30 Potential Causes of Part Length Variation On Screw Machine Parts

 There are many different ways that part length can vary when using a cut-off tool on Multiple Spindle Automatic Screw Machines.

Cut off Tool and Holders for Acme Gridley Multispindle Screw Machine

Here are some of the major reasons grouped into a rough classification by where the cause exists.

The Cut-off Tool itself

  • Tool is dull
  • Tool is improperly ground (point angle too large)
  • Tool loose / improperly inserted into holder
  • Tool Blade too thin
  • Cut-off tool hitting while in high speed
  • Cut off tool being hit by die head or chasers

The Cut-off Tool Holder

  • Tool holder itself is loose
  • Tool holder is hitting work spindle
  • Tool holder is hitting tool post
  • Tool holder is warped or bent
  • Tool holder is worn

The Work Spindle

  • Spindle has end play
  • Spindle has worn bearings
  • Spindle carrier has end play
  • Index Lock Pin Spring is broken
  • Finger holder not adjusted properly
  • Broken pins or fingers in finger holder
  • Feed tubes bent or beat up
  • Wrong stock feed cam- Overfeeding stock will cause bounce back from stock stop resulting in short part
  • Incorrect collet tension

The Cross Slide

  • Cross slide play
  • Cross slide loose
  • Cam is loose
  • Cut off cam too large causes too much feed
  • Cam Drum is loose

Other Tools

  • Stock pushed back into collet by drill (dull drill pushing stock rather than cutting chip)
  • Stock pushed back into collet by reamer
  • Face-off tool is loose
  • Face-off tool is dull
  • Face-off tool holder is loose
  • Die head pulling stock out of collet making part long

Part length can occasionally go awry when using cut-off tools on automatic screw machines.

This post lists  over 30 reasons that I can think of- what did we miss?

Photo Credit- Acme Gridley Multiple Spindle Bar Machine Manual First Edition 1961 page C11.

 

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