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Re: pros and cons of   V.P.D.

From: Steve Hoas
Date: 14 Dec 2002
Time: 11:42:31
Remote Name:


A few years ago we tried the variable pitch saws on a 8 foot double cut head saw and our 6 foot horizontal twin to see if it would help with washboarding. We didn't buy new grinding equipment or retro fit our old Armstrong grinders. What we found was that the saws still washboarded the wood right from the get go. As we sharpened the saws the thinest tooth got so thin that it became fragile and would break off, I know that if we had spent the money for the proper grinders the saws would have held their original profile and this problem would not have occured. Also, if we had tried a variable pitch/depth profiled saw there may have been further benefits, as the manufacturers claim, but as I said, the saws washboarded on their first run so we just ran them until they went out of service. The sawyers were sceptical as well about their performance and didn't like the sound of them either. The tooth profile we used was 5 tooth segment but I cannot remember the measurements but the largest tooth space was 2-3/4 inches to match our profile cams.This was on the head saw. The 6 foot twin was based on a 2-1/2 inch tooh space. I feel that the washboarding came from having tooth spacing grouped in larger segment rather than our normal 2-3/4 inch tooth space so the pattern repeated itself but with a wider space due to the 5 tooth segment. It was deemed that the experiment was uneventful and with out spending a huge amount of money to get the computor controlled grinders it was not worth our while to do so as it may not have improved the sawing performance of these saws. Our sawmill is in Revelstoke British Columbia, Canada, and we tried these saw in Western Red Cedar as well as Spruce, Douglas Fir and Hemlock. Our sawing conditions include high mountain growth as well as sub-zero temperatures. The machine centers were a 8' Letsun Burpee with mechanical strain (18,000# using 16in wide 13 gauge saws) and a 6' L/B USNR horizontal twin with air strain (22,000# using 10 inch wide 16 guage saws). I hope that this information is of some value to you. I am sure that there are a lot of happy customers out there using these saws but at one of our Filers Conventions I asked a number of filers about their experiences with these saw and they were much the same as mine and they opted not to continue using them as well. Best of luck , Steve Hoas