Sand, plane or scrape?

mr · 27 Jan 2007

Ive never had much success with sand paper, praps Im using too coarse a grade but I seem to end up with a load of scratches after the coarsest paper which successive grades don't remove. In the end I always find my self burning my thumbs and cutting fingers on the corners of card scrapers while getting the scratches out caused by the sandpaper. Looking at the grades David C mentions praps the problem is that Im using too coarse a paper. My finest being equal to his coarsest it seems.
Cheers Mike

David C · 27 Jan 2007

I do aim to get things pretty damn flat with my planes, or scraper planes (if veneer).

Also a well tuned plane, sharp blade, and knowledge of high effective pitch technique should mean no tearout that might tempt one to use a card scraper.

I do realize that none of this is that easy for the beginner, and that I have been practising for a very long time..........

best wishes,
David

garywayne · 27 Jan 2007

Sorry to appear ignorant, but David C said:-

and knowledge of high effective pitch technique

Could someone please explain.
Thank you.

David C · 28 Jan 2007

Gary,

An extreme example for interlocked Rosewood or Tasmanian Blackwood.

Hone a very narrow bevel on the flat side of your bevel down plane blade at 25 degrees.
The wood now thinks you have a plane pitched at 70 degrees.

In a low angle bevel up plane, the blade would be honed at 58 degrees.

When very fine shavings are taken, say about 0.001" you will get no tearout as the chip production has changed to type 2.

You can read about this splendid technique in Hoadley, Leonard Lee and my book 1.

You don't always have to go to 70 deg, some woods will respond at 60 or 65 degrees.

David

MIGNAL · 28 Jan 2007

I think your wood finishing technique is very dependant on what it is you are trying to achieve. If your goal is a high gloss highly reflective surface then sandpaper wrapped around a sanding block is the way to go. As David C mentions; any imperfections and hollows in the surface will be magnified by a highly reflective finish. It is possible to polish these out using the French polishing method but that does take forever.
Not everyone likes that type of finish. Card scrapers should leave a good enough finish for oil and wax finishes. Violin makers rarely use sandpapers and the very good makers deliberately create a slight textured surface by using scrapers - they hate the so called 'Ferrari look'.
If you want your scraper to leave a very fine finish then make sure the edges of it are very smooth, perhaps not mirror polished but definately no file marks either. When you turn the edge do so with little pressure, you are trying to create a small burr that will still make shavings; these will be fine shavings - think of it almost like the difference between a scrub and a smoothing plane.