According to :
You guys all had some very good info...
Here's a link to some photos I took earlier:
http://pg.photos.yahoo.com/ph/cj1210...548scd&.src=ph
These photos do it!
Right now trying to get the thread chasing dial working is not my
biggest concern. I've got to get an accurate TPI first. For some reason
though I think this may be all intertwined...
As you can see from the photos I've strictly kept the setting
(according to the charts and gears) to 16tpi. The leadscrew is exactly
16tpi (not anything metric as you can see from the picture). When I
turn the chuck over one rotation by hand I don't get a complete
rotation in the leadscrew.
Maybe the leadscrew is not metric, but your gear train is set up
for metric. In the photo "b2e3scd.jpg", which shows the entirity of
the threading chart, it shows that the input to the gearbox should have
its gear engaging the 127 tooth gear for inch thread 'n/1"', and it
should engage the 120 tooth gear for the metric thread "mm"
And looking at the photo "b1fascd.jpg", it is obvious that the
gear from the quick-change gearbox is engaging the 120 tooth gear.
So -- you need to loosen the various nut, exchange the spacer
and gear on the input shaft to the QC gearbox, and then re-mesh all of
the gears and tighten them back in place.
When you had initially posted your question, I was thinking that
you had the other common pair of gears for metric/inch transpostion,
100/127, which would introduce more error than you were observing.
However, with 120/127 you would get (depending on the direction of the
transposition) either 15.12 TPI or 16.93 TPI -- the latter being rather
close to your observed 17 TPI.
This is probably enough all by itself. I presume that the flat
paddle lever on the right of the apron is your half nuts engage, and
the long round lever in the bottom center of the apron is your power
feed, either longitudinal or cross-feed. If you had been using that by
mistake, you would have gotten a much greater mismatch.
This obviously points to some kind of gear miscalculation on the
manufacturer's part... (at least that's the only explanation I can
think of at the moment).
Nope -- simple mis-positioning of one gear -- you are set up for
metric threading.
Now, as far as the thread chasing dial, I've tried pulling it away from
the headstock while cutting in order to take all of the play out. This
doesn't do anything. I've also tried giving it resistance with the
carriage wheel.
Your thread chasing dial will not work properly for metric
threading, even when you *know* that is what you are doing. For it to
work properly, you would need to have the leadscrew and half-nuts metric
as well.
Maybe the thread chasing dial can't work properly if the gears are
messed up. For example maybe when it's set to 16tpi and it's really
cutting close to 17tpi this will then proceed to not let the half nut
engage at the proper time, which will defeat the whole purpose of the
thread chasing dial.
It truly will not work properly when you are set up for cutting
*any* metric threads.
There is about .007" play in the leadscrew itself which I can probably
fix with a thin washer.
Don't worry about it.
There is about .014" play in the half nut unit.
Again -- don't worry about it. These are normal amounts of
play, and since the carriage is always moving in the same direction when
cutting, the play is taken out. And especially so if you use the 29.5
degree compound infeed, so the cutting load is always on the left side
of the tool.
This I'll have to pull apart to see if I can tighten it up.
You can't -- and if you could, it would still wear back to that
much play rather quickly.
This could
definitly be part of my problem with not getting the same cut to line
up and is just not right, but something tells me there's more to it.
Yep -- that one gear in the train before the QC box.
Like I said up above I've tried keeping pressure on the carriage (away
from the headstock) and it hasn't done any good...
Any other ideas!?
Yep -- re-set the gears. Then you should be fine.
Enjoy,
DoN.
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