Jerky bandsaw cuts

[Kalia Kliban]

I have a Powermatic 1500 bandsaw, and am using 3/8" 3tpi blades since I mostly cut green wood. Occasionally the saw will start jerking forward in little bursts during a cut, leaving rough, nasty-looking ridges on the cut surfaces. It started today between one cut and the next as I was chunking up some birch (varying thicknesses from 3-8"). After the first jerky cut I stopped the saw, checked the guides (AOK), made sure there wasn't any gunk on the tires and tried again. Same result. The blade is really clean and new (a few days of gentle use), the tires are in good shape and the guides are all where they're supposed to be. The bad cuts feel like the sawblade is suddenly grabbing in a weird way, and jerking forward a little. I also checked to make absolutely sure the work piece was flat on the table and it was. Anyone else encountered this? Did you figure out what was causing it?

 

[Brian Gustin]

Hmm I'd wonder about the rake on the teeth? I havent encountered anything like that (indeed I only have a teeny little 9 inch bandsaw with a 3 inch-ish resaw capacity.. LOL!) but I seem to recall reading something while reading about bandsaw blades, something about different rake on the teeth.. and as you mention a new blade, I wonder , since there seems to be more to a bandsaw blade than width, thickness, and TPI... just a thought..

 

[Keith Mombourquette]

I tried a 3/8 3 tpi blade on my Rikon 10-326. I was having the same problem, so I contact my blade supplier and they recommended a 4 tpi blade, which has solved the problem for me.

 

[Dave Bunge]

I have experienced the same thing on occasion. I suspect it's caused by the wood lifting slightly off of the table, then getting caught by the teeth and slammed down against the table. Possibly caused by a not completely flat surface on the blank (chain sawed surface). Slowing down the feed rate seems to help.

 

[Kalia Kliban]

On closer inspection I realized that my upper thrust bearing (the one behind the blade) was a little too close. It's possible that as the blade settled in it started tracking a smidge further back. I eased that off and it solved the problem. It was a small adjustment that made a huge difference. Now the big question is whether I'll remember that the next time my saw does this.

In general, I haven't been too pleased with the stay-put-ability of the blade guides on this saw. I had to use Loctite on all the knurled locking screws, which made them a pain to adjust by hand. At least they're not all working loose on their own anymore...

 

[Clifton C]

I'm with Keith, except I was using 4tpi, my suppler recommended 3 and I got the same results you got and went back to 4. The blade kind of zipped forward as if self feeding. Looking at the cut, there were the normal vertical lines from the teeth but also some lines or ridges slanting back along the cut, maybe 30°ish. So I've stuck with the 4 tpi,

Ps. Delta 18" boat anchor...

 

[Clifton C]

Glad you found the problem, I had a terrible time with the guides on my delta 18" B/A. Went with the Carter Guides and it helped...
Still wouldn't recommend the saw.

 

[Kalia Kliban]

They're surprisingly finicky tools, but indispensable. I'll look into getting a 4 tpi blade next time I order blades, and see if it makes a difference.

 

[Gary Beasley]

I second those Carter guides, made a world of difference on my Grizzly.

 

[Timothy Allen]

That jerky cut could be due to a kink in the blade - a fore-and-aft kink.... Rotate the blade slowly by hand and watch closely.

 

[Kalia Kliban]

That jerky cut could be due to a kink in the blade - a fore-and-aft kink.... Rotate the blade slowly by hand and watch closely.

I checked that. There's a very small side-to-side wobble, maybe 1/64", in one spot but the jerkiness is really irregular, and it seems like a blade kink would cause a tiktiktik kind of defect in the cut, very regular with each rotation. Adjusting that upper thrust bearing totally fixed it, whatever it is.
I'll take a look at the Carter guides. Heard lots of good things about them.

 

[Russell Nugent]

I get that sometimes on brand-new 3tpi blades in green wood. after a while the problem goes away for me.

 

[odie]

I get a lot of rough cut exotic bowl blanks that aren't quite square. Some are straight from the chain saw. Uneven surfaces are commonplace with the wood I have to deal with. I've had the same problems with the jerkiness. Three and four teeth per inch were problematic for me. I've since gone to more teeth per inch......I'd have to look, but I think the current blade is 8 TPI. All the problems I had been having are solved with more teeth per inch.

edit: I checked, and my bandsaw blade is indeed 8tpi.....

