TK 1220 mill. The blade drops about 1/4" after a cut. The blade looks in exact same position before it started doing this and appears to be setting properly on the wheels. So what causes the blade drop?
dull blade
Lower teeth duller than top teeth. Try new good blade and see what happens.
More than likely its the blade, But for the sake of it what are you sawing? And how dry is it? The blade could be heating up in the cut and dipping/dropping due to many reasons, most commonly a dull blade but also could be no/poor lube and or buildup on the blade. You could also be sawing year old hickory and that would just be wrong :D. is it only dropping as it exists the cut or is it a wavy cut through out?
OP here. The blades seemed to have always dropped very slightly, maybe 1/64" just enough to require a slight lift of the blade for a return. Notice I mention blades as in plural. Never concerned myself with it, but over recent time seems to be worse and yesterday it drops a 1/4" and the end of a 13' cut. Been cutting alder, maple and yesterdays cottonwood. What a strange wood cottonwood is!! However, my focus on this forum is cause for the blade drop.
I will look at a blade change next time i jump on the mill but might still be facing this problem.
Thanks!!
It sounds like the blade is climbing through the cut, then the guides correct after the exit, it could be as simple as a blade issue, and it could very well be an alignment issue, this is a toughy by not seeing it in person, david
I would then go through a blade alignment, it has to be climbing to some degree, then going back to the machine setting at the exit, david
Mill misalignment, pitch buildup on under side of blade, going faster at the end of the cut, any of these can cause this I found, but the biggest culprit to cause this is not enough "set" in the blade! I have learned after exiting each cut to remove cut piece and drag the blade back over the cut when I finished sawing and if the blade comes back onto the log w/o help and is tight to the piece I have cut, blade set is good (blade not turning of course) Your bottom teeth could be touching the guides and removing some of the set in them also.
I'm reading....blade dropping AFTER the cut. So when the blade exits, the blade drops.
Could it be the head of the mill dropping?
When the blade is dull it is pushed off the log as it cuts. So when it's exits the log it drops down.
This, I read somewhere, is called "blade push off ". It is because the blade is dull as mentioned and is not cutting truly on line with the guide wheels setting.
When you see; this is an "tell" that the blade is dull. A sharp blade should not drop when exiting the log.
Jim Rogers
You are missing one thing. If the blade drops when exiting the cut, it's a sure bet it climbed somewhere else. Find the cause of the climb and fix that. Most likely dull/not enough set blade, but there are some other not so obvious causes. I assume the TK mill uses blade guide rollers. A mis-aligned roller can push the back edge of the blade downward, causing the blade to climb. Gets worse when the blade is dull and gets pushed back against the roller flange with more force. A worn roller will usually have a curved ramp where the flange meets the flat part of the roller. If the blade gets pushed back against the flange, the back edge of the blade will be shoved downward by that ramp, resulting in climb. Guide rollers aren't nearly as simple as they look, and they can cause a sawyer a bunch of grief...
Blade push off is a common problem, that's why it is recommended that you bump the head up before gigging back. Logs that have sat any amount of time dry on the ends, that can cause the blade to push off, even with a sharp blade.
I've had this problem with my 1220. Took me a while to figure it out but in my situation it was either dull blades or mill being unlevel. Since my mill is portable - and I've learned more and always run sharp blades now - it seems to always be mill being unlevel. The 1220's sections are bolted together so there are a lot of places it can be unlevel. Right or wrong and after initial leveling - I use a tight string line now stretched from one end of rail to the other and jack it up until the mill rail/runner or whatever just touches the string all the way down. This has worked well for me.
Check guide roller wear. Measure diameter at end and then next to flange. Should be the same. Cone shaped guide rollers cause problems. Check that set is same on both sides of blade. Also check that blade is not dished. Put a straight edge on blade and see if it rocks or you can see light through the middle. This can cause nightmares. The more the blade is used the more prone it is to dishing.
What do the boards coming off the mill look like? are they thicker on one end, as in tapered, or thinner just at the start and then uniformly thicker the rest of the way?. I suspect dull blades or perhaps entering the cut too fast.
X2 for the guide rollers. I have a well used TK B16 and was having the same issue. After trying several new blades, I checked the guide rollers and replaced the bearings in both. My idle side roller must have had the bearing lock up at some point and turn inside the roller causing a very loose fit. I'm currently waiting on new guide rollers and bolts from Cook's. Good luck with yours.