Measuring Wall Thickness with a Laser Pointer
by Fred Holder
This photo shows the mounting of the laser pointer to the boring bar shaft and the laser beam hitting the outside of the vessel.
Dave Thompson of Seattle, Washington started turning in 1991. He’s been interested in hollow turning for some time. However, it took the AAW Symposium in Tacoma, Washington in June 1999 and Frank Sudol’s presentation on the Boring Bar to really get him going.
Dave returned home from the conference charged with enthusiasm and built a boring bar set up so that he could start making hollow vessels. Frank Sudol uses wet birch for his deep hollow vessels and a light bulb on the boring bar near the cutter. Frank judges wall thickness by the density of the light showing through the wall of the vessel. It must work for him, because he turns vessels with 1/16th inch wall thicknesses. Frank notes that darker woods prevent the use of this method of judging wall thickness.
The light inside impressed Dave, but it also got him to thinking. If you can use a light inside to help determine wall thickness, why not use a light beam on the outside for the same purpose. Of course, you need a very condensed light beam that is no bigger than the tip of your cutting tool. Enter the laser pointer. The laser pointer has a very condensed beam of red light and seemed to offer what Dave needed.
This photo shows the setting of the laser beam to hit the very tip of the cutter.
Now, how do you make this work. He deduced, if you mount the laser pointer above the work, but pointed onto the very edge of the cutter and if you could keep your tool level so that the pointer would hit the workpiece on the outside to indicate where the cutter was on the inside, you would know where your cutter was inside the hollow vessel at all times. The boring bar that Dave had built would provide the stability needed. The laser pointer would provide the light beam.
This close-up view shows the laser beam moving down the side of the vessel as the cutter approaches the outside.
With a $16.00 laser pointer and miscellaneous handrail fittings and boat hardware, Dave added a laser pointer to his boring bar. The pointer was mounted high enough to clear the workpiece and adjusted to point directly onto the tip of his cutting tool. He was ready togive it a try.
Here Dave Thompson makes a cut on a hollow vessel, his laser beam shows the location of the cutter.
Dave says, that he has only turned pieces with walls down to 1/8 inch thick, but sees no reason why one couldn’t make them thinner. He says that he simply hasn’t yet had the nerve to go ahead and cut through the wall.
A finished hollow vessel. Wall thickness is one eighth inch.
With any thin walled hollow vessel, one must final turn the outside of the workpiece so that you can accurately judge the thickness of the walls. As mentioned, Frank Sudol uses a light inside his vessels and judges the brightness to maintain a uniform wall thickness. Dave Thompson’s laser beam makes this a bit easier. You don’t have to be able to judge the brightness of the light showing through the wall of your vessel to determine your wall thickness. You just look where the laser beam is falling. If the beam is set on the cutter’s edge and it goes over the side of the wood, expect a breakthrough, big time!
As long as you use a boring bar set up or some other method of holding your tool in a stable position to keep the laser pointer directly above the cutter’s edge, there is no reason why this method of judging wall thickness will not work on deep hollowed vessels or even simple bowls.
By clamping the laser pointer to the handle of the McNaughtonCenter Saver System one can accurately determine where the cutter is located and when it is time to stop and pop out the center.
Another such application of the laser pointer to determine location of the cutter is the McNaughton Center Saver System. Dave found that by clamping his laser pointer onto the handle of the McNaughton Center Saver and aiming the beam onto the end of the cutter, he was able to tell exactly where his cutter was in the blank at all times. He could tell, for example, exactly when to stop cutting and pop out the center. This application of a laser beam to the McNaughton System should greatly simplify its use.
This view shows the wall of the bowl near the end of the cut with the McNaughton Center Saver System.
A clean separation, with plenty of material remaining at the bottom of the bowl.
The application of the boring bar used by Frank Sudol and Lyle Jamieson and the laser beam wall thickness measuring device devised by Dave Thompson,will make deep hollowing and thin walled vessels much easier. It is quite likely that we will begin seeing a lot more deep-hollowed, thin-walled turnings in Instant Galleries. Imagine what the Instant Gallery at the AAW Conference in 2000 and 2001 will bring!