The rotary table is a recent acquisition, purchased when it was the subject of their monthly internet offer. Like all Sherline accessories, is a well-made and cost-effective item (i.e. it is not the cheapest on the market, but much better made and finished than the cheap ones), and works with all the other Sherline components. The two little items shown with it are parts I made to facilitate its use. They can be seen more clearly below.
The one on the left is used to find the centre of rotation of the table. It is a good running fit in the central hole (7/16 in. diameter) of the table, and has a punch mark dead centre on the upper face. This was made by mounting the part dead centre in the lathe (I used a 4-jaw chuck and a dial gauge), touching the end with a centre drill, then enlarging it using a piece of silver steel that had been turned to a cone and cut back to exactly half thickness, and hardened. Think of a very sharp-edged half centre. It was then faced off until just the little depression that can be seen in the photograph remained.
The part on the right screws into the thread in the centre of the rotary table. This is 3/8 in. diameter by 16 TPI. I didn't have the correct die to hand so rather than order one and wait for it to be delivered, I turned the thread on the Myford lathe (impatient as ever!). I don't think a Sherline lathe would be up to the job. The head is turned 7/16 in. to fit the table, and when fully home, is slightly below the level of the table surface. The reason for the slot is so it can be screwed in and out using a flat screwdriver. Before being parted off, it was drilled through and tapped 10-32, which is the standard Sherline thread for clamping screws and just about everything. When I get round to it, or more likely find a pressing need for it, I will make a similar part with a drilled and reamed central hole, in which a variety of plug gauges can be fitted.
Sherline suggest that when using the rotary table, it is often easier to do the necessary machining on the table as a first operation, then from this define the centre of the part, which is then used for setting up in subsequent operations. Using these two little parts that is not necessary. First the plug is inserted, and with the centre finder in the milling cutter holder, the table is set so that its centre is aligned with the milling spindle.
The plug is then removed from the table and the work is clamped into place. If the centre of the work is identified by a punch mark, this is aligned with the centre finder. If the work already has a central drilling, the socket is screwed into the table centre, and a bolt through the work holds it in place on the table. Either way, alignment is assured, and the cutter can be offset to the correct dimension using the x- and/or y-axes.