The lathe's cross-slide bed must be level in both directions.
Quick Change Tool Post (QCTP) & Tool Bits
Upgraded Bolt Post,
Holders,
Carbide Insert Tool Bit Set,
Carbide Insert Cut-off Tool,
Carbide
Insert Tool Bits,
Tool Bit Height Gages,
Tool Bit Types & Shapes,
Brazed Carbide,
HSS, Storage, Surface Feet per
Minute
The lathe's cross-slide bed must be level in both
directions.
Upgraded Bolt Post
Adapted a
Phase2+ wedge-type QCTP,
Model 250-111.
Wedge-type tool posts are purportedly
more accurate & repeatable
than the piston type. Quick-Change Tool Posts allow fast tool changes,
exact tool bit height
& position/angle adjustments.
A long,
22mm Craftsman box wrench is used
to
loosen & tighten the
hardened tool post
nut for rotational positioning.
Full-sized lathes have a large T-slot to mount the tool post. The Jet BD 920N is too small for
a T-slot but this
mod parallels that design.
The new design uses a machined M14-1.5 x
120mm long bolt (same size as the
Phase2+ OEM post) with a counter-bored cross slide.
To keep the bolt head as large as possible, it was turned
down just enough to
remove the hex flats.
Also replaced
all the gib
M4-0.7 x 10mm set screws with higher
quality US parts. The lock
nuts are stainless steel. Replaced the three compound bearing plate
Philips-head
mounting screws with stronger,
hex cap-head bolts. These bolt heads had to be ground down enough to
allow
sufficient clearance when the plate is clamped down to the cross slide.
Phase2+ wedge-type Quick Change Tool Post Set
manual.
Old modification design (top), M14-1.5 x 120mm bolt (middle) & new design (bottom).
My first QCTP modification (some years ago, before I had a
larger mill
& a boring head), was accomplished
by turning down the Phase2+ OEM 14mm post to fit into the original
cross slide hole, but it was a weak design.
Used
a (centered) 1-in. end mill to cut a relief in the dovetail to keep the
bolt head as large as possible.
This clearance cut to the dove tail does not seem to have affected the
compound's mechanical
performance.
The counter bore is about 0.83" & the clearance hole is a very close fit to the
14mm bolt.
The counter-bore depth is the same as that used by the original bolt post.
To allow complete seating into the hole, the bolt-head & counter-bore edges were
properly chamfered.
The machined bolt head is an interference fit so it had to be hammered in using a
brass rod.
This was the first test part fabricated & it was flush to the
surface. I made a second part with a longer bolt.
Also, the head was machined a little thicker (not flush) for more strength & it used the available
2mm slide clearance area between the bottom of the slide & the top of the
dove-tail base.
Note the small amount of brass that was left on t he bolt head surface from the
installation.
Used a
rotary
table to mill the four corners of the compound's raised, square tool post platform.
Rounding the
corners allows the QCTP dovetail
tool holder to be adjusted lower than the surface of the platform,
thereby enabling
adjustment of larger tools (e.g.,
scissors knurling, cut-off tool,
½" bits) at or below centerline of the work
piece.
The compound slide shown reassembled with the 14mm bolt & rounded
base corners.
Tool post bottom is shown
with a tool holder in place. The holder dovetail corners have to clear the base.
Used the
Phase2+ OEM hardened, flanged nut.
Maximum tool bit size is ½". The
increased rigidity is outstanding.
When combined with a negative-rake carbide insert
tool bit holder, steel-cutting performance has dramatically improved.
I have now
increased the size of the
compound pivoting base making it about 50% larger than the OEM in all
dimensions.
An auxiliary handle can be screwed
into QCTP body.
Holders
QCTP
tools left to right,
top row: an
MT-2
arbor holder
with a drill chuck, ¾" &
⅝" (with a
split insert) boring bar
holder, a
conventional knurling tool (also holds a bit),
two scissors-type knurlers. Left to right,
bottom row:
small boring bar, a cut-off blade holder
& tool bit holders. Some of the tool-bit holders have a V-groove to
hold
a round shank like those found on a
⅜" boring
bar. The cut-off tool holder was ground along the inner
top corner to relieve the
wider top of some cutting blades. The blade's side sits
flush against the holder.
Note this Phase2+ tool holder has a V-groove to hold round shanks.
