[Bruno]

A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Thanks!

[Jon Elson]

Bruno wrote:
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?
Have him get a magnifier and count again. It is IMPOSSIBLE that
a lathe was built with a 14-T threading dial gear, unless the
guy who sold it to him is well known for practical jokes!

I'd expect if 2 teeth were missing, he'd clearly notice.

Jon

[Bruno]

Jon Elson wrote:

Bruno wrote:
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?
Have him get a magnifier and count again. It is IMPOSSIBLE that
a lathe was built with a 14-T threading dial gear, unless the
guy who sold it to him is well known for practical jokes!

I'd expect if 2 teeth were missing, he'd clearly notice.

Jon
I asked him twice. He said he checked three times and always came up
14. He just got the lathe delivered yesterday and he's about 1500
miles from me, otherwise I'd run over and count myself.

I can't figure out how it would work, so I'm trying to figure out what
they were thinking when they made it. Perhaps they also made a 7 TPI
leadscrew ;-).

-Bruno

[Don Young]

"Bruno" wrote in message
...
Jon Elson wrote:

Bruno wrote:
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?
Have him get a magnifier and count again. It is IMPOSSIBLE that
a lathe was built with a 14-T threading dial gear, unless the
guy who sold it to him is well known for practical jokes!

I'd expect if 2 teeth were missing, he'd clearly notice.

Jon
I asked him twice. He said he checked three times and always came up
14. He just got the lathe delivered yesterday and he's about 1500
miles from me, otherwise I'd run over and count myself.

I can't figure out how it would work, so I'm trying to figure out what
they were thinking when they made it. Perhaps they also made a 7 TPI
leadscrew ;-).

-Bruno
I would strongly suspect a practical joke or a manufacturing error. It would
not be the first time.

Don Young

[Lew Hartswick]

Bruno wrote:

A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Thanks!
Sure the Clausing/Metosa have a 40 tooth gear and 20 marks on
the thread dial. Just don't engage between the marks.
...lew...

[Jim Wilkins]

Bruno wrote:
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.

Masybe someone put it on for a special job and forgot it. The
threading dial gear on my South Bend has 32 teeth.

Thanks for reminding me to check it. It came from a different lathe
and needed cleaning and re-timing.

[Wes[_2_]]

Bruno wrote:

A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Thanks!

That makes no sense at all other than the 8 TPI screw. Does your friend
imbibe a bit too much?

Wes

[John Martin]

On Feb 11, 9:49*pm, Jon Elson wrote:
Bruno wrote:
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? *I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Have him get a magnifier and count again. *It is IMPOSSIBLE that
a lathe was built with a 14-T threading dial gear, unless the
guy who sold it to him is well known for practical jokes!

I'd expect if 2 teeth were missing, he'd clearly notice.

Jon

Nothing is impossible, although it of course would not work. Could a
manufacturer have gotten some 14 tooth gears mixed in with the 16's?
Maybe....

It is possible that the guy doesn't know how to count thread pitch,
and is including the first AND last thread in his count. Sort of like
saw teeth, where a handsaw of 8 points and 7 teeth per inch is the
same thing.

That said, I've never heard of a 7 TPI lead screw, and can't imagine
why you'd want one.

John Martin

[Mechanical Magic]

On Feb 11, 6:18 pm, Bruno wrote:
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Thanks!



I suspect it is for a Metric lead screw. Screwup at the Chinese
factory.
DJ

[Mark Rand]

On Tue, 12 Feb 2008 07:37:32 -0800 (PST), John Martin
wrote:



That said, I've never heard of a 7 TPI lead screw, and can't imagine
why you'd want one.

John Martin


Does it count that my BCA jig borer (actually an Excel Model "0" ) has got
14tpi leadscrews on both axes of the table?


In this case, someone installed 7/16" Whitworth screws, either when it was
made in the middle of WWII, or at some later date. They'll get replaced with
10 or 20tpi ACME ones when I rebuild it.

Mark Rand
RTFM

[Steve Lusardi]

Sounds like he's got a metric thread dial or he's blind.
Steve

"Bruno" wrote in message
...
A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Thanks!

[John Martin]

On Feb 12, 1:50*pm, Mark Rand wrote:
On Tue, 12 Feb 2008 07:37:32 -0800 (PST), John Martin
wrote:



That said, I've never heard of a 7 TPI lead screw, and can't imagine
why you'd want one.

John Martin

Does it count that my BCA jig borer (actually an Excel Model "0" ) has got
14tpi leadscrews on both axes of the table?

