You may be better off buying it with a brushed or annodised surface with a plastic protective sheet on the top.

J

All I recall about grinding and aluminium is being told very forcefully that it should never be done – soft metal clogs the stone and can lead to it shattering. Now there may be some specialist process that avoids that – others may know?

Rolled aluminium will be flat to a pretty high standard. Keeping protective coating in place until late in the day will reduce chances of marking.

You don't mention what coating is planned – for paint an etch primer is typical on aluminium. Others have already suggested anodising, which might work well for some coatings (be aware there are several variations on anodising with differing end properties).

The cutting technique used may introduce variations in flatness.

Roger, you won't improve on the plate as bought, and unless it is going to be anodised, or painted with some sort of coating, a layer of oxide will form on exposure to air. Ian S C

Ian, just had a try with the 4 platters I have here, I can just about detect some indication that they might wring together , and they might if they were absolutely clean, and dust free. It might be either the magnetic properties in the disc, or the teflon type lubricant layer on the surface of the disc that keeps them apart.     Ian S C

Edited By Ian S C on 11/08/2013 14:34:35

Just noticed the posting by Ken King where he mentioned using thin MDF board for making a vacuum table. How thin are we talking about here and how much grip do these tables give? Is it possible to do light milling on an aluminium sheet or would that be rather dodgy.

Doug

The reason for not grinding Aluminium is that many people have been injured by trying to grind on a conventional bench grinder. The soft metal very rapidly cloggs the stone then can weld to the job so the stone can shatter and do a lot of damage to the people around the machine. The spinning stone has a lot of kinetic energy that gets released in miliseconds.

Specialists know exactly how to grind Alloys but they do it under carefully controlled conditions which are not available in the home workshop.

The OP is looking to produce Ali blanks for direct disc cutting – LP style. So the requirement is to have the surface locally smooth to idealy well under a tenth of a micron. Milling or turning might not quite do…!!!!

Billy.

I'm not sure Roger mentioned what he was using the plates for ?

Sheet ally is "reasonably" flat as is.

• Anodizing would require a polished surface if scratches/blemishes are not to be visible. Probably the same for powder coating.
• For painting I'd use a self etch primer and wet sand and polish the painted finish.
• If it's for recording onto i'd be looking at chemical degreasing and sonic water cleaning before an electrolytic coating process. But I'd question the size of the plate if it's spinning. It would require some pretty fine balancing if mounted on a spindle.

My first job at HP was building disk drives and all parts for the drives except the platters and circuit boards were cleaned using sonic water tanks and surfactants. The platters were bought in already plated with the magnetic coating.

Hi Roger

It is a pity you want 2mm thick material, You can purchase aluminium sandwedge panel as used to face buildings and by sign writers, it is supplied ready coated with baked enamel and in various plain metal and anodised finishes. and colours. It is very flat and quite strong being two layers of aluminium bonded with a high density plastic core, typically 4mm thick overall although I did see a few links showing 3mm material. Maybe by asking around there are thinner materials.

If you purchase it from a sign writers supply company it is reasonably priced.

I have a piece on my desk waiting for an idea to use it. The OZ company who gave me the sample have a CNC router and were happy to machine it for an extra charge. I guess there are similar companies in the UK with similar facilities. CNC routing would be a good way to cut your disks. Circular shearing as done by sheet metal workers would be likely to raise a burr and distort or stretch the edge. Laser cutting (Yes cutters with more recently built machines can cut aluminium) or water jet cutting would be good alternatives.

You sometimes see this material on buildings with a neat folded corner. This is done by "V" routing the back layer of aluminium and the core then folding the piece. a very neat bend is created

Sheet sizes start at 1200 x 2400.

Regards
John

Don't know if there's been a change, but is aluminium not all in imperial sizes, and gauge thickness for sheet? Ian S C