Tag: diamond

It is possible to put a great edge onto a knife with very basic equipment and a lot of time. However, with the ever harder and more abrasion resistant steels, diamond stones make it much easier and faster to achieve that edge. DMT are one of the best, if not the best, makers of diamond sharpening stones. If you have checked my ‘Recommended’ page you will have seen that DMT was actually already my favourite diamond sharpener brand, with a pair of DiaFolds (Coarse/Extra Coarse and Fine/Extra Fine) always with me for field maintenance.

In this review I’m looking at two very different sharpeners, a large bench stone (Duo Sharp 10″ Bench Stone) and a guided precision sharpening system (Aligner ProKit).

“Getting your EDGE back”:

There are so many variations in knife design, size and purpose, and I shall continue to try and review as many as I can, but the one thing that they all have in common is a cutting edge, and it is that edge which makes a knife into a tool. When you buy a knife, the factory put an edge on the blade, but this can vary considerably in quality even from good manufacturers. Relying on the factory edge is like buying a car and only driving it as far as the original tank of fuel will take you. You can transform the performance of a knife, so it is worth investing in quality sharpening equipment.

Actually this section title uses the name of a sharpening service I offer to neighbours (100% going to charity), and is absolutely appropriate for anyone who wants to have the best performance from their cutting tools.

I’ve used just about every method of sharpening, both manual methods and powered. These range from the humble carborundum bench-stone to high-end guided sharpening systems, as well as various wet/dry grinders and belt sanders. Manual sharpening does take longer, but gives you greater control and removes less metal. Where Diamond sharpeners really stand out is the speed they cut, and a quality diamond stone can cut 6-10 times faster than other stones. That is a lot fewer strokes you need to make.

There are many diamond stones to choose from with very different prices. DMT claim the flattest sharpening surfaces with the highest quality of diamond particle and density of coating. I can’t examine this to confirm or deny their claim, but what I can say is that where other diamond stones have let me down and worn out quickly, the DMT stones I have, have worked very very hard and are still going strong.

A few more details of the Aligner ProKit:

The Aligner ProKit comes in a storage/carry case.

For this review DMT have also included the Extra-Extra-Fine stone (pink colour) so this is not normally in the ProKit pack. What is included are the three grits Coarse, Fine and Extra Fine, the stone holder/guide-rod, the Aligner adjustable clamp and guide, a tapered serration sharpening diamond coated rod plus the instructions.

Laying everything out, this is what is in the box (remember the pink stone is not part of the ProKit).

As it can’t be fitted into the stone holder, the tapered rod has its own guide rod which screws into the widest end.

I don’t have a microscope to really go in ultra-close to the different grit stones, but this series of images at the same scale give an indication of the different grits.
First up is the Extra-Extra-Fine where the surface appears almost as if there were no particles in it.

Moving up to Extra-Fine and the surface is starting to take on a textured appearance.

With Fine you can see the grainy surface.

Finally with Coarse there is a distinct texture to the surface of the stone.

Each of the different grit stones are fitted into the holder for use.

The stone is pressed into the pocket in the holder.

Then the lock at the end of the holder is turned to hold the stone securely in place.

A closer look at the rotating lock. Initially the fit of the stones into the holder is snug enough to not need the lock, but as you use it more they loosen up slightly and you do need to use the lock.

Being a portable kit, the stone holder has a folding guide rod. Here it is folded over the stone.

The rod hinges round and locks into place in the open position.

Then we have the crucial part of a guided system, the guide itself. This is a clamp which fits onto the blade spine and has adjustable guide rings for the guide rods to run in.

Looking in close at the clamp jaws. There is a brass screw for adjusting the width of the jaws.

With the jaws adjusted to the right size, a locking screw is used to tighten the jaws onto the blade.

Each of the two guides have a number of positions they can be set to. Each of these positions has a groove moulded into the guide arm.

Here we have the clamp fitted onto a blade and the guides set to position 3.

A few more details of the DuoSharp Bench Stone:

The box was shown earlier along with the Aligner ProKit. Inside the box you get the DuoSharp, a sharpening guide (showing other DMT products) and a set of rubber feet.

There are eight feet which need to be fitted to the eight pegs (two in each corner).

While the bench stone is upside-down one of its stand-out features can be seen – a handle. This is part of the DuoBase design.

The handle means that you can take the stone to the blade instead of the blade to the stone. For larger blades this is ideal and makes the DMT benchstone pretty unique. Later on I show an example of exactly this with a ham knife.

The Diamond stone slab is double-sided, so for the other grit you need to flip it over. It is held onto the base with two plastic clamps. Turning the base over you can see the two tabs that click into place. (you can also see the positions these can be put for the smaller 8″ stone.)

Simply pinch these together to release the stone clamp.

You only need to remove one of the clamps to allow the stone to come free.

Fitting in with the colour coding across the DMT range the Red dot represents the Fine grit. The smaller blue dot shows what grit the other side of the stone has – in this case Blue/Coarse.

The DuoSharp 10″ benchstone has an ‘interrupted’ surface which helps clear the filings produced during use. There are a couple of pin marks into the plastic which probably relate to location pins used during the moulding of the plastic part.

