Cutting large dowels is generally not easy and usually quite dangerous. I needed some very straight cuts in a two inch dowel and made this simple jig to help me do it precisely and safely. Without something to keep the cylinder stable it would have a tendency to roll when cutting on a router table, resulting in a crooked cut or sometimes a violent and dangerous twisting. Cutting on band saw or table saw presents even more danger and potential for messed up cuts. This jig can hold work in place well for cross cutting as well.
Step 1: Materials and Tools
About 3 Feet of 2X4 (or similar size lumber)
2 Inch Bullnose Router Bit (or a bit corresponding to the dowel size you want to cut) (these are big and expensive and awesome)
Chop Saw (optional)
Step 2: Cut
The first step, after you put your safety glasses on, is to prep your lumber. I ripped the pieces down to about 2.5 by 1.5 inches and then cut them into two 8 inch lengths and 3 inch lengths. The dimensions are not crucial as long as you have three identical parts.
The two long parts will clamp your dowel in place and the two shorter parts will provide a notch for clamping.
Step 3: Rout
Making a channel that fits your dowel is the most important part of this jig. In my case I was concerned about 2 inch dowels so I needed to match that with a 2 inch channel, which meant I needed a GIANT router bit. Big router bits are fun but be super careful because they are also dangerous. Make sure you take small passes on the router table raising the bit only a small fraction of an inch each time. Trying to take out the entire radius at once will not work, I guarantee it.
You don't need the channel completely encapsulate the dowel, in fact this will be counterproductive. The cut should be about 120º (once again the dimension is not crucial but just a rough guideline.
Step 4: Glue and Trim
Once you have the channel routed out in the two long pieces it is time to glue on the two shorter blocks. These should be glued to the side of one of the long pieces leaving a space in the middle as shown in the picture above. The space is where the clamp will go so make sure it will be deep enough to clear your clamp before you glue the pieces on. If it isn't you may need to make larger blocks.
Since these pieces are what rides against the fence on the router table they should be perfectly parallel and flat. The best way to make sure this is the case is by using the table saw again and taking of just a small amount of material to flatten the side. It is also a good idea to flatten the bottom part.
Step 5: Round the Edge
I ran into problems the first time I used this jig because the edge was catching on the router table as I made each pass. In order to ensure this doesn't happen it is a good idea to round over the corners just slightly on a sander or with a knife.
Step 6: Clamp and Use
This is a really simple jig but has a huge potential for saving your fingers and your work piece. Use a simple bar clamp or 'C' clamp to secure the material in the jig and tighten snugly. Once it is secure you can use this jig to cut the dowel with a router table or cut it with a table saw or band saw. I used it only for router table applications, which will appear in an Instructable soon. As with the making of this jig, make sure your cuts are small and incremental rather than trying to carve everything out at once.