First Hollow Form

First Hollow Form:
Richard Findley turns his first hollow form.

You would think that, at some point, I would have turned a hollow form. I’ve seen it done plenty of times in demos and at shows, I’ve read about it in books and in magazines, but I’ve never turned one, start to finish, on my own. There are two main reasons I never got into turning hollow forms: firstly, the tools always seemed wildly expensive (although recently manufacturers have been developing tools for wallets of
all sizes) not to mention the mind boggling array there is to choose from. Secondly, I’ve always worked with seasoned timber and I don’t really want to introduce wet logs full of creepy crawlies into my timber pile. All of this means I have stuck with turning seasoned timber, and if I’m honest, that’s the way I like it. 

Plan
As you might guess, I am looking at this article with mixed emotions. Part of me is itching to try a new project that I’ve fancied doing for years, and part of me is thinking ‘yuck, wet wood!’. While I don’t have a supply of fresh logs, I am fortunate to have a friend that does. George Watkins is a well known turner of hollow forms and boxes, and has considerably more experience than myself, so I not only blag wood from him, but also pick his brains on the subject. Not owning any of the appropriate tooling, Mark Baker sends me a package of tools that I might be able to use. Now armed with everything I might need, my plan is to turn two hollow forms, the first being a fairly straightforward open ‘vase’, which should give me a chance to get the feel of the tools and become comfortable with the process, before turning a second form with a more enclosed shape, which is likely to challenge me a little more.

Theory
A hollow form is, in theory, just a large turned box, without a lid and I’ve turned plenty of boxes, so it should be a case of practising with the tools on the early part of the job, before getting to the deeper and potentially more tricky part of the turning. As long as I can get to grips with the tools and get them cutting how I want them to, it should be reasonably straightforward, but we shall see! 

A word on tools
There is a truly mind-blowing number of hollowing tools on the market at the moment, but they can be loosely grouped into three types: scrapers, carbide tipped cutters, shielded cutters. Within each group, there are variations for different specialities, allowing one tool to do several jobs. With such a wide variety of tools out there, it seems obvious to me there is going to be a lot of mixed opinions, which of course
will be entirely subjective. It would probably be a good idea to try a few different tools before buying.  

Timber
I call around to see George and he shows me to his wood store. Neatly stacked under cover and behind his garage workshop are logs of all sorts. He pulls out a piece of oak (Quercus robur) and a piece of ash (Fraxinus excelsior), explaining that ash is a great place to start as it is one of the more stable timbers and is quite user friendly. He explains that the key to successful hollow form work is to get rid of the pith, which is the very centre of the tree, this is where nearly all splits and associated problems stem from. Alternatively, you can keep the pith in, if (and it’s a pretty big ‘if’) the pith is dead central and the growth rings are quite
even on both sides, i.e.: the tree grew straight. If I am to do this though, I would probably need to drill out and plug the pith in the base of the form otherwise cracks are sure to follow.
He slices up the logs for me, explaining that the ash, once cut through the pith, can be cut into two larger squares or four smaller ones. I went with a mix of both. He explains that the single larger one may move slightly unevenly because of where the pith was, but he would expect the two smaller pieces to have very little movement. Of the four he cuts for me, I already know which I’m going to use: I’m usually up for a challenge, but sometimes, especially when it’s your first time, the easiest option is the best option!
He then wraps the blanks in black bin bags, which should prevent them from drying out too much and allow me a week or so to get them turned before they start to crack.

Moisture content
Out of interest I put my moisture meter on the ash after turning it into a cylinder. The reading is 38%. To put that into context, the seasoned timber I usually use is rarely above 12%, some of the imported American oak can be as low as 6 or 7%.  

Design
I am a big advocate of doing a sketch, or taking a picture to the lathe with you, just to give a loose target to aim for. Before doing anything I do some internet searches for ‘hollow forms’ and ‘vase forms’ among other things. I also check a couple of my books to see if anything catches my eye. From the internet search I made some very rough sketches and I spotted a picture in Mark Baker’s book, which was of interest to me. With these in hand, I am ready to make some shavings!

Work holding
My first step is to hold the blank between my four prong drive and live centre and rough it down to round. As it is around 160mm square I go with my big bowl gouge rather than my spindle roughing gouge. Sure enough, big shavings are soon flying and despite the mess, I am quite enjoying myself.

