TM 9-3419-234-14&P
SECTION VI
trouble--free operation
f.
The revoking die heads are opened and closed
automatically by a yoke.
Design Features
wide range coverage
The simplicity of setting the chasers to the correct cutting
position facilitates rapid yet accurate set-ups.
a. An outstanding feature of the Heat Treated Heads is
their wide range coverage and oversize capacity. The
range of each Head is listed in the general specifications.
The chaser holders for the various heads, with respective
ranges and thread standards for which they are suitable,
are included under Standard Chaser Holder specifications,
page 35.
b. Oversize chaser holders, which make possible the
threading of diameters larger than the standard rated
capacity of the die head are also available. When oversize
holders are used, the thread length obtainable is limited as
usually the workpiece is too large to enter the bore of the
die head. The range of these holders, their thread length
and pitch limitations are listed under Oversize Chaser
Holder specifications page 35.
Fig 40
I.
The simple opening and closing action of the Heads
sturdy construction
provides trouble-free operation and peak performance.
The component rings of the head, when in the closed
c. The Heat Treated Heads are made of specially
position, are locked by the engagement of hardened pins
selected alloy steel. All operating parts are heat treated
in hardened bushings.
after machining and then precision ground. This treatment
I.
Opening action is effected through the withdrawal of
assures both threading accuracy and excellent wearing
the pins from their bullings and the operation of the head
qualities.
The small number of working parts, sturdy
opening spring on the dosing ring which pivots the chaser
construction, accurate machining and careful assembly
and chaser holder combination away from the workpiece.
produce a die head unexcelled for threading to commercial
The compression of this spring assures a uniform head
tolerances on a production basis.
opening action on all diameters within the range of the die
head.
size adjustment ease
chaser holder design
d. Size adjustment of the Heat Treated Heads can be
easily obtained by the rotation of a size adjusting worm.
j.
The seating surface on which the chaser is seated in
This mechanism is under tension and need not be locked
the chaser holder is machined it an angle to the face of the
after an adjustment is made.
die head. Thus, when the chaser is clamped into position,
it becomes inclined to the work at a suitable helix angle.
set-up ease
The practice of controlling the helix angle setting of the
chaser in the chaser holder provides these important
a. The simplicity of the method and the gage employed
advantages.
in setting the chasers to the correct position facilitate rapid
(1) Simplifies the setting and grinding of chasers.
set-up. The chaser setting gage is merely laid on the
(2) Eliminates the necessity of grinding chasers in
outer face of the chaser holder with its hooked portion in
sets.
contact with the cutting edge of the chaser. With the
(3) Allows interchange ability to the extent that any
chaser clamp released, the chaser is then moved forward
individual chaser may be replaced without replacing the
in the chaser holder by rotating the chaser abutting screw
entire set.
until the graduations on the setting gage correspond to
(4) Makes possible the use of standard chasers of a
those on the chaser holder, thus establishing the correct
given pitch for cutting threads of the same pitch on any
cutting position.
diameter of work within the range of the die head.
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