On 11/11/2018 00:34, wrote:
On Saturday, 10 November 2018 23:10:12 UTC, John Rumm wrote:
On 10/11/2018 19:41, tabbypurr wrote:
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.

Well you should...

(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.

ok, and here are the results:

http://wiki.diyfaq.org.uk/index.php/Inline_Sanding_Hack

So you accept (on the wiki) it's not suitable for the OP to sand his ceilings with,

I was not actually suggesting that it was a solution for the OP - just
exploring a possibility. I was responding to Robin's reposting of Bill's
original comment, about using sandpaper fixed to a multimaster blade.

I said: "Actually that gives me an idea for a poor man's festool style
linear action sander....".

Having now tried that idea and proved that it does work, I would
maintain that it does indeed give you a poor man's[1] linear sander.

[1] Now for the avoidance of doubt, by "poor man's" I mean a hack that
is austere in nature - it will do a similar job but with less finesse,
effectiveness, comfort and all that.

As a champion of the cheap tool, and hacked solution I would have
thought that would be right up your street?

even after you improved the design by using a flat sanding pad

The flat sanding pad is not an improvement - it would be better with a
slight curve so that it could maintain contact with the surface better
and not put excessive wear on the paper on the ends of the block like a
flat one does. However it was more than adequate to establish if the
idea works, how controllable it was, what the material removal rate was
like, and how bad the vibration was going to be.

I'm done on this.

We can live in hope...



--
Cheers,

John.

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