I am trying to make my first real part. A replacement pivot pin for a lock
blade knife. It's a cheap knife. I could have thrown it away and bought 50
of them for the time I have spent so far, but it's a learning process. Its
taught me a lot so far, and the knife was a gift from my son a couple years
ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems. Since
the cap on the pin is .383 that part is easy. The shaft of the pin is .204
however. Whenever I get down to about .225 - .230 the tool bit wants to
climb down under the work piece. At this point several things go wrong all
at once. My tool post tilts towards the work piece no matter how tightly I
have adjusted the slide tension bolts (and the slide will still move)
forcing me to have to adjust it again. And it usually bends the work piece.
Also, sometimes I get nasty gouges and galls on the stainless steel rod I am
working with. Also it chips the carbide cutter and I have to resharpen it.

Not sure what I should do. Obviously finding a way to stiffen the tool post
would help, but I am not sure how to do that. The first idea I have had is
to put the slide tension adjustment bolts and spacer on the back side of the
slide. Then there is no mechanical room for the tool post to lift up on the
front side. That in itself will require some work on the mill. It would
make it more difficult to adjust tension on the slide, but I think it would
need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex shaft
handle, and chuck it up in the tool post with a small end mill. I would
have to watch the speed very carefully as in one direction I'll get a
combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.

A manual should have come with the lathe showing the correct turning
speed for the diameter you are working with. At this point you should
be using the highest speed possible for your lathe. Second possibility
is your tool is not exactly centered on the shaft you are turning, and
finally, the tool may not be sharp enough. Any and all could
contribute to what you are experiencing, and there are probably some
other possibilities, but check these first.

Paul


On Jan 3, 10:53*am, "Bob La Londe" wrote:
I am trying to make my first real part. *A replacement pivot pin for a lock
blade knife. *It's a cheap knife. *I could have thrown it away and bought 50
of them for the time I have spent so far, but it's a learning process. *Its
taught me a lot so far, and the knife was a gift from my son a couple years
ago for Christmas.

Here is my problem. *I Can turn down to about .250 with no problems. *Since
the cap on the pin is .383 that part is easy. *The shaft of the pin is ..204
however. *Whenever I get down to about .225 - .230 the tool bit wants to
climb down under the work piece. *At this point several things go wrong all
at once. *My tool post tilts towards the work piece no matter how tightly I
have adjusted the slide tension bolts (and the slide will still move)
forcing me to have to adjust it again. *And it usually bends the work piece.
Also, sometimes I get nasty gouges and galls on the stainless steel rod I am
working with. *Also it chips the carbide cutter and I have to resharpen it.

Not sure what I should do. *Obviously finding a way to stiffen the tool post
would help, but I am not sure how to do that. *The first idea I have had is
to put the slide tension adjustment bolts and spacer on the back side of the
slide. *Then there is no mechanical room for the tool post to lift up on the
front side. *That in itself will require some work on the mill. *It would
make it more difficult to adjust tension on the slide, but I think it would
need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex shaft
handle, and chuck it up in the tool post with a small end mill. *I would
have to watch the speed very carefully as in one direction I'll get a
combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. *I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.

Bob La Londe wrote:
I am trying to make my first real part. A replacement pivot pin for a
lock blade knife. It's a cheap knife. I could have thrown it away and
bought 50 of them for the time I have spent so far, but it's a learning
process. Its taught me a lot so far, and the knife was a gift from my
son a couple years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the
pin is .204 however. Whenever I get down to about .225 - .230 the tool
bit wants to climb down under the work piece.

You prolly have forgotten more about this than I will never know
so please pardon the question.

Is your tool bit set a tad low in the tool post?
As on page 21:
http://www.littlemachineshop.com/Inf...UsersGuide.pdf

--Winston

--

Congratulations Robert Piccinini and Steven A. Burd, WalMart Publicists of the Year!

On Jan 3, 1:53*pm, "Bob La Londe" wrote:
...
Here is my problem. *I Can turn down to about .250 with no problems. *Since
the cap on the pin is .383 that part is easy. *The shaft of the pin is ..204
however. *Whenever I get down to about .225 - .230 the tool bit wants to
climb down under the work piece. *At this point several things go wrong all
at once. *...

HSS, honed sharp after grinding, at center height, removing ~0.005 per
pass. Support the work with the tailstock. I've made stainless #0-80
screws 1.25" long that way.

jsw

" wrote in message
...
A manual should have come with the lathe showing the correct turning
speed for the diameter you are working with.

Not really. It showed gear change and safety stuff, but not much else.

At this point you should
be using the highest speed possible for your lathe.

I did not know that. I will try max speed and see what happens.

Second possibility
is your tool is not exactly centered on the shaft you are turning,

Well, if I look closely it actually looks like it is a tiny bit above
center, but that could be an illusion. Maybe a few thousandths.

and
finally, the tool may not be sharp enough.

A good possibility. I suppose I could swap out to a brand new tool for last
few hundredths.

Any and all could
contribute to what you are experiencing, and there are probably some
other possibilities, but check these first.

Thanks Paul.

