Band-saw Cutting poorly

[Finn_olsen]

I have recently come into possession of an older Kalamazoo 7AW Horizontal band saw. I use to work in a fab shop around larger saws and I'm familiar with how to run them and keep them cutting well, but this machine has me scratching my head. To start, the plug was bad so I separated the wire harness and got the pump detached from the saw, un-seized the pump and replaced the plug, slapped it together and the whole thing ran great, a few taps with a wrench and the pump came alive as well. Everything seemed to run great but after adjusting the arms that hold the blade in place and getting a piece of rec tube in it to test cut, it cut a slight curve instead of a straight cut. I adjusted the arms further so that the bearings pinching the blade would cover more of the blade and I even shimmed the arms so the blade would have a more square cut and I was able to get the cut closer to square, but its still off by about a 1/32th of an inch. I know when I go to cut larger material the cut will only walk off further and I desperately need to get this thing cutting straight for an upcoming project. any tips? additionally it has a new blade and it has coolant running through it as well.

 

[F0307 Loss Parameter]

Seems obvious, but is the blade tight enough? I got a Marvel for a song because "it didn't cut straight" and they didn't feel like dealing with it. Looked up the manual how to adjust the tension, set it to the proper tension for the blade, and was able to hold .0005 over a 5" cut.

 

[Houdini]

If blade tension, and feed force are reasonable, its usually the blade guides are worn and need replaced.
You could also make sure the pivot on the saw isn't worn and allowing the whole thing to move at an angle.

 

[Metalurgent]

Maybe try another "new" blade. I've had blades badly set on one side that walked.
Check the setup of the rear pivot vs. the back fence and base through the range of motion of the saw. Pull/ push on the casting to check for wear ( basically do what Houdini suggested..) Saw doesn't need to be running.
Make sure the guides are good and the support arms are far enough apart that the twist is fully out of the blade in the cutting zone. Check the guide support arms for wear

 

[guythatbrews]

You could also make sure the pivot on the saw isn't worn and allowing the whole thing to move at an angle.

This is often overlooked. Raise the saw and grab the free end. Give it a good push back and forth.

You've been around saws so you likely know this., but never uncoil a blade by throwing it on a concrete floor. Resulting tooth damage can make it drift.

 

[memphisjed]

Curved cut is almost always a bad blade.
Replace blade and tension blade. Run blade +_ 30 seconds and retention.

When blade is off monkey dance on guide arms and look for movement.

 

[plastikdreams]

This is often overlooked. Raise the saw and grab the free end. Give it a good push back and forth.

You've been around saws so you likely know this., but never uncoil a blade by throwing it on a concrete floor. Resulting tooth damage can make it drift.

But it's so cool watching the sparks fly...

 

[animal12]

There's a io group for the import 4x6 band saws like the ones that HF sells . theres all sorts of info there on how to fix saws that don't cut straight . May be some info there that can help ya . https://groups.io/g/4x6bandsaw
good luck . I know these saws can be pretty darn temperamental at times .
animal

 

[atex57]

I had an old saw that started cutting a curve also. Turned out it was the head balance spring adjustment had slacked off giving too much weight on the blade. Set it up and it was right back to cutting straight.

Ed.

 

[Bill D]

With a name like Olsen I assume the OP knows bandsaw blades. Does Olsen make anything besides bandsaw blades? When I saw his name before opening this thread I thought this might be spam for selling blades
Bill D

 

[13engines]

Seems obvious, but is the blade tight enough? I got a Marvel for a song because "it didn't cut straight" and they didn't feel like dealing with it. Looked up the manual how to adjust the tension, set it to the proper tension for the blade, and was able to hold .0005 over a 5" cut.

That's one too many zeros for any saw. Maybe once in a lifetime, but not all day. Even on a good day.

 

[Gordon Heaton]

I'd try another blade too, like Metalurgent said in post 4. Did someone stand the saw up and cut a 'test' curve on your new blade? No quicker way to screw up one side of a blade than trying to cut anything than the most gentle curve.

 

[F0307 Loss Parameter]

That's one too many zeros for any saw. Maybe once in a lifetime, but not all day. Even on a good day.

Right when I got it running, I admit I haven't measured to that precision since then though, not usually a need to.

 

[Finn_olsen]

I feel stupid admitting this, but I set the blade tension to just whatever felt generally tight. how tight should I make the blade? is there a too tight for those little blades? I'm hoping I didn't already ruin that new blade if that's the case. I have one more blade for the time being, and additionally I was careful to unravel the blade without throwing it on the ground