Below are excerpts from an article I wrote for American Woodturner magazine about lasers.
RED HOT” LASER MEASURING
Accurate, fast, and fun, but how do we use it?
Lasers, lasers, lasers, everyone is talking about lasers! Lasers help measure hollow form wall thickness. Lasers have more uses and provide exciting technical short cuts to understand problems such as measuring the bottom of bowls while using coring systems, or showing the shape and depth of the inside bottom contour of any turned form, even though the waste block area. There are many methods of measuring the wall thickness of hollow forms; many have been around for quite some time. I didn’t get too excited about the old measuring systems because they had limitations and I didn’t want to work within any set of parameters that would limit my creativity. Some of the new measuring systems also have limitations. I want to open up possibilities, not limit them.
My laser system can be used to measure anything, any place, any wood, any thickness desired, tiny Christmas ornaments, or huge vessels. It doesn’t impede the tool movement to get into those hard to reach places you have been dreaming of creating.
The whole idea of the laser is really simple. You set the laser light so that the beam of light passes by the cutting tip at the distance you want your wall thickness. The “gap” or distance between the light and the cutter is your wall thickness. (See Illustration 1) While the light shines on top of the hollow form, the cutting tip is hogging away wood inside the vessel. When the laser shines around on the side of the vessel, slow down and watch your cutting pace. As the light no longer shines on the turning, it skips off the edge of the form and shines on the floor, you stop cutting! The set gap between the light and the cutter is now the desired wall thickness. Go back lightly now and smooth away any tool marks without reducing wall thickness any further.
To set the laser, lock down all supporting hardware so that all you have to move for an adjustment is the bracket holding the laser. Now all future adjustments can be made easily by moving or swiveling the laser holding bracket at the end of the tubing that supports it.
To prepare for measuring with the laser system, the first step is to set the boring bar at the angle that you need to get through the little entry hole and put the cutting tip in a position to cut. Note the angle of the boring bar assembly. Pull the boring bar out of the vessel and support the boring bar on the front and back stabilizing tool rest at the same angle that is needed to cut. If you set the laser at one boring bar position and go into the vessel and cut with the boring bar swung around at a different angle you will get a false measurement. With the boring bar supported on both tool rests, you can now position the laser to measure perpendicularly, or at 90 degrees through the wall. In a hollow form or deep sided bowl the standard caliper won’t reach the bottom contours. It is necessary to keep the measuring at right angles or 90 degrees to the surface at the point where the measurement occurs. If you measure at an angle through the wall thickness at more or less than 90 degrees, you will get a false reading. Figure A above shows the difficulty keeping the perpendicularity with regular calipers. Now the laser measuring process uses the laser and the cutter as measuring points in contrast to the calipers. The gap in the calipers is the same as the gap used by the laser. The success in measuring accurately is dependent on measuring straight through or perpendicular to the wall. I use the lines on a plastic card as an aid to show me where to adjust the laser light. The line drawn near the edge on the business card is my wall thickness and the arrow line indicates the direction that would measure perpendicular through the wall. The star on the card is the laser position. (See Illustration 3) Now place the card along the outside of the hollow form where you will need to hollow and at the angle needed to measure perpendicularly. Move the card from the work, keeping it at the same angle, and place the card next to the cutting tip. Move the laser holding bracket to shine the laser light dot on the star on the card. The cutting tip is inside the vessel and the light will be outside the thickness. You are ready to hollow.
As with any of the other measuring methods, the measurement must be close to perpendicular to the side of the vessel. The position of the laser in relationship to the cutting edge must be kept perpendicular. The laser needs to be moved periodically depending on the shape of the vessel. See Illustration 3 above to see an example of the positions I would put the laser in to measure accurately. The setting of the laser with the card helper only takes a few seconds with one hand on the laser holding bracket and one hand on the card. Now measuring is easier, faster, a lot faster, and accurate, plus a lot more fun. Maybe it’s not fair for those using the laser, since they can do hollow forms in half the time. Does that mean they make twice as much money if they sell their work, and have twice as much fun?
Let’s explore even more exciting uses for the laser. There is the inside bottom of the vessel to deal with, which is hidden in the waste wood of the face plate. You can reset the laser to do bottoms so the gap between the laser and the cutting tip is zero. (See Illustration 4) Now with the cutting tip down in the middle of the bottom of the vessel you can see exactly where the inside depth is. Draw a line on the outside of waste block at the edge of the laser. That’s the bottom!! No more attempting to measure the inside depth and extrapolate it somehow to the outside. Is that cool or what! No more cutting a hole in the bottom when you finish the foot of the form.
Hang on! It gets even better!! With the laser still set with a zero gap, you can watch the light as you cut the bottom contour inside the waste block area. As you make a cut inside the vessel, the light will flow from the previously measured center of the bottom to the previously measured side wall thickness where the waste block ends. (See spots on Illustration 4) Watching the laser light move on top of the waste wood allows you to make any shape bottom you want to create. Flat bottoms, cone shape bottoms, or just a nice rounded bottom are all a piece of cake. Take care not to cut in the previously measured wall because the laser will be at the tip and not set to measure the wall again.
I manufacture the laser system to fit any boring bar unit.