Bob

"Winston" wrote in message
...
Bob La Londe wrote:
I am trying to make my first real part. A replacement pivot pin for a
lock blade knife. It's a cheap knife. I could have thrown it away and
bought 50 of them for the time I have spent so far, but it's a learning
process. Its taught me a lot so far, and the knife was a gift from my
son a couple years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the pin
is .204 however. Whenever I get down to about .225 - .230 the tool bit
wants to climb down under the work piece.

You prolly have forgotten more about this than I will never know
so please pardon the question.

LOL. I know next to nothing about running a metal lathe so I don't think
so.

Is your tool bit set a tad low in the tool post?

I do not think so. Not sure how to measure it, but if anything when I bring
the free center upto the tool the tool looks like it might be a couple
thousandths above center.

As on page 21:
http://www.littlemachineshop.com/Inf...UsersGuide.pdf

I will read.

Bob

"Jim Wilkins" wrote in message
...
On Jan 3, 1:53 pm, "Bob La Londe" wrote:
...
Here is my problem. I Can turn down to about .250 with no problems. Since
the cap on the pin is .383 that part is easy. The shaft of the pin is
.204
however. Whenever I get down to about .225 - .230 the tool bit wants to
climb down under the work piece. At this point several things go wrong
all
at once. ...

HSS, honed sharp after grinding, at center height, removing ~0.005 per

Wow, that's pretty aggressive. I have been only removing .002 .003 per
pass. I will try a much faster turn rate as one poster suggested.

pass. Support the work with the tailstock.

I need to get some center drills I guess.

I've made stainless #0-80
screws 1.25" long that way.

With my beginning level of skill that task looks all but impossible. I am
impressed.

Bob La Londe wrote:

I am trying to make my first real part. A replacement pivot pin for a lock
blade knife. It's a cheap knife. I could have thrown it away and bought 50
of them for the time I have spent so far, but it's a learning process. Its
taught me a lot so far, and the knife was a gift from my son a couple years
ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems. Since
the cap on the pin is .383 that part is easy. The shaft of the pin is .204
however. Whenever I get down to about .225 - .230 the tool bit wants to
climb down under the work piece. At this point several things go wrong all
at once. My tool post tilts towards the work piece no matter how tightly I
have adjusted the slide tension bolts (and the slide will still move)
forcing me to have to adjust it again. And it usually bends the work piece.
Also, sometimes I get nasty gouges and galls on the stainless steel rod I am
working with. Also it chips the carbide cutter and I have to resharpen it.

Not sure what I should do. Obviously finding a way to stiffen the tool post
would help, but I am not sure how to do that. The first idea I have had is
to put the slide tension adjustment bolts and spacer on the back side of the
slide. Then there is no mechanical room for the tool post to lift up on the
front side. That in itself will require some work on the mill. It would
make it more difficult to adjust tension on the slide, but I think it would
need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex shaft
handle, and chuck it up in the tool post with a small end mill. I would
have to watch the speed very carefully as in one direction I'll get a
combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.



Follow rest to prevent the part from climbing up over the tool bit?

"Bob La Londe" wrote in message
...
I am trying to make my first real part. A replacement pivot pin for a lock
blade knife. It's a cheap knife. I could have thrown it away and bought
50 of them for the time I have spent so far, but it's a learning process.
Its taught me a lot so far, and the knife was a gift from my son a couple
years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the pin
is .204 however. Whenever I get down to about .225 - .230 the tool bit
wants to climb down under the work piece. At this point several things go
wrong all at once. My tool post tilts towards the work piece no matter
how tightly I have adjusted the slide tension bolts (and the slide will
still move) forcing me to have to adjust it again. And it usually bends
the work piece. Also, sometimes I get nasty gouges and galls on the
stainless steel rod I am working with. Also it chips the carbide cutter
and I have to resharpen it.

Not sure what I should do. Obviously finding a way to stiffen the tool
post would help, but I am not sure how to do that. The first idea I have
had is to put the slide tension adjustment bolts and spacer on the back
side of the slide. Then there is no mechanical room for the tool post to
lift up on the front side. That in itself will require some work on the
mill. It would make it more difficult to adjust tension on the slide, but
I think it would need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex
shaft handle, and chuck it up in the tool post with a small end mill. I
would have to watch the speed very carefully as in one direction I'll get
a combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.


When I got my mini lathe, one of the many issues I found was that the slide
could rock slightly even with the gib plates tight. I took off the slide,
put sharpie marker on the ways, and set it back down and slid it back and
forth. The areas where the marker rubbed off showed where it was making
contact. As expected there were high spots in the middle of both the flat
and V-shaped ways on the slide. After adjusting this with some careful
manual filing and grinding, the slide was much more stable.

Bob,
The problem is caused because you have more load on the tool than the lathe can handle. Small lathes do not like carbide because
they generate more drag than HSS. This is caused by not having enough tool relief in the cutting tool. This is actually easy to
see. Set the tool right up to the work and look from the tail stock. use a light and a magnifying glass if required. You can
further reduce drag by redusing the radius on the nose of the tool. Also the scoring you see in the work is an indicator of this
excessive drag. The scores are being cut by the chips, because they are being trapped between the tool and the work. You need
more relief after the cutting nose. Please also note that very often the finish can be improved with a coarser feed. The larger
chip will clear the work easier than a very fine one. In theory the nose radius must be equal to 2.5 times the feed distance in
one revolution.

