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Newbie turns green

pencheff

pencheff

Joined
Nov 2, 2005
Messages
224
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1
Location
Lancaster, PA
Website
www.gvpencheff.com
I was at Hollister's sawmill today picking out some big fat pieces of kiln dried cherry and walnut to practice my bowl and box making. When I told Bob I was gonna use the stuff for bowls he asked me if I'd ever "turned green." Well, I actually did one time on a whale watch when the sea was really rough, but that's another story. I told Bob I've been hesitant to try turning green wood so to convince me what fun it is he gave me a great honkin' big cherry slab that was in the cutoff pile. Enough material for 2 8" x 4" bowls. Free is good.

As usual, I learned some good lessons and have rather open ended question.

Lessons learned:

1) If you use a regular compass to draw a circle on the outside face of a log when you're done at the band saw you will have an ellipse, not a circle. Duh. Should have seen that one coming.

2) If you use a brad nailer to tack some support pieces of scrap on the sides of your blank in order to level it out on the drill press table for the screw center hole, those little 18ga devils will NOT come out. They will however sheer off nicely right at the surface. Got to practice some good vocabulary words over that one.

3) Do what you can to eliminate out of balance problems before you chuck that baby up on your not-bolted-down-yet-cause-you're-too-busy-turning-stuff lightweight little midi-lathe. Unless of course you enjoy watching machinery dance.

4) Put a good coat of paste wax on the ways before you start turning. Or just plan on getting out the rubbing compound afterwards. It is simply amazing how fast bare steel can oxidize, ain't it?

5) Just like the Canyon River Rapids at Hershey Park you will get wet on this ride.

Like I've read in all the forums, web pages, etc I roughed out a bowl, left the sides and bottom about 1" thick. It's in a plastic bag in the shop.

Question: What's my next step all you green turning gurus?

Greg
Lancaster PA
 
Take it out of the plastic bag and put it in a paper bag. You want to slow down the drying process, not stop it. It will just get moldy and rot if left in the plastic.

Mike
 
Looks like you're having fun learning! I turn almost every wood green - it's softer and self lubricating from the sap.

When turning green, there are 2 ways to go.
  1. Turn it thick as a roughout, and return it later (weeks or months) when it dries
  2. Turn it real thin to the finished thickness and let it dry and warp.

There is never one right way to go. My preference is to make roughouts and return them once dry. To dry them I use Anchorseal. Do a search in this forum to read all about it.

I can't tell if you have a chainsaw from your posting. Usually I slice a log in half with the chainsaw. Then on both flats I use a compass to draw the circle. Then the 4 corners get lopped off. You could also use this technique on a bandsaw if you are careful while slicing thru the log.

Also I generally stand to the side when doing the initial roughing. But you're going to get some spray anyhow, and it can easily be cleaned off the faceshield.
 
Some things I do to help.

Use a scrub plane or scrub and block plane to get a level and sufficient surface to reference on the bandsaw table.

Use a circle-cutting jig to reduce sideloads on the blade.

Tilt the table and nibble off the ends which will be turned away anyway to help with balance before mounting to the lathe.

Use the tailstock as long as possible.

Stay out of the throw zone when cutting. If you're getting water in the face, it could as well be bark or splinters. If you’re not there, can’t hit you.

Guard all other iron in the shop when cutting green. Not just acid water in the throw zone, but a neglected chip on the jointer table can do some creative things for your vocabulary.

Start with science to help you decide how thin or thick to cut, and how to control relative humidity. http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/ch03.pdf Is both free and informative.

The ten percent "rule" is bunk, as is the inch per year "rule." Reality is that endgrain dries ten times or more faster than face grain, and no part of your bowl is likely to be more than an inch away from open air via endgrain. Use Table 3-5 to determine wall thickness. Since radial shrinkage is the predominant one in a face-grain bowl (Figure 3-3), you can add half the radial shrinkage value to your desired final wall thickness for best drying. Remember, twice as thick, three times as long drying.

Since the fall to the FSP (Fiber Saturation Point of ~30%) is without distortion or drying damage, getting there quickly is a no-brainer. Spin excess moisture out, or blow it out with compressed air, then sit the piece in open air until the surface appears dry before taking secondary measures to control relative humidity.

Get a hygrometer for your wood area, and use it to help you decide how aggressively you need or want to control relative humidity. Could vary from doing nothing, as I do, to tenting with newsprint, bagging in paper, painting with wax, or more extreme. Use Table 3-4 as your guide to control moisture loss, and weight with 3-4 to determine moisture content.
 
Roughout #2

Everyone, thanks for the input and feedback. I took my first blank out of the plastic bag (thanks Mike) and not having a paper bag just left it on the bench overnight. As an experiment I weighed the thing on a triple beam balance before going to bed. 544 grams. This morning it weighed 529 grams. Whoa... some serious moisture loss going on here. I saw no evidence of an impending crevasse so I left it on the scale and checked it intermittently all day between sessions of grocery shopping, leaf raking, doing laundry, going to the gym etc. It appeared to be losing a gram every time I checked. So, still not having a paper bag, I wrapped it up in a bunch of paper that Woodcraft so thoughtfully provides as packing material. That was around 1:00 this afternoon. I just checked again (8:32pm) and it now weighs 519 grams and is obviously still losing moisture. So can I keep weighing it periodically and assume it's reached equilibrium when the weight loss bottoms out?

I cut the second and considerably thicker bowl blank out of the remaining chuck of cherry slab this afternoon and am happy to say my second effort went much better. Instead of using a compass I cut a circle template out of crap (no typo) 1/4" plywood and traced that in chalk on top of the blank, got a nearly perfect circle. I skipped trying to use the drill press and simply used a power drill and jig to drill the hole for the worm screw. Dragged out my old SCVLPTVRE ASSOCIATES chisels from my one sculpture class in college and wonked off the majority of the overly thick portion of the face to balance it. Chucked it up, stood well back and tripped the power. Hey... not bad! Not bad at all. Minimal shake-rattle-and-roll. I was able to true it up and rough out the center with a minimum of fuss. Much muss however because in spite of my application of copious amounts of Simonize paste wax to the ways last evening they once again showed signs of rust when I cleared away the detritus. Ick. Okay, so it's a cheap little chinese lathe but still, rust on machinery is the big shop no-no. Had to clean that mess up all over again.

I'm still unconvinced. It is satisfying (see also: FUN)to apply a gouge to the face of that spinning chunk of green wood and watch the shavings literally stream off. I observed that I can really plow into the middle of the thing, even with my underpowered little midi lathe, and remove a lot of material quickly. On the other hand it makes a real mess, creates rust on my machinery and now I have to wait weeks (or months) to finish what I started. And then I'll still be turning dry wood. I could have started with a dry chunk of cherry this afternoon, be shooting coats of semi-gloss lacquer on it this evening, and skipped the de-rust-and-wax-the-ways session altogether.

Somebody convince me.

Greg
Lancaster, PA
 
If you don't have a paper bag, wrap it in newspaper. Leaving it out unprotected is risking cracks.

OK, maybe this will convince you. How much do you pay for kiln dried cherry? Wet wood is free for the taking. Also the selection of wood species and sizes is much broader. Just try getting dried box elder. And then there are burls. I never heard of a kiln dried burl.

I never worried about a little rust on the lathe. It just shows the tool is used. Besides a little wd40 and scotch brite pad cleans it right off.

Mike
 
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