Vacuum Chucking: Initial Impressions
by Curtis Turner
Round Rock, TX
Note: Click on any picture to see a larger version.
A Vacuum Chuck is a system designed to draw a vacuum through the headstock for the purpose of holding a work piece to a lathe without support from the tailstock. Typically, vacuum chucking is used to reverse mount a bowl or platter to provide total access to the bottom of the item. There are several advantages to this system. One of which is the ability to quickly and precisely center a work piece without marring the surface. The second advantage is the ability to turn away the chuck tenon, sand and finish the piece while the piece is still held on the lathe.
I never gave serious consideration to vacuum chucking simply due to the cost. After reverse turning a variety of sizes and species of wood, I wanted to share my experience. This article is, as the title states, my impressions of using a vacuum chuck. This is not a how to guide.
I use an integrated vacuum chuck on a Powermatic 4224B, at TechShop, where I teach wood turning classes. I have used this method on numerous bowls and found it to be a superior way to remove the tenon and refine the base of a bowl.
Not only is this faster than other methods, it seems to provide a more secure grip.
This system of holding comprises several key components:
-
A vacuum drum or chuck with a gasket
-
An
Air Fitting Adaptor
to mount the vacuum drum to the head stock
-
Rotary Air Fitting
-
Vacuum Gauge
-
Vacuum Pump
Additionally, you will need a lathe with a through hole in the headstock, various hoses, and valves with lever controls.
The Process
The process generally, is after turning the interior of the bowl/platter the piece is removed from the lathe with the chuck still attached. Ideally, the live center (or tailstock) will accept a reverse turning adapter. This accessory simplifies the re-centering of the item before the vacuum is applied. The chuck with the piece still mounted is threaded onto the adaptor. The tailstock is positioned to press the piece to the non-marring gasket of the drum chuck. Then the vacuum is turned on. Once the vacuum is engaged the chuck can be removed leaving the pieced centered and held by the vacuum. If you don’t have this adaptor, you can still center the piece by aligning the live center with a divot left in the center of the tenon.
This alternative method takes more time and requires adjustments by hand to center the bowl.
The Powermatic 4224B has hose mounted to the headstock which is connected a rotary air fitting (o-ring sealed) that is inserted to the outboard side of the headstock. Another hose and an adaptor is connected to a compressor. This feeds a pump mounted in the headstock. A dial gauge and switch are mounted to the headstock.
The vacuum is then "pulled" by opening a valve creating the suction (with your compressor turned on). It could not be simpler. Other methods will of course vary.
Once the piece is secure, the tenon can be confidently turned away, decorative details can be added and final sanding can be completed.
The piece can be removed from the drum chuck by switching off the vacuum pump. A word of caution: you must hold the completed piece prior to turning off the vacuum. The piece will fall onto the lathe once the seal is broken.
Chucks, which are typically milled from aluminum,
are available in several different sizes
. I have found the 6" size to be ideal for my needs.
The diameter of the drum will dictate the size of bowl/platter you can reverse chuck. I have yet to try this but, turning spheres could be simplified with a vacuum system provided you had the proper sized drum.
Considerations
One thing to keep in mind, is that porous materials may not lend themselves to creating a good seal. For example, a thin oak platter or a piece with piercings (natural or otherwise) may be too porous to create a vacuum.
The power of the vacuum is quite surprising. I was not able to remove the bowls by hand when the suction was applied.
A vacuum kit can be rather expensive. A production turner could justify this system based on improvements in production speed. However, reverse mounting is so easy, a vacuum system could make good sense for the hobbyist. The hobbyist can spend more time turning and virtually no time centering a bowl. Both groups gain efficiencies because a properly centered piece will require less time to re-true. This is because the outside bottom of the bowl will require little effort to blend the original profile to the reversed profile. Also, any turner will benefit from the ability to quickly and safely complete the entire bottom of the piece. Vacuum chucking eliminates the need to hand hold the piece to carve or sand away the final nib on the bottom. This reduces the risk of dropping a completed piece or injuring oneself while cutting away the tenon.
Off the shelf or home built
This is the classic case of time verses money. It is possible to put together a custom system. This route will take more effort on your part but may cost less. You will need to do the analysis for yourself. A vacuum is a "nice to have" accessory. I have found the vacuum system to be very practical and worth your consideration.
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Curtis was a former President of
Central Texas Woodturners
, is a member of the
American Association of Woodturners
, and a member of
Fine Woodworkers of Austin
. Curtis teaches and demonstrates nationally for Lie-Nielsen Toolworks. He also teaches for TechShop. He owns a studio where he teaches and works. Curtis lives in Central Texas with his wife and four young children. Take a look at his website at
www.curtisturnerstudio.com
.
