"Benchwork" Question

I first use a yardstick or some other piece of wood as a compass and draw out the cut lines on the plywood, then cut the sections out by hand with a saber saw. It's tedious work and you will go through a few blades if you have a lot of sections to cut. You can also get an attachment for the saber saw that acts as a compass and guides the saw as it makes the curved cuts, however I have never used one.

You can use the method Jerry outlines above to make a template of thin plywood, Masonite, or even cardboard. That way you only have to make compass lines once - you do the rest of the outlining with the template. 

 

A "compass" made out of a piece of wood or whatever is called a trammel arm. You can buy a "trammel point set" at a hardware store or maybe Harbor Freight, that has two pieces that clamp onto whatever you want to use as an arm. One point serves as a pivot, the other makes the marks. Generally you will be able to use either a scriber or a pencil as your marking device. Some trammel points will also accept a small knife blade to cut a curve directly in paper or cardboard. Micro-Mark has an inexpensive trammel set on sale now for $10.25. That's a good deal; the somewhat fancier ones made by General Tool go for quite a bit more. 

Several ways to do it. 

 

Quickest way is to use a circular saw with a rip blade.  Use safety glasses, you will be throwing splinters, just get used to it.  It is the quickest way to do a  lot of subroadbeds accurately.  Much more accurately than the D.I.Y. using a saber saw.  The circular blade helps keep the line consistant.

 

Do not object to it untill you do it. 

 

For small radius like you mentioned I use a small battery powered Dewalt or Ryobi circular saw with the blade set to the thickness of the material and go real slow.  It will cut a much more consistant edge than a saber saw.  

 

For larger radius curves I use a Bosch 7 1/4" circular saw set to the thickness of the material to be cut and get the same results.

 

If you are cutting real small circles use a table saw and set the job up on a pin axis and turn the wood into the blade which is preset to the actual thickness of the material.

 

Another more conventional way is to use a tremmel or template to draw a line 1/8"+  full then use a tremmel mounted router and trim the edge perfect.

 

I use templates for most of my curves and a set of 8 spirial easement templates.

 

To help a sectional 3 rail job go quicker I use a three grooved block of wood with a series of marker holes drilled to run along the outside edge of mock mounted track for free hand saber saw cutting.

 

When using my Bosch saber saw I ONLY use sheet metal blades.  They give a much cleaner edge.

 

No matter what saw method you use, consider going over the entire job with a 5" orbital sander & 100 paper to yield a smooth splinter free edge.

 

If you still want to just use a saber saw make sure there is a continuously vacumed clean dark line visable at all times and go light on the java.

 

Hint: IMO, do not use cheap plywood or dull blades.

 

www.curvedbenchwork.net

Here's my homemade compass. This is a short one used for tight radii. I made a 4' long version for wide radius curves.

 

 

 

 

 

 

 

 

Jim

I use sectional tin plate track.  Add easements at both ends of the radius. Use a black sharpee to outline your cuts then double check the track layout. Then I take the wood outside and cut with my table saw (portable). For radii I use a sabre saw. I give an extra inch or two on either side of my radial cuts, you can always take away.

Thanks to everyone for their responses. 

 

JohnS...I especially like the router trammel...in fact, I have something similar...yours of course is that of a professional.

 

Please...this will sound really dumb...describe how you use that puppy.  How thick can the material (sub road bed) be for you to make a complete cut?

Okay...thanks...a zillion. It looks like I am on the right track.  As usual, my skills are not as refined as some and my result not as good.

 

However, I will keep trying...I enjoy the effort!!