I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl

Karl Townsend wrote:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl

I think you have some slip or backlash in your measurements.

"Karl Townsend" writes:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

No. Your numbers work out to close gear ratios, but they aren't
exact. If you divide turns at drive by turns at tool, you get:

Turns at tool turns at drive Ratio
1 6.1245 6.1245
8 49.0573 6.132...
80 490.65 6.133125
163.050 1000 6.13308800981

Since the more turns you've got the more accurate your results are
going to be, I'll take a gues that the ratio is very close to
163:1000, but that's not the exact ratio you're asking for. What
happens if you turn 10,000 at the drive?

Are you sure you've got the 'turns at drive' measurement to .0001 turn
accuracy?

On Wed, 26 Nov 2008 13:14:17 -0600, "Karl Townsend"
wrote:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl

There's some inconsistency in your ratios. Using 163.05 : 1000 or
ratio of 0.16305, I get close matches for

8/49 = 0.16327
15/92 = 0.16304

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

Joe Pfeiffer wrote:

"Karl Townsend" writes:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

No. Your numbers work out to close gear ratios, but they aren't
exact. If you divide turns at drive by turns at tool, you get:

Turns at tool turns at drive Ratio
1 6.1245 6.1245
8 49.0573 6.132...
80 490.65 6.133125
163.050 1000 6.13308800981

Since the more turns you've got the more accurate your results are
going to be, I'll take a gues that the ratio is very close to
163:1000, but that's not the exact ratio you're asking for. What
happens if you turn 10,000 at the drive?

Are you sure you've got the 'turns at drive' measurement to .0001 turn
accuracy?

We can probably assume that the spindle drivetrain of his mill does not
contain a 1000 tooth gear. 16:100 perhaps? It sounds like the back gear
has perhaps a 2 stage reduction? What is the ratio when not in back
gear?

On Wed, 26 Nov 2008 13:14:17 -0600, "Karl Townsend"
wrote:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl


As asked, your question has an infinite number of answers. There are
an infinite number of ratios of integers that can yield a value of
1/6.1245 = 0.163279.

That said, plugging 0.163279 into my RFRAC program (see my page), we
find that that number can be approximated (using continued fractions)
by the integer ratio 8/49 with an accuracy of 0.008%. Thus whatever
gears are actually mounted, their tooth counts should come close to
being some multiple of 8/49, e.g., 16/98, 24/147, etc..

If you want a more accurate approximation than 0.008%, download the
program - one of its inputs is the desired accuracy of approximation.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.myvirtualnetwork.com/mklotz

turns of the spindle down to .01 revolution accuracy and took this data
....
Are you sure you've got the 'turns at drive' measurement to .0001 turn
accuracy?

No, I claimed .01, but i found the encoder I had temped in could move 1 or 2
degrees. I didn't want it too rigid, its not made to be clamped in a vice
and bolted to an endmill holder.

Karl

....
There's some inconsistency in your ratios. Using 163.05 : 1000 or
ratio of 0.16305, I get close matches for

8/49 = 0.16327
15/92 = 0.16304

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?

Karl

"Marv" wrote in message
...
On Wed, 26 Nov 2008 13:14:17 -0600, "Karl Townsend"
wrote:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure
the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl


As asked, your question has an infinite number of answers. There are
an infinite number of ratios of integers that can yield a value of
1/6.1245 = 0.163279.

That said, plugging 0.163279 into my RFRAC program (see my page), we
find that that number can be approximated (using continued fractions)
by the integer ratio 8/49 with an accuracy of 0.008%. Thus whatever
gears are actually mounted, their tooth counts should come close to
being some multiple of 8/49, e.g., 16/98, 24/147, etc..

If you want a more accurate approximation than 0.008%, download the
program - one of its inputs is the desired accuracy of approximation.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.myvirtualnetwork.com/mklotz

No way this is a substitute for Marv's method, but you could just use a
spreadsheet. Set up a column going from 1 to 100 (more if you want) and
multiply your fraction by each number in turn. It should be quick enough to
spot the close matches: here's a section

47 7.674113
48 7.837392
49 8.000671
50 8.16395
51 8.327229
52 8.490508

"Karl Townsend" wrote in message
anews.com...
...
There's some inconsistency in your ratios. Using 163.05 : 1000 or
ratio of 0.16305, I get close matches for

8/49 = 0.16327
15/92 = 0.16304

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?

Karl

First one can be by inspection. 6.1245 is about 6 and one eighth, or 49/8.

Generate a table in Excel using input gear teeth from 1 to 100, dividing those values by
..16305 and you'll see 15/92 or multiples are the best match....

On Nov 26, 3:31 pm, "Karl Townsend"
wrote:
...

