Richard Findley looks into the techniques of turning bowls without a chuck
When deciding on topics for this series, I cast my mind back to my own journey through turning and to the many questions directed to me on my travels around the turning clubs of Britain. Something I am often asked by those new to the craft, and indeed something I queried myself is: “Do I need a chuck?” The answer I usually give is: “No, but it makes life a lot easier.” This was the conclusion I came to when I started turning, so a chuck was pretty high on my ‘to buy’ list. Hence I have never turned a bowl without one.
I know it’s possible to do without a chuck and, as the working title of this series suggests, I know the theory of how it’s done, I have just never tried. I have decided to make two bowls using two of the most straightforward methods I can think of. In doing so, I am thinking of those new to turning, so I’m only using basic equipment that everyone will have. I should point out at this stage that this is not another ‘how to turn a bowl’ article. Here I am focusing specifically on the holding methods of working without a chuck.
I have chosen to use two methods to explore turning without a chuck. Both will involve using a faceplate – something that almost every lathe has as standard. The first method involves gluing on a sacrificial waste block of timber to allow the use of screws without marking the bowl. The second will rely on jam chucking
to enable me to hollow the bowl. In theory, as long as I get my holding points secure and properly formed, turning these bowls should be as simple as turning with a chuck. We shall see!
The first job is to select the timber. I choose two pieces of ash (Fraxinus excelsior), without faults or anything that may trip me up along the way, in sizes that a new turner would be likely to have: 190mm diameter and 50mm thick. As one piece will need gluing to a sacrificial block, I pass the block over the planer while it is still in board form and cut the two discs from it.
GLUE BLOCK BOWL
Gluing the waste block
Some people attach the block using a glue gun or cyanoacrylate for speed. I use neither in my workshop, so stick with proper wood glue. It quickly becomes apparent that the main drawback of the block method is that you need to plan ahead and glue the block on at least the day before you intend to turn the bowl, to allow the glue to fully cure.
Luckily I remembered the day before my photo shoot. I have picked an off-cut of sapele (Entandrophragma cylindricum), which contrasts well with the ash and shows clearly in the photos. With the meeting faces of
the bowl and the glue block planed flat, I use polyurethane glue and G-cramps to secure the block in the centre of the ash blank.
First stages of turning
With both of my bowls, I use the faceplate to mount the blank to work the base. The faceplate for my old Wadkin lathe is larger than most modern faceplates at 165mm diameter, but it’s what I have, so it is what I’ll use. I check the length of the screws, just to make sure they definitely aren’t going to mark the bowl, then drive them home with a driver. With the blank mounted, I round off the waste block and begin to shape the
underside of the bowl.
It quickly becomes apparent that without a little planning, the glue block would encourage an overly large base to the bowl, which is not something I want. A pet hate of mine is when my equipment tries to dictate to me what I can and can’t make. My plan is for a simple curve to the underside of the bowl, with a little interest added in the rim. To avoid a fat bottom, I try to visualise the curve of the bowl and cut accordingly. This means that I don’t cut the curve simply from the edge of the glue block to the rim, but cut into the bowl somewhat, giving extra ash to work into a foot and allow the curve to continue further round the bowl once the waste block is removed. The final re-turning stage is going to be all the more important for this bowl.
Once happy with the shape of the bowl, I sand by hand to 320 grit. I am acutely aware that when I re-turn the base and remove the waste block, I may need to slightly rework the curve of the bowl. Importantly, to ensure I can easily remount the bowl to do this, I use the tip of a skew to cut a small but important dimple
in the centre of the base.
Hollowing the bowl
The next issue that presents itself is that when I remove the faceplate from its initial mount, I need to try to position it perfectly on the waste block to ensure the bowl runs true. Thanks to the little dimple I cut previously, I am able to position the point of my compass in the centre and draw a circle in the position of the screw holes. Those holes are a little closer to the edge of the block than I would like, but with a small pilot hole to ensure the screw drives in true, this shouldn’t be a problem.
When I run the lathe with the bowl now mounted for hollowing, there is a tiny amount of run out, but as I want a wider, more decorative rim, this won’t be a problem. If I had wanted to make a thin walled bowl, this would cause an issue. The only way I can think of avoiding this would be to own two faceplates and mount
the second, using the tailstock to help find the exact centre.
With the bowl securely held with four 25mm screws into the sacrificial block, I am comfortable taking some quite aggressive cuts and turning the inside of the bowl as I normally would.
JAM CHUCK BOWL
The initial stages of the jam chuck bowl are the same as the glue block bowl, except that once I am ready to turn the underside, I need to cut a spigot to create the hold. Having never done this before, I’m not entirely sure of the best size to cut the spigot, so decide to use the spigot I would use on my scroll chuck as a guide. I guess I need a bit more depth for a jam chuck than for my scroll chuck, so cut it 60mm diameter and 10mm deep, initially roughing it out with my bowl gouge, then refining the spigot using my skew in scraping mode, flat on the tool rest. I cut it perfectly square rather than dovetailed, as I would on my scroll chuck.