Practice makes perfect...
Steve

Sounds like you are a tad above center. It cuts OK on large stock, binds
then grabs as the work gets smaller. Take a piece of thin stock or
feeler gage, run the tool up to the work with the gage in between. If
you are high it will tilt toward the lathe, below it will tilt toward you.

Your choice of SS for your first parts is unfortunate. If the bit ever
stops cutting, you will work harden the surface, you will never get the
cut restarted on your small machine.

You are regrinding CARBIDE? I'd be using some good cobalt high speed
steel bits. Much sharper.

Bob La Londe wrote:
I am trying to make my first real part. A replacement pivot pin for a
lock blade knife. It's a cheap knife. I could have thrown it away and
bought 50 of them for the time I have spent so far, but it's a learning
process. Its taught me a lot so far, and the knife was a gift from my
son a couple years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the
pin is .204 however. Whenever I get down to about .225 - .230 the tool
bit wants to climb down under the work piece. At this point several
things go wrong all at once. My tool post tilts towards the work piece
no matter how tightly I have adjusted the slide tension bolts (and the
slide will still move) forcing me to have to adjust it again. And it
usually bends the work piece. Also, sometimes I get nasty gouges and
galls on the stainless steel rod I am working with. Also it chips the
carbide cutter and I have to resharpen it.

Not sure what I should do. Obviously finding a way to stiffen the tool
post would help, but I am not sure how to do that. The first idea I
have had is to put the slide tension adjustment bolts and spacer on the
back side of the slide. Then there is no mechanical room for the tool
post to lift up on the front side. That in itself will require some
work on the mill. It would make it more difficult to adjust tension on
the slide, but I think it would need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex
shaft handle, and chuck it up in the tool post with a small end mill. I
would have to watch the speed very carefully as in one direction I'll
get a combined cutting speed of the lathe and the end mill. By cutting
in two directions simultaneously I should get a very good finish, and
with the cutting surface at the middle instead of the top edge of the
tool should greatly reduce the tendency of the tool to try and climb
under the work piece. I'm wondering if this is one of those things
where a combination machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.

On Jan 3, 7:14*pm, "Bob La Londe" wrote:


finally, the tool may not be sharp enough.

A good possibility. *I suppose I could swap out to a brand new tool for last
few hundredths.

Bob

If you do not have a bench grinder or belt sander, you ought to think
hard about getting one. Grinding a HSS tool bit seems to be a problem
for a lot of people. But it is really quite simple. If you already
have a HSS tool bit, you can use touch it up using a bench stone or
some sandpaper backed by something flat.

Why don't you post where you are located. There might be someone
close who could show you a lot in not too many minutes. Or maybe you
could use a digital camera or webcam to show close ups of what you are
doing. Just do not post pictures in RCM.


Dan

On Jan 3, 1:16*pm, "Bob La Londe" wrote:
"Winston" wrote in message

...

Bob La Londe wrote:
I am trying to make my first real part. *A replacement pivot pin for a
lock blade knife. *It's a cheap knife. *I could have thrown it away and
bought 50 of them for the time I have spent so far, but it's a learning
process. *Its taught me a lot so far, and the knife was a gift from my
son a couple years ago for Christmas.

Here is my problem. *I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. *The shaft of the pin
is .204 however. *Whenever I get down to about .225 - .230 the tool bit
wants to climb down under the work piece.

You prolly have forgotten more about this than I will never know
so please pardon the question.

LOL. *I know next to nothing about running a metal lathe so I don't think
so.

Is your tool bit set a tad low in the tool post?

I do not think so. *Not sure how to measure it, but if anything when I bring
the free center upto the tool the tool looks like it might be a couple
thousandths above center.

As on page 21:
http://www.littlemachineshop.com/Inf...UsersGuide.pdf

I will read.

Bob

A common trick is to pinch a 6" scale vertically between the tip of
the tool bit and the workpiece. If the top of the scale leans away
from you, then you're tip is above the workpiece centerline. If the
top of the scale is leaning towards you, then your tool bit is below
the centerline. Basically you're using the scale to indicate the
tangent of the circle (if viewed from the end).

"Denis G." wrote in message
...
On Jan 3, 1:16 pm, "Bob La Londe" wrote:
"Winston" wrote in message

...

Bob La Londe wrote:
I am trying to make my first real part. A replacement pivot pin for a
lock blade knife. It's a cheap knife. I could have thrown it away
and
bought 50 of them for the time I have spent so far, but it's a
learning
process. Its taught me a lot so far, and the knife was a gift from my
son a couple years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the
pin
is .204 however. Whenever I get down to about .225 - .230 the tool
bit
wants to climb down under the work piece.

You prolly have forgotten more about this than I will never know
so please pardon the question.

LOL. I know next to nothing about running a metal lathe so I don't think
so.

Is your tool bit set a tad low in the tool post?

I do not think so. Not sure how to measure it, but if anything when I
bring
the free center upto the tool the tool looks like it might be a couple
thousandths above center.

As on page 21:
http://www.littlemachineshop.com/Inf...UsersGuide.pdf

I will read.

