On Mon, 1 Sep 2008 23:45:23 +0200, "Steve Lusardi"
wrote:
snip
You need a proper dividing head and tail stock to match. These
come with chucks and are quite stiff. An indexing table has no chuck. If
the gears are helical or hypoid the dividing head should be differential as
well, but that also require a drive setup from the table leadscrew to a
gearcase with changeable gears.
snip
-----------------------------------
Actually this is the answer if you have bags of money and space.
Assuming you don't, and the lathe gears you are talking about are
straight cut change gears, the rotary table should work quite
well. It just won't be as quite as rigid, and there will be some
gear teeth numbers [prime generally] you can't cut because the
dividing plates won't have the correct number of holes.
The work around is to use the vernier settings and directly
machine the gears, or drill a plate with the correct number of
holes. Because of the way dividing heads work, the spacing will
be more accurate by the dividing head gear factor. If you are
extremely annal retentive you can use this plate to drill a third
yet more accurate plate.
While some of the rotary tables /dividing heads have B&S or other
tapers, most of the new ones are #2 Morse tapers in the smaller
sizes but be sure to check.
The one I have is
http://www.wttool.com/product-exec/product_id/20850
and fits [snuggly] on my Emco Compact 10.
http://mcduffee-associates.us/machining/emcoLathes.htm
The dividing plates are extra
http://www.wttool.com/product-exec/p...ding_Plate_Set
The Little Machine Shop has machinable #2 Morse taper arbors that
will greatly simplify your task, as these are pre drilled/tapped
for a spindel/retention bolt, and only need the head machined to
the correct diameter. If you don't have a #2 taper adapter for
your lathe, get one of the sleeves and use a 4 jaw chuck. [Or a
MT adapter to fit your spindle but you will most likely have to
saw the back half off.] These are also available in #3MT and work
well for making the single point fly cutter described in Law's
book.
http://littlemachineshop.com/product...2394&category=
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
Depending on the accuracy desired you can hand grind a single
point tool to fit an existing gear or buy B&S style involute
cutters. As indicated in Law's book these cover a limited range
of teeth, but for most shop use you will only #s 2,3,4 [26 to 134
teeth]
http://www.newmantools.com/cutters/gear.htm [be setting down when
checking prices also note that some of these are UK suppliers]
http://www.rdgtools.co.uk/acatalog/1...R_CUTTERS.html
one of the few US suppliers I have been able to locate is
http://www.jtsmachine.com/jtswebshop...Tools/C027.asp
Be sure and get an arbor to fit your mill spindle at the same
time.
Also order a slitting or slotting saw of the correct thickness
w/arbor to hog out most of the material to reduce the load on the
hard to grind single point cutter or expensive formed cutter.
Some hints:
(1) unless functionally required, make the gears flat sided with
no undercuts. Typically store bought cast/forged gears are
dished to reduce the amount of material. This leads directly
into hint 2.
(2) Cut the bigger gears first. Then when you ding one you can
turn it down to a smaller size blank, and not lose the work you
did machining the bore, key way and probably the thickness.
Also it may be helpful to install a pin on the gear arbor that
will engage the drive slot in the gear bore. This is
particularly helpful when lathe turning the OD and thickness of
the gear, although you can do this with an end mill and the
rotary table.
Also consider alternate materials for your change gears. In many
cases the manufacturers used cast iron because that was all they
had. Phenolic/Formica, delrin, nylon, and possibly aluminum may
be a better alternative, cheaper and more easily located. 6061
T6 has worked well for change gears for my Emco.
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
Good luck and let the group know what you decide and how you make
out.
Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).