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Hardenfast
10th August 2007, 10:52 AM
G'day Gentlemen & Gentleladies.

I'v been reading with some interest the posts from the many who have encountered problems with turning bowls and hollow forms from green timber.

Harry has a recent post here with problems relating to cracking etc in his Silky Oak bowl during the drying process, and Tokyo Stu gave us a great WIP series on the brilliant recovery process he employed on a roughed-out Cherry bowl suffering severe warping. There are many, many other posts on this general topic. The problems of course all relate to contortion and checking (cracking) of green timbers during the drying process - whether natural or artificially achieved.

I know that there must be some inevitable result to the structure of the piece given the amount of water that escapes from the timber, and that the results will vary greatly from species to species. I also know that the experienced turners have developed techniques to control (to some extent) the drying process, and to accomodate the resultant effects by roughing out their works and putting them aside for some time (months?) before returning to them once the pieces have stabilised (eg Stu's Cherry bowl).

All fair enough. Still, it got me thinking about the pros & cons of working solid blanks versus segmented or laminated pieces. The subject was amplified by my recent attempts to obtain a workable chunk from a large-ish piece of Bull Oak I retrieved from a family property at Goulburn. I started off with a promising forked section around 200mm average diameter with bark etc still attached;


52719

The piece looked quite promising with potential for nice grain & configuration, however once I began the process of removing the bark:


52720

and then removing defects & inclusions and cutting it to a workable shape, it just kept getting smaller and smaller - to the point that I don't know whether I'll bother with it.


52721

The point is, although I have very limited experience I have had some modest success with the few segmented pieces I have completed:


52723

and would like to offer my musings on the advantages/disadvantages of segmented turning and solid turning. I would be interested to hear the thoughts and further points of the learned assemblage.

Segmented Works:

Generally able to use offcuts or smaller sections available
Able to dictate final outcome as work can be assembled to any size or shape
Less material to remove during turning because piece has generally been formed to approximate shape
Great effects possible from contrasting timbers etc
Ability to finish the works immediately upon glue-up without seasoning requirement

Assembly time and usually some mathematical ability required
Solid Works:

Appeal of natural grains and characteristics in timber
Difficulty in finding a suitable sized/shaped piece
End result is to some extent dictated by factors revealed during the preparation & turning process
Wastage of timber in rounding & hollowing out the shape, unless able to access a bowl saver jig or similar
Cracking and distortion of timber during seasoning
Inability to complete the work immediatelyI didn't mean for this post to be so long. I'll now shut up, but look forward to your comments.

Wayne

Alastair
10th August 2007, 12:09 PM
Hi Wayne,

I think you have summarised it well.

For myself, my interest in SW started when I was in my early days of turning, with a lathe that could turn 24", but no knowledge of or access to big timber pieces, and no chainsaw or bandsaw to manage them if I had. When I tried, huge, gnarly, out of balance, jagged logs spinning at 1300rpm, (single speed) took years off my life expectancy. Oddles of 2"x1" offcuts of white oak and european beech picked up from the scrap pile of a local office furniture factory naturally led me into segmented work.

With time, developing equipment and technique, and more options sourcing timber, I have tended to do very little. Even with having developed a number of techniques to make the preparation less labour intensive and fiddly, I now find that there is more reward in working with solid timber.

I still do pieces occasionally, and do demos on how-to, but not to the extent of my earlier days.

Also, some of the pieces I put huge effort into have since cracked up, due to expansion effects, which I did not fully understand at the time, and the disappointment put me off to a degree.

Regards

TTIT
10th August 2007, 02:19 PM
For me it's just personal taste. I see very little SW that appeals to me and have never tried to make any myself because of this - although I did start making a sled for the tablesaw once ( now where the hell did that project end up??? :confuzzled: )
True - sometimes it's frustrating how little you get from a log but even the smallest pieces can provide items of beauty if handled well.:U

Solid Works:
Appeal of natural grains and characteristics in timber (to me this is what it's all about)
Difficulty in finding a suitable sized/shaped piece (easier for me out in the scrub but still part of the challenge)
End result is to some extent dictated by factors revealed during the preparation & turning process (that's the wood talkin' to ya!)
Wastage of timber in rounding & hollowing out the shape, unless able to access a bowl saver jig or similar (most of the wood I use for turning would have otherwise been left for the grubs or bushfires - you outta see the waste involved in gem cutting if you think turning is bad :doh:)
Cracking and distortion of timber during seasoning (challenges to be overcome with experience ........or good aim at the bin in the corner:B)
Inability to complete the work immediately (yeah, agreed, this bit sux! :~ )I

