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3-flute Fingerboard Planing and Radiusing Bits (MM3I8) - (0.125 in. shank)

PreciseBits 3-flute planing and radiusing cutters were designed for use with automated fretboard tuning and optimizing systems. The flute design and shallow helix angles minimize resonance during cutting and are capable of cutting with an 18% stepover while producing a smooth, artifact free surface. The corner-radiused high-rake tip-geometry is specifically intended to plane and/or radius fingerboards that have already been inlaid with mother-of-pearl, reconstituted mineral, thermoplastic, composite and/or precious-metal inlay components.

Manufactured in the USA, every tool is:

  • 100% measured / optically inspected to insure that EVERY tool meets, or exceeds, our published specifications
  • available with depth rings precisely positioned to ±0.004 in. (0.038mm), virtually eliminating the need for resetting Z-axis zero between tool changes (with bits of same overall length)
  • made from premium grade submicrograin tungsten carbide (HRa 92, HRc 80)

This attention to detail and the use of top quality materials result in tools with dependable cutting characteristics and one of the longest tool lives in the market. Combined with comprehensive customer support, our cutters have become the tools of choice for sign makers, model makers, artists and instrument builders around the world.

Our thanks to Adam Geraldson and Gary Brethorst for the excellent videos.


  • Geometry - 3 flute, 1/8 in. shank, fish tail point
  • Length - 1.5 in. ±0.010 in.
  • Diameter - 0.1250 in. +0.0000, -0.0010 in.
  • Max runout (TIR) - < 0.0005 in.
  • Max. depth of cut - nominal ±0.005 in.
  • Anticipated Life - 3,000 linear inches (cross-grain ebony, CNC milling)
  • Material - solid submicrograin carbide
  • Ring Set - 0.800 in. ±0.002 in. (optional)
  • Operating RPM - CNC certified operation 20k RPM to 100k RPM
  • Feeds/speeds - to determine the optimum Feed/Speed combinations,
    run our Sweet-spot Test.
  • Bull-nose tip-style minimizes "witness" lines and provides smooth, scallop-free cutting at high chiploads
  • High flute volume supports high feed rates / chip loads
  • 3-Flute design eliminates chatter at high feed rates
  • 3-Flute design brings the rigidity and precision of a stub mill to a high-aspect ratio cutter
  • Cutting edge geometry tuned for cutting all common fingerboard materials that have inlaid components of mother-of-pearl, recon stone and precious metal
  • Tool Type: Radiused End Mill
  • Diameter (D) = 0.1250 inches (3.18 nn)
  • Tip Radius (R) = 0.0250 inches (0.64mm)
  • Stepdown (pass depth, depth per pass) = 0.1250 inches (3.18 nn)
  • Stepover:
    • 0.225 inches (5.72mm)
    • 18% (of tip diameter)
  • Spindle RPM (SPEED): click on the Feeds/Speeds tab
  • Feedrate (IPM): click on the Feeds/Speeds tab
  • Plunge rate:
    • Softwood (Janka < 1,500) = 75 inches/minute
    • Medium hardness hardwood(1,500 < Janka < 2,500) = 50 inches/minute
    • High hardness hardwoodwood (2,500 < Janka) = 40 inches/minute

You can use the Feed and Speed Calculator link below to accurately determine the the optimum RPM and feed rate to use when planing or radiusing your fretboard. These number assume the you have used the tool parameters under the Application Data tab to set up the bit in your CAM tool database (CAM tool table).

After you click on the Feed and Speed Calculator:

  1. Enter the RPM (for bits this small, use your maximum RPM)
  2. Enter 3 for the number of flutes
  3. Enter 0.125 for the tool diameter
  4. In the "Percent of tool Diameter" field, enter:
    • 3 if you are planing or radiusing a naked hardwood fretboard
    • 1 if you are planing, or radiusing, a hardwood fret board that has already been inlaid with components made of mother-of-pearl or similar materials
  5. In the "Runout" field, enter:
    • 0.0003 if you are using a spindle with certified Extreme Precision collets
    • 0.0005 if you are using a consumer-grade router with certified Extreme Precision collets
    • 0.005 if you are using a consumer-grade router with a non-certified after-market collet
    • NOTE:If you are using a consumer-grade router with a non-certified 1/8 in. collet adapter you will probably NOT be able to use this bit due to excessive runout.
  6. Click on the "Calculate Feed"
Carbide 3-flute end mills for maching hardwoods, composites and reconstituted minerals

Part Number Description Reviews Price


1/8 in. (0.1250 in., 3.175 mm) 3-flute end-mill, 0° helix, 0.025in. corner radius, 0.140 in. max DOC, 1.5 in. OAL fingerboard planing bit..



1/8 in. (0.1250 in., 3.175 mm) 3-flute end-mill, 3° helix, 0.025in. corner radius, 0.31 in. max DOC, 1.5 in. OAL fingerboard planing bit..



1/8 in. (0.1250 in., 3.175 mm) 3-flute end-mill, 3° helix, 0.025in. corner radius, 0.31 in. max DOC, ZrN coated 1.5 in. OAL fingerboard planing bit..