|The author's Axminster chuck now serves her well for holding wood in spindle, bowl or re-turning applications.
Chucks for holding wood on a lathe have been around for many years, and the designs of the new models are much improved. While chucks are certainly not "must-have" accessories, they are handy for a variety of holding options, including bowl turning.
Years ago, I was the lucky winner of an Axminster chuck, complete with a variety of jaws. After it had served far too long as a heavy paperweight, I dusted it off and put it to its intended use. I now primarily use it for holding cylinders for spindle turning, but occasionally use it to attach a bowl to the lathe.
Chucks Are Useful for Bowl Turning
Bowls can be attached to the lathe in two primary ways: glue block method and chucks. One method is not necessarily better than the other; however, when you understand the usefulness of both, you can choose the one best suited for what you want to turn.
Chucks are great to use for roughing out a bowl from green wood. Once the bowl is roughed out, it can be set aside to dry, then re-chucked later for finish turning. This process takes very little time, so you can process a large amount of wood before losing it to decay.
What Chuck to Buy
Some chucks come with jaws as part of the package, while others require the purchase of jaws separately. If you will be turning large-diameter bowls, buy a larger capacity, heavy-duty chuck. Smaller capacity chucks are, of course, for smaller turnings. For bowls, you will need either jaws that compress onto a tenon or ones that expand into a recess. I've used the compression method for the photos in this article.
Chuck manufacturers make chucks to fit almost any lathe's spindle size and thread count, so buy the chuck that fits the spindle of your lathe. If you have an unusual spindle size and/or thread, you can have an adapter made.
Chucks range in price from about $170 for the basic body and one set of jaws to about $300 for a chuck body and several sets of jaws. Teknatool makes several models of chucks, including the SuperNova2. I mentioned the Axminster. Oneway Manufacturing makes the Stronghold and Talon chucks, and Vicmark has a basic body. All these brands are excellent, and all have a variety of jaws available.
Preparing the Turning Blank
|If you are going to leave the bark on, you must remove bark where the drive center will be positioned.
Cut down a tree ... actually, there's so much free wood around, you'll be inundated with logs if ever you make the mistake of letting friends and family know that you want wood! I know this firsthand.
Select a log, cut it to a bowl-diameter length, then cut it apart along the pith. You can do this with a chainsaw or on your band saw. Next, cut the half-log section round. The band saw is the best machine to use. Check your bowl blank for major cracks. I personally avoid all cracks in green wood, as they often end up expanding over time. I remove the bark before I put the wood onto the lathe as it tends to fly off in huge sections during the turning process.
Keep the center marked, and also mark the center on the opposite side. I have round cardboard forms in a variety of sizes with a hole in the center for this purpose.
Turning the Tenon
You will need to turn either a recess or a tenon on your bowl blank so the chuck will have something to grab into or onto. The method of mounting the blank onto your lathe is the same for both.
For this article, I am rough-turning a bowl blank from green wood, and the bottom of the bowl is next to the bark-edge of the bowl blank. That's where I will turn a tenon to accept the chuck.
You can mount the bowl blank between centers as shown in the photos on the next page, or you can use a screw chuck. If you use a screw chuck, you will need to drill a pilot hole to accept the screw. Screw chucks are an accessory for chucks, and they are also available as dedicated screw-center chucks or screw-center faceplates.
I mount the wood between centers so the bottom of the bowl is at the tailstock of my lathe, making it easier to turn the tenon. Make sure the wood is securely fastened between centers, as some lathe's tailstocks tend to creep backwards instead of tightening. As you progress with turning the tenon, check to make sure the tailstock is still tight.
To begin with, set your lathe's speed at a slow RPM, somewhere less than 800 RPM, just to make sure the bowl blank is mounted safely and balanced properly. Increase the speed gradually.
Begin by cutting from the bottom of the bowl to the rim. To start with, your tool will hit wood, then air, then wood. If the bowl blank is balanced, increasing the RPM will make the cutting process smoother - you will spend less time "cutting" air.
Turn a tenon. The tenon should be as large a diameter as possible yet still fit into the jaws of your chuck: the larger the tenon, the more holding power. The shoulder of the tenon (the outside bottom of the bowl) should rest on the top part of the jaws. This will provide leverage for side-cutting pressure.
Please note: if the tenon bottoms out on the inside area of the jaws, this leaves a gap between the top of the jaws and the bottom of the bowl. Your bowl blank will be much more likely to fly out of the chuck when roughing out the inside.
The jaws of your chuck should not stick out too much from the body of the chuck (somewhat common with older model chucks). If they do, that becomes a potential hazard if you should accidentally brush up against them. It hurts!
||Measure the opening of your chuck's jaws (left). This diameter will be the maximum diameter for your tenon. Do not open the jaws of your chuck beyond its maximum capacity; otherwise, one of the jaws won't be seated. Form the bowl blank's tenon with the blank between spindles.
Mounting into the Chuck
|The author ended up leaving a nub on the tenon as a result of removing some of the sapwood she didn't want included in the bowl. Remove the nub if you've done the same. Put the bowl blank into your chuck and tighten the jaws.
Remove the bowl blank, attach your chuck to the lathe, then mount the bowl blank onto the chuck. Tighten the jaws. You can use the tailstock to help hold the wood while you tighten the jaws. You can also keep the tailstock in place to help hold the bowl for initial turning.
Start the lathe at a slow speed, just to make sure the bowl blank is centered properly in your chuck.
You can further shape the outside of your bowl or begin directly with the inside. I like to refine the outside of the bowl a bit, but I always leave sufficient wood on the shoulder next to the tenon.
Now comes the fun part. Remove the wood from the inside of the bowl using a bowl gouge. (Remember, roughing gouges are only for spindle turning.) Most green wood cuts like butter, and you'll only be removing the bulk of the wood. Make the shavings fly!
Bowl Thickness and Drying Time
The wall thickness of your bowl will depend on the size of the bowl and the type of wood. Green bowls warp as they dry, so leave enough thickness for re-turning. If you leave the walls too thick, that will increase drying time and perhaps cause cracks. Experiment for a while to get it right.
Drying times vary with the season, the type of wood, and how wet or dry the wood was to begin with. Some will dry within a few weeks; others take half a year or more. If there are no cracks or voids to begin with, I find that bowl blanks don't crack when drying, so I tend to leave mine just sitting around my shop. Some turners, however, routinely cover bowl blanks with end-coat sealant and date them. Others like to put bowl blanks in shavings or in paper bags for the drying process.
It's also possible to completely turn the bowl and be done with it. You can leave whatever wall thickness you want, but you might enjoy trying to make a paper-thin bowl from very wet wood. Wet wood holds up well and cuts smoothly, with no sanding.
Re-turning Dry Bowl Blanks
Remount dry bowl blanks in your chuck for finish turning and sanding. The bowl can have a foot (the tenon) or that section can be turned off, leaving a flat bottom.
There are specialty jaws for chucks to hold bowls for turning the bottoms. You can also make your own, or invest in a vacuum chuck system. The point is, you can (and should) turn the bottom of your lovely creations!