Several members of the club have and use vacuum chucks. The topic was introduced with this drawing from the book, Woodturning Methods by Mike Darlow, pg. 33. There are also two chapters on vacuum chucks in the book Fixtures and Chucks for Woodturning by Doc Green. Both books can be checked out from the PAW library.
AAW members can also access a variety of articles on vacuum chucks. Log into your account at https://www.woodturner.org/. Click on Resources, Information: Articles, Explore! Article Search, and Search Now! Select the category “Chucks & Centers” and the key words “Vacuum Chuck.” Click on the red book and finally select the PDF to read your selected article.
Some safety parameters discussed during the meeting are listed below.
• The holding force on the base plate is directly related to the surface area under vacuum so, for the same amount of vacuum, a large bowl will be held with more force than a small bowl.
• The larger the diameter of a bowl being turned, the greater the force from the vacuum. If it’s been turned too thinly, it can be broken by the holding force.
• A small diameter bowl may not have enough holding force to keep it on the vacuum chuck when turning, especially if there is a catch.
• Altitude makes a difference in vacuum pressure. Members found their shops had different inches of mercury measurements from 16” to 25” mercury. Small leaks in the system could account for some differences.
• To test for adequate vacuum when using the system, try to pull the bowl or object off. If it can’t be pulled off without a lot of effort, it’s sealed well.
• Don’t leave the vacuum pump on between coats of sealer or between sanding times.
• The pump can be used on the top or bottom of a piece if it can be vacuum sealed safely.
• Forward pressure is good, lateral pressure when turning can be deadly. Always cut along the axial direction toward the headstock.
• Evaluate the type of wood and cracks to decide if it’s safe to use with a vacuum chuck. Seal the wood to fill any pores. Defects, inclusions, and bug holes can cause problems. Of course, open segmented pieces don’t work well with vacuum chucks. Higher density woods are less porous.
• Speed while turning should be safe. Keep it under or around 300-400 rpm without a tail stock in place. 800-1000 rpm can be used with the tailstock in place. A cleaner cut occurs with a faster speed.
• A vacuum chuck is safest with the tailstock up.
• Take light cuts. When finishing the bottom of a piece, pay attention to the sound. It can change when a piece is getting too thin.
• Too much vacuum can crack a bowl or suck in the bottom.
• Wood can leak the vacuum or fall apart due to the porosity or character of the wood. Sanding sealer or a finish can seal the wood and seal those pores. Members somehow learned the hard way that the finish needs to dry completely before applying a vacuum. Shellac takes a few hours to dry. Wipe-on polyurethane is best applied in the evening and allowed to dry overnight.
A few members shared photos and comments about vacuum chucks in their shops.
Keep the chuck on a bowl and mount it on the tailstock, then move the bowl up to the vacuum chuck to keep it centered.
Check to see if the lathe is out of alignment by moving a pointed live center up to a pointed center on the headstock to see if they meet.
Check to see if the vacuum chuck is squared up on the end.
The chuck looks like it’s missing a foam piece on the end. Glue a piece of foam along the edge so a piece can’t slip.
An old mouse pad works well when it’s glued to the end.
These vacuum chucks are, from left to right, made from 1 ½” diameter PVC, 3” ABS, 4” PVC and 6” PVC. The chuck on the right has some foam on the bottom to better secure the object being turned. Each has a maple base that has been sealed with shellac and a wooden flat on the top (~3/8”) that has been covered with a thin foam (8X12” sheet) with a self-adhesive from Walmart. The wooden plate at the base attaches to the headstock. Gary threaded the wood to match the thread of his lathe. Beall sells taps to match the thread of the lathe. Some people have lost bowls if the thread cracks and breaks.
Trex works better than wood as a base. Lowes sells 2X6 pieces for decking. It’s self-lubricating and is the easiest to tap. Walt has tapped them for several members. The integrity of the material is such that it won’t split and makes marvelous, dependable bases.
He often uses the vacuum pump between coats of finish to give him a ‘third hand’ and he doesn’t need a lot of pressure to hold the piece. More pressure would be needed when turning.
The white chuck (3 1/4” X 4 ½”) has a threaded rod (that was originally used in a lamp) that goes through the headstock to attach to the tubing. (See next photo for a view inside the chuck.)
The green self-adhesive foam material pads the ends of the of the smaller chucks. Foam material was also applied to the large chuck.
The black chuck (2 ½” X 8 ½”) was made for use in a tall vase, like those made with a zipper. Trex was used for threading the bearing and tubing.
The photo shows a bowl in place on the vacuum chuck. Bruce made a jig that has a 90° vertical board and a base in the slot of the lathe to find true vertical up and down for centering the bowl. Then the bowl could be rotated per the tool rest for additional centering.
A bowl makes an imprint on the foam which lasts for a day so the bowl can be reset in the same place again.
This is the back of the smaller vacuum plate. Epoxy was used to secure the nut.
Dick Kelly found some designs by Douglas Fisher of Canada that were created using a vacuum chuck. There were created by offset turning and rotating the piece to change the turning axis of the piece. Examples are given along with a drawing to show the various swirls in the piece. The problems are that it’s not repeatable and it would cause a big problem to get a catch. Other photos can be seen at https://www.woodsymphony.com/douglas-fisher.