Time for each grit on final finish sanding?

[HogTime]

I've decided to use Micro-Mesh for final sanding of the waterbased KTM-9 finish on my F5. I did some practice on a 3"X6" section of a flat piece of maple with several coats of KTM-9 applied months ago. This finish was nice and smooth (no runs, etc.). I went through all grits (8 total) from the equivalent of 400 sandpaper up to "super fine". Used a foam sanding block.

The result was not any glossier than the adjacent unsanded portion, maybe a bit less. However, I did see a more clear reflection of an object in the Micro-Mesh part than the unsanded one.

I know the rule is to sand until you don't see the scratches of the previous grit. Frankly, I'm not really sure my tired old eyes can detect that. I spent maybe a minute on each grit for the 3"X6" section. Any ideas on how much time is "reasonable" for an area that size (not a whole mandolin)? Just trying to get myself in the ballpark. I'm trying to use this test piece to get a feel for what the final result will look like before I start on my F5.

Thanks,

[sunburst]

No good guess as to how much time per sheet, but each finer grit is likely to take longer because finer grit cuts slower. I think one minute each for a 3X6 area is probably not enough.
Try this:
On a similar piece, sand the whole thing with your first grit and leave a little of that at one edge when you sand with the next grit. With each change of grit, leave a little strip of the previous showing, so that when you are done you have "stripes" of finish sanded to each successive grit. That should help you learn to see what the finish should look like following each grit.

[HogTime]

John, thanks for that great tip! I'll give it a try.

[Tavy]

I've decided to use Micro-Mesh for final sanding of the waterbased KTM-9 finish on my F5. I did some practice on a 3"X6" section of a flat piece of maple with several coats of KTM-9 applied months ago. This finish was nice and smooth (no runs, etc.). I went through all grits (8 total) from the equivalent of 400 sandpaper up to "super fine". Used a foam sanding block.

The result was not any glossier than the adjacent unsanded portion, maybe a bit less. However, I did see a more clear reflection of an object in the Micro-Mesh part than the unsanded one.

Well it won't be any glossier - you've sanded it after all! The gloss doesn't come back until you buff out the sanded finish. The aim is to get it as flat and smooth as you can. Annoyingly you won't know whether you've sanded enough until you buff out at which point any sanding scratches left become all too apparent

So... always sand with the grain - it will minimize the effect of any scratches that do get left, also I find a head mounted magnifier (one with it's own light as well) is a great help. The problem is made worse by the fact that it's easy to over-sand the piece and go right through the finish at almost any stage. If you're wet sanding, then you can at least see roughly how much material you're abraded - basically keep sanding until you work up a good lather of sanding dust and lubricant, and you should be in the ball park. Hopefully

[sunburst]

...The gloss doesn't come back until you buff out the sanded finish...

You can, in fact, "sand" to a gloss with Micromesh. A full, high gloss like a newly buffed quality finish is not easy, but matching the gloss of a used instrument, in for repair, usually happens before the finest grits of Micromesh. Normally, a finish touch up on a Martin guitar matches the surrounding finish after about 8000 grit Micromech, and a new finish can be brought to a gloss (call it sanding or call it buffing, I don't know...) using Micromesh and a lot of careful work.

[HogTime]

You can, in fact, "sand" to a gloss with Micromesh.

That's what I'm hoping! I'll be happy with "used instrument" gloss, though.

[Tavy]

You can, in fact, "sand" to a gloss with Micromesh. A full, high gloss like a newly buffed quality finish is not easy, but matching the gloss of a used instrument, in for repair, usually happens before the finest grits of Micromesh. Normally, a finish touch up on a Martin guitar matches the surrounding finish after about 8000 grit Micromech, and a new finish can be brought to a gloss (call it sanding or call it buffing, I don't know...) using Micromesh and a lot of careful work.

Thanks John: I had no idea you could do that with micromesh (or even that it went so fine). Part of the problem is that it's next to impossible to obtain over here... so regular 2500 grit car body paper is as fine as I can go... after that Meguiars PasticX, followed by their swirl remover will buff it up nicely - even by hand with a foam block!

[Pete Jenner]

Here you go Tavy

http://www.axminster.co.uk/micro-mes...es-prod804806/

I also found it in Oz at Carbatec if any Aussies were wondering.

http://www.carbatec.com.au/micro-mes...ng-pack_c20899

[Tavy]

Here you go Tavy

http://www.axminster.co.uk/micro-mes...es-prod804806/

Hey, too new things learned in one thread, keep 'em coming

Thanks Peter!

[mirwa]

Micromesh is good stuff, bet even on the highest grit paper 24000 grit, it leaves very fine scratches, hard to see normally but if you hold it to a light on an angle, its very apparent.

After finishing with micromesh, just get some buffing compound from your local auto shop and hand buff it.

Those that have buffers, basically buff the surface from 800-1000 grit until its smooth. We hand sand to 1500 then buff, quicker faster easier

[belbein]

Since we're talking sandpaper, I wonder if anyone has purchased from Klingspor (www.klingspor.com)? A woodworker friend of mine was kind enough to bring me over some samples. The sandpaper is backed with some sort of fabric, and this is absolutely incredible stuff. I don't think it's all that much more expensive than 3M, but it seems like it's so far superior to the Home Depot/Lowes/Ace stuff I've been using ...

(No financial or other connection to this company!)

[Tavy]

Since we're talking sandpaper, I wonder if anyone has purchased from Klingspor (www.klingspor.com)? A woodworker friend of mine was kind enough to bring me over some samples. The sandpaper is backed with some sort of fabric, and this is absolutely incredible stuff. I don't think it's all that much more expensive than 3M, but it seems like it's so far superior to the Home Depot/Lowes/Ace stuff I've been using ...

That's what I've been using to sand to 2.5K before buffing. And yes it works very well and is very durable. I use a piece about 3x1.5", wet sanding, and if you treat it with respect that one piece is all you need for a mandolin. I get mine from an eBay seller who sells whatever mixed grade sheets you want, given how long it lasts and how little you need for a mandolin it's more cost effective that way. If you were sanding out double basses it might be a different story

Only issue I've found is that 1500 grit seems less effective than the others... seems to be a step change from one manufacturing process to another at that grit... has to happen somewhere I guess, and the 2K and 2.5K grits are back up to top notch standard again, so <shrug> I guess.