Vacuum Chucking on the Lathe

Originally written for Craftsy by Ed, titled: “Working Under Pressure: Vacuum Chucking on the Lathe.”

Chucks are commonly regarded in the woodworking world as the go-to method of holding work on a lathe when creating a bowl or platter. Typically they are four-jaw, self-centering devices that grasp the work by a tenon or recess. They hold the work very securely and are quick to use, however they mar the work in some way that must be repaired, usually requiring a jam chuck.

Jam chucks offer the ability to hold work without marking it, but they take yet another piece of wood and require sometimes a fair bit of time to create. The best of both worlds, vacuum chucks hold the work without marring it and the work can be set up as quickly as a normal chuck.

Better yet, can you imagine how the natural-edge bowl in the photos below could be held by any other means while working on the foot?


I know of at least one woodturning artist who uses vacuum chucks exclusively for his multi-centered pieces, not just for holding a piece to finish the foot, switching rapidly between placements. Vacuum chucks are capable of holding work that requires serious wood removal. Creating a jam chuck to hold this bowl to finish turn the foot would be very involved and probably take longer to create than the bowl itself.

Photo shows bowl held in a vacuum chuck - Creating a jam chuck to hold this bowl to finish turn the foot would be very involved and probably take longer to create than the bowl itself

Putting the pressure on

Vacuum chucks hold the work by using atmospheric pressure to force the work against the face of the chuck by creating a vacuum inside the chuck. The face of the chuck is covered in a soft, closed-cell foam that conforms to the surface of the piece and provides friction to help drive the piece.

Considering that atmospheric pressure is 14.7 psi at sea level, it’s not hard to calculate the holding force available. The chuck in the photo has a 4.5″ inside diameter and therefore has a frontal area of almost 16 square inches. Using 14 psi as a round  number (it’s tough to get a pure vacuum), 16 x 14 psi = 224 pounds of force over the entire area holding the bowl to the chuck. That’s like me with heavy boots sitting on the bowl to hold it in place. I could make some pretty serious cuts if required.

Extrapolating that, if a 10″ chuck is used, a mighty 1,100 pounds of force will be holding the work in place. That’s like parking one wheel of a loaded pickup on the piece, so some restraint must be used if it’s a thin platter. Not to worry, we can do that. It goes without saying that you folks in Colorado will have to use a smaller number for atmospheric pressure than us folks on the coast, but you still have to be pretty tough to haul that bowl off the chuck.

Working down the line

We know our vacuum chuck has the oomph to hold the work. Working our way back from the chuck, the next thing that is required is a means of transmitting the vacuum through the rotating spindle. Stubby is at least one brand of lathe that has a connection already provided in the headstock, but for the rest of us, a rotating connector must be added to the outboard end of the spindle to connect the vacuum hose. Oneway Manufacturing provides one for their lathes that can be adapted to any others with outboard threads.

Another type uses the vacuum itself to hold the rotating adapter to the end of any spindles that only have a metal hand wheel. The hose doesn’t have to have an internal metal helix, but it has to be stout enough to prevent air pressure from flattening it like a macaroni noodle. I use a fairly heavy duty air pressure hose and it seems to be fine. Again, it’s all about the surface area.

That leaves the pump. A pump is required to produce a vacuum. These are available online or you can make one yourself.

Too much of a good thing

I mentioned that in some cases the force applied by a vacuum on a piece can be great enough to cause damage, either deflecting the piece or actually breaking it.

In the case of deflection, if the piece is thin enough that it deflects inward during turning, the shape created will distort outward when the vacuum is released. Typically, a bulge in the finished bottom is the result. To eliminate this and the danger of breaking the piece, a valve in the vacuum line is necessary to regulate the amount of suction. Almost always, there is enough leakage through the end grain in the wood itself to help, but the valve allows you to control the level of suction. In the picture below, there is a filter to prevent any gritty bits from reaching the pump. A vacuum gauge in the system is very useful to indicate how much suction is present and when a seal is failing while turning.

Equipment for controling the vacuum

Below you can see a valve, filter, gauge and rotating adapter used to transmit and control the vacuum for the chuck.

