Quick Change Indexable Tool Holder


After converting FrankenSieg to CNC, it quickly became apparent that indexable, quick change tooling is essential to getting any productivity out of the machine. Manually changing bits int he standard Sieg four way toolholder is slow, has no repeatablity, requireing re zeroing at every tool change, and encourages the use of incorrect tool set ups, just to avoid resetting.

The four way tool holder is not really usable with more than two tools in it. The lack of tool height adjustment, means shimming is a constant PITA.

The tailstock of the 7X12 is about the worst part of the machine. Although the lever lock mod has been on my to do list since day one, it doesn't solve the accuracy or lack of fine depth control. A MT#2 tool holder will be a huge time saver if the machine can consistantly place it accurately on the centerline.

My design criteria is therefore:

  • Repeatable - it will need to position the tools reliably to make use of TurboCNC's tool list function.
  • Rigid - the key to good finish
  • Two way - it needs to be able to accept boring tools and turning tools without resetting the tool block 90° each time.
  • Compact - The current four way tool block is often in the way when threading small diameters near the live center.
  • Simple to manufacture. (For me this means minimum milling)
  • Iron- I don't like Aluminium tooling.

None of the comercial products fit the bill, so There are dozens of QCTP designs available on the web, of which Frank Hoose has cataloged a bunch.

Going through them:


Home Made:

  • Frank's - One way
  • Vikki Ford's - One way.
  • Ty Hoffer's - One way.
  • Various - This style with the round pillar is attractive as it can be completely manufactured on the lathe, but lacks the indexing function, so essential to a CNC machine.
  • John Stevenson's - Initially, I skipped over this one, but eventually realised what John was saying. The use of round wedges dramatically simplifies construction, meaning the only milling is the dovetail. A wedge style, which pulls the tool holder towards the tool block is a feature of the best industrial tool holders like the Aloris AXA and the Dorians, as opposed to the pusher syle used by the TS Engineering style.