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Thread MillMade in USA

RTHR-8-32

Internal Thread Relief End Mill

Internal Thread Relief Mill 0.128 Dia, 3 Flute, 0.330 Neck Len, 0.1875 Shank, 2.0 OAL

Internal Thread Relief End Mill — RTHR-8-32
Series photo — representative of the RTHR family
Ø0.076″ neckOAL 2″Neck 0.33″Shank Ø0.1875″Cutter Ø0.128″Relief flat 0.031″ · R0.01″ · 45° back taperBlend 45°
Scaled drawing — true to this tool's dimensions (inch)
Speeds & FeedsDialed to this exact tool — free
Free CAD & DataSTEP 3DDXF 2DISO CSVCAM library
RobbJack RTHR internal thread relief end mill machining a relief at the bottom of a blind threaded hole, shown in cutaway

Internal thread relief mills — flatten the bottom of blind holes and strengthen the thread

  • Flattens the bottom of a threaded blind hole and actually strengthens the performance of the threads
  • Eliminates burrs and partial threads at the bottom of the hole
  • Companion tool to the THR series internal thread mill; best applied to blind holes
  • Nine sizes from #3-48 to 1/2-13: diameters .072 to .420-in with 2 to 6 flutes
  • 45-degree standard angle with .005 to .012-in corner radius and .021 to .077-in flat
  • Undercut diameter rules: pitches finer than 20 TPI = basic major diameter + .0075-in; 20 TPI and coarser = + .0150-in
  • Standard shanks 3/16 to 1/2-in on 2 to 2-1/2-in overall lengths; necks ground longer on request
  • Available uncoated, AlTiN coated (-A) and DLC coated (-DLC)

From the RobbJack Applications Guide.

About this series

RTHR Solid Carbide Internal Thread Relief Mills

Flatten and strengthen the bottom of a threaded hole

RTHR Solid Carbide Internal Thread Relief Mills — from the RobbJack applications guide

RobbJack's RTHR internal thread relief tool will flatten the bottom of a threaded hole and actually strengthen the performance of the threads. It also eliminates any burrs or partial threads. This tool is best applied to blind holes and is used together with RobbJack's THR series internal thread mill.

  • Flattens the bottom of a threaded hole
  • Strengthens thread performance
  • Eliminates burrs and partial threads
  • Available uncoated, AlTiN coated (-A) and DLC coated (-DLC)
  • 2, 3, 4 or 6 flute depending on size
  • Necks ground longer on request

Best applied to blind holes; used in conjunction with the RobbJack THR series internal thread mill.

Headline spec

Sized to common thread pitches from #3-48 through 1/2-13

Best for

  • Relieving the bottom of blind threaded holes
  • Eliminating burrs and partial threads
  • Strengthening internal threads

Specifications

US machining terms with ISO 13399 codes.

Cutting DiameterDC
0.128″
Shank DiameterDMM
0.1875″
Neck DiameterND
0.076″
Neck LengthLN
0.33″
Relief Flat
0.031″
Overall Length (OAL)OAL
2″
Corner RadiusRE
0.01″
Blend Angle (neck→shank)
45°
Entry
Requires a pre-drilled hole
Thread Designation
#8-32
Undercut Diameter
0.1715″
Series
RTHR — Internal Thread Relief End Mill

Cuts these materials

AluminumCopper & BrassSteelStainless Steel

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Starting at$116.35

Made & shipped in the USA · lead time confirmed at order. Buy at retail or through your distributor.

Performance guaranteed. Run it against the tool you use today — if it doesn't beat it, we'll make it right.

Adds Aluminum Titanium Nitride (AlTiN) · $118.65 — our pick for your material. Choose another finish below.

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More in the RTHR series

Same series, different size — what changes from this tool is shown in red.