Alisam Sharpening Sled and Diamond Stones

There are two main aspects of sharpening edge tools.  One is the abrasive, and the other is presenting the tool at a consistent angle to that abrasive.  The more accurately this angle is maintained, the better the result, and the easier the entire sharpening process.  Jigs that assists you in maintaining that angle are known as sleds, or honing guides.

I’ve spoken in the past about the Veritas Mark 2 sled, which runs on top of the sharpening medium.  This sled from Alisam takes a different approach, and runs on a smooth reference surface which the stone is also on.

This concept does not work for waterstones, which although flat can have any amount of tapering, rendering the sled ineffective.  However, it is ideal for diamond stones, where the thickness is very uniform, the Scary Sharp method (using sandpaper), or using powdered abrasives / lapping powders. The guide is therefore not required to travel on or through the abrasive.  I haven’t tried it, but you could imagine the potential damage to the brass wheel of the Veritas if used on the Ex Ex Coarse DMT Diamond stone (which is around the equivalent to ISO120 sandpaper), or having to push over and through lapping powder.

Diamond Stones and the Alisam Sled

Diamond Stones and the Alisam Sled

I have chosen the SS3 Alisam Sled from Professional Woodworkers Supplies here, as it is the lowest of the three, and ideal for the diamond stones I am using. There is the sled (obviously the blue thing!), the 2 DMT Diamond Stones, and an HNT Gordon Plane blade (this is a reject one because it did not meet Terry’s standards, and so I can use and abuse it without feeling I am wasting good steel (the ultimate crime!)) You could just as easily substitute a normal plane blade, or a chisel etc into this guide. I am using a base of MDF, which is remarkably flat because of its manufacturing process.

Setting up for sharpening a plane blade

Setting up for sharpening a plane blade

The guide is set up with the blade roughly in place, before fully clamping down on it.  The black ring (to the right of the blade) is used to set the blade perpendicular to the guide.  Under the stone, you can see two dark tracks, which is where I was already working the blade before taking the photos – this is some of the metal removed from the blade, where it has been forced into the board by the jig.  It doesn’t affect the accuracy, and just shows how fine the particles are that get removed.  There will be little to no abrasive there because of the quality of the diamond stones.  Unlike a waterstone, the diamond stones are not designed to shed the abrasive as part of the sharpening process.

Setting the sharpening angle

Setting the sharpening angle

To set the grinding angle, one handle on the sled is loosened, and the drawn mark lined up with the required engraved angle.  This is not an eyechrometer thing though – underneath the side (as you may be able to make out), there are accurately machined indents which positively engage on raised areas of the jig body, so the angle is perfect, and perfectly repeatable.

Angle Set

Angle Set

Here I have set the angle to 30 degrees, the blade is clamped down (and I’ve moved the alignment ring out of the way, although this was not necessary).

Working through the grades

Working through the grades

You then run back and forward over the stone to grind the blade – one interesting point is in theory if you kept going you would find it cutting lighter and lighter until the blade could no longer reach the stone. This has been addressed very cleverly by having the front two wheels spring loaded – they have a tiny amount of vertical movement allowing more or less cutting pressure to be applied to the blade.  I was quite impressed when I discovered that.  The other beauty of this jig is you can use the entire stone, and not just a half or so, as the jig is not running on the surface at the same time.  I found it a very easy honing tool to use, and it cut quickly because of both the pressure I could choose to bring to bear, and that each stroke used the entire stone length.

Coplanar Guide Wheels and Blade

Coplanar Guide Wheels and Blade

From underneath, you can see the 4 rollers (the right-hand two, which are the forward rollers are the ones that are spring loaded).  The blade in this case is close to being complete.

Flattened Blade

Flattened Blade

This is about as far as I could get on the diamond stones I had.  My next step from here would be to move onto even higher grades of abrasive to really get a mirror finish (and obviously to flatten the back of the blade to the same condition – there is no point having one mirror surface if the back of the blade is pitted, rusty, chipped etc.)

Just a point too on the apparent loss of the hollow ground in the centre of this blade – remember this was a reject blade, and the slight warping made it scrap.  Even so, that is becoming a very well dressed edge, and it wouldn’t take much from here to bring it up to being fully live.

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