Hollow Vessel Turning (Long)
Wally Dickerman at Green Valley, Az.
>For many turners, turning hollowform vessels is the next step up from turning open bowls. I've put together a few suggestions and tips that may help a beginner get started.
There are many tools to select from for hollow turning, from a simple shop-made boring bar, which can be very effective, to the many hook tools, captive tools, etc. which are on the market today. I suggest that a beginner contact one or more experienced hollowform turners for advice and suggestions on what tools to make or purchase.
It's a good idea to start by rough turning the outside between centers using a bowl gouge, and then secure the profiled blank to the lathe using your usual method. Usually that'll be a scroll chuck and a tenon, or a wasteblock and a faceplate or screwchuck, or a faceplate fastened directly to the blank. To provid support, be sure to leave heavy wood in the lower portion of the vessel, instead of turning it to it's final form. After forming the outside, I rough turn the inside, even if the wood is dry. I start by boring a 3/8 inch hole down the center to about a half inch less than the finished depth. This aids in hollowing and serves as a gauge for how deep to go. Except for very small pieces, leave the sidewalls at least 1/2 inch thick. For large pieces, especially if the wood is quite wet, up to 3/4 inch is better. Hollow vessels won't distort as much as open bowls. Try to keep the thickness constant. I start the hollowing with a 1/4 inch bowl gouge, even on very small openings. This is followed by a round boring bar that has a 1/4 inch cutter. The purpose of the boring bar is to open an area large enough for my Stewart hooker tool to get inside. It also helps if you use the boring bar to clear out the center portion of the piece as you work your way down, cutting from the center hole out.
To finish the vessel after rough turning inside and out, I completely finish the outside including sanding, except for an area around the base, where I leave heavy wood for more stable turning. The base is finished after the final hollowing is done. I remove wood chips (frequently) with a Shop Vac and a special hose tip.
I suggest that your venture into hollowform turning start by using your hollowing tool to hollow an open or nearly open bowl, so that you can familiarize yourself with the cutting action of the the tool. When you're working inside a vessel you can't actually see what's happening.
Some tips on hollowing:
If you're using a hook or swan-neck tool, place the tool on the tool rest above the curved portion. The hook shape is designed to help eliminate torque.
Set the tool rest height so that the cutting tip is cutting on center, or better yet, a little above center. Cutting below center invites a catch.
Cut with the cutter tipped down slightly. Gives a sort of shearing cut. This is especilly true when using a rounded scraper cutter.
Never allow the tool to touch the rim when cutting inside. A sure way to break the vessel if you get a catch.
Measure wall thickness frequently. It's all too easy to go through the side of the piece. Especially true when you're deep inside the vessel.
Finish hollowing a section at a time, working your way down, so that you're always cutting against heavy wood.
Because a vessel often warps a little as you turn the walls thin, I completely finish the inside area around the rim before proceeding further down the inside.
Some turners finish turn hollow vessels while the wood is still wet, but I prefer to allow the rough turned vessel to dry. When adding a collar or other rim treatment I don't want any distortion in the wood.
For deeper pieces, a steadyrest is almost a necessity.
There is a lot more to hollowform turning, but these are the basics. Good luck and have fun. Be creative. Once you've started hollowform turning, many of you'll find that you'll seldom turn open bowls.
The beaded vessel in the photo is maple and wenge and is 11 inches tall.
Wally
