I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. Enco is no help. I downloaded a Martin Gear Catalog and am
trying to figure out what to order.

I'm measuring a Pitch Diameter = .773
How do I determine what the pressure angle is?

The valley between each tooth is radiused. Martin calls that a
Shaper-cut profile. Is that significant?

The guy a Purvis Bearing talked like this is rocket science.
Is there a better way to do this?

--
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

Rex B wrote:

How do I determine what the pressure angle is?

One way is:
If you have a gear with the same TPI and a _know_ pressure angle mesh
them together and messure the distance. If it has the expected*) one,
the unknown wheel has the same pressure angle, if not then not.

Also, if you look at the kind of gear (Norton?) chances are damned high
that it has the standard pressure angle (don't know it for imperial
based gears without looking it up in a book)

*)
Have to look in a book for the imperial based system, if you want. But
it will take about 10 hours. It's time to go to bed right here. :-)


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

Rex B wrote:
I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. ...

Me too, kinda (mine is a Jet 1024). I took the gear into a local
bearing store (Eastern Bearing). The guy searched for the longest time
and concluded that it wasn't anything standard and he couldn't help me.
This place is a Boston Gear distributor, so I figured that it wasn't
worth looking anywhere else.

Leigh (CATRUCKMAN) says that he carries Jet parts and I emailed him, but
haven't had a response. I also emailed another Jet parts dealer that I
found online. Haven't heard from him either. I'm leaning toward
hobbing my own.

Bob

Rex B wrote:

I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. ...

I finally gave up and bought a set of gear tooth gages from McMaster. It was a
dollarectomy but now I absolutely know what gear something is. Well, as long as
it's 14.5° or 20° pressure angle, that is... those are the "standard two"
nowadays. I know there exist metric gear standards but I don't know at all how
to measure those.

Hmmm ... another way would be if you could borrow some time on an optical
comparator, and if you could actually trace the profile of one of the teeth at
20X, and get a bunch of measurements, I bet you could match it up that way.

GWE

I believe that the pressure angle could be determined by measuring the
diameter over pins of two different diameters. I know this can determine the
angle of a V slot. I do not know the mathematics needed for gear teeth
angles. I have a gear tooth caliper but have not tried to learn how to use
it to determine the pressure angle.
Don Young
"Grant Erwin" wrote in message
...

Rex B wrote:

I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. ...

I finally gave up and bought a set of gear tooth gages from McMaster. It
was a dollarectomy but now I absolutely know what gear something is. Well,
as long as it's 14.5° or 20° pressure angle, that is... those are the
"standard two" nowadays. I know there exist metric gear standards but I
don't know at all how to measure those.

Hmmm ... another way would be if you could borrow some time on an optical
comparator, and if you could actually trace the profile of one of the
teeth at 20X, and get a bunch of measurements, I bet you could match it up
that way.

GWE

Don Young wrote:
I believe that the pressure angle could be determined by measuring the
diameter over pins of two different diameters. I know this can determine the
angle of a V slot. I do not know the mathematics needed for gear teeth
angles. I have a gear tooth caliper but have not tried to learn how to use
it to determine the pressure angle.
Don Young

Roll a gear across some placticine on a flat surface. You can pretty
much see the pressure angle with the help of a protractor.

Look at the included angle of the two faces. If you rolled the gear
reasonably smoothly, you should have a rack impression with straight
faces on the teeth. At least, if the gear is reasonably close to correct
tooth form to begin with.

Notice that the tooth form for 14 1/2 deg rack is pretty much an Acme
thread form tool (29 deg angle) Easy reference point to determine if it
matches or is wider, which would make it 20 deg angle (40 deg included)

Rex B wrote:
I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. Enco is no help. I downloaded a Martin Gear Catalog and am
trying to figure out what to order.

I'm measuring a Pitch Diameter = .773
How do I determine what the pressure angle is?


http://www.bostongear.com/pdf/upload..._pg133-153.pdf

Print out page 136 then hold the gear up to each of the pictures.

Nate

trevor jones wrote:

Roll a gear across some placticine on a flat surface.

That is clever! will try to remember that.

Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

Bob Engelhardt wrote:
Rex B wrote:

I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. ...


Me too, kinda (mine is a Jet 1024). I took the gear into a local
bearing store (Eastern Bearing). The guy searched for the longest time
and concluded that it wasn't anything standard and he couldn't help me.
This place is a Boston Gear distributor, so I figured that it wasn't
worth looking anywhere else.

