Yep, I definitely recommend an indoctrination period of becoming familiar
with the differences in actual results compared to expected results such as
DOC depth of cut relating to feed dial scale markings.
I've gotten used to making notes and reference examples and hanging them in
plain view of the machine controls, as a deterrent to oh****! moments.
Especially in the huge numbers of imported models which are marketed to
potential owners who may be interested in either metric or inch based
features, whereas we're aware that one size does not fit all.
When trying to remove metal in thousandths results in accumulative errors by
counting metric dial ticks, it can fairly easily lead to confusion (for me,
doesn't take much to do that these days).
Wow, $250 for a quality 4" 6-jaw.. and that's still considerably less than
some new quality brand 3-jaw models that size.
I just picked up a used 4" Dunlap 4-jaw for the 7x mini lathe, since the
only spindle accessory included with this new machine was a 3" 3-jaw.
The Dunlap backplate is made to fit a 3/4" thread, so I'll be making an
aluminum backplate to replace it which will match the spindle flange of the
7x mini.
It would be easy enough to just cut the existing backplate to match, but
there may be a future use for the original threaded version, so I'll
preserve it.
I wouldn't feel that a 7x mini from China is deserving of a good 6-jaw a far
as a cost effective upgrade.. especially at new prices.
I would've then felt compelled to find a lathe of equal quality to match the
chuck, but that's just me.
--
WB
..........
"DoN. Nichols" wrote in message
...
I *did* mention that it was important when making a thread to
match another part well out of reach -- say across the continent from
you, or perhaps embedded in a machine which *has* to be kept running.
Yes, making to fit works well as long as you have that other part for
reference.
Of course -- but you can use them (and a known starting point
such as zeroing when just barely touching the OD after turning it to the
proper dimension.
And -- with a compound set to the proper angle, you can zero
both, use the cross-feed to back away prior to winding back to the
starting end, return to zero, and set in the proper additional DOC
using the compound (compensated for the angle of the compound). I
typically have the compound set to 29.5 degrees as close as I can read
the scale, and compute total needed infeed based on that using the trig
functions in a calculator.
But DOC set does not always translate to actual DOC produced.
Backlash, rake, and give in the compound and cross-slide ways can affect
this.
FWIW I was at a combination tool auction and flea market earlier
today, and one of the things which I saw, was tempted by, but
resisted, was a Buck 6-jaw, with both the inside and the outside
jaws, new condition, with adjust-tru mounting. It was about 4"
diameter. If I were still using my old Atlas/Craftsman I would
have gladly paid the asked $250.00. But it is just too small
for my 12x24" Clausing, and I already have a 6-jaw Burnard
Pratt, though without the outside jaws.
So -- not dirt cheap, but if you can use it, difficult to
resist.
Yes. Especially in combination with the 4-jaw chuck.
Yes -- any basket-of-gears threading setup can be set for almost
any thread in the same system -- and with a pair of 127/100
tooth gears, even for Metric if made for inch or vise versa.
But it does take some computation.
But the real benefit, IMHO, to a quick-change gearbox is that
you are not tempted to leave the feed in an inappropriate range when you
are switching between turning and threading -- you tend to leave the
gears set up for threading -- and on into the next project until you
have to set up for a different thread. Been there with the little 6x18
Atlas/Craftsman. And with proper lube on the pot-metal gears, you hands
take a *lot* of washing just to get to gray from black after working
with those gears. :-)
I was glad that there are sharp people who fully understand these things,
so
now I have maximum threading capabilities for both the 1220XL and the
9x20
models.
Indeed.
Enjoy,
DoN.
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