Lumber Bunker
10th August 2007, 03:01 PM
Solid works, and turning from green, once you start turning a lot, in a few months you will have a back catalouge of bowls etc to go back on. So a little time spent now will have you turning over finished items in a few months, (if you turn only on the week end it's only 8 or so bowls. one a week)
Or buy timber that is dry. $$$ :(


Solid works = see my bowl in other thread ;)

Segmented work is indeed amazing when done really well (like yours are Wayne, having seen one in person) but a poor job, is indeed a poor job.
If you use timbers that have similar sinkages cracking shall not be a problem in segmented work.

Keep the works coming wayne.

Steve

Skew ChiDAMN!!
10th August 2007, 05:08 PM
Segmented Works:

Generally able to use offcuts or smaller sections available
Able to dictate final outcome as work can be assembled to any size or shape
Less material to remove during turning because piece has generally been formed to approximate shape
Great effects possible from contrasting timbers etc
Ability to finish the works immediately upon glue-up without seasoning requirement
Assembly time and usually some mathematical ability required
Ability to cut accurate angles required. (ie. extra tooling beyond "normal" lathe tools)
Can self-destruct if timbers are poorly matched and have significantly different amounts of movement.
Requires preplanning. :oo:
A badly executed glue-up cannot be rectified on the lathe.
Solid Works:

Appeal of natural grains and characteristics in timber
Difficulty in finding a suitable sized/shaped piece
End result is to some extent dictated by factors revealed during the preparation & turning process
Wastage of timber in rounding & hollowing out the shape, unless able to access a bowl saver jig or similar
Cracking and distortion of timber during seasoning if turned green. There are those who make a feature of this, though.
Inadvisable to complete the work immediately if turned green. Can be done with a modicum of success, but never a guarantee. :wink:

:D

BANNED
11th August 2007, 02:37 AM
I agree that is very much a personal choice, even when good solid timbers are scars and joining peaces of wood together, is the only way to keep turning. I do both to a point, but I prefer to work with solid timbers, dried preferably, green when necessary. I do also prefer to finish the peace in one go, but like so many other turners, I'm stuck with double (triple) handling, the same peace.
Now, turning segmented or solid peaces, generally uses the same methods/techniques and tools, but what is a complete different "species of fish" is actually have the knowledge, ability and tools to create segmented blanks (semi-forms). There are people with an exceptional ability and knowledge to produce unique segmented turned peaces, recognised World wide. Hoping not to offend anyone, peaces like the one you made (picture shown in this thread) Hardenfast, are well beyond the average turner, indeed has a lot more to do with good carpentry, then turning.
Another "negative" (less desirable) aspect of timber segmentation, is the extraordinary amount of time (working hours) to put something together, like that peace of yours.
One thing, I believe is equal in both cases, is the personal satisfaction one gets, when a exceptional peace is finished. Ditto!

Cheers
GV

Stu in Tokyo
11th August 2007, 02:57 AM
Good topic!

I find that turning segmented pieces area LOT of work to get just to the turning part, and if you bugger that up, boy it stinks! :doh:

With green wood, I find I fall into it in large bunches, so when I have some, I have a TON of it, and I turn so much, that the garbage guys whine about the amount of chips I'm putting on the curb.........:rolleyes:

If I loose a roughed out bowl, IE dried green wood, I'm not out much, as the green wood is ALWAYS free. Segmented stuff, well, I'd have to pay for that..........:(

The other thing is, I just L-O-V-E turning green wood, that is one of the things that keeps me turning! :2tsup:

Sebastiaan56
12th August 2007, 10:39 AM
Good topic!

The other thing is, I just L-O-V-E turning green wood, that is one of the things that keeps me turning! :2tsup:

Good topic!, Ive yet to have a segmented piece that didnt explode on the lathe, so my gluing up technique needs work, maybe a tablesaw might help.