Plugging the leaks

Leaks are detrimental to the success of the whole operation, but it is possible to deal with them. Leaks in the system itself will be limited to connections, and of course the rotating adapter that connects the system to the lathe. All of these are simple to identify and repair as required.

Sometimes the wood is porous enough that there are significant loses through the end grain areas. Leaks in the wood are easy enough to limit by applying masking tape to the piece wherever air is leaking through. It is easy to feel because it actually feels sticky, to the point that sanding dust adheres to the surface. Sometimes the dust will improve the seal. A gauge will indicate the effectiveness of any taping or other jury rigging.

Below is a vacuum reading before taping the end grain. Note that the gauge reads in both inches of mercury and kilopascals. Normal atmospheric pressure is about 30 inches of mercury (30 in. Hg)

Vacuum reading after taping end grain

Below is the gauge reading after taping the end grain, effectively doubling the vacuum. This reading indicates a holding force of about 175 pounds.

Vacuum system gauge

Vacuum chucking can be a very worthwhile addition to your arsenal. Full systems are available but can be very expensive. Remember: the lathe is the cheap part.

If you are unable to manage the cost of a system, but are at least a little handy, it is possible to make the essentials using basic plumbing and air handling hardware and material from your shop. Stay tuned for posts on making a pump, assembling the necessary piping and the chucks themselves.

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Creating Beautiful Art From Junk Wood

Originally written for Craftsy by Ed, titled “How to Make Amazing Scrap Art: Turning a Multi Axis Vessel”

Typically things turned on a lathe are round because they are shaped while they rotate around a single center. While I always have enjoyed the shapes that are produced on a lathe, I also find using a single center constraining. Why limit yourself to something that is purely round when you can incorporate many circular elements in your design by using multiple sets of centers? I enjoy creating shapes that look like they were made on anything BUT a lathe. Let’s have a look at one method of creating such a form.

Multi center vessel

The pieces above were the first in a series I call “Another Man’s Treasure” (because I found the blanks in the “dollar bin” at a local wood supplier… one man’s junk is another man’s treasure). Clearly they are a success because they are now part of my wife’s “that’s not leaving the house” collection.

They had wonderful grain but the orientation was such that if I turned a bowl from them the beauty would be gone. They sat in my shop for months before I figured out how I was going to make something that would present the grain in the best way and also have an interesting shape. Ideally it would also be nice to keep the natural edge of the burl. Minus the pencil line, this is what I had.

piece of scrap wood

Turning a multi axis vessel

I knew I wanted to present the piece vertically to show off the grain but to do so meant that I would lose most of the wood if I turned a small round cylinder. Make three or four small cylinders? Not appealing. Lay it flat in a bowl form? It wouldn’t look much different than any other bowl and the natural edge would be gone. The answer was presenting the broad face vertically by orienting centers in a different plane and using more than one set of centers.

Step 1:

Keeping the natural edge meant placing a center on that edge. To do so on such a convoluted surface meant placing a spot face with a Forstner bit large enough for the drive center I would use. Turning the piece on these centers allowed me to create any form I wanted. I wanted a small foot for a lighter look and to keep as much of the natural edge as possible. Joining the two with a curved line seemed a good choice.

I wanted to eventually hollow the piece a bit from the top to remove some weight to make it more stable and also to remove the spot face and marks from the drive center. To do so I created a tenon to hold the piece with a chuck, hence the chunky bit on the bottom. Within that ugly tenon lies an elegant little foot. Notice that the bottom of the blank at the tail stock end has been trued up square to the axis. This is needed for determining the next set of centers.profile shape

Step 2:

With the basic vertical profile established I needed to turn the the vertical faces. On the first piece I finish turned the faces with a simple, lens-like curve but that looked kind of bland. To correct that in this piece, I opted to incorporate a circular element to add interest. I oriented the center so the circle would be interrupted by the natural edge to avoid to creating a “bull’s-eye” look.

To find the vertical center I had to mark the horizontal center on both faces. I chose to align these squarely across the original center but you could make them independent of each other. To keep the centers the same height, it’s a simple matter to measure from the squared bottom to find the centers on both sides. If you chose to vary the height of these centers it would begin to get quite complicated to turn, however, it would result in a very interesting design. I opted to keep the centers at one height, keeping the axis horizontal at this point because I wanted the faces to be parallel to one another.

