Large Radius Arc Jig

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Project by Tooch posted 04-20-2019 01:02 PM 1290 views 2 times favorited 7 comments Add to Favorites Watch

I’m working on a Bed frame project for my oldest daughter, and wanted to draw a really large arc across the top piece. Normally, I am able to plot out a few points and draw it freehand, but this piece required a 70” long arc that would only take off 1.5” at its highest point, so I knew I needed some help. After a quick YouTube search I found this remarkable video:

I tried to follow along with the instructions, but realized quickly the nail trick would have to be modified because it split the wood (pic 2). I used a few extra scrap pieces of plywood and mounted them to the edge grain of the piece I was drawing the arc on (pic 3, corners; pic 4, lower left).

After a failed first attempt (I forgot to keep one edge parallel to the edge of the piece) I was able to successfully transfer the large arc. The last pic shows the only downside of edge mounting a the contact points, as the pencil thickness causes a little disruption at the end of the arc. At least I was able to successfully fix this by lightly sketching it in freehand.

The First picture shows this fixture folded up and ready for storage.

I just re-read this post and realized how difficult it is to explain in written word, and the arc is so long that pictures don’t really work either. My advice would be to watch the video for better explanation or search “Large Arc Drawn on Wood” and find another similar video.

Sorry I’m not better at explaining this . haha.

-- "Well, the world needs ditch-diggers too..." - Judge Smails

7 comments so far

View kiefer's profile


5812 posts in 3717 days

#1 posted 04-20-2019 01:41 PM

I posted this when I made the arches for my garden arbor and if you notice that I remove the center nail and draw the line continuous from end to end .

-- Kiefer

View Ivan's profile


16716 posts in 3917 days

#2 posted 04-20-2019 01:47 PM

I’m Always in the mood for some good jigs

-- Ivan, Croatia, Wooddicted

View Andre's profile


4439 posts in 2856 days

#3 posted 04-20-2019 03:40 PM

And this is why I like straight lines and angles :)

-- Lifting one end of the plank.

View Jim Jakosh's profile

Jim Jakosh

26046 posts in 4155 days

#4 posted 04-20-2019 07:59 PM

Nice easy way to make the arc! .

I guess I do it the hard way. I take a long board and putt a nail in one end and a pencil in the other and draw it. I draw them on card board and cut them out for future use. I have them from 25” to over 125”. They sure come in handy for make an arc right where I need it.

Cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View hoss12992's profile


4178 posts in 2943 days

#5 posted 04-20-2019 08:32 PM

Great job buddy. I’ve always found a needle, string and pencil worked really quick and easy for larg arks.

-- The Old Rednek Workshop

View doubleDD's profile


10259 posts in 3093 days

#6 posted 04-21-2019 03:38 AM

When you do things you never did before it a great accomplishment. Good to see you fixed that problem. I’m with Jim,I guess I always do it the hard way.

-- Dave, Downers Grove, Il. -------- When you run out of ideas, start building your dreams.

View  woodshaver Tony C   's profile

woodshaver Tony C

7922 posts in 4403 days

#7 posted 04-21-2019 12:06 PM

This is good info Tooch! I see that Kiefer was on it 8 year ago (I’m not surprised).
I’m not sure what I was doing back then but I could have used this when I built our fire place mantel.

-- St Augustine FL, Experience is the sum of our mistakes!

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