Sanding green wood?

[Nathan Roper]

I turned a bowl out of some green sycamore that ended up being about 11" wide and 4' tall. I decided I didn't want to wait a year for it to dry so I "finish" turned it from the get go kind of expecting it to blow up while drying. I did do a little bit of sanding on it while it was still in the chuck and actually put some tried and true original on it as well. Ten days later it has warped but not blown up. I quiet like the look of it still despite it being a bit oblong and know I could have done better with my sanding/finishing.

When you turn a green bowl just once and expect it to move when do you sand it? Do you do that while its green or do you wait until its dry and sand it on the bench? I don't have enough meat to true this bowl back up, the tenon or the rim. Jam chuck maybe?

I appreciate any advice.

This is right off the lathe. I'll have to take another picture tonight showing its new shape.

 

[Dave Landers]

If I turn green-to-finish, I plan on the thing moving and let it happen - it is thus part of the design/intent. Important thing (which it appears you did from the photo) is having a consistent (and not too thick) wall thickness (that evens out the stresses and reduces the chance of cracking).

Sometimes, as you turn it, the surface will dry out enough that you can sand right away, or at least get thru some coarser grits. But usually the water just clogs up the sandpaper and you just have to wait.

After the bowl dries, it likely won't be round so sanding with the lathe running is mostly out of the question. You can power sand with the lathe running really slow so you can "follow the shape" (my lathe's slowest speed is 50 RPM, which can be too fast sometimes, depending on the size/warp/etc), or else with the lathe off and move it around by hand (holding the handwheel in one hand and a sander in the other is somewhat of a trick), or just sand on the bench (either with power or by hand).

 

[Vincent Vogel]

I just made a once turned live edge walnut bowl. I sanded it the same day because of the warping reasons Dave talked about above. I used abranet mesh paper and it really worked good on the wet wood. This was my first try with the abranet so it was an experiment and worked good. I'm sure it has warped in the past week but you can't tell because of the shape of the bowl, it's an oblong one. I power sanded the bottom with lathe running and did the wings with lathe stopped.

 

[hockenbery]

I sand off the lathe after the bowl has dried ( 3 days) using a 90 degree drill and 3” Velcro discs.

Exceptions ar3 any groove or bead detail. Those I sand on the lathe with abranet to 320.
Those details would be messed up sanding off the lathe.

 

[Kirk Amidon]

I've wet sanded on the lathe right after turning, which is ok - generally do this only with the coarser grits down to say 180 or so. Using water as lubricant reduces the clogging of the paper - have not yet tried abrnanet, but in theory that should be a good approach also. Still find a need to sand off the lathe in a few days/weeks/when I get around to it. The warping with once turned bowls is part of the charm, for sure.

 

[hockenbery]

If you sand wet wood abranet works well. It is a mesh abrasive.
If it clogs tapping it on the tool rest usually cleans it.
With stubborn clog you can soak it in water and the tap it clean. Use two pieces alternating between using and soaking

I have 3” wide rolls of Velcro abranet from turningwood.com that I mount on mandrels as squares.

 

[Nathan Roper]

This is all great info thanks. I've got the woodturners wonders angle drill super dee duper sanding kit coming in the mail and will do my second sanding round when it arrives. We'll see if I can find a few minutes to turn something else this weekend.

 

[robo hippy]

Most of my bowl turning is green wood. I have found it easier to sand when the bowls are dry. The problem is that you need a lathe with speeds down to 15 or less rpm. Anything over that, and you can't keep the abrasives on the wood as the lathe spins. My old PM 3520A would go that slow. My Robust would not, and I had Brent walk me through the process of making it go slower. I have a Vickmarl 240 with the pivoting headstock, and it will go a bit slower than the 15 rpm. The concerns from the manufacturers is that at the slow speeds, the motor might overheat. That was the reasoning for many going up to the 50 rpm shut off speed, and some are higher than that. After adjusting the speed range on my Robust, I was cautioned by Brent about the motor getting warm, so would constantly check it with my hand. Turns out that it runs cooler on idle speed than when I am turning bowls. When I turn, I make my lathes work hard. I tried wet sanding once or twice, and just didn't like it. Far easier to sand when dry, if your lathe will go that slow.

