Guide Alignment and Blade Breakage
Premature blade breakage could result from excess tension or misaligned drive wheels and guides. October 4, 2007
Question
I am new to sawing. I have a Timberking B20 and am cutting pine and hemlock. In the first few days, I was running blades too long, 4-5 hours, so they were breaking. I now use new blades for 2 hours and send them for resharpening. When I use them again, after an hour and a half, they break. I use Timberwolf blades under 800 pounds of pressure. I have tried running them with water and without. I also tried half diesel/chainsaw oil. Always the same problems - blades break often.
Forum Responses
(Sawing and Drying Forum)
From contributor P:
Something's wrong. Maybe too much tension. I've been sawing on Wood-Mizer blades for 2 years and never had one break yet. I bought 30 blades when I started and most of them have been sharpened 3 times. I can usually saw about 1,000 bf (of pine) before they start cutting wavy.
From contributor R:
Check your tension... I'm not sure about the PSI you mentioned, but I do know Timberwolf sells their product as requiring much less tension to operate than other saws. I've also broken blades prematurely with excessive feed rates.
From contributor B:
I have a B-20 also and had the same problem. It was a misalignment problem (from the factory). Look at your blades carefully and see if you have any cracks from the gullet or from the back side of your blades. We can go from there. Also throw the torpedo level away and get a 24" blue level at the orange box store. The torpedo level is not accurate enough to do a proper leveling and alignment job on a good band mill. 900 to 1000 lbs is a good number for your blade. Tk recommends 1200, but I feel it is a bit much. Do not buy Timber Wolf's urethane belts for your band wheels - they don't work on a B-20. You mentioned you were cutting pine and hemlock. Use a good bit of Pinesol with your water and if you see some bubbles (that's good). Also, to keep the sap from building up on your rails, rollers and guards, spray them with Pam. (Sam's has the best deal on both).
From the original questioner:
Cracks that I saw were from the gullet. The TBWolf blades run at 850 psi on a B20 and the back of the blade runs flush with the back of the wheels. My B20 has a rubber belt around the wheels. I'm not sure if it is a new feature. I will try Pinesol...
From contributor B:
I will be glad to walk you through a good alignment. This will give you an idea of where to start...
You need to level the bed of your mill very accurately, then take the good 24 inch level and put it across the face of your drive band wheel and make sure the wheel is exactly 90 deg from your bed. Then check your idler wheel and make sure it is also exactly 90 deg to your bed. Your blade tracking is set with the tow in adjustments according to the CD that is furnished with your mill. The band wheel squaring is done without tension on your blade. The guide roller's flange should be adjusted about 1/8th of an inch from the back your blade under tension. Another important adjustment to check is the bar that your adjustable guide roller slides on. It should be level with the blade under tension. Mine from the factory had 3/8th of an inch taper. Your guide rollers also should be about 1/8th below the band wheels. Your blade then should be level with your bed to cut good lumber.
From contributor J:
You state that you run the blade even with the back of the wheel. Try centering the blade on wheel. I believe a lot of stress is being created on the front of the blade. For 1 1/4" blades, Wood-Mizer specifies 1/8" from the bottom of the gullet to the face of the wheel. Your blades should get from 4 to 6 sharpenings before breaking from stress cracks or fatigue.
From contributor T:
Could this be a guide bearing problem?
From the original questioner:
I have checked the guide rollers and just by looking, they are not parallel with the wheels.
From contributor S:
When the v belts get worn down enough so the blade touches the metal on the wheels, blades will break in a hurry. Other than that, keep the back of the blade to the guide wheel flange at 1/16 to 1/8". On a B20 the back of the blade should run flush with the edge of the big wheels. B20 5500 hour blades run 5 to 6 sharpenings unless v belts get worn.
