Tools for Working Wood
Invest in your craft. Invest in yourself.

 Joel's Blog

Blade Width and Cutting Curves  


Okay, I get it, I'm not the sharpest stick in the woodshop. I was making this ridiculously simple chair and we needed to round out some corners. Toby, who was working with me, took a brand new blade and popped it into a jigsaw and I cut away. I tried to turn the corner as I powered through the material but I cut too wide. And then to compound the error I did it again.

The reason is that I'm stupid. The right way to cut a tight curve is use a narrow blade. A wider blade won't work even if you try to cut slowly. A saw can cut a curve because if you twist the blade in the cut it will turn the amount possible given the width of the blade and the width of the actual kerf of the saw cut (fig. 2). The wider the blade the less of an angle you can twist and that's the limiting factor. That's why our bow saw blades are only 1/8" wide - it's so you can turn on a dime. Wider blades are better for tracking straight.

We got the idea for 1/8" wide bow saw blades for our turning saw when we saw the blades on Duncan Phyfe's turning saw. He used 1/4" material - but for the working length of the saw blade - the blade was ground narrower to maybe 3/16".

So, if you you want to cut a curve, don't do what I did - get a narrow blade - hand or power. Otherwise you need another strategy.

Another strategy that works is to cut a series of straight saw cuts perpendicular to the final curve (fig. 3) and then cut knock out the waste with a chisel. Then work the curve smooth with rasps or a spokeshave.

Here's an old blog entry I wrote years ago about special blades for cutting curves with a circular saw.

Note: I have realized that lately I'm spending a lot of time about what happens with things go wrong. The reason for this might be is that when things go right I don't think twice about it and I don't see the blog entry in it. Of course another possibility might be that banging my head against the wall is just the story of my life and I need to write about it.
Tags:Woodworking Tools and Techniques
Comments: 4
03/27/2012Mitch Wilson 
Here's part of your problems, Joel. Age. Any and all adverse events, despite being careful to avoid, will still occur at a certain rate. You know, 1 in 10, 1 in a million, etc. The odds are ultimately stacked against us. The longer and more often that you do something, the greater the chance the unwanted outcome will finally bite you in the ass. And from reading your blog, I'd say that you've been bit.
I suspect you won't like this comment.

My 8 year old woodworking student had to to cut a curve on his project and the curve was made in 2x4 material. The tool he had to use was a jig saw with a wide blade. He had never used a jigsaw before although he did have one previous lesson on a scroll saw. I taught him the method of cutting a short distance then backing the tool up and cutting again. That way the wide blade creates its own wide path. He cut a nearly perfect, very smooth curve. Not bad for an 8 year old who has only two months of one hour lessons on a Saturday.
Won't like??!!!??

Every time I hear someone putting an 8 year in the shop I am thrilled. Congratulations to you on not being scared that your child is too young!!. Too many people are afraid of letting kids into the shop - even with tons of supervision.

Sadly, however - your technique would not have worked in my case as I needed both sides of the cut and did I mention that I had narrow blades around I just didn't think to you them. When I tell you I was being pretty stupid I was not exaggerating.
03/27/2012J. Pierce 
To squeeze a little bit more turning radius out of a blade, I've had success with bandsaw and jigsaw blades at stoning the back of the blade into a slight curve, maybe thinning it down a little bit.

The smoothest radius cut comes from when you happen to find the perfect sized saw blade and can "ride" the back of the blade in the kerf - helps keep your trajectory smooth if you aren't quite perfect at steering.
Comments are closed.
The opinions expressed in this blog are those of the blog's author and guests and in no way reflect the views of Tools for Working Wood.
 Joel's Blog
 Video Roundup
 Classes & Events
 Built-It Blog
 Work Magazine
Recent Blogs:
David R. Russell - Some Thoughts on His Legacy - 04/18/2018
eBay Fraud - 04/11/2018
Blog Entry or Filler - You Decide! - 04/05/2018
Clamp Vs. Clamp - 03/21/2018
The Seaton Chest Revisited - 03/14/2018
Cræft by Alexander Langlands - 03/07/2018
News: much is happening here & OSMO is arriving! - 02/24/2018
Beautiful Cabinet Shop Space Available for Rent in Gowanus - 02/05/2018
Safety Last - 01/31/2018
I Am a Panda - 01/19/2018
The Unheated Workshop - 01/10/2018
How to Cut a Groove in a Frame By Hand and Without a Plow Plane - 12/27/2017
How to Mortise the Moxon Way: Part 2, Chopping the Mortise - 12/20/2017
How to Mortise the Moxon Way: Part 1, Layout and Cutting Tenons - 12/17/2017
Why Schlep? - A Look at Tools Baskets and Bags - 12/13/2017
Saw Sharpening Essentials - Gramercy Tools Saw Vise (Back in Stock) + Vallorbe Saw Files (They Finally Arrived) - 12/06/2017
How to Choose the Best Dovetail Saw for Yourself - 11/29/2017
Woodwork at City Hall - 11/22/2017
The Marquetry Plane Shows Up In England 1760-1780 - 11/15/2017
Joel's Blog Ten Ways I am Doing Things Differently - Part 4 - 11/08/2017
Older Entries...