Sand paper techniques

[charlieart66]

i was wondering what you find is the best way to sand a wood ( plywood in my case ) to as smoother finish as possible while using as little resources as possible.
i tend to use
80
120
150 ( all done by a machine)
400
1200 ( all applied by hand without a block)

am i missing something, or do i have more than necessary?

[watson]

G'day Charlie,
I reckon there are a couple of grits missing.....from 150 to 400 is a bit of a jump, and from 400 to1200 is a huge jump.
As the blokes who know far more than I do will tell you, the idea is that the next grit removes the scratches of the last grit.
What sort of a machine are you using up to 400??

[joe greiner]

Why without a block? If you're relying on finger/hand pressure alone, you're sure to get ripples, because of different grain response. For best baby-butt smooth, scraping with the grain is hard to beat - almost a mirror finish. And, IMHO, high-tech scrapers aren't quite necessary; good results obtainable with utility knife blades.

Joe

[zenwood]

A recent test of sanding by FWW magazine suggests that 320 or so is sufficient sanding.

I try to avoid sanding, preferring a handplane, but when I do sand I use a ROS, 120>180>240>320 gives good results. I only use grits below 120 for 'stock removal'.

[Harry72]

Depends on what type of finish you are using, no point going all the way to 1200 if your spraying on polyU 220~240 is far enough.

[powderpost]

I use recycled polystyrene packing in a variety of thicknesses dependant on what is happening. For inside a bowl, where the surface is curved I use the styrene about 5mm thick. For flat surfaces, eg box lids, the styrene is 25mm or thicker. Very important to work down the grades in sequence. Generally finish the wood surface with up to 320# and use 400# and 600# between finish coats. IMHO finer than 600# is unnecessary. The lacquer is generally sanded with 600#, rubbed up with 0000 steel wool and buffed with EEE.
Jim

[ubeaut]

I would never use 80 grit on ply wood. Preferably start at 180 then 240, 320, 400 and stop there for a poly or other plastic coating. For shellac or any fine finish continue on with 600 and 800 then apply shellac based Sanding Sealer and when dry scuff lightly with 1200 grit. This will give a brilliant base to build a fine finish on.

Cheers - Neil

[charlieart66]

Why without a block? If you're relying on finger/hand pressure alone, you're sure to get ripples, because of different grain response. For best baby-butt smooth, scraping with the grain is hard to beat - almost a mirror finish. And, IMHO, high-tech scrapers aren't quite necessary; good results obtainable with utility knife blades.

Joe

even when using plywood?

G'day Charlie,
I reckon there are a couple of grits missing.....from 150 to 400 is a bit of a jump, and from 400 to1200 is a huge jump.
As the blokes who know far more than I do will tell you, the idea is that the next grit removes the scratches of the last grit.
What sort of a machine are you using up to 400??

just your usual half sheet hand sander

Depends on what type of finish you are using, no point going all the way to 1200 if your spraying on polyU 220~240 is far enough.

ahh. this is wood that isnt going to be finished at all, so i need a very shiny finish.

[joe greiner]

even when using plywood?
this is wood that isnt going to be finished at all, so i need a very shiny finish.

Yep. The final surface is so thin, it doesn't know that it's plywood.

I'd suggest using some sort of coating, even if only polyurethane varnish. Your smoothing efforts will be for naught otherwise, because the wood will absorb moisture from the atmosphere and/or fingerprints, and exhibit grain-raising.

Joe

[munruben]

Hey Joe,
I agree with you on the utility knife blades for scraping, I have used those for several years now and find them to do an excellent job, specially good on small projects too.

[soundman]

most plywood should be finished to P120 or better unless it real rough old stuff.
CD and DD structrual is usualy finished to P80

It realy depends on what you are doing to the plywood before you start.

If it's reasonable ply to start with and you havn't dug holes in it or messed it about starting at 150 or 180 is quite reasonable.
If you are using a conventional rectangular orbital sander you will need to be a lot more fussy than if you were using a random orbit sander.

A ROS will allow you to get away with all sorts of stuff you wouldnt otherwise.

even if you are looking for a natural finish you are much better off using something to consolidate the grain on plywood.

even then I dont see much point going much past 400.. (600 perhaps) on raw ply unless you are using some sort of finish.

If I had a ROS I wouldnt be hand sanding at all.

The only problem with a ROS is that on timber with soft and hard parts of the grain it can leave a less than flat surface if you arent carefull.

cheers