# Groove in edge of curved piece



## imrichb (Jul 5, 2007)

I'm trying to cut a semi-circular groove along the edge of a piece, pictured in the attached. I can do this easily along a straight edge using my router table and a round nose bit. The challenge is that I'd like to do this along an edge that is curved (and to make it more challenging, a concave curve).

Any advice? I had thought maybe I could use a 3/4" ball cutter bit with a 1/2" bearing around the shank to guide it along the edge of the workpiece, but unfortunately I can only find a ball cutter bit of that size with a 1/2" shank, meaning that I can't put a bearing around it.

(In case you're curious, this is for a children's toy I am working on. The groove will essentially form a track for a marble to run down.)

Thanks in advance!

Rich


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## Mike (Nov 22, 2004)

You need to make a template from 1/4" hardboard or plastic, some people prefer using 1/2" MDF. Attach it to your wood with double sided carpet tape or build a jig with hold down clamps. A guide bushing installed in your routers base plate will follow your template and a thumbnail bit should give you the profile you want.


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## kp91 (Sep 10, 2004)

Heres a couple of options

You could play with the bearing diameters to adjust your cut if desired.

http://magnate.net/index.cfm?event=showProductGroup&theID=114

http://magnate.net/index.cfm?event=showProductGroup&theID=158

I can confidently recommend the Magnate bits.


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## imrichb (Jul 5, 2007)

Perfect! That's exactly the bit that I had visualized in my mind for this, but couldn't find something like it anywhere.

Thanks for the help,

Rich


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## bobj3 (Jan 17, 2006)

Hi Rich

The bearing on router bits,,, it's just fence so to speak, that said, make a fence like the one below, this will work a guard and let do your concave curve pass easy and safe...just ease into the bit and once your on push your stock around the guide...the guide will act like a start pin and let you get on the bit
safe and let stay ,hardwood be best for the guide/jig but it can be plywood or MDF....

The bits below also work great for what you want to do...
Making toys  

Train Track Router Bits
http://www.mlcswoodworking.com/shop...tml/pages/bt_bull.html#train_track_bit_anchor


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imrichb said:


> I'm trying to cut a semi-circular groove along the edge of a piece, pictured in the attached. I can do this easily along a straight edge using my router table and a round nose bit. The challenge is that I'd like to do this along an edge that is curved (and to make it more challenging, a concave curve).
> 
> Any advice? I had thought maybe I could use a 3/4" ball cutter bit with a 1/2" bearing around the shank to guide it along the edge of the workpiece, but unfortunately I can only find a ball cutter bit of that size with a 1/2" shank, meaning that I can't put a bearing around it.
> 
> ...


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## imrichb (Jul 5, 2007)

I like that solution as well! 
Thanks,
Rich


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