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SeedsIntoTrees
7th July 2014, 11:13 AM
Hi,
Would there be any problem turning a square spindle made out of two woods of different hardness?
It would be made out of an extremely hard wood rectangular core (25mmx32mm) with semihard wood slats (3mmx32mm) glued on to the top and bottom, making a 32mm square spindle sandwich.

Skew ChiDAMN!!
7th July 2014, 07:56 PM
Turning it should be ok, provided you use sharp tools and good technique. (Rub the bevel, rub the bevel, rub the bevel!)

Sanding may be more problematic as the softer wood abrades faster. 'Tis best to to get as good a finish off the tool as you can, so you have minimal sanding... if any at all. :wink:

Be aware that greatly different hardnesses means the timbers will likely also have greatly different movement rates, which may lead to problems in the long term. eg. cracks, broken or "raised" glue joints, etc., etc.

dougturner
7th July 2014, 10:56 PM
SeedsIntoTrees, :wts: and I would use a cone centre in the tailstock and a Steb centre in the headstock, so as not to wedge the glued up blank apart, and also turn it at a much slower speed than you would turn a solid piece of the same size so that the centrifugal force doesn't cause it to fly to pieces. Doug. :U

Christos
7th July 2014, 11:28 PM
I agree with above.

But I also like to experiment a little. :doh:


Also like to add nothing wrong to sand off the lathe by hand. :o

Paul39
8th July 2014, 03:03 AM
http://cyanide-cdn.woodworkforums.com/images/smilies/smilie%20signs/wts6Ar.gif If you have the slightest doubt about the strength of the glue joint, put a few wraps of tape around the ends. It the tape is on the waste part, leave it there. If not, turn and finish up to the tape, remove tape and place on finished part, finish ends.

Mobyturns
8th July 2014, 09:09 AM
Hi,
Would there be any problem turning a square spindle made out of two woods of different hardness?
It would be made out of an extremely hard wood rectangular core (25mmx32mm) with semihard wood slats (3mmx32mm) glued on to the top and bottom, making a 32mm square spindle sandwich.

If you are adding 3 to 3.5 mm cheeks on two faces to make up the 32mm square then are taking it to a say 30 or 31mm round there will not be much visible timber from the slats or cheeks left. If the effect you are looking for is a consistent "stripe effect" then you are setting yourself a quite difficult task as your machining, centering and turning to a consistent parallel cylinder will all have to be spot on to acheive a consistent & pleasing effect. Not impossible but challenging.

If the effect you are attempting to achieve is a split turning, i.e. removing the cheeks to use in other items, then you may wish to reconsider the cheek thickness and glue joint choice to permit easy separation later; or if the cheeks are waste to be discarded then the glue choice is only important from the safety aspect of staying together during the turning process.

I turn linear laminations and thermed items (see my album) regularly so have some experience in this work. As for the glueup, a good quality PVA, aliphatic or crosslinked PVA glue something like Titebond Orig, Titebond II will be more than satisfactory. Pay attention to joint surface preparation.

The blank will be well balanced as the core & cheeks are symetrical, so therefore balanced as long as the same density timber is used for both cheeks. As the cheeks have minimal thickness i.e. mass I would not be overly concerned with balance or reducing lathe speed below normal spindle speeds for a 32mm piece - with one caveat - the glue joint must be well made and fully cured. Allow the full recommended curing time for your environmental conditions (temp & humidity).

As others have said these types of turning depending on the intent for the cheeks can also be achieved with tape alone, by using double sided tape or by well planned application of bound tape wraps. Certainly requires some experience & not recommended for a novice though.

SeedsIntoTrees
8th July 2014, 11:18 AM
Thanks everyone, so much good advice!
I took it all in, but I will go over it again until I make sure I've absorbed it all. It all makes sense.