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getting the max internal depth on a bowl

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Shay Vings

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Seems to me that thick bowl blanks ( say > 3.5 inches) are hard to obtain and quite expensive so if I want to get the max internal depth on my bowl, I need to use an approriate mounting method.

Both the dovetail/recess and the spigot/tenon approaches use up some of the overall so how about glueing (hot melt or pva) a scrap disc and turning it away at the end?

Or should I use the shallowest possible dovetail/recess and ignore the fact that - for a given wall thickness -- the base will be thinner by the depth of that recess?
 

CHJ

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Hot Melt is Ideal:
First action is to determine the centre of the blank if not previously marked during cutting.



I use OddLeg callipers and scribe centre or place pattern discs visually in centre and mark through centre hole. I then use a spur bit to drill some scrap and using the drill bit locate the scrap on the centre and mark the blank and scrap with a pencil witness marks to aid location.



I then apply Hot Melt Glue to the blank and using the drill bit as before press home the scrap wood, applying a little extra glue along the edge joins if felt necessary.

This can then be mounted on a screw chuck, or you could of course grip blank in cole jaws and turn a spigot in the scrap.
 

jumps

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pretty good summary!

when I can get the bowl rim into the cole jaws the glue chuck works well enough as 'the solution', when I can't the option to use a jamb chuck and tailstock, finishing the last few mm off the lathe, also exists.

with the right jaws, and a well cut and appropriately dimensioned recess you do not need much depth at all for a solid hold

many bowl designs incorporate a suitable spigot of course.
 

Paul Hannaby

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Jaws like the Axminster O'Donnell jaws only have a 5mm deep dovetail anyway and if using those, the spigot has to be shorter than that so it's not a huge amount of wood to waste! I often find when truing up a blank that the edges are farther out than the centre so the spigot can be formed with minimal wastage. Unless it was a very very expensive piece of wood, I don't think I would go to the trouble of gluing another bit on just for the spigot.

As Jumps said, you can always incorporate your chuck holding in with the design of the bowl anyway so the wastage can be zero.

Or another alternative - use a vacuum chuck - no spigot, no dovetail recess, it just grips!
 

loz

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As per above - hot melt,

But also - add height by turning a ring off the bottom of the bowl ( parting tool in from side, and then in from base , and glue it to the top,
 

John. B

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Another way is to use a sticky chuck from Peter Child. A great idea, IMHO 8)

You do of course still have to reverse chuck to do the bottom. :roll:

John. B
 

Richard Findley

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I almost always use a spigot to hold bowls, they give a more secure grip and offer a much wider range of options when it comes to re-working the base. Recesses are far too restrictive as far as base sizes go. You can usually grip on 4mm or 5mm with a spigot so hardly a waste.

Something to think about, what is a waste of wood? Is it using as much of the original wood as possible and finishing up with a questionable shape or is it cutting away an extra 1/2" here or there but ending up with a beautiful peice of work?

Cheers

Richard
 

Mark Hancock

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Richard Findley":b51r8itd said:
Something to think about, what is a waste of wood? Is it using as much of the original wood as possible and finishing up with a questionable shape or is it cutting away an extra 1/2" here or there but ending up with a beautiful peice of work?

Richard
I like that, Richard. Not quite as brutal as my version :lol:
 

Shay Vings

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Thanks for all the helpful replies. I agree shape and proportions should take priority over maximising depth.

But - as I said in my OP - bowl blanks deeper than 3 ins or so seem hard to find and/or expensive so those extra mm gained are sometimes important, not always.

Maybe I am going to the wrong (wood) shops !
 
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