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Thread: Stuck chuck ....
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16th July 2015, 07:37 PM #1
Stuck chuck ....
I have this pre war 13" Holbrook lathe , its really almost ready to be melted down .It weighs over 1.5 ton and its only got a short bed .
Anyway the back plate is jammed on the spindle . Holbrook used a double register on the spindle nose , a 2 1/4" BSF thread 3/4" long is between the two registers
Advice on another forum . Is to machine up a tapered plug and use the plug locked in the spindle taper to hold the spindle .
I have measured the taper in the spindle. it is .025" per inch or .3" per foot . I cannot find any taper like that in any books I have . I need to know the angle to off set my top slide . Can anyone work out the maths .... ?
Some pics of the nightmare . BTW the gearbox is almost a work of art ! The spindle runs in 3"diameter white metal bearings .
Mike
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16th July 2015, 07:50 PM #2Senior Member
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If I am interpreting your figures correctly the angle to offset the compound slide is .71616 degrees.
Looking at your setup in the first picture again I would say it is more likely that you would have to set the angle at 1.4321 degrees.
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16th July 2015, 07:54 PM #3
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16th July 2015, 08:55 PM #4Mechanical Butcher
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Is there anything on the other end of the spindle that could be gripped?
Jordan
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16th July 2015, 09:24 PM #5
grip
Not really , there is only a short length of spindle outboard of the headstock casting , where a gear is located on the spindle end . The advice I got is to lock the spindle at the back plate end , doing this will negate any twisting effect over the length of the spindle eg if it was locked at the other end . My plan is to use a long bar and hang a weight off the end of the bar and leave it under tension , while heating and cooling the back plate . If that fails I will have to turn it off, which I really don't want to do as its a complicated register and I need a intact back plate , so I can copy it
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16th July 2015, 09:41 PM #6Philomath in training
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Can you make up some sort of clamp that will hold the spindle between the gears and immobilise it? If you could I would suggest that plus penetrene and a few sharp blows to the backing plate may work.
Michael
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16th July 2015, 10:08 PM #7
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16th July 2015, 10:40 PM #8GOLD MEMBER
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16th July 2015, 10:44 PM #9Philomath in training
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16th July 2015, 10:58 PM #10Senior Member
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Does the machine have power connected Mike? If so, and if it can be run in reverse, I can suggest a method that will probably undo the chuck although the method is a bit primative.
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16th July 2015, 11:42 PM #11SENIOR MEMBER
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Why not bolt another plate to it with a big nut welded to the centre, with the g/box in a neutral position zapp it with an impact gun, 3/4" or 1" square drive if you can, you might loosen it without even holding the shaft.
shed
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17th July 2015, 12:27 AM #12Mechanical Butcher
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17th July 2015, 12:39 AM #13Mechanical Butcher
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Some suggestions for removing stuck threaded chucks here: http://tinyurl.com/37znlsc
Jordan
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17th July 2015, 07:30 AM #14SENIOR MEMBER
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I saw a variation of the long lever spanner method somewhere - the chap set up the long lever and tied a rope or chain to the end of it and dangled a very heavy wieght and left it overnight - said it worked every time. Have seen other posts advocating applying gentle heat.
http://modelenginenews.org/techniques/stuckchuck.html this might be worth a look.
Bill
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17th July 2015, 11:04 AM #15SENIOR MEMBER
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I cant see a tapered plug having enough grip to hold the spindle stationary, if you have all ready tried the low gear and bend the pipe routine. The plug will just slip.
But if you wanted to try that, no need for maths. A lot like your first picture, just use the indicator of the other side of the taper, mag base on your top slide, and just clock the taper until the top slide is true to the spindle taper.
I still think that's bad advice, you'd have to seat that plug with a sledge hammer if it was to have any chance of locking. That will expand the spindle, working against the cause.
Regards Phil.
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