Sometimes they are misadventures

Sometimes things don't go the way that you either think that they will, or more importantly that you want them to.  This weekends woodturning project was very much one of those times.  Last week I discovered some articles online about the use of a "jam chuck", it wasn't something I tried but I was keen to.

A jam chuck is a really simple but effective concept.  Basically a jam chuck can be made from a piece of scrap wood - usually attached to a faceplate. The wood is hollowed or turned to just the right size for the workpiece to be driven in/on and held securely. The obvious use for a jam chuck is when making a box or container where the workpiece has a hole where the jam chuck can be shaped to a slightly tapered plug or tenon which is a tight fit into the hole.

I set out to to make a simple lidded pot. My plan was to follow a set of simple steps which I'll share, as the method was a good one and something I will repeat.

Prepare the wood

I had chosen a piece of sweet chestnut about ten inches in length.  I mounted my workpiece between the centres and roughly rounded off  the wood, then I removed the workpiece and attached one end to a faceplate, taking care to centre as well as possible.  Re-attached to the lathe and finished rounding out the wood.

Marking out

Working from the tailstock end I roughly marked out a quarter of the piece which would become the lid of the pot, then roughly half to five eighths of the piece would be the pot base and the remaining section (attached to the faceplate) would become scrap for a jam chuck.

Turn the lid interior

Using a shallow fluted gouge I bored a hole to get the depth of my pot lid and then working out from the centre hollowed it out, moving to use a square end scraper to get definition at the edge of the pot lid - I want the insides of the lid to be as straight and square as possible.  When I was happy with the lid interior I sanded it off to a good finish, taking care not to remove too much from the the edges.  Taking a careful note of the measurement of the interior of the pot lid with a pair of callipers as this will need to match the tenon/lip of the pot base.  That done I removed the lid section using my parting tool.


It was at this point that things started to go awry...  As I removed the lid section it revealed a section of wood near the central rings that had clearly rotted, it was dark and crumbly, on first inspection it looked as though it would be a section that I would be removing from the interior of the pot anyway, so I pressed on.

A temporary jam chuck

With the lid removed I set about creating a tenon on the tailstock end of the wood.  This will become the top of the pot base and this tenon will become the lip and rim onto which the lid fits.  I took my time in creating this tenon carefully turning it to the interior diameter of the pot lid.  This will temporarily become a jam chuck allowing me to fit the lid section back onto the pot base.  This needs to be a tight fit, to the point where a soft mallet may be needed.  The result is that I then had the  pot lid firmly attached to the pot base allowing the exterior of the base and top to be worked as a single piece on the lathe.

I actually took this slightly too far and ended up with a loose fit.  I was able however to use a section cut from a rubber work glove (surgical style) as a shim to effect a secure fit, worked perfectly.

Turn the outside of the pot

Now the benefit of the previous step is that I was able to then turn the exterior  of the pot as if it was one piece.  I opted for a traditional tea-caddy shape narrow bottom, wider shoulder and rounded lid with a simple dimpled knob on top.  Finished turning and sanded the outside of both pot body and lid.  Remove the lid and set it aside it's finished!


While I was turning the outside problem number three reared its head in that the carefully measured tenon holding the lid on split clean across - I've no idea why, I guess sometimes the forces of the lathe and chisel are just too much for a piece of wood.  I didn't immediately know what had happened there was simply a loud crack.  it wasn't until I removed the lid I could see what had happened.  I nearly gave up at that point, but I was lucky that I was able to remove the tenon and cut a fresh one slightly shorter lower into the pot, luckily I hadn't shaped it too much near the shoulder.

Empty the pot

Felt like the home straight, out with the fluted gouge and my small square end chisel. As with the lid I used the shallow fluted gouge I bored a hole to get the depth of my pot and then working out from the centre hollowed it out.  Working on a faceplate for projects like this feels much more secure than using a scroll chuck or similar.  Once hollowed out sand and finish the interior and the tenon/lip of the pot.  At this stage you can sand generously and take a little away from the outside of the tenon to facilitate a nice fit for the lid.  I always sand with three grades of paper 60, 80 and 120 grain. I then removed the pot using my parting tool.


Last disaster, as I removed the pot I discovered the full extent of the rotten wood section - I thought I had removed most of it from the interior  of the pot, but as I separated the body from the remaining section on the faceplate another old knot in the wood turned out to be hiding yet more dry powdery deadwood.  As a result there is a small hole in the bottom of my pot - I like to think it adds character, but in truth it just irritates me that I didn't sufficiently examine the wood before starting my project.

Finishing the bottom

With the remaining section of wood on the faceplate of the lathe I turned down as deep a tenon as I could to match the internal dimension of my pot to act as a jam chuck, that done I reversed the pot, pushed it onto the wood and carefully finished the bottom of the pot, being careful to work towards the middle and to apply pressure squarely into the wood.  Last bit of sanding and I'm done, just a bit of careful brute strength to remove the pot base from the jam chuck.


I left the base of my pot fairly plain on account of the weak bottom and the aforementioned hole, but next time I think i will add a neat recessed base.  My finished pot stands approximately five and a half inches tall (even after having to rescue the broken lip for the pot), the body is roughly three times the height of the lid.  I finished the pot with a rough application of Carnuba wax.

The finished article.




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