Place the piece in the lathe using these centers as in the photo below and turn the face with whatever design you like. As I noted earlier, in this case I chose to incorporate a circle that was interrupted by the natural edge. The center mark has to be carved away later by hand, so enough wood was left to do that.

Because I wanted to have the same shape on the other side I marked a center line on the profile surface by rotating the piece by hand and measuring off the tool rest set square to the bed of the lathe (I’m sorry I have no photo of this). Using sharp dividers I measured from that center to the edge of the turned face then stepped off each point on the opposite, unturned side. I then connected these “dots” to create the finished shape as a guide.

Face mount

Turn the piece around on the same axis and turn the second side. By turning the second face so that the edge of the cut matches the line drawn through the dots you will replicate the first face. This is far easier than you might think. If you make light cuts, stopping the lathe to check your progress after each cut you will have no trouble matching the shape. Alternately, you may choose to have different shapes on each face.

Step 3:

Now you have the main profile (except for that ugly tenon) and the two opposing faces finish-turned. It’s time to get rid of the ugly spot face on top and hollow the inside of the form. This is where the only rule of woodturning comes into play: The inside diameter must not exceed the outside diameter. Remember that the inside diameter must be smaller than the narrowest width of the piece, so the hollow inside shape cannot reflect the outside shape of the piece as in a normal hollowform. Then again, a hollowed inside form that interferes with the outside form, creating a hole in the face, will create yet another design alternative. Something worth exploring in a piece of wood where the figured grain isn’t the highlight.

Note that the width of the tenon is much less that the width of even a single jaw. Engaging a single jaw on each side would be equally as strong as the method on the photo. I chose to engage two jaws on each side of the tenon because it was easier to keep it on center than if I tried to find the center of a single jaw.scrap wood with cuts mounted in the chuck

Use normal hollowing techniques in this step, however, be cautious and use light cuts. It is safe, but you can see that the mounting of the piece is not as stable as in most hollowing situations.

Step 4:

Now to get rid of the tenon and create a clean foot for the piece. Mounting is shown in the photo below. I made an arbor for the express purpose of mounting thin-walled hollowforms to finish-turn the bottom. It has a Morse taper to fit the spindle, long enough to engage the bottom of the hollowform and a sliding tapered collar to center the hole in the top. Although not visible in the photo, a split collar holds the taper tightly in place. You may not have have such a device but because this is a robust piece, it is a simple matter to mount a piece of waste wood in the chuck and turn a taper as a jam chuck to fit the top hole. Bring up the tail stock to secure the piece.

Remove the wood that was the tenon, completing the shape of the profile.

I prefer to have a slightly hollowed bottom creating a little shadow line at the foot with two feet rather than simply leaving a flat bottom. The slightest shadow line gives the piece a light look, as if it’s floating off the table. The nub left by the tail stock is easily carved away.

Also in the photo you can see the center left on each face. This is easily carved away as well. In this case, remember to leave enough wood so that the center point doesn’t leave a hole in the face.

turning the bottom of the workpiece on the lathe

This is a photo of the completed piece with a finish and a bit of gold leaf. Not bad considering that the material for this cost a buck.Completed Multi axis vessel

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How do I sign into a demonstration?

It’s safe to say that all woodturning Interactive Remote Demonstrations (IRD) are carried out using  Zoom “Meeting” or “Webinar” formats (see www.zoom.us). When presenting my demonstrations, I do so via Zoom in their Meeting format. When I schedule a Zoom meeting, Zoom assigns a unique meeting number and password to that meeting for security reasons. Both the meeting number and password are contained in a link that will allow anyone with that link to join the meeting. Please do not share that link with anyone.

The day before the demonstration I email everyone a Zoom invitation that contains that link as well as the actual meeting number and password. The invitation shows the start time of the meeting one hour earlier than the actual start time. I do that so that I can be ready and waiting for people to sign in, preferably 15 to 30 minutes before the start time. Usually we get to visit a bit, talk about your expectations; things like that.