Bob

A common trick is to pinch a 6" scale vertically between the tip of
the tool bit and the workpiece. If the top of the scale leans away
from you, then you're tip is above the workpiece centerline. If the
top of the scale is leaning towards you, then your tool bit is below
the centerline. Basically you're using the scale to indicate the
tangent of the circle (if viewed from the end).

That is a good trick. I will remember that one.

My screw / pin is complete. Took some doing since I don't have any of the
right tooling for this.

I do not have an center drills either so I center marked it with a 1/64 ball
mill in the drill chuck, and used that hole for my live center.

Cranking the speed up to max helped a lot. I used a very narrow cutter to
rough to size, and then a wider cutter at .001 per pass for the last .003.
The gave me my pin shaft diameter. Then I had to cut a little smaller to
make an extended shaft for a nut. The original was just pressed and peaned
over. I cut mine to press in and then have a nut threaded on. I cut a
shoulder and then extended shaft was threaded to 10x32. Didn't do that with
the lathe though. I just don't have a tool bit I felt comfortable doing
that with. Instead I used a die, and then reversed the die for the last 2
thread up to the shoulder. Sadly I got some marks on the head in the vice
even clamping the pin between two blocks of wood.

NOT GONNA POST A PICTURE. As a shoulder screw sitting on the desk it looks
pretty good, but when I snapped a picture I could see all the imperfections.
LOL.

Definitely want to get some other bits before I tackle something this small
again.

The first suggestion I would make is to use hand-ground HSS cutting tools
for use with any of the light duty imported lathes, for typical turning and
facing operations, on large or small workpieces.
Carbide cutting tools aren't a solution or subsitute/shortcut for small
lathe users. Most carbide cutting tools don't even have particularly sharp
cutting edges.

I'm not a machinist, I'm just familiar with the small lathes from China and
the issues involved with the low quality of finishing that these machines
exhibit.
I had a little previous experience from a 1 year high school machine shop
class, and later set up and operated machine shop for manufacturing light
duy machinery. More recently, I became interested in metalworking again, and
started buying small lathes and associated tooling.

There are some tool dealers that sell pre-ground HSS cutting tools in sets.
http://www.lathemaster.com/HSS%20LATHE%20TOOLS.htm
This 3/8" set isn't appropriate for a mini-lathe, but I've seen 5/16" sets
on eBay.. maybe some dealers have 1/4" sets, too.

All beginning small lathe users should familiarize themselves with tool
grinding geometry as a starting point. Get a handful of HSS blanks to begin
the learning process, and duplicate the grinds of the pre-ground tools, and
also other configurations that might be needed.

Read the excellent Tool_Grinding tutorial by Harold Vordos concerning
grinding wheels and procedures for hand grinding HSS cutting tools.
http://twoloonscoffee.com/download/

For general lathe usage, read some instructional info such as South Bend's
How To Run A Lathe booklet, or some basic machining practices type books.

Another useful source of info is Shop Reference for Students and Apprentices
available from Enco, published by the same company that produces Machinery's
Handbook.
http://www.use-enco.com/CGI/INSRIT?P...&PMPXNO=947354

As Anorton pointed out, there are often quality issues with new small lathes
from China. One can't assume that everything is snug and properly fitted.

One method that will show the user where problems are, involving fit and or
adjustments, is to place a short bar (about 8") in the toolpost (simulating
a long cutting tool) and apply finger or thumb pressure to see where
loose-fitting dovetailed components are causing problems.

Any beginner should buy some easily machined materials to work with,
starting out.
Cold and hot rolled steel are cheap, but they aren't easy to produce good
finishes with, as introductory materials. Choosing some leaded steel alloys
will generally produce much better results.
Choosing machinable grades of stainless steels will eliminate the
frustration of trying to make parts from unknown grades of stainless/mystery
metal. Some grades of stainless are very difficult to machine on small
lathes.

Setting the cutting tool edge on the centerline of the workpiece (also the
center of the spindle and tailstock bore) can be accomplished with a center
gage that the user fabricates, or aligning the cutting edge with a dead
center point in either the spindle or tailstock, or by using the steel rule
method.

The steel rule method involves placing a pocket-sized rule beween the
cutting tool tip and the outer surface of a piece of mounted round stock. As
the tool tip approaches the rule against the round workpiece (or test bar),
the rule becomes confined between two points, pointing in a direction that
indicates if the cutting tool edge/tip is on the centerline.
When the cutting tool is adjusted up or down, the rule changes position.
When the rule is "perfectly" vertical, the cutting tool edge is located on
the centerline.
The steel rule doesn't need to actually be a steel rule, it can be any flat,
straight, smooth piece of thin flat stock, such as a section of stiff feeler
gage stock.
A section of stiff feeler gage stock is actually better than a steel rule,
since it's surfaces are completely flat, where a rule is partly covered with
engraving.

Some users of small lathes from China will make a tall toolpost with a wide
base that mounts directly onto the cross slide, eliminating the compound
slide when they are just turning stock, and don't need the compound feed.
This is a work-around to eliminate the extra flexing introduced by the
compound slide.

It may be necessary to investigate many other potential quality issues with
the mini-lathe, although it can get quite involved. The spindle bearing on
my 9x20 model wasn't seated properly, and caused a lot of chatter, for
example. There were various other problems that had a detrimental effect on
performance with that model.

