Loose Grit is not always the best choice.

Here is a bad knot I decided to try grinding with loose 80 grit aluminum oxide.

I used a rough metal plate to rub and roll the grit.

It cleaned the metal plate better than it did the wood.

It did a good enough job, so I cleaned it up.  Not the best method, but it worked.

A bit dingy.  I should have scraped it clean, but I decide to use a finer grit to polish it.

This is 0.05 micron linde b aluminum oxide grit.  It sunk into the wood and polished the metal plate slowly.  It made a mess and did nothing for the wood.

So I use a scraper on it.

this fine dust embedded in soft wood is perfect for removing the bur from a scraper.  This made scraping it a real chore.  No use doing anything else, sand paper would spread it and drive it into courser cracks.  A plane would dull instantly.  So I tuned a scraper and then dulled it.  Over and over again.  This was a real pain to clean up.


4 comments to Loose Grit is not always the best choice.

  • Skip J.

    You’re a better man than me Bob! I’m not sure I’d have shown that one…..


  • It was rather brave, I do admit. Better, I doubt.

    Usually I do my experiments on more expendable and smaller sections of wood. This was a fairly time consuming and hard work causing experiment. I had to scrape it clear, having an abrasive built into a work table, is probably a bad thing.

    I may take a block of wood and treat it with the fine grit, just for cleaning off a burr before sharpening a scraper. It does a really good job.


  • Skip J.

    I hear you – I can see where that coarse grit could “clean off” the little thin layer of metal that is the burr on a scraper! Oh well, you make a new tool everyday….. might as well be scraper tools….


  • It was the fine grit bedded into wood that really did a good job of eating burr. I don’t know that the wood will stay flat and even, but for cleaning the burr off, 0.05 micron aluminum oxide works like a champ. Two scrapes about two feet long, and there is no detectable burr left on the edge of the scraper.

    I would prepare all eight edges on a scraper, and then get maybe 16 total passes before I had to burnish new edges. Fortunately the cleaning up the edge before burnishing was already done.

    16 2′ passes at a time, while trying to cleanly remove the grit from the entire surface took a bit of work. I think I probably redid the scraper 20 or so times before the scraper started to keep a burr with any consistency. Then I continued until the scraper burr seemed unaffected by the scraping. The fine dust spread by scraping, so it took a bit. Perhaps waxing or wetting it might have kept from spreading the grit.


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