I'm with you on Green wood Stu, like turning through butter, and the interesting gnarly bits can be turned with no changes of shorts or offending the overtly religious neighbours, :B

Sebastiaan

Hardenfast
13th August 2007, 09:53 AM
Thanks for the feedback, gents.

Alastair, a bit worrying to hear that some of your earlier segmented works have cracked. One does indeed need to be mindful of differential movement of timbers. No furniture factories around where I live, I'm afraid, so no access to anything of an exotic nature - even offcuts. There is no doubt that our preferences may change as our experience & equipment improves - as long it remains fun it's all good.

TTIT, personal taste is what it's all about. Good comments, by the way. The few solid pieces that I've turned to date have been mostly from "pickups" from various paddocks. Sometimes a bit difficult to work out what the hell it is that you've found, which I guess calls for another "what is this timber?" thread.

Steve, I guess that's what I've gotta do - get off my acre and create a few green projects in the rough. Build up a bit of a stockpile, as you say. Trouble is I'm a bit flighty, and by the time the pieces are ready to finish off my interests may be elsewhere. Oh, to be a disciplined genius! You're quite right, by the way - a segmented piece done badly can look very ordinary. I've seen a couple which were less than great, and in fact these were part of my inspiration to have a go at it - I knew I could do better.

Skew, quite good points. There is no doubt that general carpentry & joinery skills and equipment are an important part of segmented work. This is probably why I have a nice comfort level in this field. With 35 years of broad C&J experience I find the cutting & assembly process very stimulating and satisfying. It's the turning part where I still have plenty of catch-up work to do. As mentioned in response to Alastair above, and as you've raised many times, differential movement of incorrectly fitted or matched pieces is a major consideration. So far so good for me. Interesting that you mention making a feature of green timber distorting after its been turned. I noticed that on Neil's counter during the Sydney Wood Show he had a bowl which had been turned to quite a thin finish, but which apeared to have "dimpled and rippled" after drying. he was too busy to discuss it, but I found the finish quite intriguing.

Nyodine, the point you raise would appear to be the main reason some people are perhaps reluctant to attempt more detailed segmented pieces - that is, general Carpentry & Joinery experience. As discussed above, my background gives me a great comfort level with this aspect, which as you rightly point out, may not apply to many. Having said that, I must admit to being somewhat surprised at how much there was to learn about the turning process - a whole new ball game! Again, I agree that it's the personal satisfaction that matters in the end.

Stu, yes, as mentioned above I've just gotta bite the bullet and get stuck into creating some green blanks. Given that nearly all of the turning I have done to date has been in fully seasoned Aussie hardwoods (steel hard - brutal!), a few pieces of green stuff may well convert me. You know, I have watched your threads with great fascination & respect, including your videos. Seems to me that there's nothing you can't do, so you would appear to be a natural for detailed segmented pieces. The very first piece I completed on a lathe was a simple segmented bowl (seasoned Australian hardwoods) - surprised myself at how simple the assembly process was, and how much there was to be appreciated with the subtleties of turning.

Sebastiaan, the appeal of turning green timber seems to be a recurring theme. Definitely gonna have shot at it. Interesting (and buttock clenching!) that your segmented pieces have exploded on the lathe. As you say, you just need to refine your techniques a little. One thing which is vitally important is snug fitting of all of the pieces prior to glue-up. Quite simply, poorly fitted joints will no doubt provide structural problems and visual disappointment. Again, this is where some general C&J experience helps greatly. Correct selection of adhesives is a most important factor, and its hard to beat the cross linked PVA ranges (Selleys "Tradesmans Choice" etc) - that's all I use. Also, keep in mind Skew's often mentioned topic of differential movement of timbers as well. It's all a bit of a trial & error process, but aren't most things?

Again, many thanks all.

Alastair
13th August 2007, 02:08 PM
Hi Hard

The comments about failures I have had were more intended as a guide than a horror story to put you off. In all cases where I had failures, it was due to either not understanding, or else pushing the limits, with regard to design, and not taking into account the effects of timber movement. Projects where I was sensible are still perfect, some up to 10 years after turning.

Secondly, while I pointed out the dangers of changing moisture levels, again I was dealing with a somewhat abnormal situation. Pieces were turned in Durban where the RH probably has a low ~ 75%, and sits in the 90's in summer. I then moved straight to a Sydney winter, with the pieces sitting on the mantle above a gas heater, which ran all winter.

