Thomas Aquinas, part 2: sawing

Thomas Aquinas, part 2: sawing. Two large sandstone blocks

1. Two large sandstone blocks of Udelfanger sandstone: 1 for the statue of Thomas Aquinas, 1 for Serge's angel

Two large blocks

The work on the on copy of the statue of Thomas Aquinas has finally started. I had received two large blocks of Udelfanger sandstone some time earlier: one destined to make two angels out of it and one block from which I had to carve the two parts of the statue of St. Thomas from St John's Cathedral in Den Bosch and fit them together. So the first step was to divide both blocks into two with the diamond chainsaw.

Thomas. Aquinas, part 2: sawing.  I halved the block with the diamond chainsaw

2. The block is cut in half with the chainsaw

Thomas Aquinas, part 2: sawing. Presawing the lower body

3. Sawing the lower body

Presawing Thomas

After that I put one block on my copying saw and started presawing Thomas' lower half. The dividing line of the two parts was meant to be near the line of his hood, so that it will be almost invisible. Reminder: in an earlier post I wrote that the old statue was made from a single piece of stone, in which the layers run vertically. Because it's more desirable that the layers run through the statue horizontally (in that case, there's less chance that an entire big slice comes falling down at once, after weathering) it will be different in this copy. But the quarry has no banks in which the stone is higher than 120 cms. Therefore, the head was to be made from a separate piece.

Because of the large color differences between separate blocks of Udelfanger sandstone I was sent a very large block from which I had to cut the two parts. From this I made the body and the head of Thomas.

Thomas Aquinas, part 2: sawing. Upper body presawed.

4. The upper body was cut from the second half

Thomas Aquinas, part 2: sawing. Rough carving the head and body

5. The head and the body are roughly carved

Fitting together of the two parts

Then, the two pre-sawn parts of the head and body had to be made to fit to each other snugly. That wasn't so easy, because the dividing line doesn't run straight. It follows the wavy line of the hood and needs to be higher at the right hand, because otherwise the joint seam would run through the knuckles. These inclined faces need to fit together well. For this, it should first be clear what will be located where, and for that I needed to rough carve the two parts for quite a ways. I carved the upper body and the lower body so that I could see where it all would be going, and I could see where the dividing line was to run. Then I could find the joint surfaces.

Thomas Aquinas, part 2: sawing. Making both planes fit

6. The joint surfaces are being made to fit

Thomas. Aquinas, part 2: sawing. The head and body are bonded.

7. the two parts are bonded together

Joint surface

Because I made this joint line visible on both pieces, I could demarcate the joint surface and carve away the excess stone. By keeping on fitting the pieces together and scribing the excess stone, I could ultimately achieve a tight seam. When the fit was tight enough, I scribed off where I wanted to put the stainless steel pins and drilled four holes. Two holes in each piece, so I could adhere both parts with strong epoxy glue and two thick threaded rods. Also, the joint plane itself was bonded with a suitable breathable mortar. You should actually never make a horizontally extending closed off gluing surface on a statue sitting outside. The stone above such a dense glue layer can't lose its moisture and will start to rot right above the glue seam.

Serge's angel

Copying an angel for St. John's Cathedral

The other block was halved as well. From the one half this angel was presawn for Serge

My colleague Serge had an commission in Udelfanger sandstone as well for St. John's Cathedral in Den Bosch. He was asked to copy this angel. He had previously made one and asked me if I wanted to saw this one as well. So, here goes.

Read more soon about the continuation of this project.

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Which diamond chainsaw for which job?

My diamond chainsaw

I recently cut up a blue block of sodalite with my diamond chainsaw. Because it's quite an expensive material, I could save quite a large chunk by this method. If I'd made this sculpture in the normal way with the angle grinder, lump hammer and point chisel, I would have had some wheelbarrows full of expensive rubble for the dumpster. So in this case my chainsaw came in handy. But I actually rarely cut up or spalt large stone blocks. I actually bought this saw to remove blocks from historic buildings, or to cut loose heavily anchored statues from their foundation.

The diamond saw I chose in 2015 chose was a Cardi Coccodrillo35. But what types are there actually, what kind of job do you use them for, and which one is the best for which job?

