any tips for turning air?

[Brian Brown]

I, going to try a piece today that will be slightly out of balance, and has voids. I can usually keep the vibration down to a minimum, but am worried about the voids. In the past when I have "turned air", the tool bounces when it contacts wood vs air. This causes a deeper cutting action where it leaves the air, and contacts the wood, and can cause some increased vibration. It also can cause an uneven thickness in the piece, at the leading edge of a void. Do any of you have some magic way to keep the tool the same depth so the cut is not uneven? Would a pin in the tool rest to brace the tool against help? Any other thoughts?

[Steve Schlumpf]

Brian, I am sure everyone will have something different that works for them, but for me, I find a slightly higher speed and a slow 'feed' rate works best. The higher speed reduces the amount of time your tool is cutting air and the slow feed rate ensures that you do not push the tool forward while it is in the void. Just takes some practice but the key to the whole thing is to take your time and don't push the cut!

[daryl moses]

I agree with Steve, speed and a light touch is your friend when turning air.

[John K Jordan]

Sharp, sharp, sharp! Light cuts! I use my hand to "pin" since tiny adjustments need to be made constantly. I press the tool into the rest with the left hand to keep it stable. I'm careful to support my right arm against my side. When entering a cut from air, such as in square or winged pieces, I like up the gouge if possible on solid wood, slide forwards and backwards adjusting until it is JUST about to make a "whisper" of a cut, then back out and try to hold that same angle for my air cut.

Also, keep the heel of the gouge from rubbing and bouncing on the work. Many people, including me, grind away the or round over the heel and leave only a short bevel, maybe only 1/8" or so. Grinding away the heel prevents burnishing defects on normal work but I find it can help with bouncing on air cuts. And as Rudy Lopez said in a recent demo, don't "rub the bevel" but "float the bevel"!

I don't fret about tiny ripples left on the wings - I just take them out quickly with curved cabinet scrapers with the lathe stopped. Way better than sandpaper.

Edit: And I just read where others suggested higher speed and slow feed rate - absolutely! Of course, that is almost always the key to perfect finish cuts. I turn most of my smaller things at 3200 rpm, other things as fast as I dare. Jimmy Clewes turns up even fairly large winged pieces so fast it sounds like plane taking off. I've seen people in the line if fire slide their chairs over and lean out of the way!

JKJ

[Keith Pleas]

I'm not a turner, but this really sounds like an abrasion action would be better than a cutting action

[Terry Vaughan]

Yes speed should be as high as is safe. Things to try: It is possible to use balancing weights to cut vibration and enable higher speed. A pin in the rest does help a lot to control the tool but restricts movement and forces you to work in small steps. Make sure the tool is sharp and that the bevel doesn't get knocked back when the wood comes to it. Lift the handle very slightly so the bevel is just clear of the wood. Press the tool down onto the rest if necessary, not against the wood. Focus on moving the tool along its planned path, pushing in that direction only.

[Reed Gray]

This can also be where the 'Hold the sword/tool as you would a bird. Too tight and you kill it. Too loose and it flies away.' comes in handy. You don't want the white knuckle grip. That actually makes your tool bounce more. It does take practice to learn to be able to do smooth cuts on open wood forms. Just one hole, not bad. A rectangular bowl, much more difficult, but generally the wings are all the same distance from the center. Natural edge bowls can vary from simple to you've got to be crazy....

robo hippy

[Ken Fitzgerald]

You have gotten some pretty sage advice! Faster speeds reduce your air time.....sharp tools......light cuts........don't be overly aggressive with the feed or the tool hold!

It takes a commitment!

[Brian Brown]

I will try to balance better. I get nervous turning faster because the vibration gets word. Better balance, less vibe. Last time I tried it, my tools may not have been as sharp as they could be. I'll try some of your suggestions. Cover me, I'm going in.

[Ken Fitzgerald]

Brian,

One last thing to remember, as you turn the piece, it will become more balanced. So, you should experience less vibration as you continue to turn.

[Terry Vaughan]

You will find it difficult if the lathe is vibrating. Spin the work fast but not enough to start it shaking.

[John K Jordan]

Just to be clear for the OP: There are two completely different things discussed in this thread.

One is a balanced piece that has air to cut. (for example a square, triangular, or rectangular shape) The other is an unbalanced piece that has air. (for example, a chunk not yet turned round, an unbalanced natural edged piece, or a heavy piece unbalanced by natural voids)
My opinion:
- The balanced piece can be spun very fast.
- A light-weight but unbalanced piece MAY be spun reasonably fast.
- A heavy unbalanced piece cannot, for both mechanical and safety reasons.

