Recently three CVWA members (Neil Cryer, Terry Hulm and Bob Aitken) each purchased an Axminster Eccentric Spiralling Chuck. This chuck, made in Axminster UK using CNC techniques, is typically used for a variety of eccentric geometric patterns and spiralling stems. Here Bob, Neil and Terry describe the chuck, show some or their initial work and comment about their use of the chuck.
The Axminster chuck (Photo. 1) consists of a faceplate ring which can be held by a conventional four-jaw (dovetail) chuck, a central main plate which can be adjusted to create different amounts of offset, and a small faceplate that can be indexed to 12 positions. The 12 indexing positions on the small faceplate can be seen in Photo. 1. The small faceplate is attached to the workpiece by three screws.
For offset positions there are four settings clockwise and four anticlockwise. By loosening the counter sunk machine screws on the main plate, the plate can be rotated and set to any of the threaded holes on the faceplate ring. The extent of offsets (centres) achievable are shown on a workpiece in Photo. 2. The centre is shifted by approximately 4, 7, 11 and 14mm as the main plate is moved successively from one hole to the next. These eight offset positions combined with the 12 indexing positions on the small faceplate allow for the creation of a large number of geometric patterns.
Bob’s comments and workpieces
Prior to purchasing this chuck I had not owned an offset chuck. So initially, I explored its offset capabilities and turned a few offset items (see photos) leaving Neil and Terry to explore the pattern and inlay possibilities of combining offset and indexing.
Although the instructions mention gluing the indexed faceplate to the workpiece, I used screws that imbedded at least 15 to 20mm into the workpiece as I considered this safer. Consequently, this means that 20mm is sacrificed from bottom of the workpiece. An alternative I used for one workpiece was to attach the workpiece with wood glue to a sacrificial piece of timber screwed to the faceplate.
The Axminster eccentric spiralling chuck is probably best used for small to medium sized workpieces. The size of the workpiece is limited by the ability of your lathe to handle imbalance. However, my first item was a large (300mm diameter) offset bowl. Because of imbalance I had to turn this bowl at a very low lathe speed. Even for relatively smaller items such as the offset bud vases shown a low lathe speed was needed.
Although I have yet to do any geometric patterns, the chuck, in my view, represents good value for money. On the downside I would have preferred the indexed faceplate to be of steel rather than aluminium as it is easily scratched and marked. Instructions provided with the chuck were not particularly helpful.
Neil’s comments and workpiece
This first trial using an eccentric chuck took quite a while as the variations available take time to digest. It’s a fiddle to keep taking the chuck off the lathe for adjustments and the instructions are scant. However, it was a most entertaining first attempt and there will be much more work done with this chuck!
Terry’s comments and workpieces
To do the geometric patterns shown in the photos below, both the offset and indexing capabilities of the chuck are utilised. To change the indexing position, the Axminster chuck has to be removed from the conventional four-jaw chuck, a machine screw loosened, and the small faceplate rotated to the desired position. When remounted this can result in very slight alignment changes. Similarly, loosening the machine screws to offset the main plate results in the faceplate ring loosening in the jaws and may result in a small realignment issue. I plan to investigate the use of a spacer on the four-jaw chuck to prevent the Axminster faceplate ring moving when the machine screws are loosened.