Leigh (CATRUCKMAN) says that he carries Jet parts and I emailed him, but
haven't had a response. I also emailed another Jet parts dealer that I
found online. Haven't heard from him either. I'm leaning toward
hobbing my own.

I'm getting there myself. Never made a gear before, and frankly I don't
have that much shop-time to fool with it. I'd rather buy something even
if I have to cut the old one off the hub and size the new one to press on.
At least I have a perfect pattern, as the gear next to it is identical.

Rex

Grant Erwin wrote:

Rex B wrote:

I'm trying to replace some crashed spur gears in the QC box on an
Enco 1024. ...


I finally gave up and bought a set of gear tooth gages from McMaster. It
was a dollarectomy but now I absolutely know what gear something is.
Well, as long as it's 14.5° or 20° pressure angle, that is... those are
the "standard two" nowadays. I know there exist metric gear standards
but I don't know at all how to measure those.

The guy at the Bearing place pulled out his gear tooth gauges (didn't
know those existed) and nothing matched.

Rex

Last time I ran into this I set the gear on my scanner, took a very
large blowup of a few teeth, then compared the shape to the drawings in
machinery's handbook. Mine was very obviously a 14-1/2 degreee pressure
angle.

You can get a very accurate diametrical pitch by mating any two gears,
measuring the centerline distance, and counting the teeth in BOTH gears.
DP = total tooth count/distance.

These tricks work for inch gears, metric uses a different appoach. And
anything from ENCO should be considered to have metric gears. If you
calculate a DP that is not some nice even multiple (eg 6,10,20, 24 ,etc
etc.), more than likely you have a metric gear.

If the valley is radiused, it has no effect on gear teeth meshing, it
does reduce the ultimate load carrying capacity.

As for the rocket science, I've been experimenting with cutting sample
and prototype gears on a CNC mill. Messy yes, Rocket science, no.

Rex B wrote:
I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. Enco is no help. I downloaded a Martin Gear Catalog and am
trying to figure out what to order.

I'm measuring a Pitch Diameter = .773
How do I determine what the pressure angle is?

The valley between each tooth is radiused. Martin calls that a
Shaper-cut profile. Is that significant?

The guy a Purvis Bearing talked like this is rocket science.
Is there a better way to do this?

As the Enco 1024 is an import it is almost certain that you have
module [metric] gears and not P.D. [inch] gears.

See Law's book on gear cutting for indepth discussion of P.D. v
module. see http://www.powells.com/biblio/66-0852429118-1

I have this book and find it to be a valuable reference in
addition to telling you how to cut both involute and cycloid
gearing. Powell's is good to deal with.

======================================

On Mon, 15 Aug 2005 17:06:23 -0500, Rex B wrote:

I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. Enco is no help. I downloaded a Martin Gear Catalog and am
trying to figure out what to order.

I'm measuring a Pitch Diameter = .773
How do I determine what the pressure angle is?

The valley between each tooth is radiused. Martin calls that a
Shaper-cut profile. Is that significant?

The guy a Purvis Bearing talked like this is rocket science.
Is there a better way to do this?

F. George McDuffee wrote:
As the Enco 1024 is an import it is almost certain that you have
module [metric] gears and not P.D. [inch] gears.

See Law's book on gear cutting for indepth discussion of P.D. v
module. see http://www.powells.com/biblio/66-0852429118-1

I have this book and find it to be a valuable reference in
addition to telling you how to cut both involute and cycloid
gearing. Powell's is good to deal with.


OK, I've been eyeing this book for a while, so I ordered it. With all
respect to Powell, Amazon had it for half via some guy in Oklahoma.
I'll probably wind up grinding a single-point form tool and making a
couple of these on my minimill. I will also have to make a mandrel and
find a reamer or two. I'll probably need a better grinder, or at least
a new wheel.
And I'll get to try out that indexer I lucked onto a while back.
It's ratio is 1:48, so I won't even need to use the plate to cut this
16-tooth gear. Just cut a tooth, crank 3 times, cut, repeat 14 more
times, right?
Looks like I need to source some 1.375 round stock in leaded
steel. What alloy do I need to specify? This is a quick-change gear, so
doesn't need to be high-strength. I suspect a brass gear would do the job.
I'd enjoy this project more if I had the liesure time to give up a
day for it. I just hate having a nice tool partially assembled, so I'd
better get on it.

Much thanks for all the help, guys. I'll let you know how it goes.

