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From: Jim Benton
Categories: Filer's Training
Date: 25 Dec 1999
Time: 09:38:52
Remote Name: 216.60.209.58
This is an issue I have encountered several times over the years. The thing is that it is difficult to grasp, but simple to explain. The real issue is the tooth stop design of the 6900-B shaper. If you look closely, you will see that this design offers no support to the top of tooth during the shaping process. The pressure exerted on the sides of the tooth stock cause the metal to migrate to the point of least resistance, which is upward in this case. The best option I have found, if you choose to use this shaper is to learn to control the migration of the metal. "What does that mean?" you ask. Well, by very precisely contolling the swage performance one can control the migration of the metal during the shaping process. I realize this sounds complicated, but it really isn't...it is simple. DO NOT OVER- SWAGE. Make sure that the swaged tooth (before shaping) is not more than 0.010" wider than the target size of the shaped tooth. The theme is to swage barely enough to obtain the desired stock. Then, swage frequently, I recommend every other run of the blade. Swage & grind and run the saw, then resharpen and run it, then swage & grind again, etc. You said you were running an 0.078" blade, then your target size should not be more than 0.156" which is double the plate thickness. Steel mfgr's will not guarantee their product beyond this amount. You will find that 0.145" will work better with less crumbling. Now, when grinding make certain that you remove twice as much stock from the top of the tooth as you remove from the face and you will maintain the tooth profile properly.
From: Steve Hoas, benchman
Categories: Saw cracks
Date: 01 Apr 2000
Time: 12:10:55
Remote Name: 139.142.86.183
In regards to resaw cracks that we have been experiencing I may have finally found our problem. It seemed that the saws would run grest for the first few months of service but as they got older and were ground down an inch or so , they would start to crack badly. we went over the machines (L&B twin horizontal air strain) with a fine tooth comb and did find a few things that were instrumental to crack formation (see other posting) but the problem still persisted. I suspected that the saws my be getting case-hardened by friction and heat from the whells and guides but with out having a metalurgical test done I could not prove it. Last week another saw cracked all to hell and we cut it up. After the first cut was made and the saw was laying on the floor I noticed that the back loked unusually curved so cut a five foot section out of the saw and put a straight edge on the back and measured the center with a digital caliper. Much to my supprise the back in 5 ft. was .040. It should have been .015 which is 1/64 in 5 ft. The dial back guage that we were using had slowly gotten out of ajustment and was giving us progressivly longer backs on our saws. We have since started shortening the backs on the saws and they are running MUCH better now They are way easier to bench needing less time to level and the tension stys more consistant