On 10/11/2018 14:05, 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.

--
Cheers,

John.

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