Rex Burkheimer
Ft Worth

Just ran across this site.

http://www.aardvark.co.nz/pjet/gears.shtml

Pretty much exactly what I planned to do. I had not thought of using the
boring head, but since I have a brand new 3" R8 head ($10) I can use that.

- -
Rex B

Rex B wrote:
F. George McDuffee wrote:

As the Enco 1024 is an import it is almost certain that you have
module [metric] gears and not P.D. [inch] gears.
See Law's book on gear cutting for indepth discussion of P.D. v
module. see http://www.powells.com/biblio/66-0852429118-1

I have this book and find it to be a valuable reference in
addition to telling you how to cut both involute and cycloid
gearing. Powell's is good to deal with.


OK, I've been eyeing this book for a while, so I ordered it. With all
respect to Powell, Amazon had it for half via some guy in Oklahoma.
I'll probably wind up grinding a single-point form tool and making a
couple of these on my minimill. I will also have to make a mandrel and
find a reamer or two. I'll probably need a better grinder, or at least
a new wheel.
And I'll get to try out that indexer I lucked onto a while back.
It's ratio is 1:48, so I won't even need to use the plate to cut this
16-tooth gear. Just cut a tooth, crank 3 times, cut, repeat 14 more
times, right?
Looks like I need to source some 1.375 round stock in leaded steel.
What alloy do I need to specify? This is a quick-change gear, so
doesn't need to be high-strength. I suspect a brass gear would do the job.
I'd enjoy this project more if I had the liesure time to give up a
day for it. I just hate having a nice tool partially assembled, so I'd
better get on it.

Much thanks for all the help, guys. I'll let you know how it goes.

Rex Burkheimer
Ft Worth

snip
Looks like I need to source some 1.375 round stock in leaded
steel. What alloy do I need to specify? This is a quick-change gear, so
doesn't need to be high-strength. I suspect a brass gear would do the job.
It will be a major project to machine a steel gear. Because of
the low speeds/loading on the change gears we have found that
aluminium work fine [we sued some 6061 T6 we happened to have]
also the mechanical grade of micarta or formica makes good gears.
This was a common timing gear material.

Drimel tool or 1/8 air grinder will be very helpful in hand
grinding the involute profile into a single point cutter. Unless
you like grinding use the smallest piece of tool steel you can.
3/16 is plenty for 1.0 module. You will need to grind the top of
the tool down to center of the holder or grind in hook to avoid
negative rake.

Rex B wrote:

I'm measuring a Pitch Diameter = .773

How about posting all dimensions you have? #of teeth, outer diameter,
base diam., width (might give a hint to "metric").
So I (or others) can look up and see if I/they find out what it is?


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

F. George McDuffee wrote:
snip

Looks like I need to source some 1.375 round stock in leaded
steel. What alloy do I need to specify? This is a quick-change gear, so
doesn't need to be high-strength. I suspect a brass gear would do the job.

It will be a major project to machine a steel gear. Because of
the low speeds/loading on the change gears we have found that
aluminium work fine [we sued some 6061 T6 we happened to have]
also the mechanical grade of micarta or formica makes good gears.
This was a common timing gear material.

That's good to know. I have some 6061 It would make it much easier,
plus this gear would make a better "fuse" if it were AL.

Drimel tool or 1/8 air grinder will be very helpful in hand
grinding the involute profile into a single point cutter. Unless
you like grinding use the smallest piece of tool steel you can.
3/16 is plenty for 1.0 module. You will need to grind the top of
the tool down to center of the holder or grind in hook to avoid
negative rake.

I have some 3/16 cobalt steel stock which I'll probably use.


Thanks for the input

Nick Müller wrote:
How about posting all dimensions you have? #of teeth, outer diameter,
base diam., width (might give a hint to "metric").
So I (or others) can look up and see if I/they find out what it is?

Su
16 teeth
OD 7.890"
Base Dia. 7.577"
face width is .377" or 9.56mm

I've been trying to scan it, but I can't get enough contrast.

Rex B wrote:

16 teeth
OD 7.890"
Base Dia. 7.577"
face width is .377" or 9.56mm

Eh, sorry, are you pulling my leg? 16 teeth and about 200mm OD with less
than 4 mm height of teeth?
Or am I dumb and wrong with thinking that 7.89" are 200.406mm?
This gear would look _completely_ different from regular ones.

puzzled, confused and all
Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

Rex B wrote:

Grant Erwin wrote:


Rex B wrote:

I'm trying to replace some crashed spur gears in the QC box on an
Enco 1024. ...



