All depends on what size shaper you have as to whether you can easily mount a rotary table on it. A few years back I was demonstrating on the SMEE stand at Sandown MEX how to cut internal gears on a 8" Boxford shaper. In order to mount My BS0 dividing head, I had to put an extension onto the front of the table, this was done by bolting a heavy angle plate onto the front surface of the table, the dividing head was then mounted onto this. Cutters can be readily profiled out of the same HSS blanks used for lathe tools just as you would for single point cutting on a mill. I do mine on a Quorn using profiled grinding wheels and comparing the finished profile to an existing gear.

You only need to grind a very simple tool for this process, ie one that has the form of a straight sided rack tooth, the only thing to worry about is the pressure angle required.

The teeth are generated as the blank rotates when the table moves sideways, the indexing is to move the blank round to the next tooth after each pass of the table, the dividing head is normally linked to the movement of the table with a band of very thin spring steel around a pulley of the same diameter as the PCD of the gear being cut.

The idea is that the blank rotates and rolls the tooth space past the cutter as it does so, thus generating the gap between teeth.

Phil

Edited By Phil P on 11/02/2017 19:48:34

Thanks for the demonstration video, Mark

Mine is an Adept No.2 hand-operated shaper, but I'm determined to give this method a go [when I can get back into the workshop].

MichaelG.

I must admit I am impressed with the simplicity of the idea used in that link.

However, I think it needs one thing pointed out. The diameter of the indexing slot wheel should be the same as the outer diameter of the gear wheel, so that the rack effect of the lateral translation is replicated at the gear wheel to get a perfect form. If there is a diameter error, it would be better to be as shown, with the diameter of the indexing slot being smaller than the wheel. The effect of the indexing wheel diameter error is to alter the effective pressure angle with the smaller index wheel increasing the effective pressure angle & vice versa.

Regards,

Richard.

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Richard,

I don't quite understand your point … could you please clarify ?

As I see it, the diameter of the indexing wheel is irrelevant; it is the diameter of the 'pitch circle disc' which matters, and the dimensioning of these is explained in the text. [*]

I should mention that there are some minor drawing errors in Fig.1 the isometric view … however the portrayal of the diameter of Disc 'C' is fairly arbitrary, since the diametral pitch and the tooth count are both unstated.

If I have misunderstood, then please put me right … because I intend this to be one of my first projects when I can get back into the workshop.

Thanks

MichaelG.

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[*]

Edited By Michael Gilligan on 13/02/2017 15:07:17

MichaelG:

One thing I mis-understand from the Base-Circle article (which I read a decade+ ago when I had a Shaper) is that the PCD actually runs through (I guess) 1/2 of the "moving wire" and the actual diameter of the pulley.

IIRC, the article states that the pulley should be of PCD; but does NOT take into account the centre of bending of the wire wrapped around the pulley.

You are a (very) bright guy, and have read up on this, so you'll be able to tell me if I'm correct or not in this memory of mine.

It does look like fun, but with CNC in my workshop now, any gear cutting is focused on that machine. Please tell us how it goes (and, I like Mark's video, thanks Mark).

Opinions on the PCD and wire thickness welcome.

John.

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John,

My quote, earlier [15:00:58 today] was directly copied and pasted from the linked PDF of the article.

… and this, I think, is the missing piece in your puzzle [again a direct copy & paste]:

"Fastened to the pitch circle disc by a screw, is a length of 18 s.w.g. music wire which winds round the disc and is fastened by the ends through straining screws " G" to the adjustable ends " H " of the bracket " K " fastened to the sliding carriage of the machine. "

In my understanding, we therefore have a disc "C" of diameter = PCD of the desired gear, minus 48 thou.

[and, of course, 18swg has a diameter of 48 thou … so I think he had it sussed]

MichaelG.

[Glad to have finally roused some interest in this]

Edited By Michael Gilligan on 13/02/2017 19:17:35

I'm finding this very interesting as I need to make a wormwheel of 1" inch outside diameter but I need to check what TPI and therefor DP I can cut on my Boxford. The wheel then needs a 1/4" Acme thread in the centre but I can cheat on that as I'm waiting for some Acme nuts and threaded rod to arrive and will then silver solder a nut into the wormwheel.

Brian

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That's interesting, Bazyle … and I agree that shim should be the way to go.

I must just mention, though: If you mean flexible [multistrand] Bowden cable … I very much doubt if it is truly circular in cross-section; so perhaps your result is not so suprising [?]

MichaelG.