On 2012-03-05, Bob S wrote:
On 5 Mar 2012 05:17:22 GMT, DoN. Nichols wrote:
On 2012-03-05, Bob S wrote:
Thank you for the very comprehensive suggestions!
Comments interspersed below:
Best way to do it. Thanks!
OK, I will do it again :-)
Good!
[ ... ]
I would probably take bayonet mounts from junk lenses and bodies. But
I can see that milling and a rotary table might come in handy for many
things. My father donated an old Unimat II (not threading, but it will
convert to a mill), and amazingly I have a very small rotary table
from a yard sale!
Great! I've never had my hands on a Unimat II, but the even
older Unimat SL-1000 and DB-200 have problems with rigidity, since the
bed is only steel rods supported only at the ends. If the Unimat II has
a cast bed, then it should be significantly more rigid, like my
Emco-Maier Compact-5/CNC. (Still not up to my 12x24" Clausing, of
course. :-)
The Unimat II is from the 60's and has rods supported at the ends, so
it will never be a great mill, but it may be good enough for some
learning.
O.K. My Unimat SL-1000 is from the mid to late 1960s as well.
Perhaps the same machine? Something like about a 3" diameter 3-jaw
chuck as part of it (the lathe part, that is), and a spindle nose which
is a M12x1 thread.
[ ... micrometers ... ]
Yes, I suspect that for most lens threads and such I could survive
with even 0.1mm accuracy, which should be easy even with a calipers.
For many other things "make it fit" is probably the order of the day,
and absolute measurements are not relevant. But I suppose that it is
inevitable that something will come along requiring a real number...
In particular, if you need to make a part to fit something which
someone else has at a distance.
First off -- you need the right bore diameter for an internal
thread, or the crests of the threads are likely to bind on the roots of
the matching thread, and by the time that starts shrinking, you have way
too small a thread pitch diameter for a good fit.
The advice someone else gave for fitting a crank to the spindle
(with the lathe unplugged) for making threads which end at a shoulder is
very good -- and applies to many threads made for mounting lenses.
Also -- for measuring outside threads, the best way (if they are
at least three threads long) is thread measuring wires. You put two
wires of the right diameter into adjacent threads on one side, and one
wire of the same diameter into the thread groove on the opposite side
between the first two, and measure over the top of the wires with a
micrometer. There will be a chart, or a formula, with the set of thread
measuring wires to tell you how much to add to the pitch diameter to get
what the micrometer should read. (There are thread pitch micrometers,
but these get expensive, especially with the sets of anvils for
different thread pitches, when you need to get two or three of the same
brand of different sizes so you can share the anvils between them.
Check out eBay auction # 160636274261 for a 0-1" micrometer with
some of the anvils you would need. (Maybe all.) But, you would need
other micrometers of the same brand to use those anvils on the other
sizes.
Beware that some thread pitch micrometers do not have
interchangeable anvils, but rather are made for a narrow range of thread
pitches, such as: eBay auction # 310383570733 -- which is for 8-13 TPI,
a bit coarse for most lens threads.
This one is 1-2" (25-50mm) and has both inch and metric anvils:
eBay # 330518405934 -- brand/seller is "Shars".
This one is all three sizes in one set: eBay # 150765779502, and
you could use the inch anvils for metric threads, but it would be more
convenient to have metric micrometers for the purpose.
This is one of the ones which I have, but still not metric:
eBay # 260971726026. Note that the ones marked B&S and the ones marked
TESA are made by the same people.
I also have the 0-1" and the 1-2" ones of the same brand. And I
*still* have the thread pitch wires.
Here is an example of thread pitch wires: eBay # 380408293791.
(Hmm ... chart not included. Buy new then. Or pick up a copy of
_Machinery's Handbook_ which will have the formulas for calculating the
measurement over the wires -- and many other things which you will need.
BTW Did I earlier mention a metric thread pitch gauge? You should have
that for sure.
[ ... ]
4) A scissors style knurling tool to allow knurling parts for grip.
A "bump" style knurling tool needs a much heavier and more rigid
lathe to drive it.
Great idea; I hadn't thought of that.
I got my first one to use with the Compact-5/CNC -- way too
small for bump knurling -- and I really don't like it on any system. I
found a really nice one by Aloris to fit my BXA sized quick-change
toolpost . It has the two knurls on two arms which move in a vertical
dovetailed slide, each moving in the opposite direction with a leadscrew
with left-hand threads on one end and right-hand ones on the other.
Once it is set to the proper center height, I can just drop it on to
knurl any size within its range without having to re-adjust the height.
I did a little casual looking on the web and it looks like casual
looking is not going to do it.
Go to MSC and look there. The trick is to know how big your
tool shank slot is in the quick-change toolpost. The one I got (by
Eagle Rock) fits into a 1/2" slot, which works for the Compact-5/CNC.
This one on eBay will handle up to 2" diameter:
eBay # 300394065202
Here is the AXA version of the knurling tool which I use on my
Clausing in BXA size: eBay # 120748127351 -- also good up to 2"
diameter.
You can find articles for making your own scissors style
knurling tools, and if you make the pivot point a greater distance from
the knurls themselves, you can make them handle a larger diameter
workpiece.
Note that I've skipped over a lot of bump style knurling tools,
as well as various ones designed for use on turret lathes which would be
awkward on your lathe (but *very* quick for production of many parts if
you *do* have a bed turret attachment.)
There are many tools that will do up to about one inch, which is fine
for knobs but not so good for an 82mm filter ring.
Tools with large capacity probably don't fit on the small lathe.
Maybe a hand knurling tool is what I need.
However, it may be that no knurling tool is going to work well as the
last step on a filter ring because the ring is thin and will bend
under the load. Maybe I need to knurl first and then bore out the
center.
Not unless you make an arbor to support the ID of the ring.
But yes, knurling as the first step, then turning the OD to
produce flat areas which end at the knurls is a better way to go.
The best for working on thin material is the cut style knurling
tools -- which are amazingly expensive, so forget it unless you luck
onto one for perhaps $200.00 or so. :-)
Good Luck
DoN.
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