21September 2015 SOT Bulletin

My passion for woodturning started at school when I was 14. I now particularly like making more unusual items. These often use builders’ offcuts to make larger items, because getting wood that size to season without cracks would

be a major problem. I have run the library for the Middlesex Woodturners Association since 2003, which is now one of the biggest club libraries in the UK. I started it in memory of my Dad, who bought my Coronet Minor lathe after a family whip-round for a joint Christmas and 16th birthday present.

Richard Hoodless, a friend from Cheam Woodturners, introduced me to the SOT in 2011 to help me understand how ornamental turners work. At the SOT auction in 2013 I bought an MDF rose engine made by Tom Badger and its rosettes from Jon Magill. My intentions are to make items with the overall shape of the rosettes using a router rather than using them to guide decoration with cutting frames.

Woodturners who don’t do ornamental work in the way that SOT members have conventionally worked have produced a wide variety of non-round work. These turners include one of the first production turners like Frank Pain, who was prepared to share his skills with a wider public, innovative turners who wanted to do something different like Bert Marsh, Vic Wood, Stephen Hogbin and Nick Agar as well as SOT members. Many of them have written books or articles, demonstrate in the UK and overseas and have websites.

Getting to know my MDF rose engine

I fixed my small router with a rough Dexion set-up to my existing basic cross slide and then drilled fresh holes in the ‘turntable’ with T nuts to hold this set-up (Photo 3).The handle to rotate the mandrel had to be turned clockwise oth-erwise it became unscrewed but the mandrel also turned clockwise. Thinking this was normal, I set up the router on the far side of the wood and practised making the pattern. This seemed to work OK, but I was concerned about the chuck coming unscrewed. Also it was difficult to see where the router cutter was.

Moving the cross slide on the turntable in the XY slots so that it was on the nearside of the wood meant I could see more easily what was happening. However the chuck was still going the ‘wrong’ way.

Does it have to be round?

By Gordon Cookson

Shaped vessels using an MDF rose engine (A beginner’s efforts)

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Lock nuts either side of the handle meant I could turn it anti-clockwise without it unscrewing and the mandrel would rotate anti-clockwise. Once I got used to turning it anti-clockwise, I just had to remember which way to turn the cross slide handles! No doubt this is second nature to SOT members.

The next problem was the Y handle on the cross slide was inconveniently and dangerously on the far side and I had to reach over the router to move it—not a great idea! Fortunately this was easily moved around, but it meant unbolting the router holder and moving it to the other end of the vice part of the cross slide—a fiddly job in my case.

There was also a nuisance problem with the cross slide with the travel in one direction quite smooth and easy but in the opposite direction it was sometimes quite stiff. The problem was caused by roughness on the inside of the stop plate, which needed filing and smoothing away. Also the packing slips kept sliding out of place—the screw indents needed deepening. These problems were all caused by the cross slide being a cheaper model.

As the rubber was about 5/8 inch above the mandrel centre, I decided to move it down by cutting off part of the MDF support, as I didn’t fancy trying to make another slot for the rubber slide to fit in. Incidentally there is only just room in the vice jaws for the router cutter to be on the mandrel centre. To start with I positioned the rubber against the round holding disc for the rosettes with the mandrel holder upright so the rosette pattern shape would be concentric with that on

the wooden shape I was hoping to achieve. I now realise that the rubber should be set on the smallest rosette diameter with the mandrel holder upright so that the pressure on the rosette doesn’t slacken off. On my version of the rose engine the mandrel holder is positioned vertical by an L-shaped piece of wood behind the holder and a screw pad at the front. I think this pad can be used as a stop during phasing, but this is well beyond

my present knowledge. Obviously I have to remember to remove them so the mandrel can rock.

My first attempt

Photo 4 shows my first attempts at getting used to how shaped pieces rather than decoration might be achieved. Photo 4 bottom right shows the unsatisfactory top shape of a small heart when using a 6mm straight router cutter. Photo 5 shows my attempt at interlinked heart symbols made by offsetting two opposite chuck jaws.

As I was worried how much time I might have to make my first finished bowl for the Valentine’s Day SOT Meeting, I didn’t practise any more. As Claire, my

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wife of only 10 years, couldn’t understand why the meeting had to be on February 14th, I decided my first effort ought to be a heart shaped bowl! I made it out of beautiful Brazilian Tulipwood because we both love the colour and grain pattern—I had previously bought it in a SOT auction.

I marked a cutting template out of a piece of hardboard, duct-taped to the chuck’s dovetail jaws and bandsawed it to shape. Then I cut the wood to shape with the grain from top to bottom and then glued it to a waste plywood block. The centre part was turned out on the lathe to save time on the rose engine. The rough heart shaped bowl was put into a different chuck (with the rose engine’s thread) in line with the rosette pattern. Unfortunately my lathe mandrel threads are different to the rose engine. Some items might need a spigot as part of the design or necessary to make say a box.

Using a 12mm straight router cutter, it became clear that shaping the outside with the necessary thin cuts was going to take a very long time. This was because the wood blank from near the outside of the tree had two curved parts and two at right angles to the front face. So I angled the bandsaw table to match the curved sides and very carefully cut off the excess wood to speed up the shaping process. This made me realise that in future I need to consider not only the final outside shape when setting the angle of the bandsaw table but also the size of the waste block or spigot.

I started to remove the excess at the widest part of the rough outline in steps down the outside of the bowl with a cutter blade parallel to the finished shape. The cutter was wider than the collet nut to stop the nut from marking the piece. I made several finishing cuts from the top to the bottom of the bowl’s side. I soon realised that the work has to be kept moving otherwise the cutter will burn the work as it is being pulled towards the cutter by the elastic belts used to turn the mandrel. More on this problem later.

