Thread: 3M Imperial lapping film: first impressions

Finer grades now tested.

1. You need much more care to avoid bubbles.

2. The 5 m was not that hot at removing the scratches from the 15 m.

3. Dubbing of the whole edge (not the corners) began again at 5 m and required stepping back a grade and reworking the back on the other side of the strip.

4. The 1 m and 0.3 m are prone to clogging and need regular wiping clean with a rag.

Upshot however was a very nice edge.

I spoke to the Sandpaperman suggesting he get some of this in esp. in the coarser grades.

I've been thinking of looking into that stuff.

There was an online US supplier who had up to 80 m or more in retail quantities but it got bought out and the stuff is no longer available.

Mine came from the UK at no small expense. Ah, the cost of an obsession

My feeling is, on the basis of limited testing, that for 15 m and below the micro-finishing abrasive works better on plate glass.

But I think it's worth finding a base flatter than plate glass to save yourself some time.

I've been tinkering with this Woodpeckers Honing Plate System as a method. Like yourself, my DMT diamond plate is near the end of its life. What is swinging me on it is Woodpeck have a very good reputation, the plate system is raised and larger than say a DMT plate and I can easily gets grades from Sandpaper Man.

Back in the day (when I was still employable....) we used a wide selection of these films to polish optical assemblies, and in particular optical fibre connectors. The ends of these are made of hard ceramics (zirconia or alumina) with the tiny glass fibre in the centre.

The microfinishing films were made by 3M (mylar sheet), and the alox abrasives available down to 0.3 micron. A bead of special epoxy on the end of the ceramic connector supported the fragile glass fibre, and the alox abrasives basically just removed the glue/glass to get back down to the ceramic reference surface. Of course, alox abrasives wouldn't remove much of the actual ceramic connector material (of similar hardness), so you had to make sure you left just a very thin film of epoxy before the final 0.3 micron polishing step. This way, when you arrived back at the ceramic surface, you also had a highly polished glass optical fibre end in the middle of it.

All films were used on a perfectly smooth glass plate (no dust allowed), and there is no need for PSA 'cos the films can be stuck firmly in place with a thin film of water. These 3M films (mylar without PSA) are much more readily available here, and can be purchased in a wide range of grits.

Note that some special high performance connectors also required the ceramic material to be shaped during polishing, and for these we used similar mylar-backed abrasive sheets but with diamond dust in place of the alox. Also made by 3M, more expensive but very long lasting, and available in grits down to 1 micron or so as I recall.

Interestingly, a final polishing step used a film with 0.5 micron cerium oxide, i.e. as found in some honing compounds for woodworking. This is a soft abrasive, but breaks down into even smaller particles when used with water as a lubricant.

Thanks Mr B. Instructive as always.

It'd be good to see some of these exotic 3M films more readily available to woodies. Good to see Woodpeckers building them into their honing system and also Sandpaperman stocking them.

Ern - I just had a look at a couple of the suppliers I used to deal with for fibre optic bits and bobs, and they have some interesting abrasives...e.g.

Polishing Films- AusOptic Source for Fiber Optic Equipment,Attenuator,Patch Leads,Power Meter

Thanks. Wouldn't mind a few of those diamond sheets.

The alox films could be worth a run; prices are reasonable but still, 10 sheet packs in several grades becomes prohibitive.

More info ...

In lapping a dog ( click here ) I proceeded to hone the back and bevel on the ILF, from 40 microns down to 0.3.

Again, the jump btwn 15 and 5 seems bigger than it ought to be.

The 5 and below films seem to be quite fragile cp. with 3M micro-finishing sheets and not as efficient on plate glass. These are just impressions though.