It doesn't just stop. It retracts under the table.

David

cg wrote:

As no one offered a little more explanation on how fast
this saw-stop really stops, I would present some simple maths...

From their website they say they can stop a 4000 rpm blade
in less than five (5) milliseconds.
Now, the blade normally takes 60 seconds for 4000 rounds.
In one millisecond, the blade would rotate 1/15 round...
(that is one part of fifteen).

So, if the sawstop mechanism takes 5 milliseconds to stop,
I would expect at most 5 x (1/15) ,that is, one-third of a full
rev of the blade to plough thru before it stops.

Say, I'm ripping with a 24 teeth blade. In 1/3 rev, I would
expect no more than 8 of those teeth to bite me. If I had
been using a 60 teeth cuutoff blade, watch out! 1/3 of 60
is 20!

To be honest, I would reduce the fraction from 1/3 to 1/4 or
1/5 because I have not taken into account the deceleration...
once the brake is applied, the blade is spinning down and it
is not rotating at 4000 RPM during the entire 5 milliseconds.
(So, how long it takes for brake shoes to engage? 1 millisec?)

Even then, for a 24 teeth ripper, 1/5 is 4+ teeth and
for a 60 teeth cutoff, 1/5 is 12 teeth. Little
consolation for me!

I wish the sawstop folks could give out details like
these. In particular, they must already have exact figures for the
rotation before complete stoppage. Instead of telling in terms
of time (like milliseconds) it would be better to state the same
in terms of percentage of a full rev of a 10" standard kerf blade
spinning at 4000 RPM.
Although I must agree there is more truth in their statement
compared to claims like 3.25 HP routers on 115v, or 12" SP/ 1200 cfm
with a 10" impeller 2 HP DC, and the like!

Afterall, they certainly have the brain to see through my simple math...
don't they?

cg


(David Hall) wrote in message . com...

(Charlie Self) wrote in message While I don't want to be flippant about the injury rates

listed in the article, I DO want to point out that there are
likely millions (or tens of millions) of usages of saws every year
in the USA. While taken out of context, the idea of thousands of
accidents seems like a lot, in context of the total number of times a
table saw is used, it is a drop in the ocean.

My big gripe is the use of the word "amputations" in place of injuries. I'd
also know where they get their statistics. I sure haven't found them. Of
course, I don't have a marketing impetus to actually spend money looking, but
if I had cites to back up such claims, I think I'd make them available. So far,
I've seen nothing but claims.

I am certainly not a big fan of this type of regulations. However,
someone did provide a source citation for the number of amputations.
That was the Federal Consumer Safety Protection Commission. See
http://www.cpsc.gov/library/neiss.html

I also understand that there would be few affordable cars with airbags
if they were not required and that deployment of an airbag adds quite
a bit to smaller accident repair costs. On the other hand a $250 to
$500 Sawstop will pretty much eliminate the $200 tablesaw and it is
doubtful one could be put onto a cheap tabletop saw anyhow. How many
fewer people are simply not going to be able to realistically
participate in the hobby if something like this is mandated. I am not
sure that, even though I consider myself a conservative, I am ready to
eliminate all regulartory aspects of government - I just would want to
err on the side of "freedom" in this area.

Dave Hall


Most of us who have been fooling and fiddling with tablesaws over the years
have received injuries of one sort or another, everything from blade-changing
knicks to kickback bruises the size of a draft horse's shoe and, very
occasionally, something more serious. If we're at all wise, we learn from the
smaller incidents and remain slightly in awe of what the tablesaw can do to us
if our attention wanders. If we're not particularly wise, we continue to use
unsafe working methods and eventually get hurt worse. It may not catch up to
the inattentive user today, tomorrow or even next year, but it will catch up.

Charlie Self
"Health nuts are going to feel stupid someday, lying in hospitals dying of
nothing."
Redd Foxx