Thursday, 21 July 2016

Homemade pantograph...

Recently I found myself in need of a way of enlarging a smallish item for a project (which I haven't actually got round to yet) my son has a number of those 3D wooden models, all of which are dinosaurs and I decided that I'd use some of the odd plywood off cuts I have lying about to make a large skull in the same style as the models.

The problem was getting the template to the right size, the template in this case is just a section of skull from one of his models.

Template -

He has loads.

It's a pretty simple shape, but I wanted it to be bigger, around a4 size the problem was how to get it to the size I wanted ?

So I made a pantograph (well I actually I made two, I'll get to why later) which is basically an old way of enlarging or shrinking images, artists and planners have been using them for years (since about 1600) yes I could have scanned the template and printed it out to the sizes I wanted, but to be honest this was quicker and printer ink isn't as cheap as wood.

Here's the second one I made - 

This one worked much better than the first.

Why did I make two ? simple really the first one wasn't as good as it could have been, it did work but due to some mistakes I made every enlarged image was slanted (think italic writing) and not what I was after, simply put I didn't take enough time on it and as a result it wasn't good enough, so I did more research and took my time with the second one and got a much better result, patience is a virtue.

The first one - 

Close but no cigar.

As you can see there is a difference between the two, but both are made in a similar way from strips of pine about 25mm wide and 7mm thick (left over from a project) the main difference being where they are connected and pivot.

So ignoring the first effort here's how I made the second one, I cut five strips of wood four to make up the pantograph frame and one so that I could clamp it to the table.

Here's a cut list, allow an extra 50mm on each piece for fixing -

Click to make bigger.

Here's what it should look like when done (red dots are where fixings go) - 

Click to make bigger.

Once you've cut your wood you should have five pieces, two at around 55cm long one at 35cm long, one at 25cm long and a short piece for clamping (around 15cm is fine) next you need to drill holes for fixings, on one of the longest pieces put a mark at 2.5cm and then measure 20cm along from that and put another mark then from that mark measure 30cm and make another mark, this is where you'll need to drill holes.

You can just tape the two longest pieces together to save putting marks on each bit, for the shorter pieces again measure down 2.5cm and mark, then measure another 30cm and mark and do the same for the shorter piece, measure down 2.5cm and mark then another 20cm and mark.

When you have your marks sorted then drill holes, I used a smallish drill bit (5mm) in my post drill to keep the holes nice and straight although you can do it with any drill, just keep the holes as straight as possible, once that's done fix the pieces together so it looks like the diagram above, I used small nuts and bolts, it's also a good idea to use some washers between the pieces of wood for smoother movement.

Nuts and bolts from a pound shop - 

Useful for all kinds of things.

I made some small plastic washers from a section of milk container using a homemade cutter, which is just a bit of steel tube with one end sharpened, a good tip is to drill holes in the plastic to the size you want and then cut them out, it's a nightmare trying to make small holes in small bits of plastic.

Homemade washers - 

Recycling is always good.

For the pencil holder I used one of my wood threading kits to make an adjustable holder from a bit of old dowel and plywood.

Making the pencil holder - 

You don't need a lathe for this, just a wood threading kit.
I turned a bit of dowel down to the right size and then put a thread on it, so it was like a wooden bolt, next I cut a section from the dowel so I had a flat edge for fixing to the pantograph frame, I also drilled a hole roughly the size of a pencil through the bit I cut a thread into.

Notch cut - 

I just used a coping saw.

For the part that will clamp the pencil I took a bit of old plywood which is good for this kind of thing and drilled a hole and using the wood thread kit made what is basically a wooden nut.

Making the nut, thread cutting - 

A bit of linseed oil makes for a smoother cut.

Marked and ready to cut out - 

I cut it out roughly.

Once I had the nut part cut out roughly I screwed it onto the bolt part and turned it until it was smooth(ish) and round, all this could be done without a lathe, but you would need a thread cutting kit.

The finished pencil holder - 

It works well.

The tracer is a piece of threaded bar with one end sharpened to a point and held in place with a couple of nuts, I made it slightly longer than it needed to be to allow for adjustments.

The tracer - 

Simple but effective.

I also made some small wooden feet to raise the frame up a bit this makes the movement of the whole thing much smoother when tracing, they're just bits of dowel stuck to the frame work and not essential.

Wooden feet - 

The feet are made from a scrap piece of dowel.

To stop it moving about a simple clamp is all that's needed to hold it down, this is where the short piece of wood comes in, it allows the pantograph to pivot but doesn't allow it to slide about all over the place.

The clamp - 

You could make a more permanent clamp.

And that's it, it works well and does exactly what I want it to, you can also use it for shrinking images as well if you use it in reverse (switch the pencil and tracer around) I did have to trace the image a couple of times to get it to the size I want, but this isn't a problem, obviously if I made it bigger the scaling factor would be bigger.

Success, no slanted images and the size I want and all from scrap bits of wood - 

Near perfect replication and to the size I want.

Thanks for reading.

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