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Sawing frozen logsQuestion
Forum Responses
Gene Wengert, forum technical advisor
Sounds like you have a frost chair in the face of your tooth. Bring the swage down on your tooth (drop your kerf). If you have fine dust, you may be feeding too slow. I assume you are running a wide band with swaged and shaped teeth, not a narrow band set toothed saw. The idea in frost is to keep the sawdust from spilling out of the gullet of the tooth and making the saw run. The frost chair will catch a wad of dust and tends to wipe the cut clean. You can not feed as hard in frozen wood, because your saw will run and you will break teeth. But when you feed slower, your sawdust will be finer. So do not swage your tooth as wide as you normally would, to make for less clearance between the saw and the cut, to keep the finer dust from spilling out of the gullet. Expect some problems no matter what in the fall and spring when your wood is not frozen all the way through. The running in the cut is not all a result of sawdust spilling out of the gullet of the tooth. Frozen wood cuts harder, loads the saw more and eventually pulls the tension out of the saw. I have used the above system on a 5 foot Horz. slatt bed resaw and a 54" McDonough line bar with good results.
From the original questioner: I dropped the kerf by one gauge after sharpening and swaging, and I am going to try dropping one more size. The next thing I am going to try is slowing down the speed of the blade by changing the pulley on the drive motor. I would look at changing the feed rate rather than the speed of the saw. Your saw speed should be between 7,000 - 10,000 surface feet per minute. As a starting point, the tooth bite for a saw with 1 3/4" tooth spacing and a 5/8" gullet depth (.625 square inch gullet area) with an average depth of cut of 11.5" would be .043" per tooth. You can figure out how many teeth per minute for a given tooth space, wheel diameter and wheel RPM and figure feed rate in feet per minute. Normal tooth bite may be .043" to .052", depending on depth of cut, gage of saw plate and width of saw. That is for unfrozen wood. A book named "Sawmill Feeds and Speeds" Published by Armstrong Mfg. Co., Copyright 1964, gives this formula for tooth bite: "Tooth bite equals saw thickness, less 4% for each inch less than 10" of saw width, or plus 4% for each inch over 10" of saw width. On a saw 10" wide tooth bite equals saw thickness." Quelch, in the "Armstrong Saw Filers Handbook" recommends the following average speeds in lineal feet per minute: Softwood 8,500 to 10,000
RPM of a 4 1/2 ft. wheel for a given saw speed in feet per minute is:
I would drop the kerf a bit more and make sure you are not under feeding and you are not short on HP.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment). Comment from contributor A:
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