Scrolling circles.

[caveman]

I need to cut out a large, 300mm diameter circle and thought the best way to get it accurate was to mount a (somewhat basic) jig on the scroll saw table onto which I could attach the wood to be cut. I have made a small hole at the circle centre point and secured it at this point to the jig with a screw/washer so that it turns smoothly. Well, my attempt first attempt was a complete failure with the blade wandering inside the required diameter. It di however cut a circle but about 10-15mm too small.
Is there a certain position the centre should be in relation to the blade to make this work? I have a couple of these to cut and don't want to waste any more wood! The blade is under quite high tension and I've had no problems cutting scrolls etc.

Is there a "trick" to doing this??

Any help will be appreciated. Thanks.

 

[NazNomad]

Because of the way the blades are manufactured (stamped from a sheet of metal), they will to wander to one side and need constant correction. Such is the hardship of a scroller, I suppose?

You're probably better off drawing the circle, cutting as close to the line as you can freehand, then sanding to the line.

 

[Claymore]

Do you have your jig mounted to the side or in front of the saw ? I would have thought you would need the jig to one side so when you turn the wood the wood is going directly into the front of the blade? hope that makes sense.
I have done similar on my bandsaw and if the wood is turning directly into the blade you cannot bend the blade so easier to cut an accurate disc.
I'm probably wrong but might be worth checking, I cannot tell from your photo where the jig is positioned.
Cheers
Brian

 

[novocaine]

Do it by hand any jig is pointless. As you cut make sure you hand is acting as a pivot along side the blade a bit like your fixed pivot point.

 

[caveman]

Do you have your jig mounted to the side or in front of the saw ? I would have thought you would need the jig to one side so when you turn the wood the wood is going directly into the front of the blade? hope that makes sense.
Brian

Yes it is off to the side so the wood is feeding directly into the blade.

Yes, look like a hand cut and sand job!!

 

[MrTeroo]

Would this work for you?

https://www.youtube.com/watch?v=Ybv0R15YV6I

 

[caveman]

Would this work for you?

https://www.youtube.com/watch?v=Ybv0R15YV6I

Thanks, that's almost exactly what I have done, not quite so elaborate but the same principle. I don't have a spiral blade available, just s straight 18TPI that came with the saw. I have some 24TPI on the way. Can't find (here in the UK) a pin end spiral blade - yet!

 

[whatknot]

Personally I think you are wasting your time with a jig, you might cut mdf that way but anything with a grain of any sort will wander offline

As has been said cut by hand and sand to the line

Or use a band saw

I need to cut out a large, 300mm diameter circle and thought the best way to get it accurate was to mount a (somewhat basic) jig on the scroll saw table onto which I could attach the wood to be cut. I have made a small hole at the circle centre point and secured it at this point to the jig with a screw/washer so that it turns smoothly. Well, my attempt first attempt was a complete failure with the blade wandering inside the required diameter. It di however cut a circle but about 10-15mm too small.
Is there a certain position the centre should be in relation to the blade to make this work? I have a couple of these to cut and don't want to waste any more wood! The blade is under quite high tension and I've had no problems cutting scrolls etc.

Is there a "trick" to doing this??

Any help will be appreciated. Thanks.

 

[martinka]

I recently cut two 250mm circles from 18mm external ply as part of making Dobsonian mount for a telescope. I considered cutting them on the scroll saw, but I ended up using my decrepit old Burgess bandsaw with a 1/4" blade. Then I made a jig for the belt/disc sander to finish them off. Of course, this post is of no use to the O/P if he doesn't have either of those.