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Best way to improve fit of main spindle quill in casting (long)

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Ian P17/07/2011 16:36:39
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Posted by Michael Gilligan on 17/07/2011 14:56:35:
Ian,

I have just been reading this thread out of curiousity ... one never knows what useful hints will be found.

You obviously need to get the bore to the right size, and the quill running true, but the underlying problem of that poorly designed locking mechanism remains.

My suggestion would be to fill the "clamping slit" with a nice piece of gauge plate [dowelled and screwed in place] before you do anything else. Then correct the bore, by your method of choice. Then make a proper locking mechanism, along the lines of those preferred by the late/great Geo H. Thomas.
... This "split cotter" design is vastly superior to the "split clamp" arrangement and should be easy to fit by slightly modifying the existing hole.

MichaelG.

P.S. I have found this photograph of "Versatile Dividing Head" parts, which might be useful for reference.

http://staff.um.edu.mt/ccam1/tooldh2.jpg
http://staff.um.edu.mt/ccam1/tooldh2.jpg


On this machine there is not enough room to use a split cotter type of clamp as the existing bolt hole position is too close to the outer edge of the casting so the cotter would break through the outer face and probably even then not be of a large enough diameter to intercept the quill.
 
On reflection, I'm not sure there is much to chose between the cotter and the split clamp. An ideal clamp would hold the quill without applying any force to it that would result in it moving to a different position. In reality either type of clamp mentioned will push the spindle sideways by an amount equal to the clearance.
 
Not having seen the article or book I dont know what GH Thomas suggested but I think the perfect clamp only exist as an ultimate goal, like perpetual motion!
 
Ian P
 
PS What did Geo Thomas
Michael Gilligan17/07/2011 16:52:20
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Ian,

You say:
On reflection, I''m not sure there is much to chose between the cotter and the split clamp. An ideal clamp would hold the quill without applying any force to it that would result in it moving to a different position. In reality either type of clamp mentioned will push the spindle sideways by an amount equal to the clearance.

I beg to differ; but of course it is your choice.

The Split Cotter effectively provides 3 point [or, hopefully, 3 line] clamping, which is inherently more stable.

I do, however, agree that the perfect clamp can only exist as an ultimate goal, like perpetual motion!

MichaelG.
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