Question
I have a saw blade that has been running fine for several years on my farm/woodlot mill. Just this week it got hot, dished away from the log, very unstable. It developed a very hot spot - blue hot - about one foot out from the center. The bluing is very concentrated , about 2" in diameter. It seems as though there developed a lump, although I cannot feel the lump with my fingers. The tension seems to be gone, as I can no longer saw without it heating up right away, with that same 2" spot getting very, very hot in just a few feet into the cut. Also, I noticed that at standstill, it is slightly dished with the rim area away from the log.
I had been sawing oak before, but just before this occurred, I replaced 4 of the 38 carbide tips chipped tips), and was sawing pine that had some knots. Before I get it tensioned again, I would like to know what caused this lump to happen, and how it can be avoided in the future.
Saw data:
48 " Dia
B style Bits
No of Bits/ Shanks 38
Carbide bits
6/8 Gauge
2" dia Hole
2 ea 5/8" pin holes 3" bolt circle
Hammered 650 RPM Right Hand.
Question
It will have to be hammered and re-tensioned to your specs that you already have. Sawing with dull teeth will cause the rim to get hot and wobble but most of the time you can run the blade cool and then sharpen and it will be fine. When you rub the middle and get it hot you are out of luck. The blue spot may remain after the hammer job but will not be a problem.
It’s just the cost of doing business. Also if you replace a few teeth you should sharpen the others. You can set your blade out of balance or the blade will cut harder in some areas then the rest and set up a harmonic wobble in the blade that can cause problems. All the teeth should be sharp or dull but not a mixture.
Unless you have a piece of wood get stuck on the side of the saw or other obvious event that heats the saw, a saw will lose tension slowly enough that you will notice it and can change it before this catastrophic failure happens. It is possible that when you changed the few teeth that these teeth had to work much harder because they were longer. Do not replace a few damaged teeth if all of the rest are fairly worn.
Maybe these logs were partly dried out? It is best to send this saw to a shop that can re-tension it. Before sending it, change all the teeth.
It is possible that the new teeth were a little longer. I’ll have to check that. However, the teeth are carbide tipped, and all others seemed to be sharp and square, showing little if any wear. I changed the 4 bits because they were chipped. The pine logs I was sawing were dry, as they had fallen in a windstorm several years ago. How does partial dryness come into play re: this problem?
I do plan to send the saw back to the manufacturer for re hammering, but need to think more about replacing all of these relatively expensive carbide teeth. On the other hand, compared to shipping cost and re-hammering cost, this may be advisable. Any more thoughts on this would be appreciated.
