What grit do I sand down to ...

[Phil Pascoe]

My friend sands down to 2500 grit. He uses sanding sealer and wax to finish. Please tell him why this fine a grit is unnecessary.

 

[RobinBHM]

I think he may be stopping too early, buy him some 10,000 grit for Christmas

 

[n0legs]

My friend sands down to 2500 grit. He uses sanding sealer and wax to finish. Please tell him why this fine a grit is unnecessary.

What are his finishes like though Phil?
Does it appear any better than just finishing to, lets say, 600 ?

 

[Phil Pascoe]

His finishes are OK - but I can't see they are better than mine at 240/320 and 0000 wire wool. His theory is that you are polishing a finish (usually a resin, a plastic of sorts) and if you were using a plastic in another context 2500 wouldn't be unusual - and if you are using 2500 on the finish you should use the same on the substrate.

 

[Paul Hannaby]

I would say for a clear finish on wood, you sand to the point where you are unable to see the scratches left by the abrasive. This varies depending on the type of wood and also the type of finish.

 

[CHJ]

My understanding is if you polish the substrate to the micro level mentioned then any coating is going to be presented with worst case scenario to key on to.
Most wood species in common use do not have a grain structure that betters that obtained with 240-320 grit sanded with the grain.
As long as cross grain scratches aren't visible to the naked eye, your coating whatever it is has best chance of a key.
Once fully cured then is the time to burnish the surface of the well bonded coating.

Go on a fine furniture course or visit a commercial furniture factory and see what they sand to if at all.

 

[strat]

A little story. Yesterday I was turning a cherry blank into a coin dish. In some of my coin dishes I insert a coin, as i was intending to do in this case. I turned the bottom of the dish and sanded down to 320, no problem and for cherry what I would expect. Turned the blank around and sanded to 320 after shaping, however this time some cross grain marks remained, So I power sanded 400 grit and hand sanded with the grain, still had marks showing, sanded again with 600 grit and finally 800 before I was satisfied. I can see different blanks of the same wood may vary in sanding requirements but opposite sides of the same blank :? Especially when the turning process for each side was the same.

Strat

 

[Phil Pascoe]

Chas, Paul, I agree totally.
"Go on a fine furniture course or visit a commercial furniture factory and see what they sand to if at all."
That's a thought provoking statement for him.

 

[chaoticbob]

P2500 is around 10 microns grit size, which is smaller than the typical length scale of the structural components of wood I think. You might ask your friend to try polishing slices of toast with different grits and observe the difference. This is why we have marmalade.
Robin

 

[woodpig]

I use Abranet and go down to 600.