Hi Dave,
It sounds like you are off to a good start cuting threads. One thing
you may want to keep in mind is that the chart is just a reference.
It is meant to let you know where to stop well short of the final
thread depth. At that point you can start checking for thread
clearance with the mating part while taking light cuts. The more
experienced you become, the closer to the theoretical depth you can
go before you start checking. Also if you reduce the diameter of the
work by .005 before you start cutting, you have reduced the depth of
thread by .0025. (that is assuming that the depth of thread is based
on the nominal diameter)
Like Dennis said, with a .100 dial ring you are measuring the radius
of the work and with a .200 dial ring you are measuring the
diameter. With a .100 dial, if you turn the dial .027, the tool will
advance .027 (and reduce the diamter .054)
It's a funny thing about cutting threads, ask 10 different machinists
how they do it and you'll get at least 5 different answeres. :-)
With these little machines, I think you pretty much have to do it by
the book and feed with the compound slide. I have never used a lathe
that didn't have a dial ring on the compound. Maybe you can mount a
dial indicator on the compound and get the "feel" of how much to turn
the handle to advance the slide .001 0r .002. (which as a beginner,
is about all you want to advance the tool after the first pass at
about .005 or so) While you are learning, take is slow. When cuting
coarse threads, there is a lot of pressure on the tool and
a lot of torque at the spindle.
One more thing that sometimes confuses beginners.... When setting the
compound, use the index mark that faces the head stock. If there
isn't one there, rotate the compound until it's parallel with the
cross slide and back it up 29 or 29.5 degrees.
So Dave, if you already knew what I have posted, please disregard.
Also I should say that I never was a machinist. I worked as a
mechanic who ran machines on occasion. I know I wasn't a machinist
because where I worked the machinists got a dollar an hour more than
the mechanics :-) Oh, and if anybody tells you that I don't know
what I'm talking about, they may be right :-(
hope this helps and remember to have fun. btw, great job on the
restoration.
Jim
--- In daltonlathes@..., "Dave" <dkirk_4@...> wrote:
Hi all,
I was looking at the threading charts posted yesterday and of
course
I have a couple of questions here. First one being, since there is
no
dial ring on the top slide, can I assume that if I feed the tool
with
the cross slide that I am giong to use the Single Depth column? For
instance, at 24 TPI, the SD column is .027,so I'd just use the dial
ring on the cross slide and feed it in .027?
Ok, the second question I just answered, I think the sloppy fit
I
got on a thread I cut was due to the flat being a bit too large,
and
probably the tool being ground by eye. Gonna have to make up a jig
for
grinding the tools.
Now, if I were to put a dial indicator on the cross slide, on the
cover for the lead screw, to read the depth of the top slide, I
believe
I'd still be feeding .027? And not using the .0312 figure for the
top
slide set at 30 deg.? Thats if you're using the dial ring on the
top
slide right? Which isn't there on the lot 4, at least the one that
I
have here. But I'd be feeding it at the 30 deg angle and I'd assume
that the thread would turn out a little smoother? Or would it
matter?
Too much assuming?
Dave