It was a combination of poor design and humidity "abuse" which caused failure.

Regarding the complication, and the required accuracy of carpentry, this remains very true for some of the intricate pieces which can be seen on the web, but if your interest is to create larger pieces, as an alternative to solid timber, it is possible, by means of simple graphical methods, and simple carpentry and lathe techniques, to take out almost all the complication, without losing any of the visual. What cannot be taken out is the time factor, although again this can be reduced, and made more "people friendly"

Have to agree with you on adhesives, wot I use, and outside the extremes above, no problems. Normal PVA will probably work, but the tendency for the glue line to remain flexible, can be a problem. One pitfall which can trap you, is the attempt to reduce assembly times by using quick setting glues, and reducing (or eliminating) clamping times. Where I experimented with this, I had poor results. An interesting one I will try one day, will be hide glue, as the techniques I employ would lend themselves to it.

regards

Frank&Earnest
13th August 2007, 03:11 PM
Never tried segmented, didn't have the tools. It intrigues me, however, especially because I hate to waste wood and,as somebody said some time ago (Skew?), I would try laminating leaves. My first project will be to reproduce this apple, that I have pinched from my older cousin. He had a business producing punch cutting templates and loved to make small boxes etc. in 2-3 dozen batches using the scrap wood of pallets. He would then give them with a season's greetings card to his major clients at Christmas. Shouldn't be too difficult to reverse engineer!

Skew ChiDAMN!!
13th August 2007, 05:54 PM
I'm in awe of some of the seg pieces I've seen people post, a few of Powderposts have me absolutely flabbergasted!


There is no doubt that general carpentry & joinery skills and equipment are an important part of segmented work. This is probably why I have a nice comfort level in this field.

And why I don't. :D

My first few attempts were utter and absolute failures because I was using 20 or so pieces per ring. With that many cuts your angles have to be absolutely spot on, or any error accumulates and that last piece just doesn't fit no matter how you hold your tongue. (Language doesn't help, either. :- ) Or so I thought, until I was given the tip of gluing semi-circular arcs and then using a linisher/belt-sander to "square" the ends before gluing the two halves together. :rolleyes: Wish I'd known that before I wasted so many pen blanks! :D

Now my problem is another cumulative error... the thickness of each ring. No matter how carefully I cut each segment to size on the TS, there's always a bit of thickness variation between timber types. Only a fraction of a mm, but it all adds up. By the time I build up only 5 or so layers, I start getting "wonky" levels that makes for either undulating rings that get worse the more layers are added, or obvious glue lines if I try to "pack" the gap with glue as a "mortar." :(

I'm guessing that the answer to this is to either send each ring individually through a drum sander (which I don't have... yet) or to glue each ring to the WIP and then sand the upper surface flat on a large linisher (which I also don't have... yet) in preperation for the next ring?

Hardenfast
15th August 2007, 09:29 AM
G'day Skew. Accurate thicknessing of the individual segments is a problem. Like yourself I don't have a drum sander (although it's next on the list!), so have to attend to this using the tools & machinery available. Luckily, I do have an Altendorf panel saw which I also use as a general table saw. I'm able to run my segment pieces through this with remarkable accuracy, certainly good enough to complete the glue-up of the individual rings straight from the saw.
I assemble the rings on a nice flat piece of melamine so that the bottoms are all flush, and usually end up giving the top a few seconds on the linisher once the ring is dried - just to knock off any slight ridges or irregularities. Obviously, one needs to be careful with the linisher as it will quickly remove material unevenly unless you have a nice steady hand. Just a quick, light pass should be all that's necessary.
For hexagonal or octagonal rings I usually assemble each half separately, then run the open edges of each half through the table saw again (just a millimetre or two) to ensure that the two halves fit snugly - similar to your suggestion using the sander. Otherwise, as you've found, it's very difficult to try to get that last segment fitting in there without some amount of filler - which doesn't look good in the finished item.

Frank - the apple looks excellent. I've saved a few photos for future reference. Given that it's been made from pallet timber the end result is impressive. I will definitely have a shot at one in due course, but my biggest problem is the amount of time I seem to have available to spend in the workshop (such as it is). I have not switched on a saw or lathe down there now for 3 weeks, and still have a list of chores prioritised over preferred projects. Sometimes you've just gotta do what you've gotta do, I guess.

