DIY Pointing Machine

If you’re a stone carver and would like to try the traditional method of reproducing an existing sculpture or cast in stone, then you’re going to need a pointing machine.

These tools have been around, more or less unchanged, for hundreds of years and allow the artist to transfer points in three dimensions from one object to another.

They are quite rare and can be very expensive, with most coming from Italy and costing somewhere around 300 Euros.

I didn’t have that kind of money to spend on a hobby so I made my own and now I’d like to show you how to make one too.

SHOPPING LIST

1. "Magic Arm" camera mount
2. old tripod or camera
3. scrap wood
4. metal rod
5. metal angle brackets
6. metal fixing strip OR plastic pipe clip
7. screws / glue / nuts & bolts

TOOLS

1. saw / hack saw
2. drill
3. tin snips
4. screwdriver
5. chisels

There are two main components to a pointing machine, the frame (or crochet) and the pointing device (or macchinetta). Both are important, but the crochet is just a simple wooden frame which can potentially be re-made to suit each project so this isn’t something that I’ll be going into here.

Instead, let's look at the pointing machine, this consists of an articulated arm and a pointing head.

For the first part, I discovered these articulated camera arms online – they are often called ‘magic arms’ and are used either to hold a camera, camera phone or lights and are pretty much identical to a pointing machine arm but cost a fraction of the price – mine was under £20.

You only need the one with two arms as long as it's big enough to reach around the piece you want to work on. I ended up with a three arm version which is fine too. You'll also want one with at least one clamp at one end and some kind of camera mount at the other (although another clamp could also be handy).

Got one? Great, what next?

This is the thing you use to measure your points. It needs to be hard wearing, straight, smooth, rigid and end in a point. Metal is going to be best, you don’t want this bending or wearing down over the course of a project.

I used a piece of approximately 4mm thick metal wire from a garden plant support because I had some laying around but another option might be chopping a piece off a simple wire clothes horse.

I ground the end to a point on a bench grinder, but a file would work just as well.

This is where the needle slides back and forth, it needs to provide a bit of friction so your needle doesn’t fall out. It also needs to be long enough to hold the needle straight so it doesn’t stray off axis during use (which it might if it was just passing through a single thickness – like a small block of wood)

I used metal corner brackets set end to end to provide a nice distance and the pre-drilled holes matched the size of my needle nicely. These were simply screwed onto a small piece of scrap wood for a base.

To provide some friction, I improvised a brake with some thin springy metal – in this case some masonry fixing band, but again, see what you have laying around. (a pipe clip could work too – attach one end and leave the other free floating ) - Both methods are described below.

1. Start with the basic holder frame.
2. Attach the metal strip at one end to the base.
3. Bend it over to just above the height of the needle position .
4. With the needle in place the bent metal strip should be just pressing against it to provide a braking effect.

1. Start with the basic holder frame.
2. Check the height of the pipe clip compared to the needle position (this one needed packing at the bottom)
3. Cut one end off the clip so it can flex under the needle.
4. Attach it to the bottom of the holder frame.
5. With the needle in place the clip should be just pressing against it to provide a braking effect.

*An alternative to a brake would be to provide the necessary friction in the holes the needle passes through, for example, by using some rubber grommets or making the holes just tight enough to hold the needle.

This is a small block fitted with a screw that can travel up and down the needle and which is then locked in place to mark the depth of each point that you measure.

When the needle is withdrawn from the sculpture through the holder, the back stop stays attached to the needle to act as a measuring guide when the pointing machine is moved over to your stone. (It will show you how much material to remove and subsequently when to stop carving when you reach the same level as your point.)

This piece was a little rough and ready on mine, maybe you can find a more elegant solution...

1) Start with a small block of wood (it can be longer than you need for ease of handling).

Drill a hole all the way through (at the diameter of your needle).

Drill another hole at 90 degrees to the first, stopping half way through when you reach the first hole, this is for the locking screw.

2) At the top of the shorter hole, chisel out a space to fit a nut.

3) Fit the nut into the top of the hole.

4) Secure it well with glue.

Cut your block down to size.

5) To prevent the nut being pushed out when the screw is fastened against the needle I added a small metal plate over the top as extra security.

Fit the locking screw (mine was a bolt with the end set into a block of epoxy resin to act as a handle - it's not pretty but it works!).

Next, we’ll consider how to fix our needle assembly to our purchased magic arm.

Being a photography tool, the screw threads are going to be one of two possible sizes:

1. ¼ inch 20 threads per inch or
2. 3/8 inch 16 threads per inch (although this latter one is generally for more heavy duty kit).

Finding a nut with the correct thread may prove tricky (especially anywhere with metric hardware measurements) so some more cannibalising may be in order.

For mine, I managed to find an old tripod with a mounting piece on the top that was detachable and of the same thread size.

If you can’t find anything similar anywhere (car boot sale, charity shop, ebay..) then how about chopping up an old camera? It should have the tripod mount underneath and if you can cut away a section of the case too then you have something that can be attached both to your magic arm mount and the wooden base of the head assembly we’ve just made.

Attach the tripod or camera piece that includes the threaded hole to your wooden base with some small screws.

Then simply screw it on to the magic arm attachment and you’re done!