Dave Hout Demonstrates August 2005

Overview: Dave Hout, host of “Woodturning Basics” and “Woodturning Techniques (DIY Network), is a well respected teacher in the woodworking field. He has led many workshops and seminars on woodworking, with an emphasis on woodturning. He has taught at various schools, including the Conover School in Parkman, Ohio, Arrowmont School of Arts and Crafts in Gatlinburg, Tennessee, and the John C. Campbell Folk School in Brasstown, North Carolina. Dave is a founding member of the American Association of Woodturners (AAW) and has presented at several of its national symposiums. In addition to his full time studio work he designs woodworking tools for a local company.

Morning Session:

Vacuum Generator PIAB Model M125 that Dave purchased as surplus. Feed pressure air is 58 PSI and consumption 4.4 CFM

Gast Vacuum Pump - note muffler on exhaust port.

Dave began the session with a discussion of vacuum chucking. First you need a vacuum source. The most common one is a pump (CFM greater than 3). [Source: www.surpluscenter.com] Another source is a vacuum generator that works on the Venturi principle and is driven by compressed air. In general you need about 4 to 5 square inches of surface area on the work piece in order for the vacuum to hold it in place. A vacuum gauge is useful to show you how much vacuum is being generated so you can avoid crushing the piece with too much vacuum. Harbor Freight is a source of vacuum generators and www.overstock.com is another source of vacuum pumps. Complete vacuum chucking systems are available at Packard and Craft Supplies. Where you purchase these depends on how much you are willing to spend. A third source of vacuum is a vacuum cleaner. The motor needs to be cooled by an outside air supply and not that drawn up by the vacuum motor. Otherwise the motor will overheat and eventually burn out.

Headstock bearing shown with quick disconnect fitting (not recommended)

Once the vacuum is generated (pump vs. generator vs. vacuum cleaner) you need to transfer the vacuum to the piece via the headstock. A bearing is fitted on the outboard end – this is attached to a lamp rod that goes through the headstock and attaches to another adaptor on the inboard end of the headstock. Quick fitting adapters such as are used with compressed air lines are not ideal for vacuum use. In time they will leak. For vacuum use you can simply put the hose on the fitting. When using the vacuum pump a vacuum reserve tank can be fitted into the system so that in the event of a power failure the work piece does not immediately come off the lathe.

Note flat plate adapter on lathe bed. Dave is holding the imitation chamois.

Another view of the flat plate adapter on lathe bed. The drum chuck is in the lathe

When the source of vacuum and how to transfer it through the headstock have been determined, a fixture that is airtight which attaches the work piece to the chuck is needed. The chuck alone is not airtight. Dave showed a flat, circular adapter that could be used to hold a plate or a platter. The plate was covered with imitation chamois that the work piece comes in contact with. Be sure the chamois does not have holes or perforations in it. Some of the ones sold at automotive supply stores do have holes. Some sold at marine supply stores do not. The imitation chamois is a piece of fabric that is covered on both sides by polyurethane. This enables it to collapse when vacuum is applied and thus to securely hold the piece. Liquid “Tacky” can be used to glue the chamois to the board. It produces a soft glue line that can be peeled away. 3M #74 spray adhesive is also available but because it is a spray it is not as controllable when applied.

At this point the vacuum plate with the imitation chamois covering was placed on the chuck with expansion jaws fitting into a recess on the back side. This recess is marked so that the jaws can always be returned to the same position. Circles are scribed on the chamois surface using alternating colors. This facilitates centering the work piece. If the piece is warped it may not hold on the plate in which case you need to change to another means of holding the piece. This is a vacuum drum chuck. The drum chuck is held by your chuck – a small hose extends from the drum to the vacuum transfer rod in the headstock. This gives an airtight fit. The work piece is centered on the drum by eye-balling it when it is rotated by hand. Once centered the base can be finished. [Note: Do not put the pump on/off switch near your work area – it could be inadvertently hit and the piece would come off.] When using the drum with a chamois edge the work piece cannot be too warped, especially if thick. It will not hold. To correct for this a soft, closed-cell neoprene strip is used around the contacting edge of the drum. Because it is closed-cell and soft it will mold to the surface of the work piece and keep it in place. The drum is made from a PVC coupler with a second PVC pipe inside as a sleeve. When working on the bottom of a piece the rubber strip is placed on the outside lip. (The sleeve extends past the edge of the coupler.) When working on the interior the strip is placed on the inside lip (the sleeve is inside the coupler). If there are any worm holes in the piece you can tape over the holes on the OUTSIDE. The tape will not be pulled off by the vacuum.

This concluded the morning session.

Afternoon Session: Dave began the session using a bowl blank. He encouraged members to participate with questions and comments. An adapted drive center was used because the vacuum tube in the headstock precluded the use of a regular drive center. The blank was placed between centers and balanced as to shape. Before turning rotate the piece by hand to be sure the tool rest is not in the way. Loose bark was removed for safety. Speed was started out slowly. A guideline for speed is: diameter in inches x RPM = 6000 to 9000. Thus for a 10 inch bowl the initial speed should be about 600. Once rounded the speed can be increased to about 900 RPM.

"Right handed" turning puts you in the line of fire. Note chips hit Dave in the chest.

With "left handed" turning the chips go right by.

When turning stay out of the line of fire of the lathe. One way to achieve this is to turn left handed. It’s a pretty good idea to be able to turn both ways. The piece was then rounded. The tool rest should provide most of the support for the tool. This also makes turning less tiresome. The support for the tool should be under that part of the tool that is cutting. When turning comfort is a factor. Second, the angle of the gouge is important. This is determined by factor number one – comfort. This angle can be from 30 degrees to 50 degrees. There does not need to be any strict rule. However, once you know your most comfortable position then your grind becomes specific for you. Third, the diameter of the piece is a factor. Once rounded the final shape of the piece is achieved by turning right handed. This permits the turner to observe the shape by looking over the upper edge of the piece. After shaping the tool was turned to full bevel contact on the side. Rolling the tool then determines the cut. This shears the fibers as does a skew on spindle turning. This cut eliminates or greatly reduces frizz on the end-grain and decreases sanding. Increasing speed lets you cover more work piece surface in a shorter time but it does not, however, change the cut.

The piece was then reversed and placed on the chuck. A very lively and amusing discussion occurred pertaining to the Vicmarc vs. One Way chucks. – No real winner as far as this author is concerned but Dave definitely feels that the One Way serrated jaws are superior. The tailstock was used initially, especially when roughing the piece. The interior of the piece was roughed from center outwards. This peeled the wood off. Then the interior was formed with multiple cuts straight into the piece. This avoided end-grain. If you make a thin wall bowl you need to do it in stages and not return to previously thinned areas. Sanding is done 120 to 220 grit. Then ScotchBrite pads. Oil/mineral spirits/urethane varnish finish is used – three coats. Be sure any rags are disposed of properly so they do not combust.

This completed a detailed and informative demonstration. Dave will have his source list posted on our website. A tape of this demo will be available in the CMW library in October 2005. The library will not be open when we have our auction on September 24, 2005.

--Bob Gunther

Dave's Website

Dave's First CMW Demonstration