Petrol engines

rough block of stone for Aachen Cathedral. Made a piercing cut with the diamond chainsaw

deep cuts in tight corners

The first type diamond chain saw for stone and concrete was made by the American company ICS. The older types ran on an extra greasy oil mixture, were heavy and noisy, and often choked because of a wet air filter, caused by the water spray thrown up by the chain. I hope that they have solved this now. ICS has also developed the first diamond chain, and now make it for a lot of other manufacturers as well. ICS has several petrol versions on offer and make different kinds of chains.

Then also Husqvarna came with their own machine. They obviously have been making gasoline engines for chain saws and also for power cutters since a long time , so it fitted in well with their own range of machines. I know no further details. The price is around 3400 euros.

So their competitor Stihl could of course not lag behind. They have also developed their own version, plus their own chain with twice as many diamond bits on it.

Hydraulically driven

Now a gasoline engine makes a lot of noise and stench, and the torque at low revs is not great. That's why ICS soon developed a hydraulically powered version in the beginning, in three types. Hydraulic power is supplied by a separate hydraulic drive. This hydrostation of course also needs power supply, and this may be either via a gasoline engine (yet again noise and stench) or with an electric motor on 400 Volts (and then you'll need a 400 Volt power supply). The oil pressure goes to the chainsaw through two thick heavy hydraulic ducts. These are quite rigid and make the operation very difficult because they continually work against the operator.

Electric chainsaws

Then since the last few years there are also electric diamond chainsaws. I happen to own the machine shown above, the Cardi Coccodrillo35, by the Italian brand that also makes diamond drills and wall saws. It works on 230 volts at 3420 Watt.

But the German brand Dr. Schulze (if it says Herr Doktor in front of it, then it must be good!) has created a competitor to it that runs on both 230 Volt and on 400 volt. For the latter, you'll need a separate frequency converter, but then it suddenly consumes 6500 Watt, so it's a lot stronger on 3-phase power. Dr. Schulze uses the same motor for both their cutter and their ring saw as well. It is striking that this machine also has a kind of quick-tensioning knob, and a handle that can be adjusted in a variety of positions. Electric diamond chainsaws are a lot quieter, but not necessarily lighter than gasoline versions.

Pneumatic concrete chainsaw

For applications where sparks are absolutely undesirable because of fire hazard, an air powered version is also available. ICS provides one of those, for use in places where for example many power lines are running.

Advantages and- disadvantages of the various types

Strong and light

sculptor Koen van Velzen cutting the statue of Moses from Lambertus church in Veghel with a concrete chainsaw / diamond chainsaw

cutting statues free with the chainsaw

I do not pretend that I know all about the different types of diamond chainsaw. I worked in the past with hydraulic chainsaws from ICS, with older petrol versions from ICS which kept choking and were very noisy and smelly, and now with my own 230Volt saw. But in short: gasoline saws are very flexible to use because they only require a water supply. This can already be done with a tank and a pump, though the pump will need to be powered by a generator or gasoline motor. It gets a lot easier if a water supply is simply available. Drawback therefore is their noise and stench. For the latter, you can adjust the fuel, that makes a bit of a difference already. But, just as when I was was working in Nijmegen at the Stevens Church, if you need to cut for hours on end in a densely populated area, then it just wouldn't be right to start chainsawing right in the middle of city centre. Stihl would be my choice if I ever wanted a gasoline powered saw, because I've worked a lot with Stihl (chainsaw for wood, hedge trimmers and brushcutters), and was impressed by their quality. In addition, it's also fairly lightweight.

Much power and deep cutting

The hydraulic version is already a lot quieter. You can hear it clearly, but not deafening. The hydraulic power unit on gasoline makes a bit more noise. This machine is actually particularly suited to work in a well-organized construction site. You can cut very deep with the hydraulic version and have a lot of torque, but with that big power pack for the oil pressure it's just not as easy to move. Especially if you work on 3-phase power. I've always hated these machines because those heavy hydraulic hoses make using them so exhausting. I was always searching for places that I could hang them up on with a length of rope or I had them slung over my shoulder. But it's a very reliable machine; not much to get damaged on it. It can take a beating and can even do its work under water just fine.

No sparks

I'm not familiar with the pneumatic version of the diamond chainsaw, but judging from all air powered equipment, it seems to me that these don't have much torque left at low rpms. Added to that, a large air consumption always leads to a cooling effect, So I wonder how this would work at lower ambient temperatures. Maybe then you'll need to have an air dryer as well. Plus, you'll need to rent a large diesel compressor. I expect this one would also make a pretty loud howling noise.

