The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?
Thanks,
Eric

In article ,
wrote:

The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?
Thanks,
Eric

Is the blade tension high enough? It sounds like the thickness of metal
currently being cut is the key. The blade want's to wander, and only
the blade tension keeps this in check.

Joe Gwinn

On Sun, 24 Jun 2012 11:49:51 -0700, etpm wrote:


5" diameter aluminum the cut is square for about a third of the cut and
then the cut becomes concave for a little more than a third, and finally
the cut straightens out. The roller saw guides are adjusted properly and
the saw cuts square otherwise. The concavity is about 1/16 inch. Anybody
seen this before? Thanks,
Eric

I've seen it a few times. The chip load and friction is quite a bit
higher in the middle of a big round cut. I've found it's alway been blade
tension in my case. A squirt of kerosene now and then seems to help a
little.

My opinion only.

wrote in message
...
The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?
Thanks,
Eric

I've seen this too, even with proper blade tension. As Yooper
says it's the chip load filling up the gullets on a wide piece. A
blade with bigger gullets (fewer TPI) or reduced feed rate/pressure
usually fixes the problem.
Art

On Sun, 24 Jun 2012 13:20:57 -0700, Artemus wrote:


I've seen this too, even with proper blade tension. As Yooper says it's
the chip load filling up the gullets on a wide piece. A blade with
bigger gullets (fewer TPI) or reduced feed rate/pressure usually fixes
the problem.
Art

A good point on the teeth per inch. I hadn't considered that.

On Sunday, June 24, 2012 2:49:51 PM UTC-4, (unknown) wrote:
The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?
Thanks,
Eric

It sounds as if the blade gets hot , expands , and loses tension. I wonder if a belleville washer could keep the tension more constant. Coolant might help.

Have you tried stopping the cut and rotating the part so the saw is not cutting a full 5 inches?

Dan

On 2012-06-24, wrote:
The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?

What it sounds to me like is that the blade tension is not high
enough. I know that on the 4x6 saws, the tension needs to be as high as
you can manage with the little knob provided -- a bit of pain is needed
to get it close to where it should be.

But those saws will not handle a 3/4 blade, so you must have
something larger.

Another possibility is that the teeth are losing their set on
one side of the blade, causing it to bow towards that side. On the 4x6,
there is a step turned in the wheels so the blade teeth are not
contacted at all. If you try to use a smaller blade in there, it will
iron the set out of the teeth towards the wheel. Saws made to handle a
range of blade sizes use a rubber tire on each wheel for drive -- and to
protect the teeth from contact with the cast iron of the wheel. If
yours has the tires -- make sure that they are still in good shape.

Good Luck,
DoN.

--
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On Jun 24, 3:20*pm, "Artemus" wrote:
wrote in message

...

The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?
Thanks,
Eric

I've seen this too, even with proper blade tension. *As Yooper
says it's the chip load filling up the gullets on a wide piece. *A
blade with bigger gullets (fewer TPI) or reduced feed rate/pressure
usually fixes the problem.
Art

Chip load calculation and recommended chip load for various materials
on page 18:
http://www.snaponindustrialbrands.co...%20Catalog.pdf

On Mon, 25 Jun 2012 04:52:32 -0700 (PDT), "Denis G."
wrote:

On Jun 24, 3:20*pm, "Artemus" wrote:
wrote in message

...

The saw is a horizontal band saw using a 3/4 blade. The problem is new
and is not related to blade pitch or to a particular blade. When
sawing 5" diameter aluminum the cut is square for about a third of the
cut and then the cut becomes concave for a little more than a third,
and finally the cut straightens out. The roller saw guides are
adjusted properly and the saw cuts square otherwise. The concavity is
about 1/16 inch. Anybody seen this before?
Thanks,
Eric

I've seen this too, even with proper blade tension. *As Yooper
says it's the chip load filling up the gullets on a wide piece. *A
blade with bigger gullets (fewer TPI) or reduced feed rate/pressure
usually fixes the problem.
Art

Chip load calculation and recommended chip load for various materials
on page 18:
http://www.snaponindustrialbrands.co...%20Catalog.pdf
Thanks to everyone who replied so far. It looks like it might be
tension related. I thought I had the blade tight enough but maybe I've
gotten weak. And thanks Dennis for the above link.
Eric

On Jun 24, 2:41*pm, Yooper wrote:
On Sun, 24 Jun 2012 13:20:57 -0700, Artemus wrote:
I've seen this too, even with proper blade tension. *As Yooper says it's
the chip load filling up the gullets on a wide piece. *A blade with
bigger gullets (fewer TPI) or reduced feed rate/pressure usually fixes
the problem.
Art

* A good point on the teeth per inch. I hadn't considered that.

You can get blades with varying TPI that are just for rounds and
oddball shapes where a fixed TPI blade doesn't work that well. I
think Starrett was one of the first with them, but most of the other
makers have them now. That's if you're going to be doing a lot of
that kind of cutting. Otherwise, get some Castrol stick lube and
carry on.

Stan

"Stanley Schaefer" wrote in message
...
On Jun 24, 2:41 pm, Yooper wrote:
...
You can get blades with varying TPI that are just for rounds and
oddball shapes where a fixed TPI blade doesn't work that well. ...
Stan

I've had acceptable results with a 10/14 TPI, 1/2" blade on a 4x6
bandsaw cutting 6" wide CRS plate the hard (but straight) way. A 6 TPI
blade does work better.

jsw

On Mon, 25 Jun 2012 07:35:26 -0700 (PDT), Stanley Schaefer
wrote:

On Jun 24, 2:41*pm, Yooper wrote:
On Sun, 24 Jun 2012 13:20:57 -0700, Artemus wrote:
I've seen this too, even with proper blade tension. *As Yooper says it's
the chip load filling up the gullets on a wide piece. *A blade with
bigger gullets (fewer TPI) or reduced feed rate/pressure usually fixes
the problem.
Art

* A good point on the teeth per inch. I hadn't considered that.

You can get blades with varying TPI that are just for rounds and
oddball shapes where a fixed TPI blade doesn't work that well. I
think Starrett was one of the first with them, but most of the other
makers have them now. That's if you're going to be doing a lot of
that kind of cutting. Otherwise, get some Castrol stick lube and
carry on.

Stan
I do use variable pitch blades. And flood coolant. What has me
flummoxed is that this problem is new, occurs with different, new
blades, and with blades of different pitches. So I think the problem
is not related to the blades themselves. I'm thinking it may well be
blade tension. The next saw job I'll try more tension and if that
doesn't work I'll investigate the pivot points.
Eric