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Xanthorrhoeas
23rd October 2016, 06:09 PM
I am just starting out woodturning and have done an intro to bowls and platters course. Now, I would like to try something challenging and, some years ago I bought a beautiful bowl blank in fiddleback Tasmanian Blackwood. it is about 280 mm diameter and 70 mm thick. I have turned and part sanded the outside of the bowl and the dovetail to fit it to the chuck. That is when I realised that it would be a terrible waste if if I just turned the centre of this beautiful fiddleback into shavings. So, i thought - why not slice the top off (after smoothing of course) and keep it as a lid to show off the figure.

My question is how to do it? As you can see from the photos I have kept the outer wall of the bowl fairly steep so show off the figure. I am planning on finishing the sanding then taking the bowl off the face plate and putting it on the chuck. At that stage I thought, that after cleaning up the surface (currently rough and with wax on it) I could bring the live centre up to steady it and try to slice off about 8-10 mm to serve as a lid.

I am presuming i might use a parting tool to do this? I can see some issues in getting a lip on the lid to fit neatly inside the bowl (accurate measurement needed and no calipers owned yet!) i would appreciate any advice/suggestions.

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powderpost
23rd October 2016, 07:00 PM
I would use a parting tool and cut in as far as is comfortable, then complete the cut with a hand saw. Not very technical I know, but it is a method I now use after getting into strife trying to turn the top off.

Jim

Big A
23rd October 2016, 07:51 PM
Grasstree,
(That is easier to type than Xan.......!)

How deep do the screws holding the faceplate go? That will complicate the issue for slicing off a bit for the lid - by the time you cut out the screw holes, will there be enough left for the lid? Or can you make a design feature of the four holes?

Nice piece of wood. I hope you can get what you want out of it now.

Cheers,
Alister.

Xanthorrhoeas
23rd October 2016, 08:05 PM
Thanks Jim and Alister,

The parting tool followed by saw is what I sort of planned, but wasn't sure of and have never done. I was planning to use a Japanese pull saw resting lightly in the cut as I spin the lathe at low speed. Does that sound feasible?

The screw depth? Yes, could be an issue there - 25 mm screws, 10 mm faceplate - 15 mm penetration! I was planning on attaching a "handle" of another turning (Tasmanian Musk or Myrtle burl I think) to the front of the lid to cover the screw holes. Maybe I'll just use the holes to attach from beneath the lid with 4 round-head brass screws to make a feature of it. It will depend on how obvious those holes are and whether I can make them 'disappear' with some hot water and steam iron or coloured epoxy.

As a final question: are there readily available calipers that will accurately measure to the approx. 250 mm of the lid "drop-in" section?

Regards

David (aka Grasstrees and Xanthorrhoeas)

Big A
23rd October 2016, 08:34 PM
Starrett make a nice digital 300mm vernier caliper, but it is a bit expensive at over AU$420.

Why measure? Cut the recess, and then cut the lid to fit. Wouldn't you need a bit of "slop" to allow for movement in the wood? It does not have to be a machinists fit.

A.

powderpost
23rd October 2016, 08:39 PM
I was planning to use a Japanese pull saw resting lightly in the cut as I spin the lathe at low speed. Does that sound feasible?
As a final question: are there readily available calipers that will accurately measure to the approx. 250 mm of the lid "drop-in" section?

Regards

David (aka Grasstrees and Xanthorrhoeas)

David, I like to keep things simple. I would suggest you turn either the top or the bottom, what ever suits, then use a thin piece of timber (25 x 5, or similar) and mark on it the width and use that to measure it's mate. That way there is ,"no miss reading of numbers", and far less chance of making a mistake.
Also, I found it much better to use the hand saw while the lathe is stationary. You will find it better to use the spindle lock on the head stock and shift the "bowl" around a bit as you progress.

Jim

Xanthorrhoeas
23rd October 2016, 09:11 PM
Thanks Alister and Jim,

Good points. I do like tools (who of us can deny that?) BUT $420 for a rarely used item, nah. I like Jim's solution better, I've plenty of wood around and it cost a lot less. I'll also saw while stationary. I suppose that is more controllable - I was wondering whether the saw might develop a mind of its own on a spinning object.

David

joe greiner
24th October 2016, 02:00 PM
It certainly would develop a mind of its own; a crazy mind at that, especially when the cut completes.

Also, the lathe is spinning in the wrong direction for a pull saw above.

Cheers,
Joe

Mobyturns
24th October 2016, 04:35 PM
I was wondering whether the saw might develop a mind of its own on a spinning object.

David

Start the cut / parting off with a thin but sturdy parting tool with the tool rest up as close as possible. Make sure you create clearance in the parting slot by using at least 1.5 times the width of the parting tool. Go in an inch or so then turn the lathe off. Engage the spindle lock on the lathe then complete the cut with a handsaw / pull saw.

Remember that parting tools are normally used on cross grain (spindle orientation) and will encounter end grain and face grain so they tend to be much more "grabby" when used on bowl blanks.

Using the lathe under power with a hand saw even with ultra low speeds on a variable speed lathe is a pretty dodgy practice! Sure to get very ugly if things go wrong.