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