Alastair, failures and fly-offs seem to be an occupational hazard. I've been quite lucky so far in that I have never had a piece fly apart, although I have had several bowls come off (at low speed) because the base mortice has broken out - including the segmented bowl pictured in the thread above.
I notice that Nyodine has started a thread regarding "Timber Projectiles" and fly-offs, and shows a solid lump of hardwood which came adrift at speed. I will watch that thread with interest.
The whole process certainly involves a lot of trial and error, even after one has done plenty of reasearch here and elsewhere. Nothing like just getting in and having a go. I have so far experienced very minor (miniscule) amounts of differential movement after completion of segmented bowls, but nothing to be concerned about. Maybe beginner's luck.
The cross linked PVA is definitely the way to go for these works. I have never had a joint fail with this stuff to date. Interesting that you mention hide glue. My father-in-law is a woodcarver who makes rocking horses by hand and he has used this in the past, although I notice he has now hung up the glue pot and switched to PVA. Let us know how your experience with this stuff goes.

Regards. Wayne

Alastair
15th August 2007, 01:07 PM
Hi guys

Just some ideas which work for me, bearing in mind that they will not necessarily apply to really complicated work, like chevron cuts, and triangular segments. I have never had the patience to go there. The pieces I make have either been based on building up a big blank of a single timber, or at most looking for mosiac like patterns using similar segments of dissimilar timbers. Will get around to posting pics eventually.

Firstly, I stick to standard number of segments, and build a cutting jig for each. Adjustable jigs are seductive, but too fiddly to adjust. I do not attempt to get the jig accurate to the milimeter. The problem is that no matter how well you cut, any sanding of glue faces you do is going to cause the cumulative error mentioned above. Provided the rough sawn segments will dry assemble into a circle, without visible gaps, good enough. I have been cutting on the tablesaw, but bandsaw is ideal. Now I have one, will make up jigs and try.

A clean gluing surface is more important than perfect angular accuracy, as any burning/kerf marks will show up like d-g's b-lls, and the defect inevitably is buried in the middle of the segment, where it only shows itself when you are sanding the final 40 hr piece. I sand to a clean surface on a disc sander, again concentrating on even sanding, rather than trying to keep to a standard angle. What I do do, however is flip the piece around the "radius", so that any error from the disc being not square to the table, is cancelled out.

I don't worry about thicknessing the segments. More on this later.

I originally tried to fit full rings, sand to fit, and do a single glue up, but gave that away years ago. I build up the rings sequentially, by rub-jointing with "yellow" pva glue as above. I use a melamine workboard, group sements in pairs, spread glue, and rub together, on the melamine, with pressure. As glue spreads and is pushed out, the joint becomes "grabby", and when the friction is high enough, adjust the final position, (by eye is good enough), and leave to dry on workboard. Repeat for pairs of segments until all done, and leave to dry, (4 hours or o/n). When dry, a knock with a mallet or scrap timber will break the adhesion to the melamine without problem. Repeat process for 2's to 4's, and 4's to 8's. You could combine these subsequent steps with the sanding above, if you find the growing segments tend to "cup", but I generally don't bother.

When you get to semicircles, is where you go back to the sander, and deal with the cumulative error. While it will depend on your overall accuracy, I generally find that I am close, as errors tend to cancel out. Small variations in cupping, (up to 2-3mm) or ovality (up to 10mm or so) are not significant, except if you expecting the centre of a "solid" ring to show, as in the bottom or lid of a bowl or box. Even then, an insert or button covers a multitude of sins. Touch the 2 halfs of each ring on the sander, again flipping to eliminate error, and rub joint or clamp into final rings.

Now move straight to the lathe. I use a suitably trued up wooden faceplate, gripped in the chuck. For a bowl, I take the top ring, and roughly centring it on the faceplate, glue it on with 4-6 blobs of hotmelt glue. Let this set, then true up the exposed face using light cuts, checking with a straightedge. This is where you deal with minor cupping, or differences in the thickness of segments. In my early days, there were times I had some segments nearly twice as thick as others, depending on the scraps I was using.

