On 2012-03-10, Wild_Bill wrote:
Man overboard..
There is essentially no value of knowing a precise measurement of thread
pitch to duplicate or match a threaded piece directly in front of me.
Pitch diameter may be an important spec for hardware design engineering, or
QC quality control compliance, but not really necessary for duplicating or
matching a thread, IMO.
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.
I Will xxxcan only state that I will neither confirm nor deny that I'm
involved in sceret project contracting utilizing my Chinese home shop
machines.
My machine dials don't indicate pitch diameter.. they indicate DOC depth of
cut.
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.
A 6-jaw chuck would be a great accessory for a variety of reasons, but
pricing a small Bison or other precision brand will cause many/most HSMs to
consider alternatives.
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.
When the company or university is paying for accessories and tooling, it's a
great idea.. otherwise a chunk of hardwood may produce very good results.
Yes. Especially in combination with the 4-jaw chuck.
I managed to set up my 1220XL Smithy (no QC gear box) for microphone 5/8-27
thread cutting, by receiving the generous help from a earlier RCM
participant Ted Edwards.
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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