Thread: Power Sanding Question

Icor,

I regularly sand up to 1500 with a Metabo random orbital sander, and achieve what I think are excellent results, but I do not have the machine running flat out.

Hand sanding - no way

Colin Howkins

What do you mean by "flat out?"

And, thanks!

I find that once I get it sanded to 400 grit, it takes very little time to go through each successive stage. I am using a lathe and the bowl is spinning so I guess that is still power sanding.
I bought some Micro grits and have sanded up to 2500 grit but, honestly, I can't see any difference to just sanding to 800 grit, on timber.
The fine grits do burn easily and the secret is to have a very light touch and to make sure the paper doesn't load up with sawdust.

I'm using MDF, and will be sanding:

MDF
Primer
Paint
Polyurethane.

Does this change any thing?

The Metabo sander is variable speed with 2 levels of random orbit. I use it on the largest random orbit, and never use over about half speed, and I find 1500 grit just about polishes the timber particularly hardwood.

Grits above 800# , are really for sealed /painted surfaces.

due to the grain in timber you are really not achieving anything, expect more work for little return, these ultra fine grain abrasives are for sealed surfaces , and some are used fro artificial stone benches just prior to polishing.

I have over 30years in the abrasives industry, and I have never seen a wood workshop that held paper above 400# for finishing.

Jeff

Vk4,

What I am trying to do, is get the best "piano black" finish I can. Super reflective black finish, on an MDF box (speakers.)

Do you have any suggestions for me, mate?

Bump.

They are also of use in the process of friction sealing a finish using Hard Burnishing (or other) oils, to give a resilient finish. I routinely sand to 4000 and get excellent mirror finish results. Better than 800 will provide. These table tops have been oiled and sanded through to 4000g. There is no wax or Poly on them, this is just the oil finish. I have to say that I am not the only one who uses this kind of sanding regimen.

Originally Posted by vk4

Grits above 800# , are really for sealed /painted surfaces.

due to the grain in timber you are really not achieving anything, expect more work for little return, these ultra fine grain abrasives are for sealed surfaces , and some are used fro artificial stone benches just prior to polishing.

I have over 30years in the abrasives industry, and I have never seen a wood workshop that held paper above 400# for finishing.

Jeff

The base material needs to be sanded to 400# finish, then remove ALL dust &contamination,

Have a professional Spray Painter spray the cases , 1 primer 2 undercoats , rub back between each coat , ensure that the cases remain dust free for each coat.

Then apply 3+ coats of gloss black , 2pack Polyurethane Paint , each coat must be allowed to dry properly, then lightly rubbed back, and cleaned before the next coat.

when you are happy with the BLACK, you can then apply several coats of CLEAR Polyurethane , this will give depth to the Black, and will last for several years , with minimal maintenance.

If this is too much for your time allowance, there are companies that specialize in 2 pack application.

Jeff

Vk4,

Thanks for the info, mate.
Are you saying not to sand the primer/undercoat? Also, what should I use for an undercoat?

When you say the 'lightly rub back' the black paint, you mean to lightly sand it - correct? If so, which grits should I use?

Thanks!

you should give all coats a light sand, this will remove any ridges etc, then use aTACK CLOTH to remove any dust / contamination, .
The rub back should be with 320# Sterated (no-fil)Paper and only very lightly done.

With the black the same should be done but here , use 1000-1200# wet&dry, with Metho, or Alcohol as a lubricant, then wipe over with a TACK CLOTH .

Once you get to the clear finishes carefully inspect between each coat, you can give a light rub over with 1500-2000# between coats,.

The more coats of clear, the deeper depth of gloss, coats should be thin light coats not heavy.

Jeff

Denatured alcohol, or Rubbing alcohol - VK4?
Thanks.

either as long as it does not affect the coatings.

water is also an option, but surface MUST BE DRY & CLEAN prior to next coat.

Jeff