On Mar 13, 1:56*pm, Robatoy wrote:
On Mar 12, 9:25*pm, allen476 wrote:



On Mar 12, 11:34*am, " wrote:

On Mar 12, 9:47*am, "J. Clarke" wrote:

On 3/12/2010 10:11 AM, allen476 wrote:

On Mar 12, 9:07 am, *wrote:
On Mar 12, 6:11 am, "Mike
wrote:

wrote:

Breaking the blade, if done in the right place, might work. *Baring
that, a wrench in the gears would do a lot. *Remember, the tool
doesn't have to survive.

Well..... you're close Keith. *How about "braking the blade", rather than
"breaking the blade"? *Forcing an instant reversal of the motor direction to
stop the blade? *Or clamping a brake on the pulley or on the arbor.

Sure, there are ways of stopping the blade quickly but Allen thought
that braking the blade would break it. *;-) *My point was that this
might not be a bad thing, if done in the right spot (or at least not
the wrong one). *I also wouldn't think a band saw would have to be
stopped as quickly as a table saw to minimize damage.

Poor choice of words at 10:30 last night, teach me to type half
asleep.

A bandsaw however would have to stop at the same amount of time. If it
was a 3 tpi blade, it would do some damage rather quickly. The only
solution would be either a guard that came up from the table or a
mechanism that would cut the blade then retract both ends away from
the work area.

A braking system, hmmmm, might be an alternative. Then it wouldn't be
destroying a nice blade. But how?

The Sawstop on table saws forces a piece of metal into the blade in
addition to retracting it. *The same would work on a band saw except
without the retraction. *Not sure retracting the band saw blade would be
a good thing anyway unless it can reliably be broken in a specific spot
then moved reliably in a way that doesn't cause more harm than it prevents.

Breaking the blade not only removes power but also the momentum of the
wheels and motor from driving the blade further. *It seems reasonable
to break the blade to me, although as you say, it has to be done in
the right spot. *A broken end shooting out of the saw doesn't seem
like a good idea.

It's important to remember that just pulling the blade straight down
into the table will likely cause as much harm as continuing to run the
saw, while folding it back away from the teeth risks pinching fingers
that are behind the blade--one can touch a band saw blade from all sides.

Breaking the blade during stopping is a non-issue--if the device breaks
it so be it. *They never let that be a consideration on the table saw
device so why would it be a consideration with a band saw? *You're
weighing a hundred buck blade against a thousand times that much in
medical costs.

The argument is exactly the same as the SS. *Are false positives worth
the price for that one time where it saves your hand.

After thinking about it, one could design a braking system *in a 2
part design. A set of steel jaws that clamp the blade and a mechanism
to disengage the motor from the wheels. Instead of direct drive, one
could use 2 gears to drive the wheels, when the safety engages, a
spring would retract the motor and the jaws would engage stopping the
blade. Shouldn't damage the machine and a good chance that it won't
damage the blade as well.

Allen

I got my head around that and like that idea. But... there's a reason
the SawStop works as well and as quick as it does and that is that it
uses its own kinetic energy. A bandsaw's system would have to be pre-
loaded with instant release energy..such as hefty springs or shotgun-
type shells electrically fired. You wouldn't need much of a charge to
make stuff happen in a hurry. If you used energy stored in springs,
the release mechanisms themselves would add unwanted time to the event.


The design I suggested would be for a bandsaw. I would use
electromagnetic releases for the safety with a spring counter to that.
Almost the same idea for the blade clamping system, except using what
looks like jaws from a pair of vice grips. My goal would be not to
destroy some expensive part along with an expensive blade.

Tablesaw design however would be more difficult. I did think about a
caliper type system. Dadoes would be the negating factor to that
though.

Allen