How to mill a symmetrical slot in a ring

[Martin DowingParticipant @martindowing58466]

Hi,

I am an owner of ML7 and my only milling facility is a swiveling vertical slide used with said lathe.

I have a problem related to slotting a ring in such a fashion that produced slot is symmetrical to the diameter of a ring, say like in perfectly slotted screw head.

However that must be done up to a single thou in per inch of diameter or better…

One could advise to fit this ring on vertical slide in such a way that its centre is on the centreheight of lathe.This can be done with an aid of DTI fitted on the centerheight of lathe and fiddling with vertical slide. Then make a slot with a crosslide. Seems to be accurate by principles but what in practice?

The other idea is to localise center of ring by observation of very fine scrolls (machine marks) produced during facing of that ring. So the center is found using combination of vertical and cross slide, maked with lathe hard center for confirmation and slotting can proceed. However those machine marks not always are there…

Yet another idea relies on V- block fitted on the centre height but this is more useful for longer bar and not really for a ring.

How to proceed? What is best in your opinion? Do I miss someting?

[Martin DowingParticipant @martindowing58466]

[JasonBModerator @jasonb]

Put say a bit of 1/4" round bar in your chuck or collet. Hold a ruler approx vertical and trap it between this bar and your work then as you move the vertical slide up and down the rule will move one way or the other. When you reach a point where the rule is held vertically between rod and work your work will be on ctr height to within a thou or so depending on actual dia of work.

[Neil WyattModerator @neilwyatt]

How big is the ring?

If small use a centre to hold it in place on the slide?

If larger, make a wooden plug, find the centre with a centre square, and align using a centre in the headstock?

Subtract radius from centre height and make a block of that size to support it while fitting to slide?

Neil

[Martin DowingParticipant @martindowing58466]

Many thanks for these ideas. That should help.

Martin

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