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THE FOUR TIMING PULLEY SETS
FOR THE KNAELL-THREADER
FOR THE TAIG LATHE
WHAT THEY ARE :
It is possible to do exact metric threading using a leadscrew with a pitch
of 14/11mm (1.27272..mm). This is the pitch of the Metric leadscrew.
The spindle pulley that gives a complete set of Metric thread pitches
with this leadscrew is an 11 tooth one.
The set of pulleys that work best with this 11 tooth drive
pulley(N1 position) and the Metric leadscrew are 10,14,15,18, 20,24,25,
and 28 tooth count ones. These along with the Metric leadscrew and 11
tooth spindle pulley is the
"METRIC-8" set.
Since Inch and Metric leadscrews and 11 and 14 tooth spindle pulleys are
now made available then the 4 additional pulley sizes to complete a set
to allow Inch-Based threading with the 11 tooth spindle pulley are also
made available. The best set for doing this are 10,11,14,16,20,22,24,
and 36 tooth count. These along with the Inch-Based leadscrew and 11
tooth spindle pulley are called the "INCH-8" set. In addition, a set of
12 pulleys, both leadscrews, and 11-tooth spindle pulley combining the
INCH-8 and METRIC-8 capability is called the COMBINED-12 set.
The following table summarizes the pulleys(tooth count),
the Spindle Pulley(N1 position), and type of leadscrew for the four pulley
sets. "M-LS" and "INCH-LS" stand for "Metric Leadscrew" and "Inch Leadscrew".
The Metric leadscrew and Inch-Based leadscrew are so nearly identical that
they work with the same split-nuts.
"METRIC-8" "INCH-8" COMBINED-12 "BASIC-8"
(N1=11) (N1=11) (N1=11) (N1=14)
(M-LS) (INCH-LS) (M&INCH-LS's)(INCH-LS)
-----------------------------------------------
10 10 10 10
11 11
14 14 14 14
15 15 15
16 16
18 18
20 20 20 20
21
22 22 22
24 24 24 24
25 25
28 28 28
36 36
-----------------------------------------------
HAVE/NEED TABLE
Pulleys required to complete another set given a set at hand:
-------------------------------------------------------------
HAVE BASIC8 BASIC8 BASIC8 ICH8 ICH8 MET8 MET8
NEED COMB12 ICH8 MET8 MET8 BASIC8 ICH8 BASIC8
need 11 11 18 15 15 11 21
need 16 16 25 18 21 16 22
need 18 36 25 28 22
need 25 28 36
need 36
-------------------------------------------------------------
** MET8, ICH8,& COMB12 are abbreviations for "METRIC-8","INCH-8",&
COMBINED-12 pulley sets. One needs also the appropriate Spindle Pulley and
Leadscrew previously described.
HOW TO CHOOSE :
If you have a clearcut knowledge that you will only be cutting Inch based
threads (UNC or UNF) then the BASIC-8 set based on the 14 tooth spindle
pulley is the way to go. Also this set is somewhat more robust and better
oriented toward coarser threads because of its slightly larger pulleys
and the 14 tooth spindle pulley.
If you are not sure whether you will be cutting Inch or Metric based threads
or you want to most economically retain the option to cut both, then the
two systems based on the smaller 11-tooth-spindle-pulley are the best choice.
These are the METRIC-8 and INCH-8 sets. With either choice(of the METRIC-8
or INCH-8) it takes only four other pulleys and the other leadscrew to update
to the COMBINED-12 set. The smaller drive pulley allows cutting of somewhat
finer threads with change pulleys that fit within the pulley carrier frame.
CALCULATE YOUR OWN PULLEY SETUPS:
*For the original "BASIC-8" system:
TPI = 20*(N2*N4)/(N1*N3) = 20*(N2*N4)/(14*N3)
The 20/14 is equal to 10/7 so this equal to:
TPI = (10*N2*N4)/(7*N3)
*For the "INCH-8" system:
TPI = 20*(N2*N4)/(N1/N3) = 20*(N2*N4)/(11*N3)
Nothing cancels here so:
TPI = (20*N2*N4)/(11*N3)
*For the "METRIC-8" system:
PITCH(mm) = 14/11*(N1*N3)/(N2/N4) = 14/11*(11*N3)/(N2*N4)
The 11's cancel so:
Pitch(mm) = (14*N3)/(N2*N4)
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