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Post by Deleted on Jul 4, 2017 14:15:13 GMT -8
Just wondered if anyone has experience in selecting proper grits for the job at hand.
I spend the weekend sanding two wooden benches that were coated with Thomson Deck sealant four years ago. Using an orbital sander, I started with 80 grit paper, and immediately started getting a gummy solution building up on both the sandpaper and in globs on the surface. I went through a bunch of disks and slowly got the surface cleaned on the first section.
Having run out of sandpaper disks (80 grit), I went out and bought some 60 grit. This stuff cut through the sealant like butter, cleaned both benches just perfectly with using only about another 5 disks......which I was thrilled with.
So my question, is there a general rule in choosing the right sandpaper for the job?
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Post by Deleted on Jul 5, 2017 17:28:30 GMT -8
Not really any choice other than to start with the highest number grit that will remove what you need. I would say that 60 grit is pretty aggressive, but with the Thompson's water seal I suspect the reason your sandpaper kept filling up is that particular product has wax in it. For my purposes on the other stuff I make, I progress from say 120 grit to 180, 220, 320, 400 and then 800. If you make sure you spend as much time on each grit as you spent on the previous one, it usually works out the best. You just have to make sure you remove the scars from the previous grit size.
If on my carvings the bit is not super sharp I will start with something like 220 grit for the flat areas and work my way up. A fairly new bit which carves smoother I start with 320 or 400 grit and that is usually enough.
3M or Norton brand sandpapers are some of the best out there, stay away from the "cheapies"
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Post by Deleted on Jul 6, 2017 3:34:07 GMT -8
Thanks Bob, not sure that I've even seen an 800 paper before. With these benches I wasn't too concerned with a totally smooth finish, although the 60 grit did a pretty good job with just a few areas that I redid with 120. Like anything that sits outside, after 4 years the seat and back just needed an update for looks. I think a total restrip and reseal may be a winter project this year for me.
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Post by Deleted on Aug 13, 2017 16:18:56 GMT -8
On a wood, walnut, that has reasonable large pores in the grain..........does sanding with the higher grits (say 320) help substantially with the end grains when you polyurethane the piece? I did 320 on the cherry version of a couch table and now am doing a copy in walnut. The cherry felt like glass when sanding was done and now I'm seasoning it in the sun for a couple weeks before varnishing it. I'm just wondering about walnut, this is my first project using such an expensive wood and I'd like the best results.
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Post by Deleted on Aug 15, 2017 2:21:21 GMT -8
Sanding with 320 to 400 does give a very smooth surface but end grain usually needs to be filled with either your finish choice or sanding sealer. Without doing something to fill the pores in the end grain your finish usually will wick into the wood on the ends until it has been filled enough to stop the finish from soaking in.
I generally just do a few coats on the ends with my finish choice to fill the end grain sanding smooth between coats. On walnut that would be the method to use because while sanding sealer works well on light to medium colored woods it is not so great on a darker wood like walnut or cherry. Sanding sealer on walnut will often leave the ends looking kind of waxy and not match the color of the rest of the wood after you apply your finish.
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Post by Deleted on Aug 16, 2017 16:52:14 GMT -8
Thanks Bob, I'd pretty much come to that conclusion as a way to go.....great to hear I'm not completely nuts.
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Post by Deleted on Aug 24, 2017 9:18:23 GMT -8
I completed both couch tables today, one in cherry and one in walnut. I used the 320 sandpaper as my final go around, and I am really impressed with the results. I utilized spray marine spar varnish on both pieces, and the end grains (rounded over with router) came out just as smooth and shiny as the flat table top did. I'm really impressed with the results, and since this was my first use of walnut I'm really happy with the way it looks.....now if it wasn't sooooo very expensive. A 4/4 piece of wood, 11.5 inches wide, 8' long: cherry $42.00, walnut $62.00. Time to make two Notre Dame versions, need to figure out a different wood to use on them.
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