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So you want to make a dovetail chisel?



Clark needed a 1/8” dovetail chisel and I offered to make it for him. I said, “That should take under an hour from beginning to end”. Talk about shooting my mouth off!

The ideal dovetail chisel has very narrow – almost nonexistent – shoulders to avoid bruising the walls of a tail when paring out the waste. Examples of chisels that have narrow shoulders include those from Blue Spruce and Lie-Nielsen.

Blue Spruce

Lie-Nielsen



The BS is a tanged design, while the LN is a socket design based on the Stanley 750. Each of these chisel designs has a part to play in this story.

A few weeks went by, and then Clark called to say that he had a 1/8” square bar of steel, and could he come over? Now I had to put my money where my mouth was.

Actually I was looking forward to this. I did have a plan. A couple of years ago I had built a chisel jig for a 6” grinder. It worked, but it was rudimentary and I knew I could now do better. Since that time I have upgraded my grinder to an 8” half speed, and I added the Tormek BGM-100 blade rest (I also have a Tormek wet grinder, and can switch between grinders using this tool rest).



The BGM-100 is not an essential piece of the kit if you wish to replicate my method, but it does help to use a sliding tool rest. One may be created simply out of a steel rod/pipe anchored to wooden blocks at each end.

The other tool of relevance is the Veritas Small Blade Holder. (Again, you can replicate this by recessing and epoxying rare earth magnets into hardwood).

The plan was simple – use the small blade holder (SBH) to clamp the blade in the Tormek blade holder and use the BGM-100 to run it past the grinder wheel to grind the chisel shoulders.

I tested it out…



The chisel used above is an old Stanley that started life as a bevelled firmer. Here it is one shoulder ground …



To grind the other shoulder, turn the chisel around on the SMH. Below is a partially ground shoulder.



This was looking good, and in fact it was easier than I had imagined. While Clark’s request had started the brain ticking in earnest, I had been planning to grind a bunch of mangy Stanley 750 chisels (we will get to these shortly) as well as some Japanese dovetail chisels (which have high shoulders).

I was feeling confident enough now to grind the Stanleys. Below is a picture of the four I had – ¾”, ½”, 3/8”, and ¼”. The ¼” has been ground and may be compared with the ½” for a before and after.



Here all four have been ground. I shall return to these chisels later.



Grinding a dovetail chisel blade

Clark arrived and had brought along a 1/8” square length of HSS. OK, not quite what I was expecting – which was O1 – but there are pros and cons here. The advantage of grinding HSS is that you do not need to worry about heat affecting the temper (although I found the white 46 grit wheel on the grinder ran quite cool. In addition I sprayed water over the Stanley’s steel ever minute or so, with the result that they never reached more than warm). The disadvantage of HSS is that it is pretty wear resistant and would be harder to grind, and harder to hone.



We set the steel on the magnetic blade holder, and ground one side ….



and then the other …



Time out to turn a handle out of length of Lilac wood he brought along (his favourite), and the final result was this …



The HSS was hollow ground on the Tormek at 25 degrees, then honed freehand on 1000/5000/12000 Shapton Pros. These had no difficulty with the HSS.

How does it work? A few test shavings …

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Making handles for my dovetail chisels

Why did I want to make dovetail chisels out of these old Stanleys when I already have a wonderful set of Blue Spruce dovetail chisels? The reason lies in a set I saw a couple of years ago. Dave Jeske (of BS) made handles for a set of handles for LN chisels owned by Jim Shaver. These were (and are) simply stunning! Dave’s designs are out-of-this-world, and I consider this set of chisels to be among the most beautiful I have ever seen …

Essentially these handles are lengthened versions of the standard BS dovetail chisel handle. The original BS handle is longer than the LN handle, and these are longer still ..

Now this is where it gets interesting for me.

I wanted to recreate these handles for the Stanley 750s (which are the same shape as the LNs). In my experience it is very difficult to accurately copy the design of another turner. I have seen many attempts to copy the design of my marking knife, for example, and no one has been able to do so. The results are not so much variations of my design, but a difficulty in recognising the structure and the sequence of how I worked. There is a little bit of muscle memory and a little bit of individual flare that combines to create the personality that is expressed in a turning.

I needed to work out Dave’s music – the progression of hand movements that would allow me to follow his beat and play his song. This is what I came up with ..

These are handles for socketed blades. Unlike Clark’s chisel handle, which was drilled for a tang, these handles have a tenon, and this needs to mate perfectly with the chisel socket. And each one is a different size/dimension.



Measurements required

There are three important measurements to take. The first is to obtain the internal diameter of the top of the socket. This will provide the dimension for the base of the tenon …



The second is to measure the diameter at the bottom of the socket, which will provide the dimension for the top of the tenon …

I used a drill bit of known diameter (in this case a 5/16”), which was inserted into the socket …



Record the depth of the tenon, and transfer this diameter to a calliper …



The last measurement that you will require is the diameter of the “transition” (my term – the section between the socket and the handle. This will enable multiple handles to have the same dimension. Measurement was taken from a handle that I had already turned …



Wood used for the handles is West Australian She-oak, a gift from Clark.

After marking the body and tenon lengths, begin by creating the tenon. Remember to add a 1/16” for the gap between the socket and the shoulder of the handle. This is to take up any length lost as a result of the wood shrinking over time.

In the picture below I have created the base of the tenon. The tip of the tenon is turned next. This is pretty standard stuff so far.



Below is the completed tenon. The shape of the transition is created by following the fine of the tenon and leaving the thickness of the steel.



Now remove the waste so that the handle is the same diameter as the transition.



Shape the curve at the base of the transition.



Square off the end of the handle. This end will have a curve added.



Using a curved skew, shape the handle working from the hollow back.



Here is the final shape with a finish added.



Finish used is Shellawax (a favourite among Aussie turners).



The final tuning of the tenon-socket fit is achieved by pushing them together and twisting. If there are any high spots that cause binding these will show up as black marks. Remove these with a chisel and/or sandpaper ..



Final results ..





Four in all – the handles are slightly narrower, following the slightly narrower sockets used as the blades reduced in size.



Postscript

A couple of points to add to the write up.



While the jigs used here were factory-made, I simply used them because I had them. If you do not have these you can make your own in your shop quite easily: a length of pipe attached to wooden blocks, angle iron for a slide, and rare earth magnets morticed into hardwood as a holder.


The rare earth magnets are quite powerful, but not that powerful, and there is movement (I may make up my own holder with a greater number of rare earth magnets). To minimise movement make sure that you reduce the leverage on the blade by reducing the extension over the end of the holder.

Keep in mind - the narrower the steel, the less magnetic support. Still, you can see I managed to grind a 1/8" bar quite accurately. Just take your time.

I also do not rely on the magnets alone to secure the blade, but keep my finger tips on top. This additionally enables me to monitor the temperature of the steel. I keep a spray bottle of water handy and mist the steel every 20 or 30 seconds as a precaution.

When starting the grinding with a square bar you will find that the wheel is apt to catch the edge and want to pull it off the holder (in a similar way when you round an irregular chunk of wood on the lathe). Just go slow here and take very fine "bite". It gets easier as the side grinds to the hollowed profile.



Hoping this inspires you …

Regards from Perth

Derek

April 2010