I have been making some bowls from green wood lately. I am relatively new to turning and I have two questions.
Question 1. I have been having trouble with cracking. Some methods that I have tried to prevent cracking are,
– Putting a finish on as soon as possible. So far all that I have rally tried are linseed oil and then I tried some lacquer. They seem to help a bit but I continue to get some smaller cracks. Some of these smaller cracks disappeared or closed back up after the piece continued to dry.
– I have also tried putting the piece into a paper bag full of shaving from the same piece and letting it sit.
I guess what I am looking for as a short term fix or any other little tricks that might aid me in my turning.
Question 2. I am also having trouble with tear out when the grain of the piece is against the cutter. I have tried using a shear cut with a bowl gouge that is freshly sharpened. That works pretty well and I have had a lot of success with that. Is this the fastest way to get a nice smooth surface or is there another faster way to get the smooth surface. Would a scraper work better and what would anyone suggest. I don’t have a huge budget for this type of this but I am willing to spend some money.
Any help would be appreciated. Thanks.
Matt
Replies
Matt ,
The cracking is from the moisture and removal of itself all at once . The piece of wood may try and move 2 directions at the same time , crack .
I tried finishing the pieces while still on the lathe , before they had time to crack , I used paste wax and burnished it in . Cracks still happened , but less in some pieces .
There are several products that are made to stabilize green woods .PEG is one and another or two are also available .
If the gouge is pulling chips imo try the scraper , actually you are working end grain and a scraper can be the tool .
good luck dusty
I have tried PEG before and I just haven't been happy with its performance. You need an oven to dry it and you need to heat it when soaking the piece to get better faster penetration and then you have to remount the piece to sand it when finished. It is just more of a pain than having a crack sometimes. I am thinking about trying some segmented turning with dried wood. That should help eliminate some cracking.
By all means , using dry stock would be a safer bet .
you would have no cracks to deal with and more stable projects
good luck dusty
You do not say to what extent you turn initially, do you rough turn and allow to stabalize under control or are you hoping to get a finished bowl from one session. The point is that turning green seems easier than turning dry but pro turners do things in stages from what I have read on the subject. And tools have to be very sharp, try turning a scrap of hard balsa to see what I mean.
Cracks ! The agony and ecstasy of green wood. To "help" prevent cracks maintain an even wall thickness through out the whole turning session, but nothing is ever for sure.
Shear scraping with the side grind on a bowl gouge and having the leading edge on a downward slope similar to using a card scraper works for me.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
Edited 2/23/2007 2:50 pm ET by BruceS
This will probably help you out,
http://woodcentral.com/cgi-bin/readarticle.pl?dir=turning&file=articles_473.shtml
Lee
Lee,Thanks for that link. I have a lathe on order and it's stuff like that which take away alot of the mystery. Any others you could pass along are appreciated.Thanks againAndy
...sure will, Andy.Lee
Andy,WoodCentral.com has a quite active turning message board you may want to check out.Here's a belly full of articles from that same site on turning. http://woodcentral.com/cgi-bin/articles.pl#turningYou know, talking to indusrty people, editors and show people many feel that woodworking is tending more towards turning and (some say) carving. The idea is that people can turn a bowl in an afternoon in a small workshop so that's the general direction many woodworkers will take their hobby. Taunton puts very little emphasis on turning so I'm posting these links to another site knowing they won't mind. The turnings I do are almost entirely for furniture with the odd bowl or vase thrown in as a gift. There are some extraordinary turners out there.Lee
Thanks Lee.I have been reading and studying for a while now. I finally took the plunge and should have a lathe in my driveway in a week or two. I have joined the AAW and am planning to attend the symposium this summer in Portland.Maybe I am more aware of it now because of my own interest, but there does seem to be more out there about it. As a kid when I went with my parents to their craft shows, I always seemed to spend a lot of time in the turners booths'. Ahhh destiny.Stay warm.Andy
Matt,
I carve bowls from green wood - half-trunk sections from trees 6 - 12 inches in diameter.
The only way I know of preventing the cracking is to 1) carve them in a damp atmosphere, such as outdoors and 2) keep them in a plastic bag for most hours each day, gradually allowing them out for longer and longer as they slowly give up their moisture (seen on the inside of the bag).
They go a funny shape sometimes; but so far no cracks.
There is no quick route, I suspect, if you want the wood to remain in its natural state (eg unPEGed). Ordinary finishes, such as oil or wax, will not of themselves stop rapid evaporation from green wood I think.
Lataxe
Lataxe and Matt
Among other things, I carve masks, sometimes in green wood (firewood - usually rock maple or sometimes sugar maple) and sometimes in KD wood. One of the things I learned is that when the piece is of even thickness it has less tendency to split and crack, so it became important for me to get out the calipers and work the back of the mask as I worked the front. I expect this will help reduce the cracking and splitting some in bowl making. I also make bowls, but always out of KD wood, and never on the lathe. I build the bowls using concentric rings cut from the same blank.
Your method of keeping the bowl in a plastic bag and slowly acclimating it to the surroundings is wise. It reminds me of keeping a clay sculpture or bowl covered in plastic film to keep it moist. JL
You might want to read the article I posted the link to as well. There are quick ways and there is really no need to reinvent the wheel unless that's where your fun lies.Lee
Lee,
I had a look at the article in the link you posted; use of alcohol seems one effective way to speed up the drying process. It does strike me that the method is not exactly "simple" as claimed - all that messing about with containers, wrapping and straining. Perhaps I am just a lazy boy. :-)
One little aside early on in the article caught my attention - boiling bowls to (paradoxically) drive out the water a bit faster. I know from steaming green chair parts that the process does ineed cause the water content to drop rapidly - from 30-35% when green to 20% post-steaming. (I guess it's because the sugars and other water-retaining chmcals are steamed out of the wood, which often exits the steamer smelling like a good Christmas pudding).
So, perhaps I will try a carved bowl in the steamer, since it is already there and working. It may reduce the time required using the plastic bag acclimatisation method.
Lataxe
Lataxe, I'm on no mission to convert you here. If it's too much trouble skip it.It's clearly stated in the article that boiling the wood ruptures the cells allowing moisture to more readily migrate out of the wood. There's nothing paradoxical about this. Perhaps you missed that part.Carry on, Lataxe, do whatever works for you.Lee
Edited 2/24/2007 9:27 am ET by LeeGrindinger
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