This ⅜" round to ½" square, slit, steel adapter eliminates set screw marring on the shaft.
The hole was reamed for a close, precision fit to the ground shank.
⅜" steel holder for a 0.083" x 0.3915" x 2.8" HSS blade.
Carbide Insert Tool Bit Set
C-6 carbide insert, ¼" shank, tool bit holders.
Key, left to right: A, B, C, D, E, F (threading), & G (cut-off).
CARBIDE INSERTS FOR ¼" HOLDERS
KEY HOLDER TYPE & ANGLE C-6 INSERT A SWGCR Right-hand 90° WCMX-50308 B SDJCR Right-hand 93° DCMT-0070202 C SCLCR Right-hand 95° CCMT-060204 D SDNCN Right-hand 62.5° DCMT-0070202 E SCLCL Left-hand 95° CCMT-060204 F LW Threading JCL-15-120 G QA Cut-off JCQ-3 Carbide Insert Cut-off Tool
GTN-3 carbide insert cut-off tool bit holder SLTHR12.7-3. Insert held in V-grooves, only. Tip is 0.122" wide.
After cutting, the tool pries out a fully seated insert. The hardened shank is 0.498" high x 3.25" long x 0.39" wide.
Capacity 0.7" cutting depth or 1.4" diameter stock.
Good performance in soft steel using heavy oil as a lubricant.
Carbide Insert Tool Bits
Carbide insert tool bits in ¼" &
½" shanks. More about tool bits
Carbide insert tool-bit
holders (negative 5° rake), from
Dorian Tools (USA) left to right:
MTGNR,
MTJNR,
MTCNN (negative 10° rake),
MTJNL,
MTGNL.
These use TNMG-style, ⅛"
thick, zero relief angle inserts which have six usable tips, each.
Different radius insert tips can be used e.g., 1/64th in. or 1/32nd
in. These holders have ½" square hardened shanks.
TNMG-style inserts are the most economical to use due to six tips apiece.
Their popularity & high industry demand
drives their cost down.
For quantities ≥10, import inserts are about $2.07 each or 34½ ¢ per tip (Sep 09).
Negative-rake tool-bit holders in QCTP adjustable-height dovetail mounts.
The middle holder is an MTENN
type having an insert with a 1/32nd
in. radius tip.
5° negative-rake
insert tool bits.
See Insert Nomenclature Chart & Indexable Tool Holder
Nomenclature Chart
Tool Bit Height Gages
Aluminum height gage used to quickly set tool bit height using a QCTP. Right side for standard settings &
left side for upside-down, backside bits. Facing cuts were made on a collet-held piece until no center nub
remained. That height operationally defines the tool bit height for the gage. A Dorian Tool, negative rake
TNMG carbide insert tool bit holder MTGNR is shown. The tool bit should be at or slightly below center for
turning & at or slightly above center for boring. The height-gage bottom rests on the cross slide.
Another quick tool bit height setting method is to gently pinch a small rule between the tip & the work
piece, then adjust the height until it is vertical. If the rule's top tilts toward you, then it is low & vice versa.
Using a center gage to setup the 60° tool bit cutting angle.Tool Bit Types & Shapes
Lathe tool standard shapes. Single point lathe tool angles.Brazed Carbide
Assorted brazed carbide tool bits: left-hand, threading, square-tipped, cut-off & right-hand.HSS
HSS tool bit blanks. Top to bottom: square ½", ⅜", 5/16", ¼", 3/16", ⅛" square & round 3/16", ¼".
Caution: the metal dust from grinding tool bits is dangerous. Wear proper protective eye & breathing gear.
HSS; small cut-off, 45º chamfer, round-nose & two views of a small boring bar.
The chamfer tool can chatter. Better to use the compound.A multi-compartmented storage bin holds & organizes the many different lathe tool bits.
Surface Feet per Minute
Converting part size & RPM to surface feet per minute (lathe SFM)Approximate cutting speeds for different materials. Surface Feet/Minute (SFM) Chart 1 SFM 2 SFM 3
Upgraded Bolt Post, Holders, Carbide Insert Tool Bit Set, Carbide Insert Cut-off Tool, Carbide Insert Tool Bits,
Tool Bit Height Gages, Tool Bit Types & Shapes, Brazed Carbide, HSS, Storage, Surface Feet per Minute