I finally gave up and bought a set of gear tooth gages from McMaster.
It was a dollarectomy but now I absolutely know what gear something
is. Well, as long as it's 14.5° or 20° pressure angle, that is...
those are the "standard two" nowadays. I know there exist metric gear
standards but I don't know at all how to measure those.


The guy at the Bearing place pulled out his gear tooth gauges (didn't
know those existed) and nothing matched.

Metric. Yuk.

GWE

Nick Müller wrote:
Rex B wrote:


16 teeth
OD 7.890"
Base Dia. 7.577"
face width is .377" or 9.56mm


Eh, sorry, are you pulling my leg? 16 teeth and about 200mm OD with less
than 4 mm height of teeth?
Or am I dumb and wrong with thinking that 7.89" are 200.406mm?
This gear would look _completely_ different from regular ones.

LOL I'm doing too many things at once (supposedly to be working for my
employer)

That should be .789" OK, .7577" base diameter, so tooth height is .031"

So this gear is about the size of a half dollar, and about 3/8" thick
My apologies.

Rex

Rex B wrote:

That should be .789" OK, .7577" base diameter, so tooth height is .031"

OK, this doesn't qualify for a module gear. Module 1 or module 1.25 are
common and standardized and they both don't fit (OD wise). With 20° (the
standard), that is. Tooth height would be way off (should be about 2mm
or 2.5mm for Mod 1 / Mod 1.25).
There also exists a Module 1.125 (have never seen that) that would badly
match the OD (20.25mm compared to your 20.04mm).
If the manufacturer quit the 20°, there is no standard to select from
(AFAIK).

But there is a last chance. It is legal to play some tricks with
tooth-height.
If you take the time and mesh two of those gears together (may have
different #of teeth, but i need to know. And no tricks this time! :-))
and messure the distance of the centers, I'll give it another try.


Nick, gonna have a beer in the meantime ...
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

Rule to find metric module [there is an inch module but seldom
used now] is to measure the OD of the gear in mm and divide by
the number of teeth + 2.
16t +2 = 18
..789 * 25.4 = 20.046 mm
round to 20
20/18 = 1.11 module [doubtful]
assuming 1.00 module
16T +2 = 18 X 1.00 = 18mm OD
18 MM/25.4 = 0.7087 inches
Any chance of a decimal slip?
BTW -- almost all metric gears are 20 degree pressure angle.

see
http://www.littlemachineshop.com/pro...ProductID=1523
for 1 m/m gear sets for mini lathes or see
http://mdmetric.com/kgear.htm
http://www.qtcgears.com/RFQ/SpurGears.htm
http://www.google.com/url?sa=t&ct=re...MpeQsQHi-fG9Dg
http://www.sdp-si.com/herb/spk/sdp-si/D780/D780cat.htm
and a bunch more

That should be .789" OK, .7577" base diameter, so tooth height is .031"
So this gear is about the size of a half dollar, and about 3/8" thick
My apologies.
Rex

Nick Müller wrote:
Rex B wrote:

That should be .789" OK, .7577" base diameter, so tooth height is .031"


OK, this doesn't qualify for a module gear. Module 1 or module 1.25 are
common and standardized and they both don't fit (OD wise). With 20° (the
standard), that is. Tooth height would be way off (should be about 2mm
or 2.5mm for Mod 1 / Mod 1.25).
There also exists a Module 1.125 (have never seen that) that would badly
match the OD (20.25mm compared to your 20.04mm).
If the manufacturer quit the 20°, there is no standard to select from
(AFAIK).

But there is a last chance. It is legal to play some tricks with
tooth-height.
If you take the time and mesh two of those gears together (may have
different #of teeth, but i need to know. And no tricks this time! :-))
and messure the distance of the centers, I'll give it another try.

Ok, I'll look at it tonight. Part of the challenge will be figuring out
which gear meshes with it.

Nick, gonna have a beer in the meantime ...

Have two. I know I will ...

F. George McDuffee wrote:
Rule to find metric module [there is an inch module but seldom
used now] is to measure the OD of the gear in mm and divide by
the number of teeth + 2.
16t +2 = 18
.789 * 25.4 = 20.046 mm
round to 20
20/18 = 1.11 module [doubtful]
assuming 1.00 module
16T +2 = 18 X 1.00 = 18mm OD
18 MM/25.4 = 0.7087 inches
Any chance of a decimal slip?

I doubt it. I read 20.05mm off a Mitutoyo digital caliper. This was off
an identical undamaged gear. The damaged gear has all the teeth laid
over a little, so I did not trust any measurements there.

