A brief demonstration of the !nstrumenTool magnetic caliper is to be delivered at 5:30PM on March 2 at the 2012 Australian Violin Makers Association conference. Click here to see what’s on and who’s coming to this year’s conference.

The Roleystone School of Violin Making featured recently in the West Australian newspaper. Click here to read the article.

Extended footage demonstrating the !nstrumenTool is now available to view here at the ABC’s The New Inventors website.

Filming of the ABC’s The New Inventors television show is now complete and the episode in which the !nstrumenTool features will go to air at 8pm this Wednesday. If you miss the show it can be seen at the ABC iView site for a week after airing, following which, the episode may be downloaded from the main New Inventors site.

Cosmetic and technical improvements have been coming along well in a frantic bid to be ready in time for the filming of the Australian television show, ABC’s The New Inventors. Quite a number of luthiers and other craftspeople worldwide have now expressed interest and we value your patience as we work towards making a top quality measurement tool available.

Note also there is no decimal point, and the unit is displaying to 0.01mm! Don’t panic! There will be a decimal point and the unit will display only to 0.1mm (avoiding much confusion caused by hairs, dust, etc).

… but… its easy for the user to accidentally tilt a little bit. Tilting relative to the wood’s (or other material’s) surface means that the distance detected by the !nstrumenTool is less accurate. However, it turns out not to be too much of a problem for an electronic device like this as any tilted measurements cause the !nstrumenTool to detect a thickness greater than what would be the most accurate reading at that point (unless the two surfaces of the material are no-where near parallel).

In our second picture (exaggerated, at right), note the ball resting “off-axis”, still being held against the back surface of the wood by magnetic attraction, but no longer aligning with the direction of the probe tip. Actually the magnetic field does try to align the ball “on-axis” but eneven or angled wood surfaces can cause slight misalignment.

The !nstrumenTool will interpret “off-axis” scenarios as being a greater thickness of material and since such scenarios are always detected as greater-than-actual thickness we can simply tell the device to report the smallest reading it has noticed while the user gently wobbles it around (intentionally or just because our muscles wobble a bit). We’re planning at this stage that the likely procedure will be to hold down a button, let’s call it the “minimize” or “accurate-ize” button for as short (eg. half a second) or as long (eg. 10 seconds) as you like while observing the “current minimum reading” on the screen drop and then stabilize. So you’d place the probe tip at the desired spot, holding the !nstrumenTool as much at a right-angle to the surface as you can, press and hold the “minimize” button and watch the display say, for example, 3.2mm, then quickly 3.1mm, then 3.0mm where it rests, no longer decreasing no matter how much wobbling around you do. Then having duly noted the number you release the button and the !nstrumenTool goes straight back to giving “live” readings.

What happens during this brief button-hold process is that the !nstrumenTool checks its input rapidly and only changes the display if it detects a smaller reading than the current minimum, thus taking its display closer to the most accurate for the point you’re measuring. One of the nice things about this feature is that during the roughing out stage of violin plate thicknessing, measurements can be taken very quickly, either by not bothering with the “minimize” button or by just holding it down very briefly. On the other hand, more accurate measurements can be taken as the plates near final thickness or when measuring completed instruments – simply by holding the “minimize” button and observing the displayed measurement drop slightly, then stabilize.

More information about this is expected to be discussed on the forums once beta testing of the production model candidate is underway. To register you’re interest in being a beta tester feel free to contact !nstrumenTool.

Here’s the prototype being calibrated using the hard plastic calibration wedge. The target ball in this case is a magnetic ball, which seems to work well for the 4 to 10 mm range as it has enough attractive force at 10 mm not to easily drop off the back side of the material. We’d suggest (and will likely supply) an ordinary steel ball for measuring in the 0 to 4 mm range if the wood is soft (eg. spruce) … This is because the force of attraction between the target object and the !nstrumenTool‘s tip is stronger when the target ball comes near it – ie. when measuring thin material. The force of attraction is much reduced, however, by using a small steel ball and this should be sufficient to prevent denting of the wood’s inner surface.

As with anything like this, the user must check that spruce of similar thicknesses does not dent with the chosen configuration before measuring the plates of a Guarneri del Gesu or other highly prized violin!

At right is a detail of the gauge tip, calibration wedge and a target ball being held in place against the back side of the calibration wedge by magnetic attraction force between itself and a magnet in the gauge tip.

As you can see, the prototype !nstrumenTool has a machined, very slightly domed aluminium tip. We’ve noticed that we sometimes accidentally let the target ball smash into the probe tip and this tends to put little crater dents into the aluminium, so we’re now considering a hard polymer that can stand up to this sort of treatment.

Extensive use and abuse of this first prototype revealed a number of minor issues that we need to address before mass production, so a second prototype is scheduled for the next couple of weeks. More news then…

magnetic caliper

A new digital thickness gauge for measuring violin family instruments, guitars and for wood bowl turning. It can measure the thickness of nearly any material (except steel) between 1mm and 10mm thick to the nearest 0.1mm. A luthier’s and woodturner’s helper, !nstrumenTool is also handy in many other situations where traditional calipers are difficult or slow to use.