I doubt that the flex shaft-endmill will work, as the setup won't be rigid
enough. The combination machines that I'm familiar with aren't capable of
operating the mill and lathe simulaneously, as most of them only have one
motor, and it's only engaged for one operation or the other.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Bob La Londe" wrote in message
...
I am trying to make my first real part. A replacement pivot pin for a lock
blade knife. It's a cheap knife. I could have thrown it away and bought
50 of them for the time I have spent so far, but it's a learning process.
Its taught me a lot so far, and the knife was a gift from my son a couple
years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the pin
is .204 however. Whenever I get down to about .225 - .230 the tool bit
wants to climb down under the work piece. At this point several things go
wrong all at once. My tool post tilts towards the work piece no matter
how tightly I have adjusted the slide tension bolts (and the slide will
still move) forcing me to have to adjust it again. And it usually bends
the work piece. Also, sometimes I get nasty gouges and galls on the
stainless steel rod I am working with. Also it chips the carbide cutter
and I have to resharpen it.

Not sure what I should do. Obviously finding a way to stiffen the tool
post would help, but I am not sure how to do that. The first idea I have
had is to put the slide tension adjustment bolts and spacer on the back
side of the slide. Then there is no mechanical room for the tool post to
lift up on the front side. That in itself will require some work on the
mill. It would make it more difficult to adjust tension on the slide, but
I think it would need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex
shaft handle, and chuck it up in the tool post with a small end mill. I
would have to watch the speed very carefully as in one direction I'll get
a combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.

In article ,
"anorton" wrote:

"Bob La Londe" wrote in message
...
I am trying to make my first real part. A replacement pivot pin for a lock
blade knife. It's a cheap knife. I could have thrown it away and bought
50 of them for the time I have spent so far, but it's a learning process.
Its taught me a lot so far, and the knife was a gift from my son a couple
years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of the pin
is .204 however. Whenever I get down to about .225 - .230 the tool bit
wants to climb down under the work piece. At this point several things go
wrong all at once. My tool post tilts towards the work piece no matter
how tightly I have adjusted the slide tension bolts (and the slide will
still move) forcing me to have to adjust it again. And it usually bends
the work piece. Also, sometimes I get nasty gouges and galls on the
stainless steel rod I am working with. Also it chips the carbide cutter
and I have to resharpen it.

Not sure what I should do. Obviously finding a way to stiffen the tool
post would help, but I am not sure how to do that. The first idea I have
had is to put the slide tension adjustment bolts and spacer on the back
side of the slide. Then there is no mechanical room for the tool post to
lift up on the front side. That in itself will require some work on the
mill. It would make it more difficult to adjust tension on the slide, but
I think it would need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex
shaft handle, and chuck it up in the tool post with a small end mill. I
would have to watch the speed very carefully as in one direction I'll get
a combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.


When I got my mini lathe, one of the many issues I found was that the slide
could rock slightly even with the gib plates tight. I took off the slide,
put sharpie marker on the ways, and set it back down and slid it back and
forth. The areas where the marker rubbed off showed where it was making
contact. As expected there were high spots in the middle of both the flat
and V-shaped ways on the slide. After adjusting this with some careful
manual filing and grinding, the slide was much more stable.

I bet that this is a good idea in any case, but I would use Hi-Spot Blue
(http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=00264101) instead of the
marker, and a set of small machinist scrapers (such as
http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=05844113) and small hand
stones in place of the files (which can cut too quickly).

The process is simple and safe albeit slow:

Disassemble sliding part and remove extraneous hardware. (Take lots of
pictures while doing this.)

Clean off the mating surfaces. Smear a very thin layer of hi-spot blue
onto the bed (not the sliding part). Set the sliding part down on the
bed and slide back and forth. Pick sliding part up carefully in a
vertical motion. Flip sliding part over and look. If everywhere that is
supposed to contact the bed is a more-or-less even mottled shade of
blue, you are done. If the pattern is uneven, which is likely
especially at first, carefully scrape a tiny bit of metal (like 0.0001")
off the highest (usually the bluest spot, unless down pressure is too
high yielding a donut pattern) spot. Repeat.

Reassemble. All rocking should be gone.

This scraping-in process always works, and cannot get away from one, but
does require patience. And wear old clothes. Hi-spot blue will stain
everything. And your hands will look like you got the dye pack at the
local bank.


Joe Gwinn

Bob La Londe wrote:
My screw / pin is complete. Took some doing since I don't have any of
the right tooling for this.


Excellent!

I took a machining course at a local community college and learned
some good stuff, very inexpensively. 'Enjoyed the heck out of it
because I had a pal along to share the experience.

Highly recommended.

--Winston


--

Congratulations Robert Piccinini and Steven A. Burd, WalMart Publicists of the Year!

On Sun, 3 Jan 2010 15:23:18 -0700, "Bob La Londe" wrote:

My screw / pin is complete. Took some doing since I don't have any of the
right tooling for this.

I do not have an center drills either so I center marked it with a 1/64 ball
mill in the drill chuck, and used that hole for my live center.

