Kiln dried ash movement

[Terry Vogel]

Using 8 quarter (two inch thick) kiln dried ash.
Turning blank is made from two pieces, from same board, edge glued to form a 16x16 square two inches thick.
Mounted to lathe with Supernova 2 chuck using woodworm screw.
Turing a platter.


I am encountering a confusing problem. As I try to flatten one side of the blank, it seems to be moving nearly as fast as I can cut it.
Instead of a nice FLAT surface after using a 1/2 inch bowl gouge I keep having to re-flatten. Its almost as if the piece has been remounted over and over between cuts.
The piece is tightly mounted, it doesn't wiggle. The chuck is tightly screwed onto the spindle, the woodworm is screwed tightly into the blank.
Turning at 500-600 rpm.
Even using a very light shear cut I experience heavy chatter and can't seem to keep the piece in plane, if you get my drift.
Have never encountered anything quite like this.
Has anyone else experienced something similar?
It must be something I am doing wrong, but i can't figure out what it might be.

[Mark Greenbaum]

Do you still have the xorners on the 16" square? Or has it been turned or sawn to a disk shape? If corners still on - perhaps the extra material at the corners is trying stretch(/) the wood from centrifugal forces? Try a sacrificial glue block instead of the worm screw. That would take the possible screw wobble out of the equation.

[Reed Gray]

Well, several things could be going on. My first suspect is the worm screw. For a platter that size, the screw will work, but you want really wide jaws on your chuck, the largest possible, say 3 to 4 inches. If the surface of the blank is not dead flat so it sits snug on the chuck jaws, that adds to the wobble. My big Vicmark has 2 5/8 inch jaws and I would drill a recess deep enough for the blank to sit on the face of the chuck. This is a bit on the minimal side. Mostly this will provide a longer lever/bigger surface to register against. If you only have 1 1/2 inch wide jaws, that is a very small lever to stabilize a 16 inch platter. Face plate would work better. This of course is for turning the bottom and outside of the platter. To turn the inside of the platter, my 2 5/8 Vickmark would be kind of minimal for 16 inches in a recess, but I might be able to get away with it, mostly because of my skill level. Since the foot of a platter is larger than what you would use on a bowl, a 3 or 4 inch recess would be much more stable. For a tenon, you would want at least 4 inch diameter. Oh, just tightening the chuck more will not help.

Other than that, having a tailstock up against it helps. Make sure all the jaw screws are tight. Make sure the lathe headstock is secure/tightened up if you pivot it or slide it.

I would expect the ash to move a little bit, but not as much as you described.

Oh yea, when you turn out the inside, the shallower form, when compared to bowls, will want to vibrate more as you hollow out the inside. Do it in stages of about 1 inch or so at a time. When you go to stage two, turn down another inch, and then blend in the start/stop line with a shear scrape, or a NRS (negative rake scraper). Once you go to stage two, you can not go all the way back to stage one.

robo hippy

[Prashun Patel]

I suspect vibration not wood movement.

Are the set screws on your chuck tight?

I get vibration when using smaller jaws even on 8" pieces. Can you use a face plate?

[Jason Edwards]

Agree with the mounting comments and also note that just because you bought it as kiln dried does not mean it is really consistently dry throughout the board. 8 quarter is pretty thick and moisture differences throughout the board are to be expected and the center of the board may be quite a bit wetter than the the surface. As you cut through the dry wood into the wetter wood movement would be expected.

[Leo Van Der Loo]

Using 8 quarter (two inch thick) kiln dried ash.
Turning blank is made from two pieces, from same board, edge glued to form a 16x16 square two inches thick.
Mounted to lathe with Supernova 2 chuck using woodworm screw.
Turing a platter.


I am encountering a confusing problem. As I try to flatten one side of the blank, it seems to be moving nearly as fast as I can cut it.
Instead of a nice FLAT surface after using a 1/2 inch bowl gouge I keep having to re-flatten. Its almost as if the piece has been remounted over and over between cuts.
The piece is tightly mounted, it doesn't wiggle. The chuck is tightly screwed onto the spindle, the woodworm is screwed tightly into the blank.
Turning at 500-600 rpm.
Even using a very light shear cut I experience heavy chatter and can't seem to keep the piece in plane, if you get my drift.
Have never encountered anything quite like this.
Has anyone else experienced something similar?
It must be something I am doing wrong, but i can't figure out what it might be.

