How do I cut a Verge [Crown] Escape Wheel ?

I am planning to build a Verge Escapement for a Seconds Pendulum.

... Yes, I know there are much better timekeepers [this one is for 'research'].

I am having some difficulty understanding how a rotating cutter can produce the required surfaces. [maybe I'm just being thick].

The process is demonstrated in this YouTube video:

**LINK**

But I cannot see how the radial surface of each tooth is maintained when the next tooth is cut.

My wheel will have 15 teeth, and should be very similar to the one in this video.

For 3D drawing, I only have Sketchup [v8 Pro], which is driving me to distraction, trying to 'model' this apparently simple piece. ... If someone with proper 3D software could model the cutting of two adjacent teeth, I would be most grateful.

MichaelG.

Edited By Michael Gilligan on 15/11/2015 19:42:16

Something like this, the cutter only cuts the tooth at the bottom on each pass

Or if the slope is curved just make the cutter to profile

Don't know why you can't file it by hand and eye

Edited By JasonB on 15/11/2015 20:04:08

Jasons both

Yes it looks fine in those diagrams ... and is exactly what I thought should happen.

Maybe it's just my clumsy attempt at drafting, but it appeared that the curved face of the cutter would upset the geometry of the previous surface when the blank is indexed for the next cut.

I may now crawl away and hide in the corner for a while

MichaelG.

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Updated to reflect Jason's second diagram

Edited By Michael Gilligan on 15/11/2015 20:35:06

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I could ... it was the geometry of the mechanised process that I was struggling with.

MichaelG.

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P.S. ... the slope is curved; it's there to clear the Verge 'Flags' as per the second video.

Edited By Michael Gilligan on 15/11/2015 20:23:27

Verging on the ridiculous, Michael.

N.

Michael You could have problems geting a one second pendulum to swing far enough for the verge flags to clear the escape wheel

Just a thought   Please let us know how you get on

Roy

Edited By roy entwistle on 15/11/2015 21:07:06

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Ha ###### Ha

GOTO your own thread and update the title.

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Roy,

Many thanks for the thought, but; as I mentioned, this is 'research' and I'm basing it on Huygens' original.

MichaelG.

Michael, If you let me know the dimensions of your wheel and the size of the "flags" i will try and sketch it up for you and check the geometry so you will know it will work before you cut anything.

Mark

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Thanks, Mark

Hopefully, I can send that tomorrow ...

I'm scaling some details from a woodcut !!

MichaelG.

Mark C,

I have sent you a PM

MichaelG.

just uploading it now!

Mark,

That is a thing of beauty

THANK YOU

MichaelG.

Michael

For my ( only! ) attempt at cutting an escape wheel I ground up a cutter ( from a broken centre drill - always plenty of those to hand!) and fly cut it. OK your "teeth" are at right angles to the one I made but it should still be possible I feel.

Do let us see your progress!

Regards

Norman

NJH, you beat me to it, I use that method for gear cutting, and see no reason not to use it in this case.

Ian S C

Roy, surely the pendulum period doesn't matter? Yes, you need quite a big pendulum amplitude for a verge escapement, which affects accuracy as circular deviation is large. That's why the anchor and deadbeat escapements were invented, to operate with small deflections.

Norman, and Ian

Thank you for the comments regarding single-point cutters

Although I do need to collect & configure some equipment or this job; I am pleased to say that I am happy with the general wheelcutting process [I even went on a short tutorial course at BHI Upton Hall a while ago] ... But I have, to date, only cut flat wheels; and it was specifically the geometry of the cutting process for Contrate & Crown Wheels that concerned me.

It appears that my concerns were ill-founded, and it was simply that [using SketchUp] I couldn't correctly draw a cutter going through a tubular workpiece. ... Lesson Learned !!

Thanks again ... and I am quite content for this thread to morph into a general discussion of wheelcutting if anyone so-wishes.

MichaelG.