Once the blank is round and one end is suitably flattened I can fix my faceplate. There are two main ways of holding hollow forms: on a faceplate or in a chuck. George uses a faceplate every time while others prefer a chuck. As I am mostly taking my guidance from George, I decide to do as he does and use a faceplate with four good sturdy 45mm No.10 screws. I mark out the area where the screws will be, an area about 25mm wide for waste to give me working room when finishing the bottom of the form, my projected size of the form and the remaining waste. 

With the tailstock in place I get rid of the waste from the top of the form and begin to put in a little shaping. It is loosely based on my earlier sketches, but as I am, for once, not bound by a CAD drawing, I let it develop as I turn. The opening is still a good size, but is not quite the wide opening I had originally planned, hopefully this shouldn’t cause too many problems. The form, all being well, should end up 150mm diameter and around 180mm tall. I have no idea if the tools I have will cope with this depth, but as they are specialist hollowing tools I assume that they must be able to. 

Hollowing
From all of my theoretical experience of this type of turning, I know that the first step is to drill a decent sized hole down the centre of the form to roughly the final depth. I find a 21mm twist drill in my box of drill bits and decide that will probably do the job. Having drilled this with the bit held in a Jacobs chuck in the tailstock, I’m ready to start hollowing.
Nothing I have done so far is out of my comfort zone as it’s basically spindle turning, but hollowing is where it gets interesting. I have various tools in the box from Mark, but I’m keen to try the shielded ring tool as this is what I tend to think of when someone says ‘hollowing tool’.
I get it out of the pack and can see it’s been used, probably in a tool test review for the magazine, so I assume it is good to go, which is a school boy error. Tools are never just ‘good to go’ because everyone likes their tools a bit different, even down to a spindle gouge where turners can argue among themselves for hours over the best bevel angle or the shape of grind. On a specialist tool like this there is likely to be a huge variation of ideas as to the ‘perfect’ setting. Whoever used it before me had it set up in such a way that when I try to use it, the tool wanted to twist with the rotation of the wood. Not violently, but enough that it just couldn’t be right.
I persisted for a few cuts before deciding to try to tweak the set up a little. One of the features of these specialist hollowing tools is they usually have an adjustable section between the shaft of the tool and the cutting head. This allows it to be adjusted to work on almost any shape of hollow form. I looked at it for a few moments scratching my head before realising that the problem lies in the alignment of the cutting head to the shaft. An important factor of any hollowing tool with a swan neck or some sort of crank to it, is that the cutter should still be in line with the shaft and handle, otherwise the twisting force is too much to control, and this was my problem, so I fiddled with the Allen screws and rearranged the position of the cutter head sightly and bingo! A controllable tool. 

As I feel like I am starting to get to grips with the tool, I realise it doesn’t seem to be cutting quite as well it should. I pay a little closer attention to what is going on and find that the cutter head seems to be clogging. Another friend of mine uses this particular tool a lot, so I give him a call to pick his brains. He tells me that it doesn’t clog unless the shield isn’t seated properly. The other possibility is that, sometimes, you need to apply a little more pressure to the wood to make it cut, particularly on fairly straight sided forms. This immediately rings true as my form is quite straight sided. As a precaution I take the shield to pieces and give it a clean and then try again, sure enough, with just a bit more pressure it cuts much better. I had been trying to refine the wall but too lightly. I just need more practice.
During the hollowing, I try a scraper tool and a carbide tipped tool. Both work really well, although the scraper seems a little less efficient at removing the wood than the other two tools. The advantage I find of the small carbide tipped tool is that it’s very slender, even at the tip, whereas the shielded tool and the
scraper both have quite bulky cutter heads, meaning I need to set my toolrest a good way back from the rim of the form to allow smooth movement. The carbide tipped tool could easily work with the toolrest up close for better control. 

A closer look inside
It amazes me just how much dust, chippings and shavings you get from the inside of a hollow form. Regular clearing is a must. Initially I was stopping the lathe and just scooping it out with my fingers but found it impossible to get it all. In the end I decided to use my air line to clear it. I know many people don’t agree with this approach as it blows debris everywhere and makes dust airborne, but as I wear my air fed helmet and run an air filter at all times I figure it has to be worth a go. The difference was unbelievable. I still find it best to stop the lathe, but the speed and efficiency of clearing the shavings this way makes it a no brainer to me.

