I'm restoring an ancient Myford ML7 for use in model engine
building.(K5973)

The spindle and whitemetal bearings are in very good condition but the
gears in the headstock are all shot.
The gears are a mixture of cast iron, mazak and bronze.
The cast iron gears seem to have stood up to the 50 years of use quite
well.
The mazak gears show some wear. The bronze gear teeth are almost worn
to a feather.
This would all point to cast iron being a better material for the
replacement gears.

My Hercus (south bend clone) is all cast iron gears and shows almost
no wear on the gear train teeth. again this points to cast iron being
a better gear material in this type of application.

What is the general consensus of opinion on the materials for making
lathe gear wheels?

I have bars of meehanite which are big enough to give me most wheels.
Of the various cast irons is meehanite a good material for making long
lasting gears?

The gears for the myford and the hercus dont match at all, even in
similar diameters. this points to one set being 20 degree pitch
angle(PA) and one set being 14.5 degree PA.
does anyone know what PA the myford gears were? even after reading
Ivan Laws book on gears and gear cutting I still cant look at a gear
in my hand and work out just by looking at it what the pressure angle
would be. are the teeth of 14 and a half degree gears fatter or
thinner than similar gear diameter 20 degree pressure angle gears?

a 65 tooth bull wheel seems near useless for detent style dividing.
has anyone rebuilt a myford bullwheel in some other tooth size that
has proven to still be adequate?

so many questions :-)

If I surrender I can still buy replacement gears from myford but
cutting my replacement gears would be quite cool.

comments welcome.
Stealth Pilot

"Stealth Pilot" wrote in message
...

I'm restoring an ancient Myford ML7 for use in model engine
building.(K5973)

The spindle and whitemetal bearings are in very good condition but the
gears in the headstock are all shot.
The gears are a mixture of cast iron, mazak and bronze.
The cast iron gears seem to have stood up to the 50 years of use quite
well.
The mazak gears show some wear. The bronze gear teeth are almost worn
to a feather.
This would all point to cast iron being a better material for the
replacement gears.

My Hercus (south bend clone) is all cast iron gears and shows almost
no wear on the gear train teeth. again this points to cast iron being
a better gear material in this type of application.

What is the general consensus of opinion on the materials for making
lathe gear wheels?

I have bars of meehanite which are big enough to give me most wheels.
Of the various cast irons is meehanite a good material for making long
lasting gears?

The gears for the myford and the hercus dont match at all, even in
similar diameters. this points to one set being 20 degree pitch
angle(PA) and one set being 14.5 degree PA.
does anyone know what PA the myford gears were? even after reading
Ivan Laws book on gears and gear cutting I still cant look at a gear
in my hand and work out just by looking at it what the pressure angle
would be. are the teeth of 14 and a half degree gears fatter or
thinner than similar gear diameter 20 degree pressure angle gears?

a 65 tooth bull wheel seems near useless for detent style dividing.
has anyone rebuilt a myford bullwheel in some other tooth size that
has proven to still be adequate?

so many questions :-)

If I surrender I can still buy replacement gears from myford but
cutting my replacement gears would be quite cool.

What is your capability for cutting gears? Are you using gear cutters on a
mill?

Having done that, commercially and with good equipment, I'd say you're in
for more work that it's worth -- in money, at least. If you enjoy the
work...well, you enjoy the work. Then it doesn't matter.

As for materials, I'll leave that to others with more experience. My
experience with highly-loaded bronze gears starts and stops with a '57 Alfa
Romeo engine that had a bronze distributor-drive gear. My '58 had a steel
gear. The bronze wore out in a hurry; the steel never wore out when I had
it, and that was a high-rpm race engine. But there are many different grades
of bronze, and their performance in high-load-bearing applications also
varies widely. I wouldn't attempt to generalize.

--
Ed Huntress

Stealth Pilot wrote:

I'm restoring an ancient Myford ML7 for use in model engine
building.(K5973)

The spindle and whitemetal bearings are in very good condition but the
gears in the headstock are all shot.
The gears are a mixture of cast iron, mazak and bronze.
The cast iron gears seem to have stood up to the 50 years of use quite
well.
The mazak gears show some wear. The bronze gear teeth are almost worn
to a feather.
This would all point to cast iron being a better material for the
replacement gears.

My Hercus (south bend clone) is all cast iron gears and shows almost
no wear on the gear train teeth. again this points to cast iron being
a better gear material in this type of application.

What is the general consensus of opinion on the materials for making
lathe gear wheels?

I have bars of meehanite which are big enough to give me most wheels.
Of the various cast irons is meehanite a good material for making long
lasting gears?