In my opinion the backing that your jaws give to this 16” size blank is not adequate, also might it be possible that the Nova woodworm screw might rotate in the jaws ??

To compare this with a tenon, one should have a larger tenon than a 2 inch one for a 16” blank, as that is about all the jaws are supporting against the back of the wood, the leverage of that big a blank against such a small area would make it certainly possible to move the wood in and out even compress the wood against the jaws small surface area.

I would use a 5" or 6” faceplate, glue a waste piece on if you don’t like to use screws in the blank, anyway that is my opinion on this problem.

[John K Jordan]

I and others have turned plenty of 2" blanks larger than that using the wormwood screw held in a chuck. It should work fine. What size jaws? For a bigger platter bearing against bigger jaws can help.

Are the jaws bearing against a flat surface with the hole drilled perpendicular? And the right sized hole? (not too loose) If the blank needs to be flattened to fit perfectly you can use a hand plane. Or cut a temporary recess on the bottom to hold with the chuck, flatten the face, then mount on the screw chuck. Then recut the recess true while shaping the bottom.

It does sound like something is moving. I can't imagine the wood in a 2" thick platter blank moving enough from humidity change to do what you describe (assuming the wood is good and dry and it wasn't glued up just this morning). Movement from relief of stress could do it but that's usually only after cutting away a bunch of wood. Also, is the blank relatively balanced or way out of balance? If out of balance from the corners or off-center mounting you could draw a circle while it's on the lathe then round with the bandsaw. But this shouldn't matter at a low speed on a sturdy lathe. Frank Penta's off-center platter base design is way off center on purpose - the times I turned platters like that was with 2" thick sapele and it turned smoothly. I have never tried an Ash platter but no problems with other things turned from Ash.

Just guessing here, without seeing it in person.

JKJ

[Terry Vogel]

Further information:
Using SuperNova2 chuck with 100mm jaws (4 inch)
Blank was round to start, cut on bandsaw using circle jig.
screw was tight, blank did not move at all once tightened. Used recommended 5/16 drill bit for screw hole.
blank was glued up and left to cure for a week before turning. glue was yellow pva tightbond (don't recall which version)
I don't have a moisture meter, but the wood never felt cool to the touch, as it might if wet it was wet enough.
After reversing (turned bottom first, with recess for jaws cut properly) put in on the chuck, tightened it well, brought up the tailstock and set it close and tight too.
Same issue with the cuts.
??????????????

[Justin Stephen]

I had a piece of anigre that did this to me sometime back, similar thing, a larger 8/4 platter blank. I was using a faceplate. I just could not get sustained clean cuts to true up the blank. I "solved" the issue by truing the blank with a carbide tool.

Try forcing the issue with a carbide rougher or a scraper, just trying to get the thing true and not worrying about surface quality for now and see if it still moves on you after that.

[Dale Miner]

Further information:
Using SuperNova2 chuck with 100mm jaws (4 inch)
Blank was round to start, cut on bandsaw using circle jig.
screw was tight, blank did not move at all once tightened. Used recommended 5/16 drill bit for screw hole.
blank was glued up and left to cure for a week before turning. glue was yellow pva tightbond (don't recall which version)
I don't have a moisture meter, but the wood never felt cool to the touch, as it might if wet it was wet enough.
After reversing (turned bottom first, with recess for jaws cut properly) put in on the chuck, tightened it well, brought up the tailstock and set it close and tight too.
Same issue with the cuts.
??????????????

Kiln dried does not equal 'no internal stress'.

I didn't catch how much stock you have removed from the thickness, but it is very possible (likely) that as you are removing stock, the internal stress is being relieved and allowing the wood to move.

[Brian Tymchak]

Kiln dried does not equal 'no internal stress'.

I didn't catch how much stock you have removed from the thickness, but it is very possible (likely) that as you are removing stock, the internal stress is being relieved and allowing the wood to move.

It might be that the board was case hardened during drying, dried too quickly. The outer portion of the board is dried but the interior is still quite wet.

[Leo Van Der Loo]

Further information:
Using SuperNova2 chuck with 100mm jaws (4 inch)
Blank was round to start, cut on bandsaw using circle jig.
screw was tight, blank did not move at all once tightened. Used recommended 5/16 drill bit for screw hole.
blank was glued up and left to cure for a week before turning. glue was yellow pva tightbond (don't recall which version)
I don't have a moisture meter, but the wood never felt cool to the touch, as it might if wet it was wet enough.
After reversing (turned bottom first, with recess for jaws cut properly) put in on the chuck, tightened it well, brought up the tailstock and set it close and tight too.
Same issue with the cuts.
??????????????