Having cleared out the debris, I could take a good look inside. I regularly check the wall thickness with my callipers and have settled on 6–7mm as a suitably thin – but not too thin – wall thickness for my first attempt. The inside is coming along well, if a little ridged at this stage. I decide to try to refine it before getting to the bottom. After trying a few options I come back to the shielded ring tool, making long, slow, smooth passes to improve the inside wall surface. Once I feel happy, I carry on to finish the bottom.
Working on the bottom corner and across the base, it becomes clear to me that I am working on the limit of these tools. I passed the limit for the scraper a while ago, but both the shielded tool and the carbide tipped tool are now pretty well maxed out. Looking through the respective tool manufacturers’ websites, it seems bigger versions of both tools are available, but I have the smaller ones and now know the limit of their reach is about the 180mm I’m working on.
Trying to perfect the bottom means a lot of stopping and starting, moving the toolrest to try to see the bottom. I even resorted to using the torch on my phone to have a really good look inside. At this point I remember I have one of those magnetic LED lights which stick to your toolrest. I was given it a couple of years ago to try, but as I don’t normally do this kind of thing, it had sat in a box on a shelf unused, until now. What a difference it makes. I’m sure experienced hollow form turners will tell you that you don’t need to see inside a form, you just feel your way around it. Well, they probably can, and I feel I’ve done a pretty good job so far, but for the very bottom I need the assistance of the light.
With my path now well lit, I use the shielded cutter to smooth the bottom and blend the curve. There is still that annoying little pip in the centre though. To get a better view I remove my helmet and switch to safety glasses. Now fully illuminated, I use the carbide tipped tool to slice away the nib while being careful not to let the tool handle hit me in the face (you only tend to do this once).

Sanding
With the inside far from perfect, but as good as I can get it from the tool, I’m ready to sand. Just before I do I realise I have not yet tidied the rim of the form. Hoping I haven’t left it too late I use the wing of my spindle gouge to cut a slight inward curve. Thankfully it worked without incident, but I probably should have done it far earlier.

I take a couple of cuts on the lower portion of the outside of the form to reduce the wood that is holding it, and allow me to sand as much as possible before parting it from the waste on the faceplate. Sanding the outside is quite straightforward but inside is a different matter. I can safely reach in with my fingers a short way, but beyond this I need some help. I have a wooden stick that I use to sand twists which is fitted with Velcro and allows easy fitting of abrasive to it, so wrap it in 120 grit and use this to sand the inside. It works well but it soon becomes clear that there are a few marks that won’t sand out. On this occasion I decide to put them down to experience and hope that I will achieve a better surface on the next one, now being more familiar with the tools. I sand the whole form down to 400 grit and, with the bottom turned down to about 25mm, I saw through with a hand saw to release the form. A little sanding on the base and it sits flat as it should. 

Finishing
I realise at this point that I don’t know whether I should just finish it now or leave it to settle and season, so I ring George. His advice is to oil with lemon oil, which is a very light finishing oil, and leave it in a cool place for a couple of weeks to fully dry out. Only then should I apply my final finish. George explains that the lemon oil just lightly seals the surface and protects it from dirty finger marks until the final finish can be applied. With lemon oil being such a light oil it won’t affect any further finishes applied to it. 

Conclusion
So there we are, my first solo hollow form is done; well, coated with lemon oil and set aside to season fully anyway. I intend to turn the hollow form for the next article immediately, while the tool movements are fresh in my mind and while the wood is still crack free. By the time I have written the next article I will know for sure if this first one was a success or not. There is still lots of room for improvement. I think the overall shape works, although I need to live with it for a time to be absolutely sure. The inside is not bad, but there are a few tool marks which I’m not happy with. The positive from them though is that they are not catches or torn grain, just not totally smooth fluid cuts. Despite my intention to make my first hollow form a simple shape, I may have inadvertently chosen a shape that wasn’t as easy as I first thought, but now that I know the limitations of the tools I have, and a little more about my own limitations, I will be able to plan
the next one accordingly.