I feel an idiot for not being able to get this damned thing fixed myself,
but I have a smallish bench mounted metal cutting bandsaw of good quality.
OK, she's done a bit of work before I got her, but there's no wear in the
bearings and the cast iron wheels run true. I have played with blade
tension (tighter seems more reliable) and with the top (none powered wheel)
tilt, which is adjustable, and the blade guide ball bearings, which are
adjustable, but STILL the blade will suddenly jump off one of the wheels. 3
things look less than perfect. the wheels had some sort o gritty coating,
when new, like coarse carborundum paper, this is now quite worn. The blade
makes a noticeable jump as the welded part passes through the work piece.
Nothing much, but when worked hard it is audible and can be felt. Finally
the blade is quite old and not as sharp as it might be. Cutting alloy makes
the blade come off more than steel.. Can anyone with experience of these
machines point me in any directions to look to? Thanks!
I feel an idiot for not being able to get this damned thing fixed myself,
but I have a smallish bench mounted metal cutting bandsaw of good quality.
OK, she's done a bit of work before I got her, but there's no wear in the
bearings and the cast iron wheels run true. I have played with blade
tension (tighter seems more reliable) and with the top (none powered
wheel) tilt, which is adjustable, and the blade guide ball bearings, which
are adjustable, but STILL the blade will suddenly jump off one of the
wheels. 3 things look less than perfect. the wheels had some sort o gritty
coating, when new, like coarse carborundum paper, this is now quite worn.
The blade makes a noticeable jump as the welded part passes through the
work piece. Nothing much, but when worked hard it is audible and can be
felt. Finally the blade is quite old and not as sharp as it might be.
Cutting alloy makes the blade come off more than steel.. Can anyone with
experience of these machines point me in any directions to look to?
Thanks!
Line up the wheels. Make sure they are in the same plane.
Crown the tires.
Install a blade with a good weld.
Back off the guides and adjust the wheel tracking so the blade tracks
on the wheel crowns. Adjust the guides.
John Martin
Thanks for the replies, what do you mean by "crown the tires" please? The
wheels are flat on the blade running surface and seem to have glued on
abrasive coating, not something that looks to be (easily or cost
effectively) renewable. Cheers.
First check blade weld and make sure it is straight. Next check the rubber
tires. They should have a slight crown. If it has worn flat you need new
tires. Sort of counter intuitive but the blade seeks the high spot as it is
running. Next check the wheel alignment. Both wheels should be parallel
and in the same plane. Lay a straight edge against both wheels. It should
touch the top and bottom rim of both wheels. If not there should be a set
screw or bolt next to the top wheel axel that adjust the angle and the
powered wheel can be slipped in or out on its shaft.
The blade tension should be just tight enough that it makes a musical note
when plucked and it is good practice to back off the tension when the saw is
not being used.
The Bandsaw Book by Mark Duginski is primarily aimed at wood cutting
bandsaws but the tuning chapter applies to both wood and metal.
Sounds like the tires have been removed. They are thin rubber bands that
are glued to the wheels. They have a slight crown in the center. The crown
forces the blade back to the center of the wheel when it gets off to one
side.
There's probably some political thing going on here, if one faction want's
to believe in tires and crowning, who are you to burst the bubble and
suggest the obvious?
What is the size of this bandsaw, is it two wheel or a smaller three
wheel. Does fly off when cutting wood or metal, well it stay on when
cutting wood but fly off when you try to cut metal?
Ya right, better retread the wheels, crown them, fit new bearings,
guides, possibly rewind the motor and replace the switch.
To actually suggest replacing a consumable before overhauling
the machine was unthinkable.
Thanks for the headsup Tom, I withdraw all previous suggestions
as totally inappropriate. Hang on a minute, didn't I read somewhere,
that you suggested replacing the blade?
Tom
You might want to write to DoAll and Grob and a few others, then, and
tell them that they're wasting money by putting tires on their wheels.
Oh, wait, those must be woodworking saws. Silly me.
It probably is the blade. But there are a lot of other things he
should be checking.
John Martin
snip----
What Tom said. The typical horizontal band saw has no crown, nor rubber
tire. They typically have a shoulder, against which the back of the blade
runs. If the wheels are properly aligned with one another, the blade will
stay in place. A tired, old blade often will come off time and again.
You can usually attribute the problem to minor dissimilar stretch of the
blade. Try a new blade before anything else.
Harold
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