Mirror polishing M390?

[-Kiku-]

What happens in most polishing with fine compounds is "balling" or "clumping". The grit gets stuck together in the swarf, rolls up in a ball, and simulates a much larger grit. Sufficient lubrication and some method for the swarf being carried away (usually a slow water flow, dunking, or a drip can) helps avoid this.

I suspect the reason for those clumpings is due to electrostatic charge buildup. In dry-lapping, there's not much medium to help dissipate the charge among the particulates trapped between the blade and the lapping film. Fluids, especially polar compounds such as water, can help minimize this clumping by doing two things:

• carrying the debris away from the area being polished,
• electric dipoles formed in the polar compounds can help to shield the charged particulates

It is for this reason, in my opinion, I think that water-based polishing compounds would perform better than the oil-based counterparts. Oils are not polar.

But I've tried all sorts of diamond lapping film (and alox film) and they all seem to have some sort of cross contamination in the film itself below about 2 micron.

I suspect @razor-edge-knives was dry-lapping at or below 2 μm. Hence, clumping likely played a role.

 

[Stacy E. Apelt - Bladesmith]

Yup.

 

[-Kiku-]

Just placed an order online for some diamond lapping films (15, 3, 0.5, 0.1 microns) and a slab of float glass.

Going from 3 to 0.5 μm is a big change in grit-size so I ordered an extra sheet of 0.5 μm film just to be on the safe side.
The parts should arrive within the next two weeks.

@Stacy E. Apelt I'm thinking about placing the float glass on top of a plastic cutting board and set down the apparatus in the kitchen sink with a thin stream of tap water running onto the lapping film. But I am not at all certain whether those films (PSA type) will stay attached to the glass for an extended period of time in a very wet environment. Just how durable is PSA adhesive? I would welcome your input on this. Thank you.

 

[-Kiku-]

Oh, and I don't have access to distilled water so I am hoping the tap water will suffice even when I switch over to sub-micron size. Not sure how big of size and how many particles there are in tap water...

 

[Stacy E. Apelt - Bladesmith]

Tap water is fine, PSA holds pretty good under a drip/light spray system. You only need a small amount of water to keep the abrasive surface wet and removing the swarf.

 

[Toddman214]

Older forum, but I've still been struggling with m390, Magnacut, and Elmax polishing. Not so much the mirror finish...I can obtain that by hand. It's the very slightest amount of haze that I fight with. The eye can't see polish difference above 8,000 to 14,000 diamond grit, so I tend to stop there. Then I start polishing with water only, which cuts the remaining haze in half, but there's still a slight amount. I wonder if I'm actually starting to see the actual grain of the steel, and I'm just fighting something I can't beat.