When you go to Zoom’s website for the first time it will download a program that allows you to join meetings. That download usually take less than a minute and only happens the first time. On their home page you will see a “Join Meeting” tab at the top of the page. Clicking on that tab brings up a box that has a space for “Meeting ID or Personal Link Name”. Enter the meeting link in that box then click “Join Meeting”.

Before entering the meeting you will be in a “waiting room” but will be admitted momentarily. You may be shown how to change your name if you show up as “Linda’s Laptop” or “B&GW”. From that point on it’s pretty much like being at any ordinary meeting. Take the time to explore the task bar at the bottom and the small icons at the top right and left of the screen.

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Butterfly Crack Repair – IRD

This type of repair is also referred to as a “Dutchman”, “Bow Tie”, “Dovetail” or “Pewa”. The method demonstrated involves using a router to make both the recess and the patch but also includes an alternate method of creating patches in bulk. Applying patches to both existing or emerging cracks not only saves material that would otherwise be thrown in the fire but also saves projects that already have hours of work invested in them. In the end, a well-done butterfly patch is easy to do and represents a higher level of skill that increases the value of a project.

In this demo I show how to make a pattern for routing the recess for a patch, how to cut material to make the patch, how to cut the recess, then fit the patch.  

I discuss the features to look for in a router and router bits that I have found most suitable.

Ready to check out the demo? Visit the store: https://edswoodturning.com/shop/

When’s the next demo you ask? Check out the events calendar here: https://edswoodturning.com/events/

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Replication Made Simple – IRD

This demo focuses on turning between centres, showing traditional techniques that make replication much easier than most turners believe. I presented this demo at the AAW 2018 symposium in Portland, Oregon.

My woodturning roots are in spindle turning, learned from my father over 60 years ago. Most treatises on spindle turning include the use of patterns, often frightening people off rather than encouraging people to try turning multiples. Also, modern pattern lathes, and now CNC lathes, have led to the notion that every single piece must be identical. In traditional turning, pieces appear to be the same but are not absolutely identical, taking away the fear that “I could never turn two things the same”. Trust me, you can.

The key technique is the use of a “story stick”, which I will demonstrate making and in use. I show a variety of calipers with their own advantages and disadvantages.

I will explain and demonstrate techniques for making the three elements in spindle turning – beads, coves and barrel shapes – and the tools used to create them. Pommel cuts are an integral part of spindle turning using those shapes, so that will also be demonstrated.

Ready to give it a try? Take part in the demo first. Sign up at the store: https://edswoodturning.com/shop/

Check out the events tab for available dates: https://edswoodturning.com/events/

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Colouring Wood – IRD

I’ve applied colour in various forms to my work since the early 1990’s.  I discuss surface preparation, use of wood-compatible dyes, ebonizing, bleaching, ebonizing, fuming, liming – using both traditional lime wax and acrylic paint – and faux painting techniques.

My dye technique involves the use of only the primary colours – red, blue and yellow – and black. I show how these colours are applied to a piece separately rather than premixing colours to achieve spectacular effects on figured wood. I show how bleaching can be used to change the outcome or be used on its own.

I discuss different ways of ebonizing or darkening wood by applying an ebonizing fluid and fuming with ammonia.

I discuss and show the effects of various commercially available treatments like crackle glaze and faux metallic applications.

For available dates, check out the calendar at: https://edswoodturning.com/events/

Ready to reserve your spot now? You can do so at the store: https://edswoodturning.com/shop/

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Beyond ABC – IRD

The focus of this demo is on improving tool control in bowl turning, however is relevant to most between-center techniques. In anything, I believe that to know the “how” you must understand the “why”. It is an in-depth explanation of those things that are not covered when someone talks about Anchor, Bevel, Cut. I presented this demo at the AAW 2018 symposium in Portland, Oregon

I explain and show how the legs are used for greater power and control when making a cut.

Transverse Cut

I explain and demonstrate how the front hand and back hand have two different jobs. This is pertinent to all turners but also helps me a lot when teaching left handers bowl turning.

I demonstrate and explain when to engage the tool rest with your forward hand and when not. Many turners have anchored themselves to the tool rest completely, which greatly hinders their ability to control the tool.