Cranking the speed up to max helped a lot. I used a very narrow cutter to
rough to size, and then a wider cutter at .001 per pass for the last .003.
The gave me my pin shaft diameter. Then I had to cut a little smaller to
make an extended shaft for a nut. The original was just pressed and peaned
over. I cut mine to press in and then have a nut threaded on. I cut a
shoulder and then extended shaft was threaded to 10x32. Didn't do that with
the lathe though. I just don't have a tool bit I felt comfortable doing
that with. Instead I used a die, and then reversed the die for the last 2
thread up to the shoulder. Sadly I got some marks on the head in the vice
even clamping the pin between two blocks of wood.

NOT GONNA POST A PICTURE. As a shoulder screw sitting on the desk it looks
pretty good, but when I snapped a picture I could see all the imperfections.
LOL.

Definitely want to get some other bits before I tackle something this small
again.


Bob....what is the maximum size tool bit your lathe can use? The
"normal" size?

Ive got a fair amount of HSS kicking around and Id not mind grinding you
up a couple sets of tools and sending em off to you to play with.
Right,left, groove, cutoff and threading types ok?

send your shipping address to and Ill get
something out to you by next weekend


Gunner



"I am for doing good to the poor, but I differ in opinion of the
means. I think the best way of doing good to the poor, is not
making them easy in poverty, but leading or driving them out of
it. In my youth I travelled much, and I observed in different
countries, that the more public provisions were made for the
poor the less they provided for themselves, and of course became
poorer. And, on the contrary, the less was done for them, the
more they did for themselves, and became richer." -- Benjamin
Franklin, /The Encouragement of Idleness/, 1766

On 2010-01-03, wrote:
A manual should have come with the lathe showing the correct turning
speed for the diameter you are working with.

Hmm ... I have never seen a modern lathe manual which has this
information -- just how the controls work -- if you are lucky.

Accessory books, like the _How to Use a Lathe_ books by South
Bend and Atlas (each focused on their particular line of machines) may
have general information about how to calculate the speed for a given
SFM (Surface Feet per Minute), but you need another book (like
_Machinery's Handbook_), or to look it up on the web to determine the
proper cutting speeds for a specific combination of workpiece alloy and
tool material. You get faster speeds with carbide tools than with HSS,
and faster with HSS than with the old carbon steel tools. So -- you
look up the SFM from the workpiece alloy and the tool material, then
calculate the RPM from the starting diameter of the workpiece and the
SFM which you just looked up.

At this point you should
be using the highest speed possible for your lathe.

Given the maximum speed likely available in a "mini lathe", and
the size of your workpiece, yes, I think that this is probably right.
If you start getting chips which turn blue and you are using HSS
tooling, you may be turning too fast, but I doubt that you can turn that
fast with that diameter of workpiece.

Second possibility
is your tool is not exactly centered on the shaft you are turning, and
finally, the tool may not be sharp enough. Any and all could
contribute to what you are experiencing, and there are probably some
other possibilities, but check these first.

Indeed so.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2010-01-03, Denis G. wrote:
On Jan 3, 1:16*pm, "Bob La Londe" wrote:
"Winston" wrote in message

...

Bob La Londe wrote:
I am trying to make my first real part. *A replacement pivot pin for a
lock blade knife. *It's a cheap knife. *I could have thrown it away and
bought 50 of them for the time I have spent so far, but it's a learning
process. *Its taught me a lot so far, and the knife was a gift from my
son a couple years ago for Christmas.

Here is my problem. *I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. *The shaft of the pin
is .204 however. *Whenever I get down to about .225 - .230 the tool bit
wants to climb down under the work piece.

Looking at this part again -- I have to ask -- how far is the
workpiece sticking out of the lathe chuck? Generally, for something
held only in the chuck, the maximum extension should be about four times
the diameter -- and as you turn the diameter down, you have to shorten
the workpiece a bit. The workpiece tends to flex upward, and climb over
the tool bit.

Now -- do you have a live center for the lathe's tailstock? If
so, can you center drill the end of the workpiece and support it with
the live center? You may have to leave a piece of larger diameter near
the live center, and cut it off when you are done. Oh yes -- also
beware of parting off while the workpiece is supported with a live
center. It will jam interestingly as you get to the final cutoff point.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Jan 3, 11:53*am, "Bob La Londe" wrote:
I am trying to make my first real part. *A replacement pivot pin for a lock
blade knife. *It's a cheap knife. *I could have thrown it away and bought 50
of them for the time I have spent so far, but it's a learning process. *Its
taught me a lot so far, and the knife was a gift from my son a couple years
ago for Christmas.

Here is my problem. *I Can turn down to about .250 with no problems. *Since
the cap on the pin is .383 that part is easy. *The shaft of the pin is ..204
however. *Whenever I get down to about .225 - .230 the tool bit wants to
climb down under the work piece. *At this point several things go wrong all
at once. *My tool post tilts towards the work piece no matter how tightly I
have adjusted the slide tension bolts (and the slide will still move)
forcing me to have to adjust it again. *And it usually bends the work piece.
Also, sometimes I get nasty gouges and galls on the stainless steel rod I am
working with. *Also it chips the carbide cutter and I have to resharpen it.

