On Saturday, 10 November 2018 17:44:05 UTC, John Rumm wrote:
On 10/11/2018 16:55, tabbypurr wrote:
On Saturday, 10 November 2018 16:19:51 UTC, John Rumm wrote:
On 10/11/2018 14:05, tabbypurr wrote:
On Saturday, 10 November 2018 13:06:42 UTC, John Rumm wrote:
On 10/11/2018 01:25, tabbypurr wrote:
On Friday, 9 November 2018 17:09:22 UTC, John Rumm wrote:

Having not tried, I don't know if it will be an issue. You
could also round the face of the sanding block slightly to
ensure that there is always a (moving) point of contact.

that certainly won't work. Look at the direction of the blade
movement.

That certainly *would* work... think about it.

Since it's so obvious it would not and could not I can only
presume we have a miscommunication going on.

Quite likely... Perhaps a drawing will help (excuse the crudity of
the model):

http://wiki.diyfaq.org.uk/images/b/b...SandingPad.png

So I am going to assume that the back end of the saw stays roughly
in place, since that is where its being held and the trigger pulled
etc.

The longitudinal movement of the saw and hence pad is on a
slightly inclined plane[1], so there will be a small vertical
component of the pads movement. As the stroke shortens, the natural
movement would thus tend to pull the pad out of contact with the
ceiling. However upward pressure exerted by the operator will keep
it in contact. This will mean that there is some rotation around
the pivot point of the tool, and thus by extension some rotation of
the pad as well. A completely flat pad could therefore only ever be
in full contact at exactly one angle - tending to ride on the
trailing or leading edges at any other angle. Adding the slight
radius means that there will always be part of the pad that is
co-planar with the ceiling.




[1] You could eliminate this with a pad thick enough to allow the
body of the saw to be held horizontaly, but still clear of the
ceiling - however this would add mass to the pad, and more
vibration felt on the tool.

So you plan to have your hand bobbing the tool up & down at the
necessary rate to keep the pad touching the ceiling. Good luck with
that! I certainly won't be trying it.

So you agree it will work then...

obviously I didn't.


(Do the sums and you will see the actual amount of movement vertically
is pretty small... in use it will be similar to using the saw to plunge
cut through a surface)

Why don't you get back to us when you've tried it.


NT