"Matthew Zenkar" wrote in message
news | Please pardon me if this is not the correct forum for this message.
|
| I am working on a design that I think is best described as a precision
| positioning assembly for optics. I contacted a professional gear
| designer, and I was told by this person that the design would be
| improved if I used an acme thread for the threaded rod that is in the
| assembly.
|
| My initial design called for a 3/8"-40 thread as this is the finest
| standard thread size I could find to fit a 3/8" diameter rod. However,
| looking in Machinery's Handbook, I found that the finest standard acme
| thread is 1/4-16. I also figure that I would be able to use a 20 pitch
| with another minor adjustment in the assembly.
|
| Is it common practice to have custom threading made for those cases
| where standard threads do not meet the needs of a project? For my
| case, I would like to have acme threaded parts where the thread size
| is 3/8 or 1/2-20, more preferably, 3/8 or 1/2-40.
|
| Also, if it is not heard of to have acme threads custom acme threads
| made in those particular sizes, what about having what Machinery's
| Handbook calls "unified screw threads" cut to a non-standard size, say
| 1/2-40 - is this done for cases where standard threads do not meet the
| needs of a project?
|
| Also, does anyone have any recommendations as to where I might get
| this done (preferably by a professional shop)?
|
| Thanks in advance for your response.
|
| Best Regards,
| Matthew

Given the same amount of tolerance, the finer the thread pitch the more
precise the movement.
The diameter of the rod is really not a critical factor.