Marking an arc...

Here's how to lay out an arc when you don't have the centre point nor the radius. Accurate and easy!
More at www.stevemaskery.com

[@garycoulombe574]

Thank you for sharing this simple and effective method❤

[@TheS4ndm4n]

Thanks for the demo! It's an application of the "inscribed angle theorem", in case anyone's interested in geometry. I didn't know either, but I might be looking into making a jig for a handhelt router, which utilizes said theorem. Shouldn't be too hard and potentially very versatile.

[@eduardo_2805]

Great! Thank you for sharing artisan knowledge. That is realy important now a days. Cheers from Brasil

[@SteveMaskery]

My pleasure. I think it is important to keep these traditional techniques alive.

[@Woodgate425]

Thanks Steve, I wish I’d seen this about a week ago as I had to do the same for the arch in a heavy oak door frame. Ended up using a mathematical equation to get the radius and a very long trammel bar. I’ll know for next time!

[@handyjim]

good to know, nice one

[@SteveMaskery]

Glad you liked it!

[@209porker]

Neat Steve, knew the first method but not the circle

[@karlsjov]

Pretty clever, thanks for sharing. Everything is easy, when you know how to do it 🙂

[@SteveMaskery]

You’re welcome 😊 I think it is important to keep these traditional techniques alive.

[@FirstMM]

Genius - I'd click Like and Subscribe twice if I could!

[@TheFalconJetDriver]

I can think of a far easier way, clamp a length of wood in the center of we’re you want the arc, the length of wood will be the support for the compass, draw the arc.😁🛫

[@SteveMaskery]

Hmm. Let's just unpack that a bit, shall we? For a start you need to know the radius. We have already established that we do NOT know the radius. So we would have to calculate it by trigonometry, or draw it out in Sketchup and get the computer to tell us what that radius is. Then we would have to find a piece of wood long enough. If that bulge is very shallow, we can quite easily get to the stage where the centre is outside the workshop. That is a very long piece of wood to clamp in place. And it doesn't just need to be long, it needs to be wider than the limits of the arc (the Chord) otherwise the clamps will get in the way of actually drawing the arc. Or we can just nail two sticks together and have the job done in under three minutes and have the satisfaction of knowingthat we are keeping ancient, traditional working practices alive. "Far easier"? I don't think so! :)