The inside was made using the 6mm straight-sided cutter running parallel to the outside shape. This had the effect of making the heart shaped pattern raised in the centre of the bottom of the bowl. As I couldn’t get a clean transition at the junction of the side and bottom, this had to be cleaned up with cutters in a hand held machine and then sanded. (‘Not sanding!’ I hear SOT members saying in horror!)

Similarly the outside needed some sanding and to curve over the bowl’s edge. I didn’t have any cutters to do this especially inside the heart’s point. The finished bowl is Photo 6.

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My second attempt

I usually prefer my hand-turned bowls with curved sides rather than the straight ones described above, but how to achieve this using a rose engine ? My first solution was to have a pivot point in a piece of Dexion attached to the back of the engine with two quick release cramps. This means I can judge the arc needed by moving the Dexion. To allow more room for the cutter to reach the bottom of the bowl’s outside I glued a 2 1/4 inch diameter 3/4 inch thick plywood disc to the base and held it in O’Donnell jaws in my 4 jaw Axminster chuck.

Photo 4 top left shows my first effort using a 22mm cove bit cutter parallel to the outside because the blades are wider than the collet nut. I moved the router on the pivot in steps clamping the router base to the rose engine’s top each time. This worked reasonably well but the curve shows the steps.

My next answer to making a continuous curve was to fix a long screw thread with a round handle, through a fixed nut, through a long slot in a Dexion piece attached to the router platform. The fixed nut is attached to wood that can be clamped in different positions along the right edge of the rose engine depending the size of the work piece (Photo 7).

Photo 8 shows my second attempt using a half-inch cove box cutter at right angles to the side. This set-up worked well

but it meant turning the handle for an hour to complete the curve in one go from top to bottom. As it was cold I wore gloves, but my fingers and thumb became rather numb and slipped occasionally on the thin handle. Needless to say every time I paused in turning the handle, the router made a small burn mark on the wood. Yet another finishing sweep was needed and another hour’s handle turning! I also found that the hour’s concentration was slightly mesmerising so that I forgot which way to turn the cross slide handles! I must make two stops for the XY travel so I can pull the router back, have a rest and then return the cutter to the correct place to avoid a small step in the line of the workpiece.

I started the inside with a 12mm straight cutter at right angles to the bottom. Again there was a problem of getting a smooth transition from the sides to the bottom. I wonder if a very small round cutter would solve the problem if it could also get into the heart’s point. The inside was done with the cove cutter but at about 45º to the side so I could get my crude router holding set-up to the join with the bowl’s bottom.

Photo 2 shows my reasonably successful attempt to get curved sides on another Brazilian Tulipwood bowl. Photo 1 shows the transition problem which, even if I had time, probably couldn’t be solved as the wall thickness there was dangerously thin.

Also because time was running out the top edge was cut at an angle rather than the much longer sanding process to round it off (Photo 1). I am not sure I like this edge on a small 5 inch bowl— OK perhaps on a bigger straight sided more geometric bowl. Photo 2 shows the outside of this bowl showing two lines at the top of the heart instead of one. Could someone tell me why this has happened and how to stop it?

I am very pleased to report that my two surprise gifts on Friday 13th before the SOT meeting on Valentine’s Day went down very well and explained my long absences in the workshop not telling her what I was making! I think the pictures show that you

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can use an attractive grained wood for these bowls made on a rose engine rather than the usual plain woods for OT.

Cheam Woodturners had a practical evening on the Wednesday after the SOT meeting and I took my practice and finished bowls for the show and tell table. As lots of people wanted to know how they were made, I was asked to do the after-coffee slot. I attempted to explain it around a small fixed mandrel lathe. It was a good thing I had started this article in draft form as I began using the rose engine. so I could tell them about the pitfalls and stages of development. The idea of a rocking mandrel had some people perplexed! As the explanation went well, they have asked me to do a demo with the rose engine sometime.

More changes to the rose engine

1. I have removed some of the base to make more room for my hand when turning the handle.2. Change one belt to a figure of 8 so the handle can be turned more naturally in a clockwise direction.3. Increase the size of the handle to make it more comfortable.4. Fit stops on the cross slide so I can take a rest from handle turning, and return the cutter to the same place.5. Consider fitting the original turntable that came with the machine into a bigger surround with fixings similar to Jon Magill’s design and with more pivot holes. This would mean less moving of the cross slide on its base and more flexibility for use with larger workpieces.6. Try to get my variable speed lathe to drive the idler shaft slowly enough, as the rose engine conveniently sits on the lathe bed until I have a massive tidy up! This might mean I don’t have to turn the handle for hours, especially if I go for bigger pieces. There are pictures on the MDF Rose Engine websites of a motor being attached for OT work. I will have to see whether it will work for the way I am using it. I have my doubts espe-cially for heart shapes because I needed to slow down rounding the point to stop the cutter from jumping.7. Re-varnish new and changed parts when I have ‘finished’ making adaptations. Will I ever stop?

What shape to make next?

I have realised that the point of the heart shape probably makes it the hardest shape to start with! An oval shape might be the easiest of the rosettes to follow but how can I compete with Jean Claude Charpignon’s masterclass demonstration for the SOT in May 2014? So instead I went for an eight-lobed bowl in pine from my scrap pile and Photo 3 shows my attempt. I suspect there may be more difficulties with the inside points when there more than eight points unless the piece is much bigger than my test piece of 5 inch diameter.

This one was done with the same box cutter on the inside and outside. There were similar problems to the heart shaped bowl with getting curved sides and a neat transition between the side and the bottom on the inside.

As a footnote, I am very pleased that my efforts were considered good enough to be given a Certificate of Merit for my first heart shaped bowl (Photo 6) in the Haythornthwaite Cup 2015 competition.