How to do a layout for a radius cut

[Duane Heda]

How do I do the layout when the plans call for a radius such as a 3 3/8" radius. Does anyone know of a website that could help me?

[Jay Boutwell]

Hi Duane,  confusing  for the first time but really easy.  Here is the steps.

The easiest method to cut a radius is using a framing square and a piece of stiff paper or cardboard.  In your post you are wanting to cut a 3 & 3/8 inch radius so the easiest way is to get your self a piece of stiff cardboard like poster board.  You will need a framing square and a compass. You will be cutting yourself a template.  You could actually lay it out on the actual wood stock but being safe is a good practice until you learn the procedure.

 

Step one:  draw a straight line on both the tongue and the leg of the square that is longer than the length of the radius,  In your case 8 to 10 inches is more than enough. 

 

Step Two: make a mark on both the lines made by the square making sure that you measure accurately at the 3 & 3/8 measurement on both of the lines drawn by the leg and the tongue. 

 

Step Three:  using the intersection of the two lines made where the toe of the square was set and open the compass to exactly 3 & 3/8 inches.

 

Step four:  set the point of the compass at the exact intersection of the two lines met and scribe a compass line from the 3 & 3/8 Inch mark across to the opposite line.  It should actually be right on the 3 and 3/8 inch mark and if so then you are accurate.

 

The result of this is a 3 and 3/8 radius.  Now you can use the two pieces of the paper for a template of which would be a positive and a negative of your desired radius. 

 

In reality what a radius is, it is a 1/4 of a circle. 

 

You may not understand the parts of a square so you should become acquainted with them as you will need to know this in future projects.

 

 The framing square is composed of two pieces of steel and or aluminum and sometimes plastic.  You should invest in a good one that is made of steel as they are the most rugged.   The longer piece is known as the "toe" and the long part as the "leg".  The square made by the 90 degree bend is know as the "heel".  Easy to remember as it is like that of your leg and foot.  Where the leg bends it becomes the foot and at the end of the foot is the toe.  Since the leg is longer that the foot then the long part of the square is known as the leg.  Funny but that is the way they named the parts when they made the square.  This holds true as long as you are talking about the outside of the square however when are talking about he inside of the square it is still known as the toe and the leg however the language changes and most just call it the "inside".   The square will tell you everything you will ever need to know to frame a house and will give you rafter angles and lengths as well depths of cuts for the birds mouth cuts in rafters.  The funny thing is that they have been around much longer that the calculator and can actually in the Hands of a person who understands the square can call off the numbers faster than a person on a calculator can and it is just as accurate.  So when going to the tool store to buy one get a good one and it will last you a life time. 

 

I use this all the time when making templates to cut the arches in cabinet doors and framing for window that have the arched frames.  I occasionally need to use it to build curved cabinets and other woodworking tasks that ask for a certain radius.

 As tip for you spend some time and cut your self some of the common radius templates.  What I use is laminate (counter top) and make the common ones that I use the most.  Something that most do not realize is that like the world is a like a circle most everything requiring angles are determined from the circle of the 360 degree figure.  It is even used in determining the cutting of miters and laying out and drawing of odd sides shaped object such as the hexagon.  A person who understands the 360 degree circle and figure out most anything in building anything that requires angles.

In your case this part was  easy as it has already given you the radius.  Should you wish to learn how to obtain the other often needed numbers where is a radius or a cord I would be glad to help you learn it.   The good thing about knowing about angles and degrees is a good thing as if you really understand them and have accurate machine tools such as the table saw and practice good accurate measurements, you can throw away all the wood fillers and putties as you will no longer need them.

If I can be of any additional help, contact me and I will be glad to help you.  Have fun and enjoy your work and please work safely.

[Duane Heda]

Hi Jay,

I am so glad I found you! Every question I have asked  you has come with an answer that is very detailed, yet very easy to understand. You take a lot, if not all, of the mystery out of woodworking.

Thanks,  Duane

[Jay Boutwell]

Duane you are more than welcome as I really enjoy and have a desire to pass on the knowledge that I have in woodworking.  The world is fast loosing the woodworking class of people and someday those of us who do woodworking will be few.  It is not only a rewarding hobby but is a fasinating profession.

 

I would like nothing better than to see all the members on this organization to someday be able to hang a shingle on a business.  It is a rewarding feeling as when you do you are becoming that much more independant.  Besure and post your project during its build as well as the final.  Take care and thank you so much for the nice compliment.

Duane Heda said:

Hi Jay,

I am so glad I found you! Every question I have asked  you has come with an answer that is very detailed, yet very easy to understand. You take a lot, if not all, of the mystery out of woodworking.

Thanks,  Duane

[Anthony J Eaglebarger]

General question but would a simple compass make this easier to mark out? I know you still need the framing square but it seems if you measure the spot for the center point of the diameter the compass would work nicely along with a jig saw or even a decent band saw. Never mind, I see you did say to use a compass, I always make the template out of leftover cardboard personally, (old pizza box lid is fine for most templates), or if you get new tool do not be hasty to get rid of the box, packaging well, unless you know some other use for it then yes toss it.

[Duane Heda]

Thanks Anthony.

Anthony J Eaglebarger said:

General question but would a simple compass make this easier to mark out? I know you still need the framing square but it seems if you measure the spot for the center point of the diameter the compass would work nicely along with a jig saw or even a decent band saw. Never mind, I see you did say to use a compass, I always make the template out of leftover cardboard personally, (old pizza box lid is fine for most templates), or if you get new tool do not be hasty to get rid of the box, packaging well, unless you know some other use for it then yes toss it.

[Robert Brennan]

Well there you go, try finding that info on the net/website  explained so well !! apart from the Kreg Community of course !

[Duane Heda]

Yes, Bob, The Kreg Community is an outstanding site! It doesn't get much better than this.

[Anthony DeCesare]

wow, I just read that response and all of Jay's insights were outstanding - thanks for helping us all