# Getting The New Dividing Head To Work



## malmac (Jan 4, 2017)

Hi Fellow Machinists

Yesterday I bought a dividing head. It is a unit that comes with change gears so it can cut helical gears as well as straight cut gears. Yes I am in way over my head, but hey why not.

The problem I have is the change gears that should fit onto the end of the cross slide have a larger ID than the size of my shaft - see pic.

So as a way of thinking about the problem, I machined up a spacer/bush so the gear/s sit neatly on the shaft BUT it is a driven gear so it needs a way of transferring the drive (usually a keyway) - any really smart ideas????







Mal


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## Reeltor (Jan 4, 2017)

Congratulations on your new dividing head.  I don't follow what you mean by the OD needs a 4mm boss.  Could you post a photo or two showing how the parts go onto the mill?  If the gear with the brass spacer needs to slide onto the mill shaft shown with a key to drive the gear why can't you mill a 1.2 mm piece out of the brass spacer and then use an oversize key to lock the gear (and brass spacer) to the undersized drive shaft?


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## malmac (Jan 4, 2017)

Here is the situation, the green shaft is too small for the supplied gears - and they are change gears so there a several optional gears - so I need an adapter to effectively upsize my shaft.
Keyway in the shaft is small, compared to slot for keyway in the gears.

Option One is to make a spacer with a machined boss to transfer drive from shaft to gear.



So in this option, a key between shaft and spacer - however the boss to drive the gear would be machined onto the spacer.

In the second option, the spacer would fill the gap between the shaft and the gear - a custom machined key would transfer drive from shaft to gear.


I hope that makes it clearer. Maybe there is other options I have not thought of.


Mal


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## mickri (Jan 4, 2017)

I ran into this problem when I changed the propeller on my sailboat.  The new propeller was made for a larger shaft size and required a bushing and a thicker key.  The solution is a key where one edge is machined to fit the narrower key way and the other edge is machine to fit the wider key way.  This is so common in the marine world that you can buy these keys online.  You might find one in the size you need.  Try a google search for propeller bushings and key.   Or just make one.  I have seen people do it in a boat yard with a file.
Chuck


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## malmac (Jan 4, 2017)

Thanks Chuck.

So the spacer bushing is effectively an almost closed "C"?

Or am I misunderstanding you?

Mal


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## mickri (Jan 4, 2017)

In cross section the bushing looks just like your drawing.  An almost closed "C".  The slot in the bushing is the same width as the width of the wider key way.  You might be able to use a marine key if in the right size but you won't be able to use a marine bushing because propeller shafts are tapered and so the marine bushings are tapered.  Both the bushing and the key should be simple to make for your application.


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## malmac (Jan 5, 2017)

Thank, you sounds relatively easy.

Mal


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