"Bruno" wrote in message
...
Thanks for the cigar, Bill!
To clarify, my last sentence referenced "the number you have for the
depth of thread". The reason for including this is that the original
poster will do my calculation and find that the result (0.0546875) is
very very close to the result he obtained (0.054125) even though they
are two different things that are only marginally related.
Yes the poster called .0625 * .866 = .054125 the thread depth. It is
not.
The sharp point thread depth is .875 * .0625 * .866 = .047359
Yes the .866 is the sq root of (1*1 - .5*.5) or (1/2 of the square root
of 3)
Enjoy the stoggy!
Your 7/8 * 1/16 = .0546875 is a great way to calc the compound feed.
FYI, .866 is really an approximation of 1/2 of the square root of 3,
being the relationship between the long side and the hypotenuse of a
30-60-90 degree triangle (half the 60-60-60 triangle form for the
thread, discounting any flats). The hypotenuse is equivalent to the
pitch, and the long side is equivalent to the "depth of thread", which
in this case could also be thought of as half the difference between
the major and minor diameters of a 60 degree V formed thread with no
flats at either the crest or the root.
Now, do I have to give the cigar back?
-Bruno
"Bill Darby" wrote:
You get my cigar!
Mind you, I would recommend that you leave off the last sentence as
it
tends to make the simple truth of your statement up to that point,
possibly subject to confusion owing to your reference to "the term
depth of thread" because your math has nothing to do with the depth
of
thread.
IE:
On each pass you have the cross feed at the same position and bring
the compound slide in. Assuming a sharp V formed tool, and the fact
that you want to leave a flat on the thread which is 1/8 the pitch,
the formula is to feed the compound 7/8 times the pitch. In your
case
that would be 7/8 times 1/16.
Bill (O:
"Bruno" wrote in message
.. .
On each pass you have the cross feed at the same position and bring
the compound slide in. Assuming a sharp V formed tool, and the fact
that you want to leave a flat on the thread which is 1/8 the pitch,
the formula is to feed the compound 7/8 times the pitch. In your
case
that would be 7/8 times 1/16. The result is very close to the
number
you have for the depth of thread, but remember that that number is
not
accounting for the flat.
-Bruno
(Tony Alcocer) wrote:
I've been learning how to thread with my lathe. One question I
can't
seem get is how far do I infeed on the cross feed? Lets say that I
am
going to use 16 TPI and these are standard 60 degree sharp V
threads.
The formula for figuring out the depth of the thread is .866
divide
by
TPI..in this case 16TPI which gives me .054..but with the cross
slide
set a 29.5 degrees how far do I infeed to get a thread depth of
..054?
There has to be a math formula for figuring it out.
Thanks for any and all help.
Tony