It coincided with the release of a very popular DVD called Brian McEvoy's Secrets to Creating Two Piece Hollow Forms. Between the demos I've done in Australia, throughout North America and the DVD, this has become a very popular project amongst hundreds of turners around the globe.  I can't tell you how much it's thrilled me to see photos of all of the variations of this project. 

For relatively new turners in particular, one of the scary parts of the first newsletter article, as well as the DVD's featured piece, was the fact that the turned piece, though 12 inches in diameter, was only 3/32 of an inch thick.  The thinness was due to the fact that in most cases I pierce my work, so being thin was critical. Though I touched briefly in the last newsletter as well as on the DVD,  some of the possible variations of this project, I thought I would share some of my other favorite two piece hollow form designs.  One  is modeled after a South West Native seed pot (that was traditionally clay), the other Native Pacific Northwest style carvings.  Doug Fisher, an extremely talented artist and turner has become well known for this style.  As I embellish most of these forms with some sort of relief carving thickness is required.  For the one we're going to turn in this project, I have intentions of beading similar to Native woven baskets and the beads will be a full ¼ inch deep, so I'll be turning the hollow form 5/8" thick. 

I prefer the two piece hollow form method rather than the one piece for a number of reasons:

- Even if you're a novice you can complete this project with whatever tools you now use to turn a simple bowl.

- You can turn most any size and not have to worry about reaching a long way over the tool rest.  I've turned these forms up to 22".

-Thickness is not an issue; with simple calipers for measuring you can turn to a delicate 1/8 inch or any wall thickness you desire.  And you can do it safely and accurately.

- You can finish the inside so when friends or customers poke there finger in the opening (as they all seem to do) they will be impressed by the finished quality.

- Probably the most important advantage using this method is the safety issue.  Though there are a number of wonderful hollowing tools on the market, in my opinion, none of them work with the simplicity of the two piece method.

The results of this exercise can be stunning and they make great gifts, sell well and you should have a blast creating them. 

I like to turn a dovetail recess to accommodate the chuck.  I find the use of a dovetail scraper very handy and it ensures accuracy.  Once this has been established, keeping in mind that this recess will become your opening, be careful to leave a ridge to seat the chuck jaws against, then turn your recess a further distance, leaving the ridge intact.  The reason for this will become apparent when you turn out the inside of the form. 

Reverse the piece on your lathe and carefully proceed with turning the inside.  The vital part of this step is to not turn off more of the top lip than is necessary. 

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This is a very critical step to ensure your glue joint is tight and true.  In many cases, if care is taken at this step, the glue joint is barely visible.  I use my bowl gouge to true the edge as close as possible, and then I lay a straight edge across the top edge to determine the high and low spots.  I then use a skew on its side, acting like a scraper, to refine the edge.  You'll be surprised how easy this is, but good light is important and if you're in doubt, magnifiers can also help a great deal.  The bottom line is that you don't want any gap between the straight edge and the top lip of the form. 

Now that you have the consistent thickness you were after, sand the interior to finished quality. Be very careful not to sand the top edge - you don't want to be rounding off the flat surface. 

Now the real fun begins.  Turn out the interior as you would any bowl you've turned.  The fun part comes when you break through the bottom deliberately (not by accident as most of us have done). Keeping a consistent thickness, work your way down to the bottom until the recess you turned earlier appears. On most occasions you will hear a higher pitch when you're getting close. Note the disk flying free as I reached the critical stage.  (Good photography Gord!)

Now that you have the consistent thickness you were after, sand the interior to finished quality. Be very careful not to sand the top edge - you don't want to be rounding off the flat surface. 

Now that you've completed the top portion, follow the exact steps for the bottom half, with the exception of breaking through as we did on the top.  I also sand the bottom to finished standards as I won't easily have access to this part once it's mounted in the chuck. Remember you want to turn the bottom half pretty close to the exact size as you did the top.  When you're turning these thick walled pieces, the exact size isn't as critical because of the width of the glue joint.  On the other hand, if you are going to be turning very thin then you have very little wiggle room. 

Once you've sanded the inside of the bottom half, I like to give it two or three quick shots of Deft semi gloss spray lacquer.  With the lathe running, buff the sprayed portion between coats. 

This whole process only takes a few minutes and when people look inside they see a nicely finished product.  If the opening is small enough, this is of no concern.  Obviously you can use whatever finish you're comfortable with.

With the bottom still mounted in the chuck on the lathe (this is why we did the top first) move the tailstock in position with a cone live centre to position the top.  I use the Oneway live centre that comes with a perfect cone.  If you don't have one of these, just turn a wood cone to slip over your live centre.  I've done this many times with my larger pieces with a large opening.  The beauty of this technique is that the cone in the tailstock automatically centers the top half to match the bottom, and acts as a clamp to ensure a good glue joint.

After a dry test run where I mark the best position to achieve the book match I'm after, I mark the spot with a pencil.  This way, once I have the glue applied to both sides I can automatically place both halves in the correct position.  I then apply carpenter's yellow glue to both halves, ensuring full coverage.

Place the two halves together in the predetermined position and gently move your tailstock cone into the center of the top portion.  Apply firm pressure until both halves are perfectly flush with proper glue squeeze out.  Let this set up for ½ an hour or so.

Note the perfect glue joint.

Sand the whole form down to finished quality.  Though the opening will be a little rough from the dovetail you turned for chucking purposes, a minute or two with 80 grit usually does the trick.

I can't emphasize enough how much fun these are to turn and the possibilities are endless.  My favorite two piece hollow form turning was actually 13 sections!  These became the pagoda shown here on the left.  As piercing and hand carving Oriental style art designs were to be added they were only 3/32 in thickness. The top room features authentic script that could be the woodturners' creed of  "Patience, Determination, Honour, Faith and Friendship.  The rooms and finial are guilded in 22k Gold Leaf with the roofs and staired base in Copper Leaf.   The final piece weighed in at 11 pounds with a base measurement of 22 inches and 43 inches tall.  I used Yellow Cedar that I cut and milled in the Queen Charlotte Islands of northwest Canada. Turned 7 or 8 years back I think I had more than 200 hours into what has become one of my signature turnings.