BTW -- almost all metric gears are 20 degree pressure angle.

see
http://www.littlemachineshop.com/pro...ProductID=1523
for 1 m/m gear sets for mini lathes or see
http://mdmetric.com/kgear.htm
http://www.qtcgears.com/RFQ/SpurGears.htm
http://www.google.com/url?sa=t&ct=re...MpeQsQHi-fG9Dg
http://www.sdp-si.com/herb/spk/sdp-si/D780/D780cat.htm
and a bunch more

I'll study on those later - thanks

Rex

Rex B wrote:

Have two. I know I will ...

Oh no! :-)
OK, it's midnight here in ol' Germany. I'll have a sleep and you have to
wait 9 hours to see me posting again ...

Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

Nate Weber wrote:
http://www.bostongear.com/pdf/upload..._pg133-153.pdf

That's a great link, thanks.

Print out page 136 then hold the gear up to each of the pictures.

I think you meant p 137.

Doesn't match mine. I scanned mine at high res and it appears as though
the teeth are not even involute. I.e., they are straight sided. Why
did they have to do it that way?

Bob

It is entirely possible that the gear is not a standard pitch or module. I
have checked a bunch of engine timing gears and transmission gears and have
not found any to be standard sizes.
Don Young

"Rex B" wrote in message
...

F. George McDuffee wrote:
Rule to find metric module [there is an inch module but seldom
used now] is to measure the OD of the gear in mm and divide by
the number of teeth + 2.
16t +2 = 18
.789 * 25.4 = 20.046 mm round to 20
20/18 = 1.11 module [doubtful]
assuming 1.00 module
16T +2 = 18 X 1.00 = 18mm OD
18 MM/25.4 = 0.7087 inches
Any chance of a decimal slip?

I doubt it. I read 20.05mm off a Mitutoyo digital caliper. This was off an
identical undamaged gear. The damaged gear has all the teeth laid over a
little, so I did not trust any measurements there.

BTW -- almost all metric gears are 20 degree pressure angle.

see
http://www.littlemachineshop.com/pro...ProductID=1523
for 1 m/m gear sets for mini lathes or see
http://mdmetric.com/kgear.htm
http://www.qtcgears.com/RFQ/SpurGears.htm
http://www.google.com/url?sa=t&ct=re...MpeQsQHi-fG9Dg
http://www.sdp-si.com/herb/spk/sdp-si/D780/D780cat.htm
and a bunch more

I'll study on those later - thanks

Rex

In article ,
says...
Nate Weber wrote:
http://www.bostongear.com/pdf/upload..._pg133-153.pdf

That's a great link, thanks.

Print out page 136 then hold the gear up to each of the pictures.

I think you meant p 137.

Doesn't match mine. I scanned mine at high res and it appears as though
the teeth are not even involute. I.e., they are straight sided. Why
did they have to do it that way?



How many teeth on the gear? The shape of the involute changes with the
number of teeth - the more teeth the closer they'll get to straight
sided. 135 teeth is usually the point where gear cutters call it close
enough and switch to straight teeth, but the involute form may not be
apparent to the nekkid eye well below that.

Ned Simmons

In article ,
says...
It is entirely possible that the gear is not a standard pitch or module. I
have checked a bunch of engine timing gears and transmission gears and have
not found any to be standard sizes.

Yup. Often true in machine tools as well, with the exception of change
gears, which are usually standards.

Ned Simmons

20.05mm od/(16 + 2) teeth = 1.1139
Another poster suggested there was such a thing as a 1.125 module
gear. If so this looks like a good candidate. Next question:
why would anyone spec a 1-1/8 mm module gear?

GmcD

On Tue, 16 Aug 2005 16:51:05 -0500, Rex B wrote:

F. George McDuffee wrote:
Rule to find metric module [there is an inch module but seldom
used now] is to measure the OD of the gear in mm and divide by
the number of teeth + 2.
16t +2 = 18
.789 * 25.4 = 20.046 mm
round to 20
20/18 = 1.11 module [doubtful]
assuming 1.00 module
16T +2 = 18 X 1.00 = 18mm OD
18 MM/25.4 = 0.7087 inches
Any chance of a decimal slip?

I doubt it. I read 20.05mm off a Mitutoyo digital caliper. This was off
an identical undamaged gear. The damaged gear has all the teeth laid
over a little, so I did not trust any measurements there.

