Re: Re: Engraving and engine turning

Hi Pete,

I have come across tensator springs in clocks but I have only seen them
used winding from one drum onto another. I can see this working on a
rack and pinion feed mill/drill but my effort is having the 'z' axis
driven by a normal feedscrew just like the other major axes. Another
reason I thought of using weights and pulleys is that I am making the
'Z' axis pivot around a point on a level with the table so that I can
feed down at an angle ( depending on developments of emc etc. I may even
motorise this adjustment in the future as I have the desire in the back
of my mind to generate the strange gear-tooth profiles required for
watch escape wheels using a tiny slitting saw in the quill and
simultaneously manipulating a dividing head, the 3 axes and possibly the
angle of the cutter to the work (the tooth profiles I am thinking of
resembles a leg and foot sticking out of the wheel 15 times around its
periphery). Using a weight system will allow for this so long as I make
the pulleys deep enough.

Ian

Pete Jarman wrote:

> Another solution is to use a "Tensator " spring, like a clock spring,
> pulling up the quill, not fixed to the downfeed spindle. This is wound up to
> counterbalance the weight of the quill and give you some preload against the
> downfeed gears. Over the travel of the quill it will exert a constant force
> like the weight but it takes up less room. There was an article by
> G.F.A.M.Turner in Model Engineer of 20th January 1989 describing this system
> as a modification to a Far Eastern mill/drill. I used it successfully on a
> small home made mill but I haven't yet got round to adding it to my latest
> machine.

Best wishes

Ian

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Ian W. Wright LBHI
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