The gears for the myford and the hercus dont match at all, even in
similar diameters. this points to one set being 20 degree pitch
angle(PA) and one set being 14.5 degree PA.
does anyone know what PA the myford gears were? even after reading
Ivan Laws book on gears and gear cutting I still cant look at a gear
in my hand and work out just by looking at it what the pressure angle
would be. are the teeth of 14 and a half degree gears fatter or
thinner than similar gear diameter 20 degree pressure angle gears?

a 65 tooth bull wheel seems near useless for detent style dividing.
has anyone rebuilt a myford bullwheel in some other tooth size that
has proven to still be adequate?

so many questions :-)

If I surrender I can still buy replacement gears from myford but
cutting my replacement gears would be quite cool.

comments welcome.
Stealth Pilot


Pressure Angle

Diametrical Pitch.

Myford gears are 20 DP, 14.5 PA. You won't need a full set of cutters,
just most of the set of eight.
There are a couple sources of replacement gears for Myfords, other
than the factory, and if you have to buy the set of cutters retail, the
replacement gears are a pretty attractive proposition.

If Hercus followed South Bend's lead (it is a licenced clone of South
Bend) then the gears are IIRC 18 DP(or 16 DP) 14.5 PA. These are
not a "preferred" size, and thus limit the number of sources.

Myford gears will be iron. Any other materials will be from some other
source,except the first gears in the train from the spindle to the
leadscrew, which may be fibre, and are meant to provide a "fuse" in the
event of a crash.

If you roll out a snake of plasticine and roll the gear over it, it
will leave a rack form impression. The number of degrees either side of
90, is equal to the PA of the gear.
Got a protractor?

The Super 7 bull gear is 60 teeth.. The most cost effective way to
change over is to rebuild the ML7, sell it, and buy a Super7. Decide if
you wish to rebuild the lathe, or build engines as a hobby.

The ML7 I had, had a 60 tooth worm grafted on to the spindle, to allow
the use of a dividing mechanism similar to a Radford dividing
attachment. I had the worm gear, but not the attachmentshrug. I have
some pictures around, somewhere, and will email them if you email a request.
To direct index, the cheapest method would be to mount a plate on the
back end of the spindle, with a index pin on an arm.

Cheers
Trevor Jones

On Fri, 2 Nov 2007 09:54:31 -0400, "Ed Huntress"
wrote:


"Stealth Pilot" wrote in message
.. .

I'm restoring an ancient Myford ML7 for use in model engine
building.(K5973)


If I surrender I can still buy replacement gears from myford but
cutting my replacement gears would be quite cool.

What is your capability for cutting gears? Are you using gear cutters on a
mill?

I am about to buy a mill.
I've been looking for ages for an australian supplier of involute
cutters. I'm fairly certain that Suttons, Patience and Nicholson and
Frost all make them but havent been able to find a distributor.
the local engineering suppliers (Blackwoods) seem to have dropped them
as an item in their catalogue.
There is an online model suppliers in Sydney selling involute cutters
at $105 each. I'll try them.

Having done that, commercially and with good equipment, I'd say you're in
for more work that it's worth -- in money, at least. If you enjoy the
work...well, you enjoy the work. Then it doesn't matter.

cant say that I am discouraged here. I set myself two targets for my
workshop upgrade. I want to master screw cutting and gear cutting.
My frustrations with screw cutting are due to the properties of the
alloy I'm trying to use and not having sufficient back rake.

gear cutting in a non commercial environment should not be a torture.
I could use the hercus cross slide as a shaper and plane the inter
tooth gap out.
I could do similar in the shaper.
looking at the wear patterns on the ML7 it is apparent that one gear
was machined with the cutter slightly above or below centre. this
slight misalignment seems to be the root cause of all the wear in the
headstock gear train so it is motivating me to get sorted out with a
proper involute gear cutter instead of just approximating the shape as
is so often done.

As for materials, I'll leave that to others with more experience. My
experience with highly-loaded bronze gears starts and stops with a '57 Alfa
Romeo engine that had a bronze distributor-drive gear. My '58 had a steel
gear. The bronze wore out in a hurry; the steel never wore out when I had
it, and that was a high-rpm race engine. But there are many different grades
of bronze, and their performance in high-load-bearing applications also
varies widely. I wouldn't attempt to generalize.