Not sure what I should do. *Obviously finding a way to stiffen the tool post
would help, but I am not sure how to do that. *The first idea I have had is
to put the slide tension adjustment bolts and spacer on the back side of the
slide. *Then there is no mechanical room for the tool post to lift up on the
front side. *That in itself will require some work on the mill. *It would
make it more difficult to adjust tension on the slide, but I think it would
need to be adjusted less often as well.

The other idea I had is to make a tool holder for a good quality flex shaft
handle, and chuck it up in the tool post with a small end mill. *I would
have to watch the speed very carefully as in one direction I'll get a
combined cutting speed of the lathe and the end mill. By cutting in two
directions simultaneously I should get a very good finish, and with the
cutting surface at the middle instead of the top edge of the tool should
greatly reduce the tendency of the tool to try and climb under the work
piece. *I'm wondering if this is one of those things where a combination
machine might be able to do the job faster and easier.

Or maybe I am totally missing the point.

You REALLY need this book:
http://www.amazon.com/Mini-Lathe-Wor...2586475&sr=1-1

Has how to actually set the thing up to do various tasks as well as
improvements. It's the manual that should have come with.

I've not used carbide in those small lathes, it really needs something
more rigid. HSS is easy to grind to whatever profile is needed and if
you pick up a thread gauge, you can make your own threading tools.

There are also mini-lathe web sites devoted to the 7xs, you might want
to google up a few.

Stan

On Sun, 3 Jan 2010 12:14:25 -0700, "Bob La Londe"
wrote:

" wrote in message
...
A manual should have come with the lathe showing the correct turning
speed for the diameter you are working with.

Not really. It showed gear change and safety stuff, but not much else.

At this point you should
be using the highest speed possible for your lathe.

I did not know that. I will try max speed and see what happens.

Second possibility
is your tool is not exactly centered on the shaft you are turning,

Well, if I look closely it actually looks like it is a tiny bit above
center, but that could be an illusion. Maybe a few thousandths.

Hold your 6" steel scale vertically between the tool bit and the work.
Advance the cross feed until the tool bit holds the scale against the
work piece. Is the scale vertical or tilted forward or back? Figure
out whether the tool is center height, above or below center?

Center it!

and
finally, the tool may not be sharp enough.

A good possibility. I suppose I could swap out to a brand new tool for last
few hundredths.

Any and all could
contribute to what you are experiencing, and there are probably some
other possibilities, but check these first.

Thanks Paul.

Bob

Learn to sharpen a HHS tool and use them! Save the carbide for hard
stuff and production. Self ground HSS tool bits allow you considerable
more flexibility in tooling then pre-ground carbide tools.

As far as speed goes, learn to calculate cutting speeds. Make up a
chart of "recommended cutting speeds" and use it until you get a feel
for the material (then use it anyway :-)

Regards,

J.B.

On Jan 4, 5:40*am, "DoN. Nichols" wrote:

* * * * Given the maximum speed likely available in a "mini lathe", and
the size of your workpiece, yes, I think that this is probably right.
If you start getting chips which turn blue and you are using HSS
tooling, you may be turning too fast, but I doubt that you can turn that
fast with that diameter of workpiece.

* * * * Good Luck,
* * * * * * * * DoN.

When I took a night school machinging course years ago, the
instructor said that you should be getting chips that come off shiny
but turn light blue as they cool. He also said that HSS tools should
last about an hour before you need to resharpen them. He was talking
about using bigger machines and optimizing the time machining versus
the time sharpening tools. I usually do not try to remove metal that
fast, but I am not trying to make a living doing machining.

Dan

Hi, Bob.
I see that you have already gotten a ton of great input on this
topic. I read all the first level posts, but not all of the deeper ones,
so I hope I'm not wasting your time, but here's my 2 cents:

The work should never stick out of the chuck more than 3 times the diameter.
This means that you really need to get some center drills and get
used to turning between centers.
In case it didn't come clear already, the reason that carbide cutting
tools aren't good for you is that carbide chips easily and therefore
they have to make the cutting edge very strong, which means,
essentially, dull. The posts that say to switch to HSS are "right on".
But, here's a thought about the carbide tools, just don't tell anyone
I told you this:
Suppose you have a chipped carbide cutter. You may be able to
actually use the chipped part as a sharper-than-normal cutting edge.

Last point: To get the final finish, you may be able to mount a Dremel
tool on the tool post and use that as a tool post grinder to get that
last tenth or two off. Just make sure to cover EVERYTHING around the
lathe to keep abrasive dust off important surfaces.

Pete Stanaitis
-----------------------

On Mon, 4 Jan 2010 05:16:51 -0800 (PST), "
wrote:

On Jan 4, 5:40*am, "DoN. Nichols" wrote:

* * * * Given the maximum speed likely available in a "mini lathe", and
the size of your workpiece, yes, I think that this is probably right.
If you start getting chips which turn blue and you are using HSS
tooling, you may be turning too fast, but I doubt that you can turn that
fast with that diameter of workpiece.

* * * * Good Luck,
* * * * * * * * DoN.

When I took a night school machinging course years ago, the
instructor said that you should be getting chips that come off shiny
but turn light blue as they cool. He also said that HSS tools should
last about an hour before you need to resharpen them. He was talking
about using bigger machines and optimizing the time machining versus
the time sharpening tools. I usually do not try to remove metal that
fast, but I am not trying to make a living doing machining.

