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.

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.

Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.