Wel it looks like you used larger jaws as backing up the blank and those should be large enough, the question then becomes does the change in flatness happen to be on the ends of the pieces glued or the side of those, meaning could the glue joint give or is the long grain moving ??

what size lathe are you using and are the bearings tight and not so close together that the spindle is able to move because of bearing clearances.

Something has to be moving, if it isn’t the wood, which I doubt is it is still a thick slab, then it got to be either the mounting or the lathe components, like a rotating or sliding headstock that is able to oh so slightly move.

Maybe a steady rest can help preventing the piece from moving if that is what is causing this movement, rather than the wood itself.

[John K Jordan]

Reading your original post again - you said you get "heavy chatter." Since you are sure the blank is securely mounted, could simple chatter itself be the issue? Kiln dried Ash is quite hard and coarse grained compared to some others - do you usually turn dry or wet wood? (I almost always turn hard, dry wood.) A light shear cut could still chatter wildly until an irregular surface is well smoothed. Tool grind, tool size, grip and stance, presentation, tool overhang, and even tool rest flexing can contribute to chatter.

What tools and types of cuts have you tried? If you haven't tried this with your platter blank, you might try a shallow facing cut with a sturdy (and very sharp) bowl gouge. If necessary, first cut a shallow flat-bottom recessed ring on the face near the outside diameter (with a parting tool, perhaps), down below any surface irregularities. Then, with the bowl gouge bevel riding in the flat, rotate the tool slightly CCW and very slowly and gently guide the gouge forward just as with a normal platter face or making a finish cut on the inside of a bowl. This should cut away any irregularity on the face of the blank and leave it perfectly smooth (although not necessarily flat!) with zero chatter. (IF the problem is simple chatter)

I apologize if this sounds too much like basic Platter 101 instruction or this has already been addressed. I don't know your level of experience and didn't study all the posts carefully. If it is truly chatter instead of something else, that one cleanup cut should fix it. (A less elegant way might be to use brute force and flatten the face with a flat carbide tool, a wide parting tool, a bedan, or a relatively narrow or curved flat or negative rake scraper - but none of these will work if the problem is not simple tool chatter.)

JKJ

[Reed Gray]

Hmm, if the blank was spinning true when you turned the outside, and was pretty true when you reversed it, and you only got chatter when turning the inside, the only other thing I can think of is too much bevel rub. Tendency is that when you get chatter, you clamp down on your tool, which only makes chatter worse. "Hold the sword as you would a bird. Too tight and you kill it. Too loose and it flies away."

robo hippy

[Mike Peace]

Teknatool 4" jaws? My understanding is that the woodworm screw only fit with the 50mm jaws and the Powergrip jaws altho the powergrip uses a longer ww screw. Wonder if that could be the problem?

[Terry Vogel]

Finally got a chance to get home and back in the shop.
Spent a lot of time looking at the workpiece and thinking about all of the hints and suggestions.

Decided to give it another go.
There was plenty of material left to remove (design opportunity?) so I chucked it up and applied a freshly sharp 5/8 bowl gouge to it. After a few minutes I decided to switch to a round carbide cutter from Easywood (home grown tool shaft, only the cutter was theirs). Trued up both sides, took a while since I took VERY light cuts, nice wispy curly tiny shavings. The piece was definitely NOT true when I started. It was when I finished. I had to step away for about an hour and when i got back to it, it was back to NOT true. When spinning slowly I could see the rim was way out of true again.

So i did what any stubborn old man would do, I trued it again! Then I set the tool rest parallel to the bed and right up next to the rim. I put a piece of tape on it and marked where the trued rim top and bottom were. I left it for a couple of hours and came back to it. Out of true again.

I left it for a couple of days, still chucked up and on the lathe. When I came back to it I expected to see it still out of true. My mistake, it had returned to true all by itself !?!? This piece of wood has a life of its own!

My observations on the chatter I was getting. The difference between hard and soft was dramatic. I suspect that the tool would catch on the very hard portions and dive into the softer, even with fairly light cuts. In order to succeed I was forced to barely shave it. Only with the lightest cut I could manage did I get a decent result. I have turned ash before, but never with this much difference between hard and soft.