There's some inconsistency in your ratios. Using 163.05 : 1000 or
ratio of 0.16305, I get close matches for

8/49 = 0.16327
15/92 = 0.16304

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?

Karl

Karl

Put the turns numbers in an excel spread sheet, divide, format to
display as a 3 digit fraction, 15/92, solved

CarlBoyd

"newshound" wrote: No way this is a substitute for Marv's method, but you
could just use a
spreadsheet. Set up a column going from 1 to 100 (more if you want) and
multiply your fraction by each number in turn. It should be quick enough
to
spot the close matches: here's a section

47 7.674113
48 7.837392
49 8.000671
50 8.16395
51 8.327229
52 8.490508
^^^^^^^^^^^^^^^^^^^^^
I came to the conclusion that it is 49/8, using a similar method. I used
the average ratio in Townsend's list, which was .163118, and then set up a
chart assuming thew small gear had 1 tooth, 2 teeth, 3 teeth... etc until I
came to 8 teeth, which gave me 49.04 on the large gear. Continuing the
process, I didn't come to anything close until 16/98.09. This tells me that
it has to be one of those two, or a multiple, which would be out of
reasonable range.

There may be a mathematical reason to get a weighted average from Townsend's
numbers, but what I did produces a pretty solid conclusion.

Rick wrote:
"Karl Townsend" wrote in message
anews.com...

...

There's some inconsistency in your ratios. Using 163.05 : 1000 or
ratio of 0.16305, I get close matches for

8/49 = 0.16327
15/92 = 0.16304

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?

Karl


First one can be by inspection. 6.1245 is about 6 and one eighth, or 49/8.

Generate a table in Excel using input gear teeth from 1 to 100, dividing those values by
.16305 and you'll see 15/92 or multiples are the best match....




Also I think that if the encoders don't have a common denominator with
the gears the ratios will never be exact and you will just be trying to
find the most likely gear teeth numbers based on the data and what gear
teeth numbers are sensible for the application.

"Karl Townsend" writes:

turns of the spindle down to .01 revolution accuracy and took this data
...
Are you sure you've got the 'turns at drive' measurement to .0001 turn
accuracy?

No, I claimed .01, but i found the encoder I had temped in could move 1 or 2
degrees. I didn't want it too rigid, its not made to be clamped in a vice
and bolted to an endmill holder.

I asked about .0001 because that's the accuracy of the numbers you
gave.

On Wed, 26 Nov 2008 14:31:25 -0600, "Karl Townsend"
wrote:

...
There's some inconsistency in your ratios. Using 163.05 : 1000 or
ratio of 0.16305, I get close matches for

8/49 = 0.16327
15/92 = 0.16304

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?

Karl

I used MathCAD. No doubt others will provide more erudite approaches.

Excuse my ignorance, but if you are tapping, the tap is going to self feed
once it gets started. Don't you only need to concern yourself with the
depth of the tap prior to the spindle reversing?

Seems to me that that would then be a function of the number of revolutions
rather than the speed that the tap is turning. (unless you are going too
fast in which case you will hear the snap and then call on your reserve of
magic words!)

--

__
Roger Shoaf

Important factors in selecting a mate:
1] Depth of gene pool
2] Position on the food chain.



"Karl Townsend" wrote in message
anews.com...
I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure
the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl

....
Excuse my ignorance, but if you are tapping, the tap is going to self feed
once it gets started. Don't you only need to concern yourself with the
depth of the tap prior to the spindle reversing?

Seems to me that that would then be a function of the number of
revolutions
rather than the speed that the tap is turning. (unless you are going too
fast in which case you will hear the snap and then call on your reserve of
magic words!)

I'm setting up the machine for rigid tapping on the large taps. Put the tap
right in the collet. To do this, you slave the Z-axis to the spindle. For
example, for a 3/4 x 10 tap, the spindle will move down 0.100" inches for
every revolution of the tap.

The machine can also hob gears. With a 4rth axis, advance the gear blank one
tooth for every one revolution of the spindle. This is the reason I needed
the extreme accuracy, it takes 1000s of turns of the spindle to make one
gear. For tapping, 20 turns is a lot.

Karl

In article ,
Don Foreman wrote:

Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?

A slide rule is an amazing tool for guessing gear ratios ratios, just
set up the ratio and look across the slide for matching integers

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
** Posted from http://www.teranews.com **

nick hull wrote:
In article ,
Don Foreman wrote:


Using your ratio of 1 : 6.1245 = 0.16304, 15/92 is a good match.

I might have known you'd be the one to figure it out. Surely you didn't just
guess this ratio. How'd you do it?


