LV Honing Plates

[John Kananis]

I finally picked up three of the Lee Valley steel honing plates (until now I was using diamond paste on MDF) and I am VERY VERY happy with these juxtaposed to MDF. The cut on steel is much faster this way.

Curious about something though: The paste now produces a hazy finish on the blades - I use 45 micron, 15 micron and finally 1/2 micron; even the 1/2 micron produces a hazy finish (very sharp though). I still use a bit of the 1/2 micron on MDF for final stropping (it seems to me that the MDF causes the grit to become finer? or perhaps its just helping to burnish in order to produce the mirror finish?) insight on this would be useful.

Anywho, my waterstones have collected more dust and it seems that they will continue to do so.

[george wilson]

The diamond chips sink into the MDF,leaving only a bit of the grains showing. This gives the effect of the diamonds being finer than those on the steel plates.

[John Kananis]

Makes all the sense in the world, thank you, George.

EDIT: But why does the paste produce a hazy finish (I understand this makes little difference to the cutting edge, just wanted to know).

[Patrick Chase]

Makes all the sense in the world, thank you, George.

EDIT: But why does the paste produce a hazy finish (I understand this makes little difference to the cutting edge, just wanted to know).

There's a lot to "shininess", but one grossly simplified answer is that diamonds cut rather than polishing. You can get mirror finishes with diamonds at very fine sizes (0.5 um and below). though as you point out there's no reason to do that.

I also use diamond paste on mild steel plates for certain metals and situations. It's a very fast and effective system. I've switched from the Veritas plates to ground 1018 plates bought from McMaster-Carr and Online Metals though, for a couple reasons:

1. Flatness is better. The Veritas plates are spec'd at 5 mil surface flatness IIRC, and I've seen up to ~3 mils of bow in my samples. The McMaster and Online Metals plates consistently come in at ~1 mil (and sometimes better) flatness. 3 mils may not sounds like much, but it matters when you're working the backs of wide blades using very finely graded pastes (1 micron or below). The issue is that the next-finer paste won't uniformly "refine" the surface left by he previous one unless the respective plates have very similar surface profiles. This isn't a problem with coarser grades of paste, because with those the abrasives are aggressive enough to quickly grind away any profile mismatch.

2. The surface texture works better with fine pastes. LV's plates appear to have been finished with a fly cutter, leaving a surface that's terrific at holding larger diamond particles. At smaller sizes (say, 3 um and below) the particles tend to "get lost" in the dips of the texture, and the peaks can scratch the tool being sharpened. The McMaster-Carr plates are surface ground (very smooth) while the Online Metals ones are Blanchard ground (medium texture). They're both finer than the LV ones. The tradeoff here is that you have to "rough up" the surfaces on the McMaster and Online Metals plates to use them effectively with coarse pastes (my collection goes up to 45 um). I lap my coarse plates with #24 or #36 SiC grit...

The Veritas plates are pretty reasonably priced IMO. McMaster in particular is cheaper per unit area (a 4x24x3/8 plate that makes 3 4x8 plates is $70 or so) but the convenience of ready-to-use plates that don't need to be cut, deburred, or lapped (in the case of plates for coarse pastes) justifies some added cost.

What I'd ideally like to see is somebody offering precision ground cast iron lapping plates. LV is obviously *very* good at making flat hunks of iron...

EDIT: If you do use the Veritas plates with fine pastes then it helps to break them in a bit with sandpaper or loose abrasive grit, so that they won't scratch up your tools. Also, and as I've said in the past I have access to a shop with a precision grinder, but I've stopped [ab]using them for simple lapping plate maintenance as I prefer to expend those favors on higher-value work that I can't do myself, hence the experiments with the McMaster and Online Metals plates.

[John Kananis]

Thank you for the clarity, Patrick. I believe it was one of your threads that got me looking at the plates.