JKJ

[Terry Vaughan]

You are right, John. That's why i said as fast as is safe. The faster the piece spins, the easier the cutting, but the greater the potential for it breaking up. Centrifugal force, a dig-in or accidentally poking the tool into the air gap could blow up the piece. A natural void is a warning sign - it's always a weak point, and may connect to hidden cracks or bark inclusions. Cutting the wood too thin away from the edge can weaken the structure. There is always a judgement to be made. The turner always has to keep the piece under review and use caution and common sense (and a face shield!)

[Adam Wager]

This one might be obvious, but I have found it helpful to make sure there is a good contrast between the wood color and the background along with good lighting, especially when the air is near the rim of the piece. You aren't turning air, you are turning the ghost of the wood that used to be there.

[Larry Matchett]

A B C
The principal is anchor, bevel, cut.
The first is the most important. I think John said press down on the tool rest with the tool. Essential. Your too should never ever bounce. Then kiss the piece with bevel of the tool. Once again it should never ever bounce. Then cut. As has been said over and over again light cuts. I too agree as fast as the piece will allow. The faster the piece turns the less time between wood and air. Hopefully you are not turning something that has more air then wood. Stay out of the line of fire and check often for cracks. Wear a good face shield and maybe even a glove on the tool hand. You never know it might blow up. Turning pieces with voids and cracks is not for the faint hearted. Don't mean to scare you but take every precaution.

[John K Jordan]

A natural void is a warning sign - it's always a weak point, and may connect to hidden cracks or bark inclusions.

Here ya go - void, bark inclusion, hidden cracks, and turning air on the corners. This one came apart on me several times while turning. I was prepared and stood to the side. Finished it with stubbornness + glue.

Wear a face shield.

331134

JKJ

[Olaf Vogel]

This one might be obvious, but I have found it helpful to make sure there is a good contrast between the wood color and the background along with good lighting, especially when the air is near the rim of the piece. You aren't turning air, you are turning the ghost of the wood that used to be there.


Good point. I try to position the light to get the best shadows.
Then take really light cuts, from the inside outwards. I use a medium gouge, with a very high angle of attack. So the cuts slice, and don't contact hard.

This one was fun.

331149

[Terry Vaughan]

On shaped pieces it can help to chalk the corners so they are visible when spinning. And you can chalk the toolrest where cutting will start.

[Keith Pleas]

Nobody commented on my (naive) idea of abrading - either a rasp or, more likely, sanding. I know you guys power sand on a lathe - why wouldn't that be a good idea on the thin rims of bowls with the "ghosts" of the wood? Almost by definition it would limit the depth of cut. Is it a principal kind of thing where you try to do everything with a blade? I'm genuinely curious. I love sanding (with Abranet, quiet sanders like a Mirka, and excellent dust collection) and how controllable the process is.

[Reed Gray]

To the A, anchor the tool on the tool rest part, to me, this is still 'hold the tool as you would a bird'. The spin of the wood will keep the tool on the tool rest, and you just rest your support arm/hand on the tool, don't push down hard.

robo hippy

[John K Jordan]

To the A, anchor the tool on the tool rest part, to me, this is still 'hold the tool as you would a bird'. The spin of the wood will keep the tool on the tool rest, and you just rest your support arm/hand on the tool, don't push down hard.


I mostly agree with this, and I usually hold the tool lightly. But if there is bounce, vibration/chatter on almost any tool, even a skew or a scraper, one thing I try besides a stouter tool is pressing the tool a little firmer onto the rest and this often helps. I have never found a need for the 800 lb gorilla death grip but when moving the tool from the air into a spinning winged piece I do better if I consciously anchor the tool on the rest. Maybe just remembering to think about it is enough.

It would be interesting to somehow quantify the exact force different turners use for different cuts. Ah, I can see it now - instrument the tool and rest with accelerometers and static force sensors, tracking movement and pressure in each axis, synchronized with a video. See how we do things differently with spindles, hollow forms, roughing big chunks, etc.

JKJ

[Reed Gray]

Well John, I am still learning... It has taken me a long time to learn to feel on spindles when the tool and bevel pressure is greater than the stabilizing hand pressure. I use the same exercise when turning the inside walls of a bowl. When going down the outside of the bowl, with a bevel rubbing cut, you always pick up some bounce, which I figure comes from grain orientation. The more I fight it, the worse it gets. I get much less if I go gently, and with almost no downward pressure on the tool rest or bevel. Pretty much the same seems to apply to unnatural edges, though I need to do some more of them. Haven't tried it in a while...

robo hippy

[Keith Pleas]

Would someone take a second to answer my question about abrading over cutting? Pretty please? ?