Dan

One of the jobs I had as an apprentice boy was making planer heads
from old line shafting that was removed from a large woolen mill.
these were 8 inch shafts and we were machining them into a two inch
shaft about 4 feet long incorporating an approximately 3 foot long
cutting head.

At the time I was working approximately 3-1/4 hours a day in the shop
and going to school the rest of the day.

We were (as best I remember it) taking approximately a 3/8th deep cut
and the chips were coming off hot - brown and blue. No one ever
started and finished a cut during his approximately 3 hour shift. We
sharpened the bit once a day.

I can't say that this was the best speed and feed but it certainly
typified the usual shop practice before carbide became commonly used.

Regards,

J.B.

On Jan 5, 12:51*am, wrote:


We were (as best I remember it) taking approximately a 3/8th deep cut
and the chips were coming off hot - brown and blue. No one ever
started and finished a cut during his approximately 3 hour shift. We
sharpened the bit once a day.

I can't say that this was the best speed and feed but it certainly
typified the usual shop practice before carbide became commonly used.

Regards,

J.B.

When you say sharpening once a day, is that once per 3 hour shift?

Dan

On Mon, 4 Jan 2010 18:17:19 -0800 (PST), "
wrote:

On Jan 5, 12:51*am, wrote:


We were (as best I remember it) taking approximately a 3/8th deep cut
and the chips were coming off hot - brown and blue. No one ever
started and finished a cut during his approximately 3 hour shift. We
sharpened the bit once a day.

I can't say that this was the best speed and feed but it certainly
typified the usual shop practice before carbide became commonly used.

Regards,

J.B.

When you say sharpening once a day, is that once per 3 hour shift?

Dan

Perhaps I should have said "approximately once a day" as I know the
bit must have got sharpened but I don't remember ever doing it. It
seemed to me that I either took over just before or just after a new
cut was started. One day I got to start a new cut; the next day I sat
there and watched the chips fall in the pan.

Regards,

J.B.

Bob La Londe wrote:


"Denis G." wrote in message
...
On Jan 3, 1:16 pm, "Bob La Londe" wrote:
"Winston" wrote in message

...

Bob La Londe wrote:
I am trying to make my first real part. A replacement pivot pin
for a
lock blade knife. It's a cheap knife. I could have thrown it
away and
bought 50 of them for the time I have spent so far, but it's a
learning
process. Its taught me a lot so far, and the knife was a gift
from my
son a couple years ago for Christmas.

Here is my problem. I Can turn down to about .250 with no problems.
Since the cap on the pin is .383 that part is easy. The shaft of
the pin
is .204 however. Whenever I get down to about .225 - .230 the
tool bit
wants to climb down under the work piece.

You prolly have forgotten more about this than I will never know
so please pardon the question.

LOL. I know next to nothing about running a metal lathe so I don't
think
so.

Is your tool bit set a tad low in the tool post?

I do not think so. Not sure how to measure it, but if anything when
I bring
the free center upto the tool the tool looks like it might be a couple
thousandths above center.

As on page 21:
http://www.littlemachineshop.com/Inf...UsersGuide.pdf

I will read.

Bob

A common trick is to pinch a 6" scale vertically between the tip of
the tool bit and the workpiece. If the top of the scale leans away
from you, then you're tip is above the workpiece centerline. If the
top of the scale is leaning towards you, then your tool bit is below
the centerline. Basically you're using the scale to indicate the
tangent of the circle (if viewed from the end).

That is a good trick. I will remember that one.

Another way to check is to run your bit across in a facing cut.
If the tool is low, you will leave a nub.
If on center, the nub will disappear when you reach the center.
If the bit is high, there will be some tool distress when you get to
center, so start low, which is what sounds like is happening.

In article , spaco
wrote:

Hi, Bob.
I see that you have already gotten a ton of great input on this
topic. I read all the first level posts, but not all of the deeper ones,
so I hope I'm not wasting your time, but here's my 2 cents:

The work should never stick out of the chuck more than 3 times the diameter.
This means that you really need to get some center drills and get
used to turning between centers.
In case it didn't come clear already, the reason that carbide cutting
tools aren't good for you is that carbide chips easily and therefore
they have to make the cutting edge very strong, which means,
essentially, dull. The posts that say to switch to HSS are "right on".
But, here's a thought about the carbide tools, just don't tell anyone
I told you this:
Suppose you have a chipped carbide cutter. You may be able to
actually use the chipped part as a sharper-than-normal cutting edge.

LOL! I thought I was the only one who did that!

A lot of the advice in this thread was right on, and I see Bob has
already machined his pivot, so there's no use adding to the confusion
except to say I make knife pivot pins like this on my mini-lathe all
the time and have finally learned what works, after wasting yards and
yards of good A2 pin stock.

-Frank

--
Here's some of my work:
http://www.franksknives.com/

On Jan 5, 6:56*pm, Frank Warner wrote:
...
...I make knife pivot pins like this on my mini-lathe all
the time and have finally learned what works, after wasting yards and
yards of good A2 pin stock.
-Frank
Here's some of my work:http://www.franksknives.com/-

Verrry nice!

For work that isn't worth $100 an ounce, does A2 hold up well enough
without hardening?

jsw