cutting these plates on a manual mill?

[Neil C]

I need to put a couple of connection parts onto an assembly of this kind:
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At first, I thought just to drop them onto a rotary table or indexer and run a 90 degree cutter back and forth every 15 degrees or so, cutting the teeth out radially from the centre but I quickly realized that that would mean contact only on the very outer edge or circumference of the part. So they would look like they are locked together but in fact, none of the faces on the inside would be in contact at all as they would all be falling away from each other.

This one left me really scratching my head. I’ve not cut gears or anything like this before so there may be something obvious I’m missing. Any advice appreciated.

[Voicecoil]

Mmmm, tricky one as ideally you want the angle of the teeth to increase as you move outwards. If you're cutting with a constant angle cutter would turning each surface to a slightly concave conical section sort the problem I wonder? That way the angle of the teeth is constant but they become wider as you go outwards. Sorry I don't have any 3D CAD here at home to check it out. Alternatively cutting them as a square (or trapezoidal) section with the width increasing radially outwards would do (2 passes for each cut offset by 1/2 the angle) might sort it, but engagement would be more clunky than with triangular teeth.

[Neil C]

Mmmm, tricky one as ideally you want the angle of the teeth to increase as you move outwards. If you're cutting with a constant angle cutter would turning each surface to a slightly concave conical section sort the problem I wonder? That way the angle of the teeth is constant but they become wider as you go outwards. Sorry, I don't have any 3D CAD here at home to check it out. Alternatively cutting them as a square (or trapezoidal) section with the width increasing radially outwards would do (2 passes for each cut offset by 1/2 the angle) might sort it, but engagement would be more clunky than with triangular teeth.


It’s tricky to get your head around, I had to mock it up in CAD before I understood it properly.
Apart from the apex of the cut at the bottom of the teeth all the other faces and angles are falling away from each other.

The easiest way to think of it is that all faces and corners are formed by the two cut faces meeting and the cutting tool paths draw closer to each other as they come closer to the centre.

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I’m not sure I even understand the geometry of mating radial teeth but I’m feeling that it’ll probably need to be a CNC path. I hope not but...