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Clarkson Chuck - removing the centre

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Ian S C19/11/2010 09:38:06
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David you got there before me, I was looking at my chuck the other day in regard to this thread, and thought perhaps if one put some gease down the hole, then a bit of rubber for a seal, then screw in a good fitting bolt, but maybe the thread is a bit coarse, someone else can work out the pressure developed.Ian S C
David Clark 119/11/2010 09:50:54
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3357 forum posts
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Hi There
How about a bolt in the end, sealed with something and a finer thread through the centre of the bolt to use as the hydraulic pressure source?
regards David
Nicholas Farr19/11/2010 10:30:37
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Hi David, your recent idea may well work. You could perhaps use thead locker solution to seal the bolt in, which should be easyly rermoved afterwards. I would choose a fairly longish bolt and longish threaded bolt as the plunger, whith as finer thread as possible, and fill as much as you can with hydraulic or extrem presure oil. I think you will still need a close fitting sealed plunger though, to stop the oil leaking out. You could always use a larger piece of BMS round, say EN8, and turn it down and thread it to fit, and then make a chamber/plunger affair at the other end. The reason for a longish plunger bolt would give you a bigger displacment area on a small cross sectional area which would give you more pressure on the bit you are trying to remove.
 
Regards Nick.

Edited By Nicholas Farr on 19/11/2010 10:36:32

Chris Trice19/11/2010 15:53:14
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It would definitely need a seal. The advantage of oil over grease is that you'll be hard pressed (ouch!) not to get some air inclusion with grease. If the bolt going in can be turned so that the nose reduces down to match the narrow body bore.....
Ian S C20/11/2010 08:26:04
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David I thought of that while I was writing out the last bit, but thought that perhaps it was impractical, but maybe not, maybe something like the .75mm pitch metric stuff. Ian S C
ady20/11/2010 08:56:12
612 forum posts
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From what I remember with dodgy jobs at sea, it needs to be a good quality fine thread or it will simply unscrew itself like a hydraulic spring loaded bolt once you take any turning pressure off, and the pressure gets huge, beyond human comfort, pretty quickly.
 
I would say that a dedicated large plug with a pressure tube for a dedicated thin long bolt would take you closer to the hydraulic jack principle of small section over large distance to move large section over small distance.(kinda thing)
 

Edited By ady on 20/11/2010 09:02:18

Nicholas Farr20/11/2010 09:49:50
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Hi, Ady your idea is much the same as mine. A hydraulic jack of course squerts a small amount of oil passed a non-return valve, repeatable to build up the pressure.
 
Another out of the box and somwhat radical idea, is maybe have a bolt that screws into the chuck which will incorperate a chamber once screwed in. You could drill a small hole through the length of the bolt and thread the head end to take a small grub screw. Fill the chuck with water then with some PTFE tape on the bolt, screw it into the chuck, letting the excess water to squert out the the hole in the bolt. Then you put in the grub screw and put the chuck into your deep freezer for a day. As water freezes it expands and of course the chuck will srink. May just work even if you have to repeat the process a couple of times.
 
Regards Nick.
Chris Trice20/11/2010 10:56:48
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Can't help feeling that if you go to that much trouble, wouldn't it be easier  just to fit a 7/16th bolt which is then drilled and tapped with a finer pitch thread for another bolt to act directly on the end of the centre?
chris stephens20/11/2010 17:23:53
1049 forum posts
1 photos
Hi Guyss,
To save me reading all the posts again, has any body suggested drilling/machining it out? All this talk of hydraulics smacks a little bit of a solution in search of a problem. Remember the K.I.S.S. principle.
chriStephens 
blowlamp20/11/2010 17:49:36
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1885 forum posts
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If it really is in that tight, then I would be thinking about setting up a toolpost grinder and either just giving it a lick in position on the miller - or probably easier in the lathe. 
If it's got a Morse taper shank and can go straight in the headstock spindle, that would be an ideal way of doing the job.  
 
Martin.
Chris Trice20/11/2010 18:14:39
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1376 forum posts
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Beat you to it Blowlamp. Since I had nothing to lose, I set the chuck up with the narrow end held in the four jaw chuck (it's an R8) and clocked it to run true while the business end was supported in the fixed steady all well lubricated with oil and running with no runout that the dial could detect. I used a 1/2" cylidrical grinding wheel mounted in an older style Dremel flexidrive shaft. The older ones are basically tubular so it was no trouble to mount into a Dickson QC toolpost. With it set at centre height and the top slide set to 30 degrees we were off and running, the lathe turning at around 100 rpm and the Dremel running at max. Much to my surprise and not to say relief, a few passes had the point suitable sharpened and looking (almost) as good as new. Neither did the wheel wear unduly. I was worried about taking too much off but as it happens, there is a lot of meat to play with and plenty of thread left with all the cutters I have subsequently test fitted. I am very happy, the moral of the story being that there are always alternatives to the hard way.

Edited By Chris Trice on 20/11/2010 18:15:39

James fortin22/11/2010 20:11:35
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46 forum posts
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this is probably a bit late now but perhaps next time you could make a SDS drill adaptor so you could power hammer it out perhaps thousands of repeated vibrations would free it?
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