-----odie-----

 

[Lou Jacobs]

I don’t think you’ve mentioned blade tension. Is the blade as tight as it should be? I have a Delta 14” saw. When I put a new or resharpened 3 tpi either 3/8” or 1/2” blade in the machine it cuts wet blanks up to its 6” capacity like butter. I slowly get poorer performance as the blade wears. I have to remind myself to consider a new blade when I start to see it struggling with cuts.

 

[Kent Jaffrey]

I’m with Dave. I have had this happen with a similar blade and it is often when the base of the blank isn’t flat and the teeth pull the wood down to the table. I found on blanks that aren’t flat it does help to make sure it is “tilted” so the area where it is cutting is touching the table so I push done a little on the cut side and lift up a little on the opposite side if needed.

 

[john lucas]

I had it happen yesterday when resawing a 2x8 piece. Pretty sure it's because there is the slightest link in the blade. It is an old blade and I had just cut a whole bunch of green wood for a friend. So I'm pretty sure it's a combination of dull blade a that little bump in the blade.

 

[Dave Landers]

I had something similar going on yesterday. Sharp / new blade, wood flat on the table, soft wood, etc. But the saw would just start bucking sometimes.
Discovered that this blade was tracking farther back than it should, and the back of the blade was hitting the insert.
Hard to see since the insert is covered with wood during the cut

Adjusted the tracking and all is well again. Sounds similar to what @Kalia Kliban found with the blade hitting the bearing.

 

[Timothy Allen]

blade kink would cause a tiktiktik kind of defect in the cut

With mine, it was a ka-chunk, ka-chunk, ka-chunk.....

 

[Kevin Weir]

I can also verify that moving from 3 tip to 4 tip eliminated the grabbing effect. I also changed to a blade designed for cutting green wood. I think the company is tufftooth.com

 

[robo hippy]

My 'fine' blade is 3 tpi. My rough blade is 1 1/4 inch with teeth at about 3/4 inch apart... Only times I have had the jerky type cuts is from not having a flat bottom on the wood I am cutting, and it really helps to have that dead flat. Seems like it may have happened with some flat boards once or twice, but can't remember. That could be an adjustment problem. When I change blades, I don't have to adjust the guides. Hand spin the wheels and mostly worry about the thrust bearing. Rather than adjust it, I use the knob on the back of the top wheel to move the blade to one side or the other of the crown of the wheel.

robo hippy

 

[John Kelsey]

my ancient Delta took to bucking in the cut, I tried diff blades and tension settings... but when I finally took it apart I found the yoke casting that holds the top wheel axle had worn itself an oval-shaped hole that needed to be round. New part wasn’t easy to install, but now with it the saw runs like a top. New tires helped too.

 

[John Jordan]

Get a piece of thin ply or masonite the size of the table. Saw into the ply as far as needed to locate the blade in the right place. Clamp the edges down. It gives you a zero clearance slot which supports the wood at the cut. I suspect it will take care of the problem.

Hope you are well.

John

 

[Kalia Kliban]

Get a piece of thin ply or masonite the size of the table. Saw into the ply as far as needed to locate the blade in the right place. Clamp the edges down. It gives you a zero clearance slot which supports the wood at the cut. I suspect it will take care of the problem.

Hope you are well.

John

Hi John,
Definitely not a clearance issue. I do have a zero-clearance auxiliary panel that I can pop on when I need one, but this is something else entirely.

 

[Bill Boehme]

I have a Powermatic 1500 bandsaw, and am using 3/8" 3tpi blades since I mostly cut green wood. Occasionally the saw will start jerking forward in little bursts during a cut, leaving rough, nasty-looking ridges on the cut surfaces. It started today between one cut and the next as I was chunking up some birch (varying thicknesses from 3-8"). After the first jerky cut I stopped the saw, checked the guides (AOK), made sure there wasn't any gunk on the tires and tried again. Same result. The blade is really clean and new (a few days of gentle use), the tires are in good shape and the guides are all where they're supposed to be. The bad cuts feel like the sawblade is suddenly grabbing in a weird way, and jerking forward a little. I also checked to make absolutely sure the work piece was flat on the table and it was. Anyone else encountered this? Did you figure out what was causing it?

That is generally caused by a combination of a dull blade and excessive feed pressure which causes the blade to twist. Sometimes wet wood that usually cuts easily will have a high silica content that will very quickly dull a blade. Excessive feed pressure dulls a blade because the gullets get packed with sawdust causing the blade to get very hot. If the guides aren't set properly the blade can twist in the kerf which leads to excessive blade heating and dulling.

 

[Michael Lamka]

Maybe consider purchasing a carbide tipped blade? 2 to 3 times the price of non-tipped blades, but cut like hot piano wire through butter and last 3 days before forever arrives.