Sticky Chucks
I have written elsewhere on this site that I am a big fan of sticky chucks. They were available in a range of sizes from the Peter Child woodturning shop in Little Yeldham until it closed when Roy Child retired, but if you have an engineering lathe then you can easily make them. At a pinch you could use your woodturning lathe, especially if you have a compound cross slide, but I know of nobody who sells them now that the Peter Child shop is closed. Roy still has an excellent website full of advice and information about woodturning and there is a section on sticky chucks. I bought a couple of them for my Masterchuck II, since then I have made my own on my engineering lathe. Peter Child used to sell waxed paper backed thin film adhesive, but I use the glue sticks for hot melt glue guns that you can buy from any DIY store. Nothing special required.
These chucks have several practical advantages:
You can mount on a finished surface without damaging it and any residual adhesive is easily removed with White Spirit.
You can finish the base of a bowl first, put a sticky plate on and and then mount it in a chuck to do the rest of the turning, so you don't need to use Cole Jaws (open form) or a Doughnut Chuck (closed form) to finish the base. I also have a sticky plate with the nose thread in the centre so I can mount directly on the lathe spindle. No chuck required.
To (usually) sufficient accuracy, you can remove and replace the work with sticky plate attached so you can use the chuck for something else.
You can use them for large projects. I have mounted bowls 250mm in diameter and 250mm long from a 90mm plate. As the plates get bigger they take longer to heat up and are harder to remove.
If a little care is taken when mounting work to the sticky plate it will be very secure. I have never had one let go, in fact the only difficulty with the larger capacity disks is that they can take a little effort to remove, which is quite reassuring. The wood surface should be sanded flat, free from dust and I would hesitate to use it on oily timber, like say Olive. If it looks a bit too greasy to stick, then it probably won't. You will need something to heat up the disc and I use the setup pictured below. When mounting the plate to the work I like to slide the plate from side to side a few times whilst pushing down firmly with a wooden block before centring. This to make sure that there is good contact between sticky plate and timber. If the work needs to be very accurately centred, then an adjustable sticky chuck will do the job, otherwise it can be a right old fiddle.
I made this heater which consists of a surface mounting double socket box and blanking plate, the innards from a brass light switch (because these ones can be removed from the switch), and a kitchen lamp holder with a 50w halogen lamp. Just place the plate on top and wait 5 minutes or so, my large chucks take 8 to 10 minutes to melt the glue. It has the added advantage that it is difficult to accidentally leave on without noticing, although I have managed it the odd time, fortunately I have not cooked anything important. Yet!
In the picture above:
1 is 90mm, the rebate was machined for a specific project.
2 (75 mm) and 4 (42mm) both bought from Peter Child.
3 (50mm), 5 (65mm), and 7 (77mm) I made.
6 (32mm) was also made by me and I use occasionally to make small centres for some projects.
The point here is that it is very easy to make one to whatever size you need, to suit whatever chuck you have handy.