BTW -- almost all metric gears are 20 degree pressure angle.

see
http://www.littlemachineshop.com/pro...ProductID=1523
for 1 m/m gear sets for mini lathes or see
http://mdmetric.com/kgear.htm
http://www.qtcgears.com/RFQ/SpurGears.htm
http://www.google.com/url?sa=t&ct=re...MpeQsQHi-fG9Dg
http://www.sdp-si.com/herb/spk/sdp-si/D780/D780cat.htm
and a bunch more

I'll study on those later - thanks

Rex

Bob Engelhardt wrote:
Nate Weber wrote:

http://www.bostongear.com/pdf/upload..._pg133-153.pdf

That's a great link, thanks.

Print out page 136 then hold the gear up to each of the pictures.


I think you meant p 137.

Doesn't match mine. I scanned mine at high res and it appears as though
the teeth are not even involute. I.e., they are straight sided. Why
did they have to do it that way?

Bob

This 16-tooth unit definitely has a break about halfway up the tooth

F. George McDuffee wrote:
20.05mm od/(16 + 2) teeth = 1.1139
Another poster suggested there was such a thing as a 1.125 module
gear. If so this looks like a good candidate. Next question:
why would anyone spec a 1-1/8 mm module gear?

GmcD

Well, it's a Chinese lathe, so we are dealing with Oriental logic, such
as it is. Probably inscrutable to us non-Asians

On Tue, 16 Aug 2005 16:51:05 -0500, Rex B wrote:

F. George McDuffee wrote:

Rule to find metric module [there is an inch module but seldom
used now] is to measure the OD of the gear in mm and divide by
the number of teeth + 2.
16t +2 = 18
.789 * 25.4 = 20.046 mm
round to 20
20/18 = 1.11 module [doubtful]
assuming 1.00 module
16T +2 = 18 X 1.00 = 18mm OD
18 MM/25.4 = 0.7087 inches
Any chance of a decimal slip?

I doubt it. I read 20.05mm off a Mitutoyo digital caliper. This was off
an identical undamaged gear. The damaged gear has all the teeth laid
over a little, so I did not trust any measurements there.


BTW -- almost all metric gears are 20 degree pressure angle.

see
http://www.littlemachineshop.com/pro...ProductID=1523
for 1 m/m gear sets for mini lathes or see
http://mdmetric.com/kgear.htm
http://www.qtcgears.com/RFQ/SpurGears.htm
http://www.google.com/url?sa=t&ct=re...MpeQsQHi-fG9Dg
http://www.sdp-si.com/herb/spk/sdp-si/D780/D780cat.htm
and a bunch more

I'll study on those later - thanks

Rex

xray wrote:
On Wed, 17 Aug 2005 13:02:02 -0500, F. George McDuffee spake

Next question:
why would anyone spec a 1-1/8 mm module gear?



I think this gear was from the QC box. Its task is to produce exact
output ratios by meshing between many gears on fixed shafts. I can't
fathom how much fun it must be to design something like that, but I'd
think using non-standard gears might be the easiest way to get it done.

This 16T gear is on the input (left) side of the box, on the shaft with
the main gear-stack. The gears on the left are 16/32-16/32-16, turning
independently on bronze bushings, then a cast boss extending from the
case, then the multi-gear progressive stack which are keyed to the shaft.

It meshes with a 32-tooth gear on one side and the change-lever gear on
the other side. The power flow goes:

Input stub shaft gear
Center shaft, left side (the gear in question is here)
left change lever gear
Change lever shaft
Right change lever gear
stepped gears
gear on leadscrew or gear on power apron drive shaft.

F. George McDuffee wrote:

Another poster suggested there was such a thing as a 1.125 module
gear.

It was me. And no, I didn't suggest it. Because it wouldn't fit and it
is damned uncommon.


If so this looks like a good candidate. Next question:
why would anyone spec a 1-1/8 mm module gear?

It has to do with logic. ;-)
In the standard, there are arithmetic rows. These are grouped. The most
preferred group is the one most common. I.e. Mod. 1, Mod. 1.5. The next
group contains Mod. 1,25. The 3rd group (and you need to have a lot of
reason to select from this) contains Mod. 1.125. Chances are damned low,
that anybody would use a module from the 3rd group. Chances that you get
a stock gear from that group in _any_ shop are even lower.

Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

xray wrote:

I can't
fathom how much fun it must be to design something like that, but I'd
think using non-standard gears might be the easiest way to get it done.

Yes. In most cases, you will find one one or two pairs that are
standard. The others are non-standard.
But, and I asked that Rex, if you do have a norton gear-box, all gears
are very likely to be standard.

Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...