Work positioning in the 4 jaw chuck

[Dave AlltonParticipant @daveallton26004]

Hello Gentlemen,

During the recent bad weather my dinghy suffered damage to the gooseneck fitting. I purchased a billet of aluminium 3.5″ in diameter 3″ long with the intention of turning a new insert for the boom.

 

After measuring the old fitting (aluminium casting) I need to turn a 2″ diameter on one end with the centre 1″ away from one of the jaws of the 4 Jaw chuck.

 

I have the use of a Harrison M400 to do the job safely (a bit big for my Boxford!) if I can manage to lift and position the 12″ cam-lock 4 jaw chuck!!

 

My thoughts are to centre punch 1″ in from the outside diameter and then try and get this running true. Is there an easier way?

Thanking you in anticipation

Dave

 

 

[Dave AlltonParticipant @daveallton26004]

[JasonBModerator @jasonb]

Thats the usual way, I would skim the two ends to get a flat face on the billet first then mark out your ctr 3/4″ from the ctr of the billet.

 

To get the ctr punch mark running true assuming you don’t have a sprung center the easiest way is to put in the tailstock ctr then use another dead center with the MT end supported by the tailstock and the point in your ctr punch mark. Then run a dial gauge against the edge of the centre at the widest point of the taper.

 

Jason

Edited By JasonB on 31/10/2009 07:45:50

[Dave AlltonParticipant @daveallton26004]

Hi Jason,

Thanks for the information I’ll let you know how I get on.

Dave 

[mgjParticipant @mgj]

Dave – you’ll do that in a Boxford – easy.( unless your 4 jaw is unusually small)

 

Set it up true exactly as Jason has said in the external jaws (tap home firmly with soft face mallet – using a bit of brass shim to prevent marking?), and then if you’re a bit worried about overall stability, centre drill first, and use a running centre.

 

It will be off centre/out of balance so don’t go mad with the revs when you centre drill, but being ali it’ll centre drill OK.

 

Hell a Myford will do a little job like that without blinking.

 

Given that ali likes to spin a bit quicker, you might think about setting it on the face plate (bolt it from behind, and then add some weight to balance. You could then run at a sensible speed with impunity. (They always say you shouldn’t use change wheels for balance weights – but most people do) 

 

You will get it anodised before use?

[John HaineParticipant @johnhaine32865]

For a job like this I’d face both ends; centre-punch where you want the hole axis; open the jaws of the 4-jaw too wide; clamp the billet with one end against the flat face of the jaws and the other with a centre in the tailstock with its point in the centre-pop mark so the pressure of the tailstock holds the billet.  The carefully run the jaws up to the billet and tighten them progressively being careful not to shift the billet.  Job done, quite accurate enough I’d think for a job like this, no need to use a DTI.

 

John.

[Dave AlltonParticipant @daveallton26004]

Hi Gentlemen,

Many thanks to Jason, Meyrick and John for their input.

I’ve now completed the turning part of the job without a hitch. (yes a thing of wonder to behold).

 

In the next stage I get to use my new X1L mill. Should be fun. When I’m finished I should either have a new gooseneck fitting or a lightweight door stop!

 

Think positive, I say to myself, don’t look for the lead just yet.

 

Thanks

Dave

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