A Q&A on Proper Holding of Small Diameter Tube Electrodes


Q: What is the best method for holding small diameter tube electrodes without crushing the ID and restricting flushing on an EDAF2 fine hole machine?

A: Preserving the integrity of small diameter electrode tubes can be challenging, especially when the electrode tube is below 0.010 inch (0.25mm) diameter. The electrode tube must be held in place with sufficient force to not move and become loose during machining, and the tube ID must be intact to provide proper flushing for efficient operation. When machining down to electrode tube sizes as small as 0.004 inch (0.1mm), any restriction of the tube electrode ID will dramatically affect machining performance. The Makino EDAF-Series Fine Hole machines use special tool holders that are designed to hold small electrodes while supporting flush pressures up to 1500psi (10MPa). These tool holders utilize four different types of collet holders (Type A, B, C, D) that are designed to provide a range of electrode sizes.

When using electrodes that are 0.010 inch (0.25mm) diameter or smaller, it is recommended to use a slightly larger collet holder (Type B – 0.2~0.5mm Ø range) and insert the electrode tube into a larger tube for clamping purposes to prevent crushing and restricting the tube ID. This tube-within-a-tube method is a bit unconventional, but it will yield easier loading and setup of small electrode tube operation.

Setup of Small Diameter Tube Electrode:

    • Parts:
      • Small Diameter Electrode Tool Holder and Nut
      • Type B Collet, Collet Nut, and Washer
      • Seal Packing (rubber)
      • Small Diameter Tube Electrode
      • Short section of Larger Tube Electrode (0.020”Ø x 2.0”/ 0.5mmØ x 50mm)
      • Super Glue / Quick Set Adhesive
      • Long Nose Pliers
    • Process:

Insert Small Diameter Tube Electrode into short section of larger tube, making sure that the small electrode extends out the back side by 2mm

  • Use a pair of Pliers to crimp and lightly squeeze the working end of the electrode assembly together
  • Use Super Glue and fill the remaining gap on the working end of the electrode assembly
  • Insert electrode assembly into Rubber Packing and load and clamp into the Type B collet
  • Insert and secure the entire collet assembly into the Fine Hole Tool Holder
  • Load the tool into the machine and test and verify proper sealing and flushing of the electrode assembly under high flushing pressure


SmallTubeHolder1 2-3-15

SmallTubeHolder2 2-3-15

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