Myford diving head

[Andrew Read 1Participant @andrewread1]

Hi all

I have brought a second hand myford dividing head to cut clock wheels, reading the instructions it advises to to set the cut depth on the 1st sweep around the wheel and then go full depth on the 2nd sweep.

The problem is on the second sweep the cut is not exactly where the 1st cut is on the wheel leaving a tiny line on the cut wheel teeth

The dividing head is adjusted for no play so the only thing I can come up with is the worm wheel and worm are worn

Has anyone got any ideas?

Andy Read

[Andrew Read 1Participant @andrewread1]

[Clive WashingtonParticipant @clivewashington54052]

I think it would be very unusual for a dividing head to go round often enough to get badly worn. I can think of two possibilities. The first is that your work moved slightly on its first pass round, due to milling vibration. The mandrel may have moved in the chuck, or the chuck tightened or loosened on the head.

The other option is that there is backlash in the worm and wheel. There has to be some clearance for it to move freely. Normally you would give the arm a couple of turns clockwise, then drop it into the hole, to ensure this backlash was taken out before cutting the first tooth. You would take care to not overshoot any hole selection for similar reasons. Just like the other dials on your machine tools. If you don't look out for this, it will result in variations in tooth spacing.

[Andrew Read 1Participant @andrewread1]

Ok thanks for the advise Clive will go back and check again

[not done it yetParticipant @notdoneityet]

Andy,

This tiny line – is it on the same side of every tooth? If so it has likely shifted. If on only teeth part way round you would see where it shifted (unless it moved just before starting the second cut).

Do you really need to make that second cut? One cut would avoid the problem.

If on one side or the other, I would look at your methodology – consistent tightening of the dividing head for every tooth. Maybe leaving some friction applied while advancing the wheel.

Are the wheels supported sufficiently?

I don't make tiny/flimsy gear wheels, so I'm just throwing out ideas.

[BazyleParticipant @bazyle]

Even with zero wear there is likely to be some backlash on worm and wheel. Does the Myford design have an option for adjusting their engagement?
If you wrap a thin wire or string around the mandrel the wheel/gear being cut is on and hang a weight off it (with pulleys as necessary) you can keep a bias on it to always keep the dividing head worm engaged on the same side.

[HopperParticipant @hopper]

Got all your slides locked up, except the one used to feed the job into the cutter?

Have you double checked how many turns of the handle and holes on the index plate you are moving every time? It is possible you are a tiny bit out and that is causing the mismatch on the second time around? Be aware that when counting holes between the fingers on the index plate, you don't count the first hole. It is, in effect "zero". This not-uncommon beginners' error leads to a one-hole error on each tooth cut, accumulating in a small error at the end of one round of the job. Which becomes evident when making the second cut over teeth that were cut without the accumulated error at the beginning of the round.

If all else fails, it's only clock wheels you are cutting – as in not very large and not very tough material – you might do better to do it all in one cut.

[Martin KyteParticipant @martinkyte99762]

Are you mounting the wheel on the dividing head and the head on the boring table or are you using it to divide the headstock. Or is it mounted on a mill.?

In either case is the cutter bang on centre?. Are all unrequired slides locked?. Can you detect any backlash in the workpiece? Are you going in the same direction for both passes?

As already mensioned you can cut brass to depth in one pass.

regards Martin

[Ian S CParticipant @iansc]

And you must turn it in one direction only, don't go past the hole, then back up.

Ian S C

[KWILParticipant @kwil]

If you do go past the hole, back up until you see the work move backwards , then re-approach the desired hole slowly and carefully. Use the centre of 3 cap heads on the mandrel to lock it before the cut.

Edited By KWIL on 04/10/2017 10:50:38

[Andrew Read 1Participant @andrewread1]

Gents

Thanks for all the helpful advice will go away and check and hopefully find the issue or maybe just do a single cut around the wheels

[Author]

Posts