Still trying to clarify overlap

Wednesday August 01 2007

A reader writes:

I still don’t get what you mean by “set” the overlap. I set my overlap when I tie, by folding the cane onto the staple with a slight overlap. Then (the abbreviated version), I scrape some, clip the tip, and scrape some more.How do you “set” the overlap once you’ve already tied, and what makes the click sound? Is it grabing the two blades with one hand×with the tip facing you, left thumb on bottom, left first finger on top and a sliding motion?

• “I set my overlap when I tie.”×I also tie so that my top blade is slide over to the right. But this isn’t setting the overlap.
• “How do you “set” the overlap once you’ve already tied”×Yes, I slide the blades apart (although I guess I’d put my right index on bottom and right thumb on top). Not a lot, just enough to click.
• “What makes the click sound? Is it grabbing the two blades in one hand?”×I’m not sure your question. What about the gouge makes the click sound or something I do with my fingers? The click sound comes from the internal shape of the blade curvature and how it gouges out and shapes the inside of the cane.

Now, what does the click say about the gouge? (or how does it function?) The overlap ensures that the side of the reed is set into the other blade’s gouged surface. The “Click” ensures that the entire side of the blade (not just a small part of it) is set. Sometimes when I tie I get most of the reed overlapped, but particularly up by the tip it doesn’t completely overlap. Most often, my click comes from the middle of the reed, up to the tip clicking into place. The lower part of the reed is already overlapped by the tie.

This tool is going to be one of your most valuable measuring instruments in your box. It includes a radius gage that is viewed from the top so youcan use a light source behind it very easily. it also includes a width gauge to check that your cane is planed to the correct widge to be used with the Opus 1 gouger. 8mm is the recommended maximum cane width.

- Robin Driscoll’s Website.

Some have also been asking me what about the gouge encourages the overlap to click into place? It’s difficult to describe since one can never describe a gouging blade curve perfectly. Even specific figures do not explain the rate of taper and what happens in between the locations of measurements of those numbers. But in general, I find that having the correct rate of taper on the side is critical to getting a decent overlap click. For example, I have a radius measurement point locator little thingy that you can buy from Mr. Driscoll over at Opus 1 Gougers (go under recommended tools). Although it does not tell me everything about the rate of taper of the gouge, it is a tool that allows me to mark locations so that I can measure the thickness of different points of my gouge with a dial indicator. For example, I know figures on my graf blade need to fall around (.62, .58, .52, .43). For these figures, the first measurement is the very center, and the following measurements are measured at 1mm out from the center consecutively. (Although I warn you, these numbers are very “loose”. For example, the first ratio of .62-.58 is equally affected by the width of much internal spine which is built in from a double radius gouge. If the internal spine is too wide, you will have a dull sounding reed with inflexibility in pitch.)

Where is all this leading me to? Back to the click, of course! I find that a good click often depends on if the rate of taper on the sides tapers fast enough. For example. If the last measurements are .52 and .48, it often doesn’t want to click audibly for me (although this isn’t always the case.) Similarly, if the last points measured at .46 and .43, I wouldn’t expect a “click” either.

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