Drawing a large radius

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Forum topic by daddywoofdawg posted 08-30-2015 03:59 PM 615 views 0 times favorited 7 replies Add to Favorites Watch
View daddywoofdawg's profile


1006 posts in 998 days

08-30-2015 03:59 PM

I have a design that requires some large radius ( 60.2”,60.45”,58.2”,57.95”radius) on narrow boards (X4,X6).How do I make radii that large? A big beam compass,A bent board (how do I figure the radii with that?) or is there a better way?

7 replies so far

View waho6o9's profile


7124 posts in 2000 days

#1 posted 08-30-2015 04:09 PM

A 4×8 sheet of plywood and a folding ruler come to mind.

Lay it out and set your trammel points / beam compass and your golden.

View Redoak49's profile


1824 posts in 1412 days

#2 posted 08-30-2015 04:12 PM

I would use a long board with a nail thru it for center and drill a hole that is a snug fit for a pencil. Getting that large a circle to the hundredths of an inch may be extremely difficult.

View BurlyBob's profile


3487 posts in 1689 days

#3 posted 08-30-2015 07:20 PM

I’ve done it exactly like Redoak says and I have to agree those are pretty exacting dimensions.

View Ghidrah's profile


667 posts in 645 days

#4 posted 08-30-2015 08:23 PM

I’d use a nail and 10 or 12’ tape measure, don’t waste the wood. I’ve used this method on arched doorways, breezeways and garages tons.

-- I meant to do that!

View JeffP's profile


573 posts in 815 days

#5 posted 08-30-2015 09:59 PM

Or just a nail and a carefully measured piece of thin wire with a pencil at the other end.

If you’re not doing a whole mess of them, I would just go with something really simple like a small nail taped in the “crook” at the end of a tape measure as your center point, then pull the tape out to desired radius and lock it…then lay a pencil in the corner between the tape and the tape-measure housing and hold it there while you scribe your line.

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.

View Kazooman's profile


616 posts in 1375 days

#6 posted 08-30-2015 10:07 PM

OK, curious minds want to know. What on earth are your up to? Arcs with 1/4” difference over a 60” radius!

I can only imagine that you are making something with a 1/4” curving band in it. If that is the case, note that you do not want to change the radius by 1/4”. You want a constant radius and need to move the center point 1/4”. You probably couldn’t see the difference by eye, but there is a difference.

So, what is the project???

View daddywoofdawg's profile


1006 posts in 998 days

#7 posted 08-31-2015 07:31 AM

It’s like 2” width on the curves,I just put them in size has a 60.45 and the 57.95 inside radii.

I’m thinking I can draw it on some Masonite,cut it out and make a template.

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