You can see how the diamond surface has been moulded into a plastic base-plate. One end has the elongated tab, only part of which fits under the stone clamp.

The other end has a smaller tab for the stone clamp to hold.

Flipping the stone over you can see the Blue grit indicator spot, this time with the smaller Red dot for the other side’s grit.

Fixing the stone back onto the base, first slide the tab under one stone clamp.

Then fit the second stone clamp.

Press the clamp down until it clicks into place.

For an idea of scale, here is the stone next to a Fällkniven F1. At 10″, this is a good sized stone.

What are they like to use?

Firstly, the Aligner fully packed in its box is not only compact, but is also light weight. This makes it a great kit to take with you on trips, to keep in the car, or to use to sharpen friends/relatives knives. With DMT diamond stones being used dry you also don’t need to carry any oils or lubricants, so overall it is very convenient.

Clamp based sharpening systems are limited by the capacity of the clamp. The Aligner’s clamp has a 6.5mm capacity if the adjustment screw is fully removed and reinserted one half turn. I’d prefer more than half a turn, so I think a 6mm blade thickness is a more realistic maximum.

It is best to have an ‘approach’ to keep your results consistent. In this case what I’m referring to is the clamp position. Moving this along the blade will change the angle the stone runs on the edge. So far my approach has been to fit the clamp in the centre of the cutting edge of the blade on every blade I sharpen. Working in this way, in future you will put the clamp into the same position for subsequent sharpening sessions.

As with this type of guided sharpening, once the clamp is fitted to the blade spine and locked on, sliding the guide rod into the guide ring you can now move the stone across the knife edge at a consistent angle.

If you are not used to working with this can be a little awkward. The instructions say to hold the knife handle in one hand and the stone holder in the other; personally I find it easier to hold the clamp in my left hand (I’m right handed) with the blade sitting on my hand. The feel is the same for both sides of the blade. If you have to hold the knife handle it means swapping round an moving the stone with your non-handed hand as well.

For narrow blades you should check for clearance (keeping the stone from wearing into the clamp). In this case there is plenty of room, but the blade is not narrow.

To select the right angle you can use the ‘Sharpie’ method (using a marker pen to blacken the edge bevel and check where the stone is cutting) and if necessary adjust the position of the guide rings. If you are using different settings for different blades, you will want to keep a note of the positions used for each blade to allow you to sharpen it properly next time without changing the bevel angle.

Once you are done, I find it best to leave the clamp on the blade when you test the edge in case you need to work on the edge a little more.

Overall the Aligner is light and efficient, and the DMT diamond stones cut very well.

Update 20 Jan 2017
Following some discussions on the clamp being liable to flex as it is plastic, I wanted to show more clearly how I use the Aligner and similar guided sharpeners. In the instructions for the Aligner it show the stone being held under the knife and the knife being moved over the stone in a similar way to using a bench stone. This means you are holding the knife by its handle and pressing down onto the stone. Like this there is maximum room for flexing. However I have always used this type of guide differently.

I hold the clamp and allow the handle to rest onto my wrist for this side of the blade.

And for the other side I again hold the clamp and support the handle (or blade depending on the blade length) with my third and fourth finger. This way round the blade also sits onto the pad of my thumb.

In this way it is possible to support where the clamp holds onto the blade while you bring the stone to the blade.

And the other way. Hopefully this show clearly why I haven’t had any actual issue with flexing from the plastic clamp.

End of Update 20 Jan 2017

Now we move onto the DuoSharp Bench stone and the technique requiring most user skill. However due to its wide flat surface and diamond cutting efficiency it certainly seems to make sharpening this way much easier than on the carborundum stones I learnt on.

The kitchen knives being sharpened are slightly magnetised due to being stored on a magnetic rack. The filings stand themselves up like this due to being magnetic themselves. A wipe over with a damp rag clears these off nicely.

A few of the knives this stone breezed through.

Now onto something a little more challenging, a 16″ ham knife. Ham knives are super flexible and thin, so are not easy to work onto a stone with.

This blade had seen some abuse in the past and the edge was a bit wavy. I wanted to tidy it up and put together a very simple jig to keep the blade straight. A couple of stop-screws on a wooden base and some masking tape to keep it in place. To the right you can see an angle guide I setup for reference to help me stay on track.

Using the handle on the back of the base I then used the bench stone hand-held. Working on the long and flexible blade in this way was so much easier and resulted in a corrected and hair-splitting edge (after a final strop).

The only real limitation with a large flat bench stone like this is with the recurve section of some blades. Those concave recurve sections just won’t get to touch the diamonds, but that is always the difficulty of a recurve blade.

Being able to hand hold the DuoSharp bench stone was an unexpected benefit of the DMT design and makes it much more versatile.

Review Summary

The views expressed in this summary table are from the point of view of the reviewer’s personal use. I am not a member of the armed forces and cannot comment on its use beyond a cutting tool or field/hunting knife.

Something that might be a ‘pro’ for one user can be a ‘con’ for another, so the comments are categorised based on my requirements. You should consider all points and if they could be beneficial to you.

 

Discussing the Review:

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