[Paul[_19_]]

I've got a Grizzly 9 x 20 lathe and need to cut some threads at 4 tpi. Any
thread charts for this lathe I've got only go down to 6 tpi. Question is,
can I cut 4 tpi on this lathe? And what gears do I use? Has anyone done
this? FWIW, when cutting coarse threads I use a hand crank to turn the
spindle.
TIA,
Paul

[Lloyd E. Sponenburgh[_3_]]

"Paul" fired this volley in
:

I've got a Grizzly 9 x 20 lathe and need to cut some threads at 4
tpi.
Any thread charts for this lathe I've got only go down to 6 tpi.
Question is, can I cut 4 tpi on this lathe? And what gears do I use?
Has anyone done this? FWIW, when cutting coarse threads I use a hand
crank to turn the spindle.

So, what's the prob. with using the backgears, and turning under
power?

Sure, you can turn that, if you have the gears to make the ratio.

You know the pitch of your leadscrew. You know the number of teeth on
your spindle gear. You can do the rest of the math yourself.

Just make sure everything is lubed well, and the gears aren't too
tight on clearance, since your lead screw will be turning faster than
your spindle.

Also, you'll probably have to custom-grind a single-point tool to make
up for the geometric changes when that high a slope in the screw is
called for. Remember, a level tool cuts narrower than its width in a
sloped cut.

You'll either have to adjust the attack angle or side-rake on the tool
to cut approximately square in the thread, or adjust the included
angle of the point wider. I haven't done the trig for you, but expect
the included angle on the point ought to be more like 70 degrees than
60.

The side-rake solution is cleaner, because then you can control the
back rake more easily.

LLoyd

[John]

Paul wrote:
I've got a Grizzly 9 x 20 lathe and need to cut some threads at 4 tpi. Any
thread charts for this lathe I've got only go down to 6 tpi. Question is,
can I cut 4 tpi on this lathe? And what gears do I use? Has anyone done
this? FWIW, when cutting coarse threads I use a hand crank to turn the
spindle.
TIA,
Paul



One way to do it is to get a set of gears that will give you a 1:2 ratio
and put them into the geartrain for the feed. Run the thread pitch
setting on the lathe at 8 tpi. I don't know what gears you have to work
with but you could also decrease the diameter of a driven gear by 2 or
increase the diameter of a driving gear by 2 and get the same result.

John

[Paul[_19_]]

Well, Jeese, you guys made me have to actually think. There's a concept. I'm
so used to just looking at the threading chart then slapping this gear here
and that gear there, I forgot what was actually going on. Thanks for the
headslap to bring me to my senses. Got it figured out. I'm happy
Paul

[Michael Koblic]

Lloyd E. Sponenburgh wrote:
"Paul" fired this volley in
:

I've got a Grizzly 9 x 20 lathe and need to cut some threads at 4
tpi. Any thread charts for this lathe I've got only go down to 6 tpi.
Question is, can I cut 4 tpi on this lathe? And what gears do I use?
Has anyone done this? FWIW, when cutting coarse threads I use a hand
crank to turn the spindle.

So, what's the prob. with using the backgears, and turning under
power?


I would be surprised if Grizzly 9x20 has backgears. Their lowest speed is
usually in excess of 100 rpm.

--
Michael Koblic,
Campbell River, BC

[Lloyd E. Sponenburgh[_3_]]

"Michael Koblic" fired this volley in
:

I would be surprised if Grizzly 9x20 has backgears. Their lowest speed
is usually in excess of 100 rpm.


Whew! I hope that's not the case. But, if it is, then that's the
genesis of "yet another project". A lathe with threading capability has
GOT to have back gears! Got to! (damn! I'll MAKE the backshaft!)

G
LLoyd

[Gunner Asch[_4_]]

On Mon, 19 Jan 2009 20:38:45 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Michael Koblic" fired this volley in
:

I would be surprised if Grizzly 9x20 has backgears. Their lowest speed
is usually in excess of 100 rpm.


Whew! I hope that's not the case. But, if it is, then that's the
genesis of "yet another project". A lathe with threading capability has
GOT to have back gears! Got to! (damn! I'll MAKE the backshaft!)

G
LLoyd


My daily driver lathe doesnt have any backgears at all. Just a two
speed motor.

And the reeves drive variable speed.

Course it is a Hardinge HLV-H......

Biggest problem I found with it is that it wont thread bigger than 11
tpi. No way to do it either.

Course on the other end...IRRC..it does thread down to 120 tpi....
And Metric.....


Shrug


Gunner

Whenever a Liberal utters the term "Common Sense approach"....grab your
wallet, your ass, and your guns because the sombitch is about to do
something damned nasty to all three of them.

[# 42]

"Michael Koblic" wrote in message
...
Lloyd E. Sponenburgh wrote:
"Paul" fired this volley in
:

I've got a Grizzly 9 x 20 lathe and need to cut some threads at 4
tpi. Any thread charts for this lathe I've got only go down to 6 tpi.
Question is, can I cut 4 tpi on this lathe? And what gears do I use?
Has anyone done this? FWIW, when cutting coarse threads I use a hand
crank to turn the spindle.

So, what's the prob. with using the backgears, and turning under
power?


I would be surprised if Grizzly 9x20 has backgears. Their lowest speed is
usually in excess of 100 rpm.

--
Michael Koblic,
Campbell River, BC



Yup. No back gears. Slowest speed is 130 rpm

[Leon Fisk]

On Mon, 19 Jan 2009 17:07:05 -0800, "Paul"
wrote:

Well, Jeese, you guys made me have to actually think. There's a concept. I'm
so used to just looking at the threading chart then slapping this gear here
and that gear there, I forgot what was actually going on. Thanks for the
headslap to bring me to my senses. Got it figured out. I'm happy
Paul


Maybe this will help some for the next time:

http://www.metalworking.com/dropbox/...he_threads.txt

http://www.metalworking.com/dropbox/...he_threads.pdf

I had to go find it again myself. Lost my copy awhile back
when the computer went down...

--
Leon Fisk
Grand Rapids MI/Zone 5b
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