Technical Thursdays – 20 Top Tips on Hollowing

Monday 9 July 2018

Soon after I started woodturning I knew I wanted to concentrate on hollow forms and hollowing projects. A few months after I started woodturning I saw the work of David Ellsworth in a magazine; I loved the simple, flowing shapes and was intrigued as to how it was done. That was nearly 14 years ago and if you ask me today if I have achieved what I wanted, I will tell you I'm still practising! Hollowing is a very challenging skill; I never feel that I've 100% mastered it and I think that is the 'hook' which keeps me coming back to it time and time again.

The 20 tips in this article aren't meant to be the 'only' way or the definitive list, but are merely 20 things that I have learnt which have helped me along the way. I hope they are of some help to you, too.

Golden rules

Tip 1 – form

Firstly, the most important factor concerning any hollow form is the attractiveness of the end form.

The hollowing out process is just a means to an end; therefore if the form is poor but it is perfectly hollowed out it will always be a poor form. My advice is to try to stay focused on the final shape of the piece at all times

Tip 2 – consistent wall thickness

Many people think that you need a paper thin wall thickness for hollow forms, but this is actually not the case. Instead, what is more important here is a consistent wall thickness

Tip 3 – know your limits

By this I mean not trying to create a very tall piece or hollowing through a very small hole straight away.

You need to start small and get used to the process then build up to more depth and smaller holes, if you wish

Tip 4 – avoid the pith

You will have a far higher success rate if the pith is not present in the final form. If you do have to include it, place it vertically through the piece; that way the top pith will be cut out by the hollowing hole and the bottom pith can either be drilled out and plugged after or reinforced with CA adhesive from both sides

General tips

Tip 5 – faceplates with screws

Use a holding method which is relative to the size/depth of the hollow form you are going to produce. The forces in hollow form work can be very big and it is important that the spigot size or faceplate, plus the length and the number of screws, is adequate enough to deal with these

Tip 6 – clear shavings often

When hollowing through a small hole it is important to keep in mind the size of the cavity inside the form and stop to clear the shavings out regularly. If you do not keep the cavity relatively clear of shavings, the shavings can build up inside the form and wrap around/bind the end of the tool, and possibly even cause an accident

Tip 7 – don't use the sides of the hollowing hole as a fulcrum point

Do not use the sides of the hollowing hole as a fulcrum point. I'm sure that everyone who has learnt how to hollow has done this at some point but it's not good practice and can break the hole or neck of the piece. Try to be very aware of where the shaft of the tool is and do not allow it to rub against the side of the hole

Tip 8 – work down from the hollowing hole to the final thickness

Once an initial cavity is created work from the hollowing hole down to the final thickness; this is done so that the piece has enough strength and rigidity to allow it to be hollowed. For example, if you reduce the middle of the form to final thickness before the area above it is complete, then when you try to go back and finish the upper area you will have lots of vibration/chatter problems and could possibly break the piece away. If you work from the top down you are always working into supported wood and can complete the wall thickness in sections until the base is reached and the hollowing complete

Tip 9 – use waste wood to support the piece

Leave extra waste wood around the bottom one-third on the outside of the form – this will increase strength and rigidity whilst you are hollowing

Tip 10 – turn green hollow forms in one session

Try to complete green turned hollow forms in one session – if you do have to leave them overnight then place them in a plastic bag with some shavings. This is because green wood will start to move and dry out as soon as you begin working with it, so to prevent the piece from cracking or losing its concentricity, it mustn't be allowed to dry out before it is completed

Tip 11 – place a mark on the ferrule of the hollowing tool

It is a good idea and good practice to place a mark on the ferrule of the hollowing tool which points upwards when the cutting tip is in the correct position to cut – this can be used as a reference so that once the head of the tool is inside the form, you know what position the cutting tip is in

Tip 12 – turn your own extra long tool handles

Make your own extra long tool handles to help counteract the overhang forces of hollowing – my handles are between 660mm and 760mm in length

Tip 13 – pre-drill a hole to aid hollowing

If you wish, pre-drill a hole to aid hollowing but never drill all the way to the base as you cannot then alter where the base of the piece will be, and once you remove the waste wood on the bottom one-third of the form, you may need to alter the curve slightly, and if you've drilled to the bottom then you won't be able to do this

Tip 14 – use CA adhesive to repair hollow form cracks

If you need to repair a small hairline crack or strengthen a punky section of the piece, apply lemon oil to the area before applying CA adhesive. The oil won't stop the glue from working but it will stop it from staining the wood

Tip 15 – practise using your hollowing tool on an open vessel

Practice using a hollowing tool on a open vessel so that you can clearly see how it cuts and why – you will find it much easier than when you are working inside a form and cannot see what is happening

Tip 16 – the smaller the cutting tip on the hollowing tool, the less forces are applied

The smaller the cutting tip on the hollowing tool, the less forces are applied. Smaller tipped tools are often easier to control in tricky areas of the form or at greater depths

Tip 17 – check that the chuck is tight when using green wood

If you are using green wood with a chuck tenon then remember to check that the chuck is still tight every so often, as the wood will start to dry as you are making the piece. It may also become loose in the chuck jaws

Tip 18 – rub screws in paste wax

If you are struggling to drive screws into the wood for a faceplate then try dipping the screws in paste wax or rubbing them on a candle; they will drive into the wood much easier but will still grip firmly

Tip 19 – use anti-corrosive inhibitor on any shielded cutters

Before you put your tools away after turning a green hollow form, remember to spray an anti-corrosive inhibitor onto any shielded cutters or you may not be able to adjust them next time you go to use them

Tip 20 – mark the outside of the piece with a pencil

As you progress inside with your hollowing, mark the outside of the piece with a pencil. Once you are at your desired wall thickness, this helps you to track progress. Remember not to go back above that line as this area is now completed