Reflections on Open Segment Methods

Reflections on open segment methods by Stan Knowles.

Over the past few years the availability of Seg-Easy discs may entice turners to have a go at this form of woodturning.

These plastic dishes with narrow strips attached in radial pattern at a predetermined number of divisions allow all the segments in a ring to be glued in one operation. At the present time are available in 8, 12, 24,36 and 48 divislons and are only available from the USA. Via UK agents.

However the cost of these Seg-Easy plates is very expensive, ranging from £45 upwards per plate plus delivery from USA. A full set is about 300 US Dollars.

Another method is a modified Seg-Easy system. This is produced by Lloyd Johnson of Woodturner Pro and is called a "Stomper". The Seg-Easy plates are modified to take a plunger through the central hole and the plates slide down the "Stomper" for gluing. Once again these come from the USA. The modified plates and the Stomper come complete with a Longworth chuck, this is required to centralise the rings. lt is very expensive, ranging from 190 US dollars with one plate to 300 US dollars with four plates. Once again the gluing of the rings is far too slow.

Videos are available online of Seg-Easy plates, Alisam Engineering of New York USA, "see Links/ customers work ll" Also Woodturner pro. Stomper, Although Lloyd Johnson shows my large open segment bowl on his video this bowl did not use the Stomper but was made using the index system.

My method for open segment work is the use of an index system along with a homemade jig. The index system I use is made by Alisam Engineering USA. lt consists of an alloy disc about 8" Diameter with a series of holes drilled around the edge, the number of holes required is twice the number of segments you want in a ring.

A steel pillar mounted on the lathe bed has a plunger which engages with holes in the disc to give the spacing of your segments. The home made jig positions the segments one at a time.

The cost of the index system from Alisam is about 100 US dollars, the homemade jig can cost as little as £10. Along wih a Sorby toolrest stem and a Sorby box rest.

That is lathe equipment you need to buy if you want to do segmented work successfully.

It all boils down as which method is the quickest and the most accurate.

The Seg-Easy plates. It is fair to say that all the segments in a ring can be glued in one go, but the glue has to be Titebond or similar. This is the problem, it can take hours to set before you can face off a ring ready for the next one. So you may only do one ring, possibly two rings per day.

The gaps in the open segment vessel must be exactly above each other, but this method relies on guess work when gluing the next rings on unless expensive laser equipment is used to line up the gaps.
The index system and jig method. By using industrial super glue even with gluing one segment at a time a 36 segment ring can be completed in 30 minutes and immediately faced off ready for the next ring, no waiting for the glue setting.
With the index system the gaps are automatically placed exactly above each other.

Many years ago when I started on open segment work I was frustrated by the glue setting time which made which made the process very disjointed, so I started experimenting with Super glues, their strength and the different viscosities available. lt proved to be a winner, oo more waiting time, it became a continues operation.

As far as super glue is concerned, don't listen to the sceptics, I have been using it for open segment work for 20 years and never had a failure or any of my work I have sold returned.
Both the above methods still have the same preparation of designing and preparation of materials. Segmented turning whether open or closed is slow work, it cannot be hurried.
Years before Alisam produced their index system I had already had the round steel plates with holes around the rim made for me with plates of 15, 18,32, and 36 holes. Along with a simple plunger to engage with the holes in the disc. These plates have a central hole the size of your lathe's spindle and goes behind your chuck. As I could not find someone o supply me a 72 hole disc, which gave me a ring with 36 segments, I had to purchase one from Alisam USA who had by then started to make them. I often wonder where they got the idea from. Some of my work is shown on their web site.

My conclusion is the index system is the best all round. Stan.