Once done, "pop" off the ring with a screwdriver or chisel, and clean the glue of the faceplate. I then glue the trued up surface to the faceplate, using PVA and a 'paper sandwich' joint. Centre as best, and clamp, using a scrap piece of timber, and the tailstock as a clamping device. Leave to set, usually overnight. When dry, true up exposed face as above, then repeat with hot glue, and next ring down, using tailstock to clamp trued ring to rim, using yellow glue. Repeat sequence down to base, (I usually use a solid piece). Recess or tenon base for chucking, and turn outside of bowl to final profile, bearing in mind that you have a finite thicknesss to work with. Sand and finish, and then carefully split the paper joint using a knife or chisel. Reverse and complete turning as for a normal bowl.

I find that although this method is not the 'precise joinery' that everyone fears, it is quick and simple, and any discrepancies in thickness, or segment accuracy/size, or the cumulative glueing errors, cannot be seen, since the eye 'averages' and sees the whole, somewhat like the 4 turned legs at the corners of a table. You can get away with differences which would show if they were put side by side.

Hope this makes sense, and helps someone.

regards

Frank&Earnest
15th August 2007, 03:01 PM
Thanks for the very informative posts above, guys. I take them to be my first tutorial. Nobody seems to mention the mitre saw, which I would have thought would be the tool of choice for angled cuts. Are there drawbacks that I can not see?

BernieP
15th August 2007, 03:26 PM
G'Day Wayne

Good post and some great answers, still learning on solid wood, so am afraid segmented way down the track.

Cheers
Bernie

Hardenfast
15th August 2007, 06:46 PM
Good luck Bernie. It's all good fun, isn't it? You know, believe it or not the first piece I turned was actually a segmented bowl. I hadn't completed any solid pieces when I had a go at this:


53171 53172

Fairly simple, three layers of old, old hardwood pieces I had laying around. I'm afraid I wasn't as brave as Skew ChiDAMN in attempting anything too sophisticated (20 pieces per ring!) to begin with. Have a look at the thread of my first piece here:

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=50076[/URL] (http://www.woodworkforums.ubeaut.com.au/showthread.php?t=53045)

I really had no hard & fast (hey!) setup in mind with the couple of segmented pieces I have done. In fact I started cutting up pieces for the latest one (pictured earlier) with virtually no finished concept in mind, and it turned out reasonably well. I really don't think its as difficult as it looks, but again, I have a carpentry & joinery background.

I was inspired to have a shot at segmenting by a fellow forumite from the USA - Bill Wyko. Bill was producing some really amazing segmented pieces after only 6 months or so experience. See if you can search for some of his posts. I haven't seen him here for a while - I think he's taking some time off to build a new shed, or something like that.

Frank, to me the Mitre Saw is indispensible, and certainly more than accurate enough for what's required with these works. In fact, if the timber to be used was already thicknessed I think I could complete the whole assembly using only the CSMS (Compound Sliding Mitre Saw). Well, except for the "coopered" pieces on the latest piece.

[URL]http://www.woodworkforums.ubeaut.com.au/showthread.php?t=53045

There's no draw back to using the Mitre Saw that I can see, other than when the pieces get a little small you have to develop a method of holding them still after the blade has gone through them. Have you ever noticed David Marks (is that his name?) using his eraser tipped pencil to hold his small pieces steady after cutting, both on the table saw and (I think) the Mitre Saw.

Alastair, great walk-through of your techniques there. Interesting that you also use a piece of Melamine and the "rub" technique for glueing. Seems to be the way to go. I can also see why the thickness of the segments is not a problem for you, as you "true" everything up on the lathe. I guess it's just a matter of what's comfortable for you. Personally, I'm not much of a jig man, I'm afraid. Probably just not organised enough, and too impatient to get around to making them. However, because of my carpentry experience I can generally seem to get most joints pretty right straight off the saw, but a jig would certainly be the better option for lots of repetitive cuts.
I also agree that minor inconsistencies in layout and symmetry generally disappear in the overall scheme of things. The finished pieces seem quite forgiving of minor imperfections in geometry, don't they?
I will look forward to some pictures of your works when you have time.

Regards. Wayne

Frank&Earnest
15th August 2007, 09:38 PM
Thanks Wayne, both for your comments and for the link to your WIP. Very useful. I was away at the time, must have missed it.
Cheers
Frank