Author Topic: 3-jaw chuck  (Read 4411 times)

Offline AdeV

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3-jaw chuck
« on: September 10, 2013, 07:59:15 AM »
OK, for donkeys years now I've been running a 2nd hand 3-jaw chuck held in a 2nd hand 4-jaw chuck on my ancient lathe. The end result is almost no chance at getting a piece even remotely concentric (typical runout on first tighten is +/- 0.010" @ 2" out). I can usually improve it by gentle taps with the plastic hammer, but getting better than +/-0.003-0.004" is rare.

As much as I like the 4-jaw, I prefer the swiftness of the 3-jaw, so I'm in the mood to  buy one. Probably a 10 or 12" job, so it's going to cost a penny or two... therefore, can anyone recommend a decent enough make?

So far, rdgtools & gloster are the only 2 companies I can find who sell brand new chucks 250mm diameter, any other suggestions welcomed. Haven't tried arc euro yet, thinking about it...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

lordedmond

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Re: 3-jaw chuck
« Reply #1 on: September 10, 2013, 08:46:34 AM »

Offline AdeV

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Re: 3-jaw chuck
« Reply #2 on: September 10, 2013, 12:56:35 PM »
2' 7"! I don't fancy having to lug 400kg on & off the lathe though, reckon that's a shortcut to a hernia and no mistake.

No - 250mm (maybe 315) is as big as I want to go. At least the Bison chucks are all comfortably rated higher than my lathe's maximum speed...


I guess the next question is; mounting plate... My lathe has a flat plate sticking out of the headstock. The proper Edgwick chucks have a register which fits over this plate, with three studs sticking out the back. These are then fastened with 3 nuts behind the plate.

One option that I always fancied doing, but I'm not sure I've got the skills to do, is to create a Dx camlock backplate, to which I can then obviously attach any matching camlock chuck. I quite like the ability to quickly swap between the 4 & 3 jaw chucks; but if I've got a dead nuts 3-jaw then I will only ever need the 4-jaw for off-set turning...; so, question time:

1) How hard is it to make a camlock backplate?

2) If the answer to (1) is "too hard for me", then I presume that making a dead accurate normal backplate will, mainly, consist of:
  a) Turn a "plug" to the exact diameter of the lathe's mounting face. Use an existing chuck to verify accuracy of the plug.
  b) Drill/tap mounting holes in mounting plate & attach to lathe.
  c) Turn the lathe side of the mounting plate, using the plug to verify accuracy.
  d) Re-mount the mounting plate on the lathe, this time on the turned side,  now turn the chuck side, using the chuck itself to verify accuracy.
  e) Drill/tap holes for chuck & bolt to mounting plate.

Did I miss anything obvious?

Cheers!
Ade.
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

lordedmond

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Re: 3-jaw chuck
« Reply #3 on: September 10, 2013, 01:28:37 PM »
IMHO

just turn up a normal adapter plate as in your 2 that would sort you out a cam lock would be interesting to say the least

shame you have wimped out on the 800mm one  :ddb:


Stuart


Offline awemawson

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Re: 3-jaw chuck
« Reply #4 on: September 10, 2013, 02:10:21 PM »
Rotagrip will sell you a camlock backplate. You can then mount it and machine it to match the recess in your chuck. I was going to do this for the A6 nose of my Traub, but they only had A6 backplates in cast iron and this is a very fast spindle - so I cheated and bought one.
Andrew Mawson
East Sussex

Offline AdeV

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Re: 3-jaw chuck
« Reply #5 on: September 10, 2013, 06:44:32 PM »
Ah, unfortunately it's the camlock spindle nose I need to make... I just have a non-standard flange on the lathe...

From googling about the place, apparently camlock spindle noses are jolly hard work to make, so I think I'll be sticking with the Edgwick method - i.e. unbolt the chuck from behind (oo-er) every time I want to remove it...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline awemawson

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Re: 3-jaw chuck
« Reply #6 on: September 11, 2013, 03:20:51 AM »
All the dimensions for the CAMLOCK nose are in that .pdf file I inculded when I replied to John S's enquiry a month or so back
Andrew Mawson
East Sussex

Offline BillTodd

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Re: 3-jaw chuck
« Reply #7 on: September 11, 2013, 04:22:07 AM »
Yes, you could make cam-lock :-)

The dis advantage is the extra over hang it woud create  (i.e. the chuck will be 2 or 3 inches out from the spindle.)

I have not seen any spec for the nose, but it would not be too difficult to reverse engineer if you have an example nearby. (The patent document may give you enough info).


Bill
Bill

Offline BillTodd

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Re: 3-jaw chuck
« Reply #8 on: September 11, 2013, 04:29:16 AM »
Ah this may help:

shopswarf.orconhosting.net.nz/chuckmt.html

Bill
Bill