Cutting a circle

[alanjm]

Other than a keen eye and a steady hand does anyone have any tips or tricks for cutting the perfect circle. Have just completed a tigers head within a circle but it is slightly marred by an ever so slight wiggle in the circle, not a lot but you know its there and you see it every time you look at it.

Alanjm

 

[StevieB]

Yes, cut just outside the line and use a disc sander to clean off to the line :wink:

Its the only way if you have trouble (like I do) cutting accurately to the line for curves over a long distance. A jig is not really feasible as the blade can wander due to variations in speed of turning the piece etc.

HTH,

Steve.

 

[Gill]

Sorry to be unhelpful, but whenever I want an absolutely perfect circle I use a router.

Gill

 

[Carter Johnson]

Slow the saw down....take your time

Drop any pretense of being a perfectionist.

Have phun

Carter

 

[Toni Burghout]

This is going to be rather hard to describe - well, maybe not hard, but I'm sure if you could SEE it done, it would be easier to understand.

When you start cutting your circle, perhaps slow the speed so you have a little better control as you feed the wood into the blade. If you are right handed, you are feeding the wood / pattern line into the blade with your right. Use your index finger on the left hand and position it in the center of your circle. Use this as your pivot point, fulcrum, etc. Slowly turn the circle and you should have fairly good results with some practice.

Hope that helps.
Take care
Toni

 

[CHJ]

__________alanjm, any chance a variation on the circle cutting jig I use on the bandsaw would help?


_________

_________ _______ click on image for larger view

For my turning blanks a small hole or centre punch mark rides on the pivot point, if I do not want to deface the surface I tape the wood to a disc with a hole in it and place a similar thickness piece under the waste wood area for support.

On the Bandsaw, the jig slides in the table tee slots from front to back and is adjusted with a stop underneath the front edge so that it stops when the leading edge of the blade is on the circle centreline or just passed, if you stop before the centreline of the circle the blade will cut in an ever decreasing spiral and jamb. I guess you could arrange some form of guide system for the scrollsaw table.

 

[Gill]

I've actually got a circle cutting jig for the scroll saw, made by Diamond. You bolt a swiveling pin through a hole drilled into the plywood table and slide a trammel bar through the top of the pin. Then you extend another pin through the end of the trammel bar and hold the wood in place at the required radius from the blade. After that, it's just a matter of spinning the wood and the blade will do the work, rather like your bandsaw jig, Chas.

That's the theory.

However, scrollsaw blades don't cut straight because they have a bias, usually to the right. So I find that in practice the blade will try to wander off course, leaving you with a misshapen piece.

If you have no choice but to cut a circle with a scroll saw, the best technique is the one that Toni outlined above. It gives you a chance to make slight adjustments as you cut so that you don't wander off-line. Indeed, I cut a couple of discs freehand in this way the other day with the table angled so that the discs were tapered. They came out rather well and made acceptable airtight bungs at either end of my new dust extraction pipes.

Nevertheless, I still advocate a router as generally being the best tool for this task.

Gill

 

[alanjm]

Thank you all for your ideas and tips. and I'm sorry Carter part of the 'phun' for me is always trying to do better the next time. Although in practice I'm pleased with my cuttings most of the time I always like to think that the next one will be better and maybe in a hundred years time turn up at the Antiques roadshow as a collecters item....ah well keep practicing and maybe the next one.....

Gill do you do fret pictures in circles and if so do you cut the circle first on your bandsaw then cut out the internal pattern or the other way round?

Rgds
Alanjm

 

[Gill]

Hi Alan

The short answer to your question is, "No, I don't fret pictures in circles" ! However, if I did I would certainly shape my wood first and then start cutting the fretwork. Doing it the other way round might lead to fragile fretwork bridges breaking when the shaping machinery is used.

If you don't have a router, can I suggest you acquire one? They're not terribly expensive nowadays and are so versatile - they'll add dimensions to your woodwork that will astound you. Cutting a circle with a router is an absolute doddle and gives you a lovely smooth finish.

Gill