bandsaw blade question

[Bob Hampton]

ok guys i need some advice
I have a jet 14" Bandsaw w/riser and i have a problem with the blade...
the blade runs true just running by itself..no side to side play ..no front to back play ..its tension is correct as far as i know..did the flutter tension when i installed it .
here is the problem..when i try to make a cut the blade suddenly become's.."jerky" is the best i can describe it ..like as if its hanging in the cut..if u dont have the stock flat on the table it will slam it to the table.
any idea's?
I have run the blade by hand and checked all the teeth and there doesnt seem to be any damage to any.
thanks
Bob

[John Coloccia]

re: slamming to the table
That's actually pretty normal. There are some cut I make, that I would NEVER in a million years recommend anyone else make, but I do them and it requires passing the stock through without being well supported....and if you're not careful, it WILL slam it down on the table. That's perfectly normal.

re: the jerkiness

I just went through this on my own bandsaw. I couldn't figure out what the heck was going on. Are you running Timberwolf blades by chance? In my case, it ended up being the blade. It looked like it was running perfectly but I'd get this weird cutting action where it would cut really well for a little bit, and then hang up....and then cut well and hang up. I never tracked down what the specific problem with the blades were but they all started doing it and changing the blade finally fixed it. Maybe they were just dulling unevenly for whatever reason. I don't know.

My suspicion was that they weren't clearing out the sawdust as well as they should have been because there was always a little poof of sawdust when the thing started cutting well again. This really drove me up a wall for a little bit, though, because it didn't seem to be related to the position of the blade at all...nothing at all rhythmic about it.

I don't think I'm helping but that's what my experience was and I think I understand very well the "jerkiness" you're experiencing because that was the only way I could think to describe it too.

[David Weaver]

Set up a piece of wood in front of the blade with the saw unplugged, clamp it or whatever.

turn one of the wheels and see if the position of the teeth changes relative to the piece of scrap as you rotate it through the full length of the blade as well as a full rotation of the wheels.

I have seen saws where the wheels weren't in plane where the blade oscillates a tiny bit back and forth, you don't see it when it's running, but when you put it to the cut, you can hear the oscillation as the blade goes back and forth in a heavier and lesser cut very quickly.

[Prashun Patel]

Describe the kind of cut your making and the specs on the blade you're using. How thick is the wood?

If the piece is not supported (like when improperly cutting bowl blanks from logs) even if you control the piece or wedge it, it is possible for the blade to pull the piece down a tad once the kerf is started, which can result in the blade twisting - maybe even so slightly that you don't notice it. This dramatically decreases the cutting efficiency and can make the cut jerky.

The piece must be supported in a single plane throughout the cut.

[Josiah Bartlett]

You also want to make sure you use a blade with a tooth count that leaves at least 3 teeth in the kerf at any one time. If you try to cut 1" thick stock with a low TPI resaw blade, this will also happen.

[ian maybury]

One of the risks with cutting with the workpiece only partially supported on a band saw is that if it does get away on you and is slammed down there's a chance of kinking the blade.

Just flying a kite, but could some sort of slight bend in the blade possibly be an issue?

Another source of issues can be the weld - no doubt they were exceptions, but the few Timberwolf blades I tried had slightly misaligned welds. As in the back of the blade wasn't quite straight. It looked to be running true from in front, and even from the side it needed a slip of wood held against the back to feel the wobble.

Could there be something about the shape of the workpiece that's causing it to flex or tilt and maybe close the cut at times?

ian