I did make an articulated arm for sanding, and need to update that video to show it in use. 2 segments to the arm. What it does is allow me to rest my drill holding arm on it while I sand. Amazing how much that reduces your work load since you only have to squeeze the drill trigger. A side benefit is that I can spin the bowl with one hand while the other holds the drill. This is pretty much how I start all of my bowls now, hand spin it through the coarser grits, 120 or so, and then once all marks are cleaned up, I turn the lathe on.

robo hippy

 

[Dean Center]

Nathan,
In arid Utah, your bagged green bowl will dry enough for sanding much quicker than Al's bowls in Florida. If it's not ready as soon as you finish turning, put it in a paper bag to slow the drying and reduce the chance of cracking, and probably the next day, maybe 2 days, you'll be able to sand. Slowly, if on the lathe, as mentioned above. Catching it as soon as the surface is dry means it will be easiest to sand. If you wait too long, it'll be fully dry and at maximum warp/oval and maximum sanding challenge.

Are you related to the Infamous Roper from west Denver?

 

[Doug Freeman]

I sand once turned bowls after they dry. I leave the tenon on. Sometimes the dry tenon needs rounded, sometimes not. Mount in the chuck and turn by hand using a close quarter drill and/or 2” ros. Takes a bit of practice but works far better than sanding off the lathe for me.

 

[Nathan Roper]

Thanks again for the additional comments.

After work yesterday I moved the belt to the slowest setting and chucked up a smaller bowl, maybe 5" wide that I had turned about the same time as the one shown above. It had warped less but was still oblong. I got it chucked as well as I could on the now oblong tenon and turned the lathe on at that slow speed. I sanded it a bit with hand held paper. I went through the grits and it went pretty well. There is an area right near the lip on the inside that doesn't transition real smooth and thats still there but I didn't have much time to finesse it and just wanted to see how it would go.

Looking at the manual I think the slowest speed mine will go to is 178 rpm which is way higher than what you all have recommended I sand at. I'm also certain you would caution me against chucking to the oblong tenon as well. I need to figure out a jam chuck but these tenons are also small enough that if I was to turn them back round I'm not sure they'd be big enough to fit in my VM120 chuck with the stock jaws. I've just bought another chuck and the VM multi step jaws (name?) but I had been turning my green wood to a real small tenon as I had misunderstood some things from a youtube video... .

I was hoping to give some bowls away to a few good friends this holiday and obviously don't have the time to wait for "proper" twice turned bowls. I also do like the character of these oddly shaped bowls.

@Dean Center yeah, without any humidity things do tend to dry out real fast here. I probably should do some weight comparisons from right off the lathe to a few days later but I haven't gotten that far. It would also be nice to check them with a moisture meter but I don't have one of those and don't know anyone here locally with one.

 

[Dave Landers]

There is an area right near the lip on the inside that doesn't transition real smooth and thats still there but I didn't have much time to finesse it and just wanted to see how it would go.

Yeah, once a bowl goes oval, it can be difficult to sand near the rim - usually gotta just turn off the lathe and do that bit by itself.

Looking at the manual I think the slowest speed mine will go to is 178 rpm which is way higher than what you all have recommended I sand at. I'm also certain you would caution me against chucking to the oblong tenon as well.

I'd say if you can keep the sandpaper on the piece as it spins then it's probably ok. If you're "catching air" or like hitting the moguls hard, then too fast - you'll end up making flats and leaving some spots un- (or under-) sanded.

As to the tenon, probably ok for sanding, as long as the jaws are grabbing - sanding shouldn't result in a lot of force. One thing you can do is make sure the widest spot falls between the jaws (align the gap with the oval) which at least helps all 4 jaws get an equal grip.

 

[hockenbery]

. I need to figure out a jam chuck but these tenons are also small enough that if I was to turn them back round I'm not sure they'd be big enough to fit in my VM120 chuck with the stock jaws.

For the next bowl… I make my tenons about 2.5” in diameter the standard 120 close to 48mm perfect circle diameter

A 2.5” tenon always dries with a 48 mm tenon inside the oval.

 

[John Walls]

When I green turn wood, I get close to final shape/size. Put in micro-wave for a minute, remove, let cool for 5 or so minutes, then nuke again for 60 seconds. After a short cool-down, back on the lathe, final cut if doing one then sand. It's fairly dry by then. I've stock-piled a lot of blanks for turning so I don't turn green much anymore. I also green turned a lot of bowls, left about an inch thick and put on rack in house for a year. They warp a little but by the time dried, still able to turn a bowl out of them.

 

[robo hippy]

Well, when sanding your bowls, you don't need the grip that you need for turning. Much higher forces at work when turning and roughing out bowls. For my warped bowls with a recess, the oval shape they take is generally pretty uniform, and with extended jaws, and a little wiggling around, I can get all 4 jaws into good contact for sanding. I would expect the same for a tenon. When sanding, slower speeds, both with the drill and the lathe, will yield faster cutting with your abrasives. With high speeds, it is kind of like a dragster. You need traction for best results. If you are going too fast, the abrasives don't really get a chance to dig in and cut.

robo hippy