4, Independent, jaw chuck

Today for the first time ever I managed to set up a piece of round bar stock in the 4 jaw chuck. Took me a good long time and a lot of trial and error but finally got run out to .00039" or .01mm. Is that considered 'good enough' ?

It was only after that I thought to look at YouTube for better ways of doing it than my lengthy trial and error method

Hello Nige, you have done very well to achieve that. 4 jaw work is often a bit long winded but for many jobs such accuracy is not needed. For example, if you used the 4 jaw to hold a piece of square bar for turning then it might be OK within 5 thou, it depends on how well the parts need to line up.

If setting up a casting, the only requirement is to ensure that everything cleans up.

Brian

Also, the "lengthy trial and error method" is not going to be either forgotten or devalued by anything which comes later as one tends never to forget that first all absorbing struggle......

Nige,

That is likely far better than most 3 jaw self centering chucks will achieve.

If you plan your work such that the item does not require rechucking, the initial chucking may not need to be centred perfectly - as long as the stock is sufficiently oversized - just the first cuts may be intermittent.

Turning between centres is the way to go if parts need to be removed from the lathe and replaced several times without fear of concentricity problems.

Trial and error is always the way it is done. Think here, if you trial it (measure) and reduce the error (run out) by one half each time, you should only need a maximum of eight repeats to reduce the error to close (enough) to zero (a bit like folding a sheet of paper in half and half again, etc). It is only that some can get there more quickly than others!

Check out the recent competition between Keith Fenner v Abom79 at the Bar Z bash 2017.**LINK**

Even they can be set a rediculous task to test their doubtless high skills.

Nige,

Search:

"4 Jaw Chuck Indicating Made Easy - YouTube"

It is by "Doubleboost" a man who knows exactly what he is talking about and he demonstrates a very simple and fast way of cantering work in a 4 jaw chuck.

Eric

I'm amazed you managed to find a bit of steel as straight and round as that.

;0)

Martin

Many years ago I was taught to dial work on a 4 jaw chuck using a dial indicator. Using the lines scribed on the chuck face get the part nearly centered. Determine the TIR of the part. Adjust opposing jaws to bring the part to the midpoint of the TIR. Keep repeating until the work is true. I don't see that method being used in the You Tube videos. I don't see that method used much in the You Tube videos.

A very good point. I took my 3-jaw apart to clean it after the run out went to pot. It turned out that the length of silver steel I was using as a reference is slightly bent! (I may have dropped it earlier.)

Dave

Good.

Now take the bar out, slacken the jaws, and do it again.

And again.

After an hour or so, everything will become 2nd nature, and you will be dialling in round bar to less than a thou within a couple of minutes.