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Posted by David Littlewood on February 20, 2008, 6:09 am
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>Hi
>My small bench lathe (an Axminster BV20) has zeroing dials on the
>feeds. Most are Ok, except the one on the compound which was always
>very stiff.
>On examination, it looks fairly standard construction - a steel 'hub'
>with a outer aluminium graduated sleeve and a gap between the two. In
>this gap was a flat piece of bowed springsteel that contacted the
>outer sleeve - giving the necessary friction.
>No matter how much fiddling with this I did, including replacing with
>thinner ,better spring steel I cannot seem to get a nice even &
>consistent 'feel' to this. Its either still far to tight or to sloppy.
>I tried replacing the spring with a thick rubber grommet & grease, it
>is generally better but still doesn't seem 'right' at times - tends to
>stick quite a bit.
>Anyone got any tips where they have had similar problems and got
>around them?
>
>Thanks
>Mike
Mike,
You seem to have got a lot of froth in reply, with one or two useful
suggestions.
I don't know whether you have a copy of The Model Engineer's Workshop
Manual, by George Thomas - if not, get one, every ME of any pretensions
should have a copy. Chapter 15 has a lengthy discussion of cross slide
micrometer collars, with various methods of achieving smooth zeroing
dials, from simple spring plungers to incredibly sophisticated designs
with locks on both feedscrew and collar.
The designs themselves are specifically for ML7 and S7 lathes, but the
principles used should be fairly easily transferable to most
medium-sized lathes. The ideas can also be used on other feedscrews,
such as vertical slides.
David
--
David Littlewood
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