Router bit for flattened round edge

Hi everyone

Does anyone happen to know a router bit that I can use to mill a flat edge on my 500 mm diameter round plate which is 27 mm thick?
I can’t find a corresponding cutter for the router… below I have tried to draw the whole thing… hope it is understandable. :slight_smile:

Thanks for any tips. :slight_smile:

Hey Kiwiki,

with a CNC, you would usually make this in a two-sided project with a ball nose as the last pass.

Or maybe in multiple single passes with vertical workholding?

However for router tables or hand routers, there exist bits like this Convex profile Bits or this Double Roundover Cutter Assembly with Ball Bearing. Or, for shaping/moulding machines, there exist interchangeable radius cutters for Universal cutter like this:

Felder 04.4.008 profile knive for universal cutter


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Thank you very much for your answer.
I have already milled a round plate with a diameter of 500 mm. So a vertical workholding wouldn’t work. And unfortunately I do not have a large moulder for an universal cutter.

But how would you do this with a ball nose cutter in v-carve pro? Because i do still have the center of my plate and may be this with a ball nose could work? :blush:

Hey Kiwiki,

I don’t use VCarve but here you can see a ball nose bit at work on a double-sided project with rounded edges. With the ball nose bit, you make a pass with very little stepover (under 0.5 mm, using a 8 mm diameter ball nose as shown in my posting above). It takes time to work the surface this way, but if you make the stepover very small, you can get a finish that requires nearly no rework (just a little sanding) (see also when doing the back with the rounded shape after having flipped it over, and also doing this for the neck profile). See also how nicely this works on fretboards (stepover 0.3 mm) to get a nearly polished surface.



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I’m not real clear on what you are trying to do. Do you want to cut this on the CNC? On a router table? Freehand?

It looks like a bullnose, can you not find a bit that fits the profile? Is it because you are limited to a 1/4" shaft?

Doing an undercut on a CNC can be challenging. Possible, but generally you avoid any undercut. You could do it with a quarter round and flip the piece over.

How many are you doing? If this is a one off, I’d just do it on a router table. Way easier.

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There are lots of cutters with varying dimensions available such as Recessed grip milling cutter - sautershop.
If you created a circle external profile cut tool path with the Z fixed at the mid point of the cutter inline with the mid point of the project
The project would need to be mounted on spacers so the bottom of the cutter didn’t foul the spoil board.
You would then just need to create several tool paths each with a smaller diameter until the desired profile is achieved.


Hey Kiwiki,

if I would not find the exact matching convex router bit, I would make it as two-sided project (with flipover) with the ball nose bit (8 mm radius cutter, as mentioned above and shown in the video).

Regarding router bits, couldn’t this one match?


By the way, what is the radius of your round edge?

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I try to make a flat rounded edge. So not nice round. Thickness is 27 mm.
I think the one from Aiph5u could work. It just would need a ball bearing.

Hey Kiwiki,

for a hand router or a router table, yes. But not on a CNC: You just need to program and probe correctly :slight_smile:

Alternatively, as you need to put it on a spacer anyway as Darren @CSM already suggested, you could simply use a slightly smaller round piece made of scrap

The radius of the Sistemi Klein convex router bit is 18 mm so a circle with 36 mm diameter (d). Seems to match:

I hope I was allowed to draw my circle on your drawing!

But I would do it with the 8 mm radius cutter (ball nose) as shown above in the video. Especially because the 8 mm radius cutter costs only half the price of the convex router bit and a radius cutter is versatile and can be used on many, many other projects!

Hey Aiph5u, thank you very much and yes, you are of corse allowed to draw in my picture. So I also see easier what you mean. :slight_smile:
I think I have to investigate some time to see how I would need to set it up (if possible) on V-Carve Pro with a Ball Nose. As you correctly mentioned, the router bit is much less expensive an I can use it for other projects as well. :slight_smile:

Thank you all for your great support!

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I have now taken a form toolpath in V-Carve Pro with a ball nose bit and milling away half of each side. At least in the V-Carve Pro program it seems to work. :slight_smile:
I will test it soon (as soon as I am able to get into my basement). Thank you all for your great support!

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Hey Kiwiki,

the suggestion of 0.4 or 0.3 mm stepover came from an example where the surface is for a rounding from horizontal to vertical. On your workpiece, you already start with a much more near to vertical surface, so stepover could be reduced even more, to about 0.1 mm or even less, to avoid visible steps.

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Thanks Aiph5u :slight_smile:
I made a stepover with 0.1 mm and did yesterday a test running. And it went well, it did work. :partying_face: So today or tomorrow I‘ll do it on my round plate. Hope it‘ll work too. :smiley:

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So, I made a few adjustments and made the run on both side. It did work well. :blush:
Thank you very much!