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Posted by Steve W on October 1, 2006, 12:11 pm
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>
>> Set up a 60mm cube of HE30 aluminium in the four jaw so the a) the hole
>> is
>> where I want it to be AND square with the front face?
>>
>> The hole will be 50mm and I can set the face square with the DTI, but
>> getting the hole on centre at the same time is driving me nuts!
>>
>> I need to leave a clearance between the back face of the cube and the
> front
>> face of the chuck so I don't hit the chuck with the boring bar and to
> allow
>> the chips to fall away.
>>
>> First attempt was square but 0.5mm off which is not good enough. For
>> personal satisfaction I'd like to get better than 0.1mm and as close to
> bob
>> on as possible.
>
> If the jaws are good and the cube is true then it should be held square
> anyway regardless of how well it's centred. However, chuck it a few mm
> further forward than you want it to end up. Set the dial gauge on the
> sides
> of the cube and adjust until it's centred but still held fairly lightly.
> What you're looking for is the lowest reading on the gauge on each face
> which will be in the centre of each face as you swing the chuck. You do
> opposite sides in turn until it's central in one plane and then the other.
> Should only take a minute or two with practice.
>
> Then bring the tailstock ram up and press the cube back a couple of mm
> against the jaw pressure. This should true the front face of the cube to
> the
> face of the ram which ought to be dead square. Then nip each jaw in turn a
> fraction at a time working round and round the chuck until it's held
> tight.
> Then a final check that it hasn't moved and you should be good to go.
>
> If you're still having problems then it's likely the cube isn't quite true
> and will need a skim across the front and rear face anyway. Check this out
> is against an angle plate or with the cube on a machine bed and run the
> DTI
> across each top face in turn. In fact with a good 4 jaw chuck there's
> nothing much you can do to alter the squareness of the front face once the
> jaws are tight so any major error tells you the cube is distorted.
> --
> Dave Baker
> www.pumaracing.co.uk
> "Why," said Ford squatting down beside him and shivering, "are you lying
> face down in the dust?"
> "It's a very effective way of being wretched," said Marvin.
>
>
Thanks guys, I'll go back and have another play
Steve
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> where I want it to be AND square with the front face?
>
> The hole will be 50mm and I can set the face square with the DTI, but
> getting the hole on centre at the same time is driving me nuts!
>
> I need to leave a clearance between the back face of the cube and the