In this case, someone installed 7/16" Whitworth screws, either when it was
made in the middle of WWII, or at some later date. They'll get replaced with
10 or 20tpi ACME ones when I rebuild it.

Mark Rand
RTFM

Yeah, it counts. Confusing, though - at least to me. On a lathe, you
can use about any pitch leadscrew you want and get the desired feed
through the change gears. On a screw used for positioning, though -
unless you've got some gears between the dial and the screw - you'd
have to be working in fourteenths (or some fraction thereof) of an
inch, no? Not in the usual thousandths. What is on the dials?

John Martin

[Lew Hartswick]

John Martin wrote:

That said, I've never heard of a 7 TPI lead screw, and can't imagine
why you'd want one.

John Martin
Well I never heard of a 9 tpi thread but that is what the
Kurt vise on one of the mills at school has in it.
...lew...

[John Martin]

On Feb 12, 6:07*pm, Lew Hartswick wrote:
John Martin wrote:

That said, I've never heard of a 7 TPI lead screw, and can't imagine
why you'd want one.

John Martin

Well I never heard of a 9 tpi thread but that is what the
Kurt vise on one of the mills at school has in it.
* * ...lew...

Big difference between a vise screw and a lead screw, though. All the
vise screw has to do is move the jaw - it doesn't matter where it is
and it doesn't have to be repeatable.

The lead or feed screw is different. If it is a 9 TPI screw, one turn
will move the tool or part one ninth of an inch. Great if you happen
to work in ninths of an inch, but most people don't. Most work in
thousandths. So you graduate the dial in thousandths. There will be
111 of them. Plus a "remainder" of .111111....... You can graduate
the dial with 111 OK, but it's pretty tough to handle that remainder.

John Martin

[Jon Elson[_2_]]

Bruno wrote:
Jon Elson wrote:


Bruno wrote:

A friend just got a Birmingham 12x36 lathe and tells me the leadscrew
is 8 TPI, yet the thread dial gear is 14 teeth, with 8 marks on it.
Anyone else out there with a similar lathe? Does it have the same
thread dial? I would think a 16 tooth thread dial would be
appropriate. What's the thinking behind 14, and will it really work?

Have him get a magnifier and count again. It is IMPOSSIBLE that
a lathe was built with a 14-T threading dial gear, unless the
guy who sold it to him is well known for practical jokes!

I'd expect if 2 teeth were missing, he'd clearly notice.

Jon

I asked him twice. He said he checked three times and always came up
14. He just got the lathe delivered yesterday and he's about 1500
miles from me, otherwise I'd run over and count myself.

I can't figure out how it would work, so I'm trying to figure out what
they were thinking when they made it. Perhaps they also made a 7 TPI
leadscrew ;-).
Oh, yeah! That would be GREAT for 4-40 and 6-32 threads! Might work OK
for the
pipe threads, though.

I know there was a 14-tooth gear as part of the set for Atlas
change-gear lathes, maybe he used what he had when the proper gear was
trashed. (I don't really see what good it would do, though, except to
make the dial turn. You couldn't really make any use of the dial.)
The gears on the thread dials I've seen have all been helical, though.

Jon

[Mark Rand]

On Tue, 12 Feb 2008 13:38:01 -0800 (PST), John Martin
wrote:

On Feb 12, 1:50*pm, Mark Rand wrote:
On Tue, 12 Feb 2008 07:37:32 -0800 (PST), John Martin
wrote:



That said, I've never heard of a 7 TPI lead screw, and can't imagine
why you'd want one.

John Martin

Does it count that my BCA jig borer (actually an Excel Model "0" ) has got
14tpi leadscrews on both axes of the table?

In this case, someone installed 7/16" Whitworth screws, either when it was
made in the middle of WWII, or at some later date. They'll get replaced with
10 or 20tpi ACME ones when I rebuild it.

Mark Rand
RTFM

Yeah, it counts. Confusing, though - at least to me. On a lathe, you
can use about any pitch leadscrew you want and get the desired feed
through the change gears. On a screw used for positioning, though -
unless you've got some gears between the dial and the screw - you'd
have to be working in fourteenths (or some fraction thereof) of an
inch, no? Not in the usual thousandths. What is on the dials?

John Martin

That's the problem. One dial is 0-100. The other dial is 0-100-0-100 (eg.
0-200). Not very useful really :-(

I'd like to have had a talk with the chap that did it and seen what was in his
mind. Possibly with the aid of an auger bit...


Mark Rand
RTFM