LAWS OF THE CHUCK
To achieve the best support when working with a scroll chuck, in either spigot or recess mode, it is important to realise that chuck jaws work in two ways. Firstly, they grip onto the spigot or recess, but they also need a surface to bear against to resist leverage which can easily force a bowl and chuck to part company. This bearing surface is easily formed as a flat for the face of the jaws to seat against. This law must also apply to a jam chuck: if I can counteract the leverage forces with a flat bearing surface, it stands the very best chance of working.
Selecting the jam chuck
I choose a piece of clear pine, European redwood (Pinus sylvestris), for the jam chuck. Firstly it is cheap and secondly, being softer than the ash of the bowl, it should have a little give in it to achieve a good tight grip on the spigot.
I mark the size on the pine block with dividers and remove the bulk of the recess with a gouge, squaring the edge with a skew in scraping mode. The pine block is around 50mm thick, despite the fact I only need enough to house the 10mm spigot. I would always recommend using overly thick material here because sure enough, I cut my first recess too big. The additional thickness allows me to remove all evidence of the first attempt and try again. My second try is better, but not quite as tight as I would like. My options are to try again or pack it out with tissue paper. Judging by how tiny the difference between it fitting and it not fitting, I decide to try a folded piece of tissue paper. A couple of firm taps with the heel of my hand seats the bowl beautifully in the jam chuck.
Turning on a jam chuck
My first few cuts are very light and tentative, but I soon gain confidence when the bowl shows no sign of flying across the workshop. Despite the theory being sound, I fully expect the bowl to come away at least once. However, I am pleasantly surprised by how secure the jam chuck feels. I make sure I pay full attention to all of my cuts to avoid a catch, because if something is going to make the bowl leave the jam chuck, it will be a catch. As I progress, my confidence grows and I risk a few more aggressive cuts. The bowl is as solid as if it were held on a scroll chuck. I turn an ogee shaped bowl down to an even 5mm wall thickness and sand to 320 grit.
Removing bowl from jam chuck
With the bowl turned and sanded, I now need to remove the bowl from the jam chuck. At 5mm, it is quite thin, so I don’t want to use too much force. I decide the best way to do it is to apply a leverage-type force by gently knocking the bowl with the heel of my hand. Sure enough, the levering action gradually twists the bowl from the chuck, but not easily, which is quite reassuring. The tissue paper comes out in a perfectly formed cup and all that remains to be done is to re-turn the bases of both bowls and form a foot. I like a foot on a bowl, but feel free to shape the bowl as you see fit.
RE-TURNING THE BASES
The method I always use to finish the underside of bowls is suitable here, as it only involves a faceplate with a disc of MDF fixed to it. The bowl is then sandwiched between the MDF and the live centre, essentially between centres, giving almost full access to the underside of the bowl. The jam chuck bowl is the most straight forward; it involves simply reducing the overall size of the spigot to a foot that is in proportion with the bowl. This is turned with a spindle gouge and just a tiny pip is left under the live centre to remove by hand at the end.
The glue block bowl requires a little more work as there is around 25mm of sapele to remove, before refining the curve of the bowl and forming the foot. Regular checks are needed to ensure the curve looks good and a foot can be formed. Once happy with the shape, it can be sanded to the same standard as the rest of the bowl and finished off, away from the lathe.
From the start, I suspected the glue block bowl would be the easiest and least likely to cause me issues during the turning process. However the jam chuck bowl proved to be the least hassle of the two.
I was pleasantly surprised by the quality of the grip on the jam chuck.
My only reservation would be that a beginner who may be more prone to catches, could well struggle with the jam chuck method. This is ironic considering it is likely to be a beginner without a scroll chuck who might want to use this method. The glue block method would certainly be most secure for a beginner, but this method does need forward planning and careful preparation to ensure the blanks are ready to turn on the day and are safe, which may also put people off. A scroll chuck certainly gives the best of both worlds and I wouldn’t be without mine, but if you want to try something a little different or to challenge yourself, I would highly recommend a jam chuck bowl as an exercise.
Alternative methods of working without a chuck
Some turners prefer not to use a scroll chuck, instead opting for the solid hold of a faceplate and sturdy screws for bowl and hollow form turning. In this case, there is always excess timber to allow the screws to do their job, while still being able to remove all evidence of them. For some, faceplates and chucks are too rigid, not allowing for creative flair. This is particularly relevant with natural edge work where balance of the rim is important. These bowls are often started between centres, until the turner is satisfied with the look of the emerging bowl and a chucking point can be fixed.