On Tue, 20 Nov 2012 16:50:00 -0800 (PST), Searcher7
wrote:
On Nov 19, 11:37*pm, "DoN. Nichols" wrote:
On 2012-11-19, Searcher7 wrote:
On Nov 17, 3:45 pm, "DoN. Nichols" wrote:
* * * * [ ... ]
Oops! I forgot not to give approximate numbers. :-)
60 tooth = 2.575"
28 tooth = 1.245"
14 tooth = 0.655
* * * * Not 16-tooth, O.K.
* * * * O.K. *A little different from my calculations. It sounds as
though the crest of the teeth has been shaved a little, No problem as
long as the pitch diameter is correct.
* * * * So the precise OD of the 28-tooth one should be 1.2500" (which
* * * * * * * * matches your 1-1/4")
* * * * The 16-tooth one: *0.750" (3/4" not your 11/16" -- if it is truly
* * * * * * * * 16 teeth.
* * * * The 60-tooth ones: * * *2.5833" *(2" and 9.3333/16", not 9/16")
* * * * [ ... ]
Thanks. Here are some pics of the 60 tooth gear:
http://i290.photobucket.com/albums/l.../Joystick%20Pr...
http://i290.photobucket.com/albums/l.../Joystick%20Pr...
http://i290.photobucket.com/albums/l.../Joystick%20Pr...
* * * * O.K. *But we knew the count of teeth there. *It was the smaller
ones which I was wondering about -- and you have now told met hat the
smallest one was 14 teeth, not 16, so my calculation for size was wrong.
On Nov 17, 3:56 pm, "DoN. Nichols" wrote:
On 2012-11-17, Searcher7 wrote:
Oops! Yes I have an HF Mini-Mill. :-) (Along with a rotary table).
O.K. Does the rotary table have a hole plate and arm with
sector arms? If not, it will be tricky for some of the gears. 60 tooh
is no problem. 16 tooth (if I am right about that gear), also no
problem. But the 26 tooth (or was it 28?) will be tricky. For each cut
you need to advance it:
26 13.8462 degrees (13 degrees 50 minutes 46 seconds)
28 12.8571 degrees (12 degrees 51 minutes 26 seconds)
With the right hole plate, and the arm and sector arms, it is
easy to set it up to avoid problems. And that is what an index head
has.
But all I have is an over sized spin index fixture. (www.ebay.com/itm/
350468227596)
The rotary table is a far better choice than this. The finest
rotation you can accomplish with the spin indexer is 1 degree. And even
for the 16 tooth gear, you need 22.500 degrees -- that half a degree you
can't get on the spin indexer. (Yes, it would work with the 60 tooth
gear, which only requires 6 degrees advance for each tooth. Still a
little tricky to calculate the position of the pin for each one.
As far as "hole plate and arm with sector arms". I have a rotary table
with dividing plates that I haven't used yet. In fact, this one:
www.ebay.com/itm/321022783132.
* * * * O.K. *That should do it. *Did it come with a table of settings
for different divisions? *If not, you will need to know how many turns
of the crank for a full turn of the table. *Common ratios are 90:1
(larger rotary tables, at least), 40:1 (my dividing head), and I believe
10:1 on some heads.
I haven't dug out my manual but an internet search says 90:1
http://www.t4i.com.au/R006
The most difficult part will be the gear cutter. (So I'm off to do my
reading).
Thanks a lot.
Darren Harris
Staten Island, New York.
The gear cutter will be easy. You can make the button cutter as
outlined in Law's book and then use that cutter to make a fly cutter
to cut the teeth. You can use water hardening or oil hardening tool
steel. Both are easily available and pretty easy to machine. And heat
treating with a propane torch will work. For that matter, since the
cutters are so small, you could use a gas stove or even an electric
burner.
Eric