When to change sandpaper?

[Geoff_S]

Whilst in the process of sanding acres of veneered boards, I was trying to think of things in general, to ensure that the monotony of sanding didn't send me brain dead.

And I came up with this

Is there an optimum time to ditch a piece of sandpaper and carry on with a new bit?

I've often wondered about this when I get to that stage when sanding, whether the money I am saving by continuing to use a piece of
sandpaper would be offset by time saved with a new piece?

 

[Eric The Viking]

Surprisingly infrequently, as long as you have good dust extraction.

I go over the orbital's pad (it has DX too, obviously) with an upholstery brush on the vacuum, and I can also get some value from using the crepe rubber stick I have for the belt sander. As long as I keep the stuft clean, if it's decent quality it lasts and lasts.

It's especially true of my Bosch GOP when used as a detail sander - I should have bought the accessory DX port (but stupidly didn't), but as long as I have said vacuum and brush handy, the pads last pretty well.

 

[ED65]

Is there an optimum time to ditch a piece of sandpaper and carry on with a new bit?

I thought the rule of thumb was when it's no longer sanding efficiently. Although with power sanding using the finer grits it gets harder to judge doesn't it?

It's a little clearer what to do and when if you're using a card scraper 8)