Last night I replaced the nut on my hercus cross slide with a new one
supplied by Hercus. The original was bronze. the new one is cast iron.
(might I add that I had a very close look at the machining of the nut.
I have to say that Hercus do immaculate! machining. The guys running
the factory now are superb machinists....but I digress)
The thing that I found interesting is that the cross slide screw is a
slop free fit in the new cast iron nut which indicates to me that all
of the noticeable wear was in the bronze nut.
I can only put all this down to cast iron being a better oil film
retainer than bronze. For cast iron components to display so little
wear they must be better at retaining an oil film. They arent any
harder.

Stealth ...ooops TUMESFFF :-)

On Fri, 02 Nov 2007 21:03:59 GMT, Trevor Jones
wrote:


The gears for the myford and the hercus dont match at all, even in
similar diameters. this points to one set being 20 degree pitch
angle(PA) and one set being 14.5 degree PA.
does anyone know what PA the myford gears were? even after reading
Ivan Laws book on gears and gear cutting I still cant look at a gear
in my hand and work out just by looking at it what the pressure angle
would be. are the teeth of 14 and a half degree gears fatter or
thinner than similar gear diameter 20 degree pressure angle gears?



Pressure Angle

Diametrical Pitch.

pitch angle ...duh! I meant pressure angle.

Myford gears are 20 DP, 14.5 PA. You won't need a full set of cutters,
just most of the set of eight.
There are a couple sources of replacement gears for Myfords, other
than the factory, and if you have to buy the set of cutters retail, the
replacement gears are a pretty attractive proposition.

If Hercus followed South Bend's lead (it is a licenced clone of South
Bend) then the gears are IIRC 18 DP(or 16 DP) 14.5 PA. These are
not a "preferred" size, and thus limit the number of sources.

Myford gears will be iron. Any other materials will be from some other
source,except the first gears in the train from the spindle to the
leadscrew, which may be fibre, and are meant to provide a "fuse" in the
event of a crash.

there are two sets of gears involved here.
the gears from the tail end of the spindle to the leadscrew are all
cast iron.
the 65tooth bullwheel is cast iron.
the21/56tooth backgear is mazak and they carry the myford part number.
the gear which drives the pulley cluster is a remanufactured gear in
bronze


If you roll out a snake of plasticine and roll the gear over it, it
will leave a rack form impression. The number of degrees either side of
90, is equal to the PA of the gear.
Got a protractor?

I initially didnt understand what you wrote there that but the diagram
in Ivan Laws book put the finger on it. the angle of the face of the
tooth in the rack form equals the pressure angle. I must admit that I
never realised the significance of that piece of information,
presented as it is in a whole sea of dry theory.
gods it is easy! plasticene it out and measure directly.


The Super 7 bull gear is 60 teeth.. The most cost effective way to
change over is to rebuild the ML7, sell it, and buy a Super7. Decide if
you wish to rebuild the lathe, or build engines as a hobby.

The ML7 I had, had a 60 tooth worm grafted on to the spindle, to allow
the use of a dividing mechanism similar to a Radford dividing
attachment. I had the worm gear, but not the attachmentshrug. I have
some pictures around, somewhere, and will email them if you email a request.
To direct index, the cheapest method would be to mount a plate on the
back end of the spindle, with a index pin on an arm.

Cheers
Trevor Jones

Trevor thanks for the gear info. I could not find it anywhere.
I dont know whether you are being pessimistic about the ML7 or not.
I guess I'll find out.
In all I want to remake 12 gears in cast iron. how hard could it be?

the model diesel engines will come later.

TUMESFFF

On Fri, 02 Nov 2007 21:03:59 GMT, Trevor Jones wrote:


Myford gears will be iron. Any other materials will be from some other
source,except the first gears in the train from the spindle to the
leadscrew, which may be fibre, and are meant to provide a "fuse" in the
event of a crash.


Slight correction. The gear that is attached to the mandrel pulley is bronze
and also forms the bearing for the pulley on the mandrel. That gear I would
re-make with bronze, since it runs at fairly high sped against the mandrel
when in back gear. If it's worn out, one must assume that the other back gear
gears are also shot. Definitely all 20DP, 14.5 PA though. That one, with the
integral pulley would set the OP back about $150 plus shipping :-O


regards
Mark Rand
RTFM

Stealth Pilot wrote:

Trevor thanks for the gear info. I could not find it anywhere.
I dont know whether you are being pessimistic about the ML7 or not.
I guess I'll find out.
In all I want to remake 12 gears in cast iron. how hard could it be?

the model diesel engines will come later.

TUMESFFF



Can you track down a copy of George H Thomas's books? He designed, and
had published in Model Engieer, among other things, a variant of the
Radford dividing attachment, that is, while mainly for the S7, shown
modified in a chapter on the ML7 and discusses at lenth, the
capabilities that are available using the 65 tooth gear.

