Re: Threading and Compound
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Actually both of my lathes have a compound.?
But I am in the long drawn out?process of automating both Z and X.
John Lindo is very enthusiastic about going straight in.
Some day I will eventually start doing threads and just thinking of the method I will use.
Ralph
On Sat, Mar 2, 2024 at 3:31?PM mike allen < animal@...> wrote:
Ralph is talking about a lathe without a compound .
animal
On 3/2/24 12:25 PM, Charles Kinzer
wrote:
The tool is advanced with the
compound.? The cross feed is used to extract the tool after a
pass.? And then the cross feed is returned to its same
position each time and the compound moved in a little.?
Sometimes, some people, make a very light finishing cut going
straight in.? But if you have everything set up properly, this
is not necessary.
One little benefit is that
the sine of 30 degrees is 0.5 so the increments of the
compound wheel will automatically refer to removal in terms of
radius instead of diameter (assuming the hand wheel is marked
for diameter removal in the first place.)? Yes, 29.5 isn't 30,
but it is so close that the error is typically negligible.
Charles E. "Chuck" Kinzer
On Saturday, March 2, 2024 at 11:37:23 AM PST, Ralph
Hulslander <rhulslander@...> wrote:
Is the tool advanced with the compound?or
the cross feed?
John Lindo was the
first that I know going straight? in. He is using
his RLS with automated Z and X.
He threw his compound?away.
Ralph
On Sat,
Mar 2, 2024 at 1:35?PM Charles Kinzer < ckinzer@...>
wrote:
This is a topic that has been
discussed repeatedly on this list.? I guess it
won't hurt to cover the same ground again.
In the hobby world, typically
making small threads, at low speeds, often in
friendly materials like brass or aluminum,
there may be little to no difference what
method is used.
In production, and with larger
threads, and harder materials like steel or
stainless steel, and at production speeds,
there is a significant difference. And the
difference is all about how the chip is
produced.? This is what the 29.5 (or 29)
degree angle is all about.? (Note:? You will
find some production work that does go
"straight in" however as there are times when
that is still possible.)
When you go straight in, you are
producing two equal size chips from the left
and right cutting edges.? The chip from the
left edge goes up and to the right.? The chip
from the right edge goes up and to the left.?
That means they collide in the air space above
nose of the tool.? This causes a tearing
effect and also puts more stress on the
cutting tool tip.? The result can be poor
surface finish, wasted power (time) dissipated
in the two chips mashing together, more heat,
and even a broken tool tip.? A poor surface
finish would be the most likely risk in a mini
lathe in my opinion.
The purpose of the angled
compound movement is to have almost all
cutting on the left edge.? By having the
compound at 29.5 (or 29) degrees there will be
a very slight skim cut on the right edge.?
This ensures a clean surface on that side of
the thread and also helps cause tool contact
for heat transfer on the right edge.? This
eliminates that chip collision problem.
Sometimes on this list I have
seen people say it makes a "stair step"
thread.? This technique, used properly, does
NOT do that.? If somebody is getting that
result, it is due to a simple geometry error
that can be one or all of these things:?
Compound not really at the correct angle (the
protractor markings on mini lathes are
notoriously inaccurate - measure with a
machinist's protractor), the tool bit is not
ground to the correct angle (double check with
a "thread gauge" a.k.a. "Fish Tail"), and/or
the tool bit is not perpendicular to the work
piece.
Charles E. "Chuck" Kinzer
On Saturday, March 2, 2024 at 09:58:47
AM PST, davesmith1800 < davesmith1@...>
wrote:
Here photo from How
to Run a Lathe
It shows two ways of threading.??
I have used both to me they work same.
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