No odor and flexible

My electric version was the solution for me. It's obviously not silent, but generates much less noise than a petrol engine. You can't cut as fast as some gasoline- and hydraulic saws, because you've got less power. The version of Dr.. Schulze promises several options for chains and sword. However, an electric motor of 3500 Watts is no light thing, so it is as heavy or heavier than a gasoline engine.

Chains and quick release

At Stihl they have developed their own sword and chain, though I do hear that a chain with diamonds on each link is not always convenient: Sometimes the chain itself wears out faster than the diamonds do, so that would unecessarily raise the costs. For example if you're cutting sandstone or brick. That is why ICS is sporting various different chains, for example, for brick, fresh concrete, hard concrete, granite and an economic version.

Now a diamond necklace stretches out really fast. While cutting, you're continually checking to ensure that the tension is still right. A too tight chain pulls the blade sideways and thus gets stuck in the kerf, and a too loose chain get unrailed and starts to 'wander about’ inside the kerf. It should hang loosely so that the links at the bottom of the blade just clear the rails. Once the engine starts pulling it will be just right. Tensioning is a tedious job: you always keep unscrewing the two nuts again that you just tightened up, then tightening a difficult to reach nut behind the chain and finally tightening the two lock nuts again . At Mito they have since found a solution: a quick release on top of the diamond chainsaw. This machine is by Chicago Diamond Supply and works on hydraulics, but I think there will be many more to follow suit soon.

Dr. Schulze has also something like that, as I think I noticed. Unfortunately no videos of how this thing works.

Applications for the diamond chainsaw

I use my diamond chain for cutting loose statues and stone blocks, if I want to cut any deeper than the 7 cm from my angle grinder. In recent times there were for example deep cuts in stone finials, cutting smaller some old tufa side flowers, cutting behind the back of Noah, and cutting Moses and Aaron free from the wall, and removing a pedestal.

In restoration these machines are used for removing large blocks from a facade with minimal damage to the surroundings. In construction they use it for all kinds of modifications to existing buildings, though large circular saws and wire saws are much in use there as well.


Table of diamond chainsaws

-Click on the image for the file in pdf (Sorry, it's in Dutch)-

Update 2 april 2019: Apparently it's all a lot cheaper if you go shopping in Germany as well (for example, the Cardi Coccodrillo costs € 1988,45 there, incl btw!)

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Crockets and finials for Aachen Cathedral

Two new finials for the Aachen Cathedral in Irish bluestone

For Aachen Cathedral some pinnacles had to be replaced. The old ones were worn and had cracked because of rusting iron and because the layering of the stone was not properly applied. The deposition direction of the stone should preferably be processed horizontal, otherwise there is a risk that a long vertical slice breaks off. In this case, they applied it vertically.

The material for these pinnacles is Irish bluestone. It is …Read the whole article…

Removing a pedestal with the concrete chainsaw

Last Wednesday I was at the gardens of Estate De Schaffelaar in Barneveld, the Netherlands. I had to remove a plinth of Belgian bluestone, that was anchored with four stainless steel pins of 2 centimetres thick to a concrete foundation. Of course the solution was the concrete chainsaw on 230 Volts (Cardi Coccodrillo 35 or Renova chainsaw). The base will in due course be reinstalled inside the main building itself, but more on that later. …Read the whole article…

Moses and Aaron-Veghel

Lambertus Veghel façade with statues of Moses and Aaron

Today I once again started on an interesting restoration job. I went to St. Lambert's church in Veghel to collect two statues: Moses and Aaron, carved in Udelfanger sandstone. The statues date back to about the construction time of the church, around 1860. …Read the whole article…

Disassembling tuffstone with a concrete chainsaw

Stide lifting a block that has been cut loose from the wall

Stide lifting a block that has been cut loose from the wall

← to the first post about this project

Today my colleague Stide and I were in Nijmegen again. We are presently replacing a number of ornaments on the South Portal of St. Stephen's Church all of them (20 trefoils, 7 consoles, 20 crockets and 3 capitals), and right now we're arriving at the removal of the last blocks. …Read the whole article…

Experiment with a Cut-n-break machine (video)

← To the first post about this project

I've arrived at the point where I can cut the openings between the ferns. It's just that some of the openings are so narrow that a normal angle grinder doesn't fit in between. Fortunately there are several solutions:

-a chain saw for stone and concrete (hydraulic, with a petrol engine, or on 230 volts)
-or an Husqvarna Cut-n-break saw. This one as well is available on petrol or electrical. …Read the whole article…