A slide rule is an amazing tool for guessing gear ratios ratios, just
set up the ratio and look across the slide for matching integers


Way to go!!!! Not too many of us left. :-)
...lew...

"Karl Townsend" wrote:

I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl


My attempt using Excel

163.05 1000 6.13308801


541 3318.001 3318 -1.1E-06 1.13E-06
278 1704.998 1705 5.52E-06 5.52E-06
556 3409.997 3410 5.52E-06 5.52E-06
263 1613.002 1613 -8.2E-06 8.16E-06
526 3226.004 3226 -8.2E-06 8.16E-06
571 3501.993 3502 1.18E-05 1.18E-05
511 3134.008 3134 -1.6E-05 1.56E-05
293 1796.995 1797 1.78E-05 1.78E-05
248 1521.006 1521 -2.3E-05 2.35E-05
496 3042.012 3042 -2.3E-05 2.35E-05
308 1888.991 1889 2.89E-05 2.89E-05
481 2950.015 2950 -3.2E-05 3.19E-05
323 1980.987 1981 3.89E-05 3.89E-05
233 1429.01 1429 -4.1E-05 4.08E-05
466 2858.019 2858 -4.1E-05 4.08E-05
338 2072.984 2073 4.81E-05 4.81E-05
451 2766.023 2766 -5E-05 5.03E-05
353 2164.98 2165 5.65E-05 5.65E-05
218 1337.013 1337 -6E-05 6.05E-05
436 2674.026 2674 -6E-05 6.05E-05
368 2256.976 2257 6.42E-05 6.42E-05
383 2348.973 2349 7.13E-05 7.13E-05
421 2582.03 2582 -7.1E-05 7.14E-05
398 2440.969 2441 7.78E-05 7.78E-05
203 1245.017 1245 -8.3E-05 8.31E-05
406 2490.034 2490 -8.3E-05 8.31E-05
413 2532.965 2533 8.39E-05 8.39E-05
428 2624.962 2625 8.96E-05 8.96E-05
443 2716.958 2717 9.48E-05 9.48E-05
391 2398.037 2398 -9.6E-05 9.57E-05
458 2808.954 2809 9.98E-05 9.98E-05
579 3551.058 3551 -0.0001 0.0001
473 2900.951 2901 0.000104 0.000104
488 2992.947 2993 0.000109 0.000109
188 1153.021 1153 -0.00011 0.000109
376 2306.041 2306 -0.00011 0.000109
564 3459.062 3459 -0.00011 0.000109
503 3084.943 3085 0.000113 0.000113
518 3176.94 3177 0.000117 0.000117
549 3367.065 3367 -0.00012 0.000119
533 3268.936 3269 0.00012 0.00012
548 3360.932 3361 0.000124 0.000124
361 2214.045 2214 -0.00012 0.000124
563 3452.929 3453 0.000127 0.000127
534 3275.069 3275 -0.00013 0.000129
578 3544.925 3545 0.00013 0.00013
173 1061.024 1061 -0.00014 0.00014
346 2122.048 2122 -0.00014 0.00014
519 3183.073 3183 -0.00014 0.00014
504 3091.076 3091 -0.00015 0.000152
331 2030.052 2030 -0.00016 0.000157
489 2999.08 2999 -0.00016 0.000164
158 969.0279 969 -0.00018 0.000177
316 1938.056 1938 -0.00018 0.000177
474 2907.084 2907 -0.00018 0.000177
459 2815.087 2815 -0.00019 0.00019
301 1846.059 1846 -0.0002 0.000198
444 2723.091 2723 -0.00021 0.000205
143 877.0316 877 -0.00022 0.000221
286 1754.063 1754 -0.00022 0.000221
429 2631.095 2631 -0.00022 0.000221
572 3508.126 3508 -0.00022 0.000221
557 3416.13 3416 -0.00023 0.000233
414 2539.098 2539 -0.00024 0.000238
15 91.99632 92 0.000245 0.000245

Karl Townsend wrote:
I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl


The bull gear on a Bridgeport J head has 89 teeth.
(Don't know how many on the pinion.) I had to
count them as I put a gear tooth sensor on it for
tachometer use.

Jon

Karl Townsend kirjoitti:
I'm setting up rigid tapping on my mill. The encoder is ahead of the
backgear so I'm wanting the exact gear ratio. I set up an encoder on both
the shaft before the backgear and at the cutting tool so I could measure the
turns of the spindle down to .01 revolution accuracy and took this data

Turns at tool turns at drive
1 6.1245
8 49.0573
80 490.65
163.050 1000

Is there a math wiz out there that can tell me how many teeth on the drive
gear and how many on the driven gear? (integer ratio of this data)

Karl


92 and 15 --6.133

--
Uljas