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Grain Orientation

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RogerJSJ

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It may be a daft beginners question but is there is a reason why face-plate work (for bowls etc.) has the grain perpendicular to the lathe bed - is it purely for aesthetics or is related to wood strength? If the latter are there are any "rules" as to what the limits are if using grain parallel to the bed?
 

Dalboy

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No real rules at all sometimes turning end grain bowls will lead to some interesting grain being exposed in the bowl. There is no reason at all that you have to follow the cross grain orientation. Just make sure that the wood does not have any cracks that will make it unsafe to turn the same as you would with any piece of wood you want to turn. However when turing remember the grain direction when making you cuts so as to get a better finish
This is a bowl that is done end grain. Not that I would recommend doing this shape until you have had a little experience keep to round shapes first

DSCF7438 (1024x768).jpg
DSCF7436 (1024x768).jpg
 

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finneyb

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My view - end grain ie parallel ( NOT perpendicular) to the bed is:
1. less able to hold the faceplate screws securely ie need longer screws which wastes wood.
2. more difficult to cut - needs more time and sharpening

I can't decide whether it weaker and more liable to split or not - it probably depends upon the wood.

Brian

EDIT Correction to parallel
 

MusicMan

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I think the main risk of splitting with spindle-turned pieces is if the pith is included; in fact, even if the pith is cut out as in a tube. For this reason, woodwind instruments are turned from a quartered log, which of course will not include the pith.

The cause is that the wood near the pith generally has different swelling/shrinkage characteristics to the bulk, hence splitting is more likely, if it is kept solid. If the pith is cut out as in a tube, shrinkage is entirely tangential (the largest component of shrinkage) and splitting is likely wherever there is a modest variation in the growth habit.

Keith
 

jurriaan

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You can orient your wood any way you like, if you're prepared for what happens when the wood dries and shrinks.

Bowls turned with grain parallel to the bed can work, if:

- the wood doesn't shrink much (yew comes to mind here)
- the wood is tough enough to build up tension without splitting (yew again, elm, black locust, honey locust)
- the wood is thin enough to bend instead of cracking (certainly less than 1/8", also depends on toughness)

what happens when drying is that the wood on the outside wants to shrink more than on the inside, because each fiber wants to shrink a certain amount and there's more fibers on the outside.
When that shrinking happens, either the outside cracks, or the inside moves (due to the form of bowls, most often down).

Here, flat teller-like bowls in yew dry without problems, even when 1/2" thick. An experiment in oak (20" diameter, 12" high, 1/8" thinkness) led to a nice crack from the rim right to the center of the bowl, from 3" wide at the rim to zero in the center. A walnut teller (16" diameter, 3" high, 1/4" think) led to 3 medium cracks in the middle, about 2" long, when the center moved downwards about 1" - meaning it now wobbles, and the cracks, while appearing small on the inside, are very much more ugly on the outside.
Flat bowls in black/honey locust have dried without problems, or with very small cracks (< 1/2" length) on the outside rim, in the sapwood.

I can only advise you to experiment - learning about wood and how it reacts depending on thickness, form, pattern etc. is one of the attractive parts about green wood turning.
 

RogerJSJ

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Thank you all for your comments - very informative. The reason I asked was that I have a lot of wood lying around (mainly ash, oak and birch) and I could get bigger pieces out of the wood by not worrying about grain direction - but I'll take on board what you have all said.
 
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