On 2007-11-18 12:14:08 +0000, John Rumm said:

Brian Sharrock wrote:

There ae many instances when it is necessary to utilise a table=saw
without a riving knife and or crown guard. Instances that spring to
mind might be _coving_ a plank; producing tenons; trenching (dado-ing)
a board etc. etc. A crown guard may only be used when a complete cut
_through_ a board is required.

Part of this is a design limitation of some saws where the crown guard
can't be remove without also taking off the riving knife. Things like
tenons, dados, trenches etc can be cut with a riving knife present. The
only operations where the knife will certainly cause a problem (that I
can think of) is cove cutting, and plunge cutting.

Generally, dado sets or equivalent tooling involve taking off the
riving knife, and in any case it doesn't do anything useful in the case
of a groove being cut.



Crown guards can be used far more often if they do not require support
metalwork that passes through the line of cut.

On larger industrial saws, this is done by having the guard
cantilevered and on rollers covering the whole blade area. e.g.

http://tinyurl.com/ynu2ev

There are also after market products such as the Excalibur, which is
fairly reasonable

http://www.just4fun.org/images/woodw...e-images/2.jpg

and

one such as that that Axminster sells (056002) which is flimsy junk.