I explain the two causes of catches by breaking them down logically into action/reaction. All of this relates directly to spindle turning tools as well. For bowl turners it eliminates the issue of ruining the rim on the last interior cut as well as the dreaded catch about ¾ the way up the outside. For spindle turners, you will be able to use the skew with confidence.

Ready to reserve your spot? Visit the store at: https://edswoodturning.com/shop/

When’s the next demo you ask? Check out the events calendar here: https://edswoodturning.com/events/

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Lee Valley Tools

Quite some time ago, Ed started instructing for Lee Valley tools in Coquitlam. He isn’t there all the time thankfully, he is after all retired. 🙂 He usually has a few classes every term. There is a 2 day beginner woodturner course, and a one day course on sharpening your woodturning tools. Every now and then he also instructs on turning a hollow form. He has done some other specialty courses like the three legged stool. Those aren’t run all the time, just when the need arises or and idea inspires.

The great thing about the courses there is that they are central in the Lower Mainland and a reasonable price. Of course Lee Valley loves it, because it gets you in the door and you will, no doubt, do some shopping.

Ed has also traveled to Kelowna to instruct in their store up there. Usually once or twice a year. If you live in the area, sign up, you won’t be disappointed.

If you live in the Lower Mainland and are interested in the courses for Lee Valley Tools Seminars Coquitlam, follow this link and sign up. http://www.leevalley.com/en/home/SeminarList.aspx?c=1&rs=60

If you live in the Okanagan and are interested in the Lee Valley Tools Seminars Kelowna, follow this link and sign up. http://www.leevalley.com/en/home/SeminarList.aspx?c=1&rs=90

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The Roundhouse

Well, as I promised earlier, I would be posting about what Ed’s been up to that has kept him too busy to being doing his own posts. Well they may not be in any specific order, but you’ll be up to date in no time.

At the end of last year Ed met a fellow named Jeremy Tomlinson. He is an accomplished woodworker who has his own shop in North Vancouver. It’s called The Urban Woodworker. Jeremy runs woodturning classes in North Vancouver at his shop and a the Roundhouse Community Recreation Center in Vancouver.

They hit it off right away which is a good thing. (Easy to do with two woodworkers, just get them started talking about wood.) Jeremy had a proposal for Ed. He asked him to be an instructor for him at the Roundhouse in Yaletown (an area of Vancouver). As most of you know already, this is right up Ed’s alley. He loves training. From his days in the Fire Service training, then onto motorcycle skills training and of course woodturning.

This new position would mean him traveling to Vancouver on most Friday’s. In no short order Jeremy added Saturday to Ed’s schedule. So, the retired guy is now a commuter. Who’d a thunk? Certainly not me. He actually takes transit which is almost unheard of from our area of Langley. He has to drive to the start of his route of course, but after a bus, three connections and 3 trains he’s there. Only an hour and half later. The price is right and it saves wear and tear on the vehicles and on Ed. He doesn’t have to fight the traffic to get there.

He started this new venture the end of November 2018 and just got his new schedule for the fall term. He is booked every Friday and Saturday at the Roundhouse. Not to mention he’s still teaching at home here and at Lee Valley in Coquitlam. Busy guy…

You can check out Jeremy’s site here: https://urbanwoodworker.com/

If you live in the Vancouver area and would like to take classes from Ed at the Roundhouse, you can sign up for the classes on either Friday or Saturday using this link: http://roundhouse.ca/programs/adult/ Scroll down the page until you reach the Woodworking Level 1: Wood Turning (19+) section.

If you’d rather have a more personal one on one woodturning experience with Ed give him a call or drop him an email. You can find the contact information on the Woodturning Classes tab above, or click on this link: https://edswoodturning.com/woodturning-classes/

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Back in the saddle

Arlene here, Ed’s wife, for those of you that don’t know me. It’s been awhile since Ed has had the time to write. Not that he has forgotten about his followers and readers, but he has been awfully busy. That’s not really an excuse I know, but the posts to come will explain what he has been up to.

In the meantime you can check out his Facebook page for his more recent posts. You can check them all out here: https://www.facebook.com/Edswoodturning/

Stay tuned…

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