How Do You Shape the Edge of a Circle? from ncwoodworker.net

In woodworking, there's often more than one way to skin a cat -- as this discussion on shaping the edges of a circle indicates. Here is the question from one woodworker. - Editor

"I'm trying to avoid the tearout associated with routing against the grain as you rotate the circle counterclockwise. (I'm shaping the edge of a 20" circular tabletop with a bearing-guided roundover bit on a router table.) I've had luck in the past with dividing the circle into four parts and climb cutting each section but just wondering what you guys have done. Is there an easier way? Also, what speed would you guys run a 3/8" roundover bit at for this process?" - Michael

And here are a variety of answers from others. - Editor

"I have had the best results by trying to rough cut the curve as close to the finish cut line as possible. The less material that there is left to remove with the router, the cleaner the cut tends to be. Climb cutting can help, but when you are going across the grain, a certain amount of tearout is almost inevitable. It also goes without saying that the bit needs to be very sharp. That is where the extra money paid for the best quality bits really pays off.

"As far as rpm's are concerned, it is really dependent upon how fast you are feeding the router. The higher the rpm, the faster the feed rate needs to be. Intuitively, one would think that if you run the rpms up, and slow the feed rate, you will get a smoother cut. The problem is that when you do that, you also increase the heat generated. That can result in burns in the wood, and worse yet, overheating the carbide in the bit ,which drastically reduces bit life. Overheating probably causes more premature dulling than any other cause. Ideally, you want to produce a certain chip size, or, as it's called by bit manufacturers, the chip load. Some manufacturers have charts on their websites that show the ideal chip load for a given bit, and a formula to calculate the rpm and feed rate necessary to create the proper chip load. Onsrud has extensive charts available on their website, downloadable as PDF files.

"One seat-of-the-pants way that you can judge if you have the rpm and feed rate right is to see if you are producing little shavings or chips or dust. If it's dust, something's wrong. Also, if everything is OK, you should be able to touch the bit immediately after cutting and find that it is just warm. If it's too hot to grab onto, then either the feed rate is too low, or the rpm too high, or both." -Matt

(This one included a reference to a technique featured on a YouTube video. - Editor)

"I've never tried it, but maybe you could use Charles Neil's bump cutting technique." - Dan B.

One suspects at least one of the responses was tongue-in-cheek. - Editor

"I have a Stanley circular plane if you want to finish by hand.-" Mike D.

Others, however, offered some useful insight. - Editor

"Try wrapping the circumference with a few layers of masking tape (only where the bearing will ride). Rout at high speed with a 3/8 bit, then remove the masking tape and rout again, this time removing just a bit of material as your final cut." - Matt F.

"Gotta say, I'd be lost without an edge sander....we do a considerable amountt of curved work. They are just so efficient at getting those last few .001's.Good luck with your project." - B.W. S.

"I keep a set of different [outside diameter] bearings, and change out the bearings, using a larger one for the hogging cut, and the flush size for the finish pass. The other trick, instead of tape or bearings, is to use a piece of .040 or similar plastic sheet or 'bearing strips' for this very purpose. I've got a bunch of strips of polystyrene for this. They hold up a lot better than the tape. You could do the same thing with veneer strips if you've got them lying around." - Fergy

"The bump edging technique is similar to what I do for piecrust edges. My warning is to not try and take too much because the bit could catch and rip off a splinter. [Don't ask me how I know this.] Just like making a piecrust, it works, but don't be overly aggressive.

"For a long time, I've used progressive bearing steps. It's comfortable to use, but it's also time-consuming. However, usually at this point in a project, I'd rather make a pass; get a [drink]; change a bearing; make a pass; catch the weather; change a bearing...you get my point. I also tried using an edge guide and incremental steps down to the bearing. I can see that, with some practice, it would be my favorite. Although, in my case, doing this once every two to three years, I'm not likely to get enough practice.

"In any event, I recommend a heavy router with a big base both for balance and control. Speeds and feeds for me is by ear. The router is working, but not laboring." - Joe S.

If You Can't Make the Tool from ncwoodworker.net

"'If you can't make the tool, how can you expect to build a violin?' That was the answer to a question asked by a visitor at a friend's shop back in the 80s. He often answered a question with a question as if he thought you already knew the answer or should know. I still don't know the answer to that question.

"So, I guess my question is: What would you consider the very smallest set of tools that would allow you to make rudimentary furniture and build more advanced tools in time? I know they are really two different sets of tools, and you could list them that way if inclined. I'm not talking CNC milling machines here. More like drill bits and make a brace. Saw blades and make the handles. Let's say you can take a suitcase to the Amazon and nothing else is available except wood and scrap metal." - Mike D.

The first response, however, wasn't exactly woodworking per se ... - Editor

"Hammer, some sort of tongs, anvil. I wouldn't mind a forge, too, but I could redneck something together from local materials. I wouldn't mind an axe, because then I could build a shelter for the forge a little quicker." - John

The next one, however, got back to our favorite hobby. - Editor

"Hmm, I didn't see Mike's actual question as being about blacksmithing, but the original title question certainly suggests that. Anyway, John has the right approach, but at my age, I'm focusing more on how to make the tools with the metal available.So omitting the axe and froe for making your lumber from trees, my recommendations are to make a couple of good planes, a marking gauge, chisel handles (for those key bench chisels, gouges, and mortise chisels), mallets, one or more spokeshaves, a bowsaw, a shaving horse and a drawknife. From there it's all easy." - Rich B.

"I would add a saw (blade). One tool that is hard to make. Altho you can get by without one, it would make life a whole lot easier. In reality, if you are in an area with igneous rocks, sharp cutting edges (i.e flint, obsidian, etc) are relatively easy to come by. With rivers and streams come the rounded stones good for hammering, as well as for fletching out the harder ones for cutting. A rain forest would definitely be a challenge, as would a sandy prairie." - Mark

"Addressing primitive furniture making:
- Gauging
- stainless vernier caliper
- framing and combo square
- tape measure
- short level (combo square level may substitute)
- Tool support
- whetstones
- files
- striking - hammer
- struck - chisels
- cutting - hand saws/bow saw, spokeshave, #3 plane,
- drilling - brace and bits
- holding - a couple of clamps, ropes and knowing the packer's knot." - Bob V.

So, eZine readers, do any of you have any primitive furniture building experience that would be relevant to this discussion? Learned any knots that have saved your skin when lost in the woods? Do tell. - Editor