Myford dividing head

[NilochParticipant @niloch]

Can someone please help?  I am unable to convert the instructions for the Myford dividing head into practice with acceptable outcomes.

 

I will, if I may, give a case study applicable to John Wilding’s Large Wheel Skeleton Clock.

 

For the 8.64″ dia. main wheel Mr Wilding states: The 290 divisions are obtained by using the 29 hole circle on the No. 2 division plate and indexing 6 holes on this circle between each pass of the cutter.

 

I am clear on the purpose of the sector arms but unclear about their positioning between each pass.

 

(1) Should the sector arms be so positioned for the above example that the plunger of the index crank drops into the 7th  hole?

 

(2) Should there be 6 completely ’empty’ holes, plus the hole that the plunger is sitting in and the hole that it will be sitting in for the next pass, making eight in total?

 

(3) Should it be something else entirely?

 

As you can see, I even find it difficult to articulate the alternatives!

 

Any  help gratefully received, thank you.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[NilochParticipant @niloch]

Sector arm positioning

[JasonBModerator @jasonb]

I think the Myford head has a 60:1 ratio

 

So 360 divided by 290 = 1.2414deg per tooth

 

1 turn = 360 div 60 = 6deg

 

therefore 6 divided by 1.2414 = 4.833

 

1 div 4.833 = 0.2069

 

And 6 holes on a 29 plate also = 0.2069.

 

7 holes between the fingers (6 plus the plunger)

 

Please test it first, I may be wrong as I’m used to a 90:1

 

Jason

 

 

Edited By JasonB on 19/05/2010 12:39:38

[DMBParticipant @dmb]

The 2 arms are meant to be locked together at a spacing of however many holes required + 1 for plunger, exactly as Jason B has said. Reason is so that the 2 locked arms can be swung round so that other finger touches plunger then plunger moved around and inserted against other arm –  a quick and foolproof way of counting holes.

 

[NilochParticipant @niloch]

Jason & John,

 

Two responses are not that many but when they concur it’s good enough for me, especially, when I’ve learnt over the life of this forum that you Jason have vast experience in model engineering, I wish you lived just a walk away, I’d probably be consulting you once a week!!

 

John I don’t ‘know’ you so well but your post was succinct and clear.

 

I finished in the garage last night at gone 22:30 at the end of which time I had achieved a measure of success, in as much as cutting teeth on an aluminium practice disc can be considered a success.

 

Now it’s time to gather up some confidence and start on the enormously expensive CZ120.

 

Thank you both very much.

 

PS: I don’t quite know how that long empty space appeared after my last sentence in my original post   –   sorry, everyone.

[NilochParticipant @niloch]

Dennis (Rushton),

Thank you very much for your PM and the offer of a copy of the Myford instructions for their dividing head.  My dividing head was s/hand (Ebay) and the instructions were a perfectly legible, elderly, Gestetner duplication.

I re-typed it all in a slightly larger font to suit my eye-sight, if anyone wants a copy, I can e-mail the file.

Best wishes.

 

[Author]

Posts