[Ron Rutter]

Would someone take a second to answer my question about abrading over cutting? Pretty please? ?
If you are talking about abrading with the machine running, it doesn't work out that well! How do you hold the abrasive just the right distance from the work?( if natural edge) How do you stop the abrasive from rounding of the corners of the work at the incoming point of contact? Bringing a blank into round would be a very slow, frustrating process i think! How do you get the precise shape you desire??

[Jamie Straw]

I will try to balance better. I get nervous turning faster because the vibration gets word. Better balance, less vibe. Last time I tried it, my tools may not have been as sharp as they could be. I'll try some of your suggestions. Cover me, I'm going in.

I spent some time Tuesday with an AAW mentor turning a bowl from rough stock, and one thing he showed me is how there can be low vibration at one speed, then it might get rougher at a higher speed, but turning it up a bit more things smoothed out. Harmonics I guess? So there may be more than one speed at which your bowl blank creates little or less vibration.

[BILL DONAHUE]

I was fortunate to spend a few days with Jimmy Clewes in his shop in Las Vegas and he addressed this question pretty much the same as Steve with the exception of "slightly higher speed." I had the lathe at 2000 rpm and he said "put it up all the way, mate." I asked him if he was serious. His reaction made me feel like a coward so I maxed it out. The lathe sounded like it was on the verge of achieving liftoff but with a light touch to the wood and a heavy and steady touch of the tool on the toolrest, it worked. Watch out for the knuckles, though.

[David Reed]

As with any piece without much support to the edge, I finish turn and finish sand the exterior of the piece completely before hollowing. Then hollow and finish sand down a short distance, often only one inch at a time allowing the solid wood below to provide support. Certainly doesn't eliminate the need for tool control but certainly reduces bounce and recoil from thin unsupported wood/air.

[Reed Gray]

Keith,
I am trying to figure out if you mean some thing like holding a rasp up to the spinning wood. I do remember seeing Norm Abrams on his New Yankee woodshop show, and he was turning some spindles and using a rasp. The problem with one of them, is that it may work, but hand tool skills are much better, and faster. With a natural edged bowl, you would get some flexing with the wood, and guiding a rasp would probably require a form, and I think it would be dangerous. I have heard of using some thing like a credit card with sand paper on it so it wouldn't dip in between the uneven surfaces, and you may be able to do a firm, or slightly flexible form, but a soft foam form would deform as soon as it hit the wood, so no real control there, and you would have very uneven surfaces. Not sure if this answers your question or not.

robo hippy

[John K Jordan]

Jimmy Clewes... I had the lathe at 2000 rpm and he said "put it up all the way, mate." ... Watch out for the knuckles, though.

i submit that watching out for the knuckles is just as important at 2000 RPM as wide open!

With continuous wood I think a higher speed works better because we can advance the tool a shorter distance for each revolution. For interrupted cuts, I suspect the inertia of the tool also contributes to a smoother cut at higher speeds.

JKJ

[Keith Pleas]

If you are talking about abrading with the machine running, it doesn't work out that well! How do you hold the abrasive just the right distance from the work?( if natural edge) How do you stop the abrasive from rounding of the corners of the work at the incoming point of contact? Bringing a blank into round would be a very slow, frustrating process i think! How do you get the precise shape you desire??
Yes, I'm imagining it must be controlled. I was thinking of something like a sanding block (or profiled sanding block for more complex shapes) held against a tool rest. Yes, super slow - but with all the cautions for turning that must be a slow process as well. And the point would be to reduce blowouts rather than high production speeds. By introducing the action supported by the rest I also believe that the piece would stay round.

But I could also imagine a rasp with the tip held on the tool rest and the rasp tilted to the workpiece for more aggressive removal. The "depth" of the cut (of the teeth) would be fixed.

Achieving a sharp edge to the turning would be difficult, but for measured and controlled removal of material the principle seems reasonable (to me :))

[Keith Pleas]

As with any piece without much support to the edge, I finish turn and finish sand the exterior of the piece completely before hollowing. Then hollow and finish sand down a short distance, often only one inch at a time allowing the solid wood below to provide support. Certainly doesn't eliminate the need for tool control but certainly reduces bounce and recoil from thin unsupported wood/air.
I think you are supporting my idea - am I right? I did have another thought about creating a temporary support for the void. I think it could be either inside or outside the workpiece depending on where support would be needed. It would have to be something with low elasticity otherwise the piece would be distorted around the void.