In there, I am certain that the DP and PA of the bull gears is
mentioned, as he discusses and shows his math for, the making of a worm
that will engage the bull gear.

Of course, you could work it out from the diameter and tooth count.

Leave the Ivan Law book in the loo, and absorb it in small doses. Each
time you go through it, a few more bits of the puzzle will fall into place.

It is reasonably safe to say that the gears would be 14.5 degrees PA,
as they were pretty much the norm. Same as an Acme screw thread cutting
tool, which I doubt is a coincidence.

Making gears on manual machines is actually quite easy. Not drooling
on yourself, and not losing your place on the dividing head, are the
major challenges. Usually the state of mind that brings on the former,
is responsible for the latter.
Direct indexing off of borrowed gears is the way! :-)

Just keep in mind that you do not mill teeth, but the spaces between them!

Do you have a foundry in your area that will entertain small lot
castings? Planning on using iron barstock?

Cheers
Trevor Jones

"Stealth Pilot" wrote in message
...
On Fri, 2 Nov 2007 09:54:31 -0400, "Ed Huntress"
wrote:


"Stealth Pilot" wrote in message
. ..

I'm restoring an ancient Myford ML7 for use in model engine
building.(K5973)


If I surrender I can still buy replacement gears from myford but
cutting my replacement gears would be quite cool.

What is your capability for cutting gears? Are you using gear cutters on a
mill?

I am about to buy a mill.
I've been looking for ages for an australian supplier of involute
cutters. I'm fairly certain that Suttons, Patience and Nicholson and
Frost all make them but havent been able to find a distributor.
the local engineering suppliers (Blackwoods) seem to have dropped them
as an item in their catalogue.
There is an online model suppliers in Sydney selling involute cutters
at $105 each. I'll try them.

Having done that, commercially and with good equipment, I'd say you're in
for more work that it's worth -- in money, at least. If you enjoy the
work...well, you enjoy the work. Then it doesn't matter.

cant say that I am discouraged here. I set myself two targets for my
workshop upgrade. I want to master screw cutting and gear cutting.
My frustrations with screw cutting are due to the properties of the
alloy I'm trying to use and not having sufficient back rake.

gear cutting in a non commercial environment should not be a torture.
I could use the hercus cross slide as a shaper and plane the inter
tooth gap out.
I could do similar in the shaper.
looking at the wear patterns on the ML7 it is apparent that one gear
was machined with the cutter slightly above or below centre. this
slight misalignment seems to be the root cause of all the wear in the
headstock gear train so it is motivating me to get sorted out with a
proper involute gear cutter instead of just approximating the shape as
is so often done.

You've set quite a task for yourself. d8-) The only comment I'll make here
is that using a lathe cross slide for a shaper will get awfully old after
your second or third tooth cut, and it's hell on the leadscrew and nut. They
aren't made to handle that much load.


As for materials, I'll leave that to others with more experience. My
experience with highly-loaded bronze gears starts and stops with a '57
Alfa
Romeo engine that had a bronze distributor-drive gear. My '58 had a steel
gear. The bronze wore out in a hurry; the steel never wore out when I had
it, and that was a high-rpm race engine. But there are many different
grades
of bronze, and their performance in high-load-bearing applications also
varies widely. I wouldn't attempt to generalize.

Last night I replaced the nut on my hercus cross slide with a new one
supplied by Hercus. The original was bronze. the new one is cast iron.
(might I add that I had a very close look at the machining of the nut.
I have to say that Hercus do immaculate! machining. The guys running
the factory now are superb machinists....but I digress)
The thing that I found interesting is that the cross slide screw is a
slop free fit in the new cast iron nut which indicates to me that all
of the noticeable wear was in the bronze nut.
I can only put all this down to cast iron being a better oil film
retainer than bronze. For cast iron components to display so little
wear they must be better at retaining an oil film. They arent any
harder.

Many cross slides have bronze nuts, and it's generally a better material for
the job than cast iron. If it's a proper bearing grade of bronze and if it's
properly lubricated, it will last a long time. Bronze on steel can run at
about half the clearance of cast iron on steel and it will exhibit less
friction. But if it's allowed to run dry, cast iron will take it a lot
better than bronze will.

It sounds like someone made a lot of parts for your lathe out of some kind
of copper alloy. Whether it's a bearing-brade bronze is a question.

Anyway, have fun with your projects. It sounds like you have the ambition
for it, so more power to you.

--
Ed Huntress