Bandsawing problem

 etpm@whidbey.com wrote:


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:



  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.  

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:



  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

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


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

Chip load calculation and recommended chip load for various materials
on page 18:
http://www.snaponindustrialbrands.com/DSN/wwwsnaponindustrialbrandscom/Cont =
ent/Bahco%20Bandsaw%20Catalog.pdf

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


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 Sunday, June 24, 2012 2:49:51 PM UTC-4, (unknown) wrote:

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

    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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