Compasses and trammels?

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Paul_B

Bushcrafter (boy, I've got a lot to say!)
Jul 14, 2008
4,667
704
Lancashire
I need a marking tool for drawing arcs and circles at work. Point one end and ability to hold a pencil or marker the other end, perhaps those pencil lead points.

I used to have an engineering drawing beam compasses capable of 300mm diameter circles. I need something capable of 600mm diameter possibly more. I'm thinking trammels, available for £13 on Amazon for use with no steel ruler. I have a 600 mm steel ruler so I think using that in the trammel clamps allows for just under 1200mm diameter circles.

Are these the best thing to get? I've also seen standard compasses capable of 600mm diameter but they're more expensive. Got to be cheap for me to get the money back from work!!!

What do you use for scribing large arcs and circles?
 

Broch

Full Member
Jan 18, 2009
3,789
2,959
Mid Wales
How accurate? how durable? how often will it be used?

I'd simply drive a nail through the end of a 600+mm wooden slat (say 20mm x 10mm or similar) and hold a pencil on the edge with a strong elastic band. I think you could draw a 1200mm diameter circle to within a few millimetres with care.
 

demographic

Bushcrafter (boy, I've got a lot to say!)
Apr 15, 2005
4,295
287
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I have some trammel points I got from Amazon. Can either have two points or one point and a pencil holder.
Can just clamp them on a slate batton or 2x1"
 

demographic

Bushcrafter (boy, I've got a lot to say!)
Apr 15, 2005
4,295
287
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Can't find them the same on Amazon but the ones I bought were about a fiver or so.
I've sometimes just fired a screw through a slate batton for the centre then drilled a hole for a pencil also.
 

Paul_B

Bushcrafter (boy, I've got a lot to say!)
Jul 14, 2008
4,667
704
Lancashire
I bought these ones. I'm thinking of clamping them to a steel ruler that goes to 600mm.

Faithful Trammels

Accuracy? Well we've always bodged a two pens and a length of string but TBH it's a rubbish way to get good accuracy. We're basically making templates for using be with a flexible materials. Accuracy to nearest 5mm probably good enough in real world use, especially if +5/-0mm. However customer quality inspectors are used to metal bashers and question the very rough tolerances that would suit our products.

So I measure to the single mm and try to achieve as good a degree of accuracy as possible.

The company bought expensive trammels and even a 300mm set of bar compasses. If it's not nailed down it goes missing so we don't have them. Even my dad's old 200mm beam compasses had gone missing.

The use is to scribe arcs and circles into cardboard for a marking out template. We may move to hardboard for more longevity which we'll want more accuracy. Our last curve was bodged by hand. Fortunately the radius was pretty close to my arm from elbow to where I held the pen. Turned out passable.

We can all bodge things but IMHO it's better to do things right and use the right piece of kit. Hopefully these trammels will work. I need a 300+ radius so the 600mm steel rule probably would work as the bar using these cheap trammel points.
 

demographic

Bushcrafter (boy, I've got a lot to say!)
Apr 15, 2005
4,295
287
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Well those Faithfull ones are identical to the ones I have.
Mine weren't branded as Faithfull but its the same product and they're as accurate as the tape measure I measure between them with.
No doubt Faithfull has bunged a few quid on the price with their name but I'm happy enough with mine.