ODDS AND ENDS.
Backlash in Worm Drives.
No backlash is wanted in a worm drive especially if the telescope is
used for photography. Bachlash is a problem in all machine tools and
certain procedures have to be adopted to counteract it, such as always
approaching a setting from the same direction; not going past it and
coming back. In the gem faceting machines I manufacture there is an
index wheel for dividing the facets on the stone. if facets do not line
up. where does the fault lie? With the machine or the operator. As I
have no control over the latter I have to ensure that the fault is not
in the index wheel. For this a very accurate dividing head is required.
I purchased an "expensive for me' Dividing Head. A test card came with
it showing its error in seconds for a full circle as tested with a "Carl
Zeiss' high precision digital index texter. It had a maximum total error
of 42 Seconds of arc. However as I found minute backlash at certain
points. I adjusted the worm engagement to eliminate this and then found
that at other points it was too tight. A friend of mine who attended
an International Machine Tool Exhibition discussed this my problem with
a Japanese manufacturer. They said they could make me a dividing head
for $40,000 which would not have this problem. This was out of the question.
As I cut enough index wheels in ten hours to last me a year I considered
the $2600 I paid for my dividing head more than enough.
Tube End Rings.
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