Passing Knife on thread rolling

[Member0]

Hi all
Have a question. First I need to clarify what do I mean with "Passing Knife", located inside thread rolling machine. It is knife (tool) which is supposted to move/pass bolts (yes bolts so no threads on them yet) forward to inbetween wheels.
I have had too big clearance in this passing knife. The causes were overused wheels and also wrong parameters on machine, wrong/poor material of passing knife. I successfuly fixed this issue with regularly changing of lubricants and also regularly reviews of clearance on this passing knife.
But I would need some deeper understanding of this. Could anyone explain please why was this even happening (I already know the causes) and why those solutions (specially changing of lubricants but also other, mentoined, one) actually worked? I didn't believe they would.

 

[msquared48]

I think you need to red-flag this and post it in the "Mechanical Engineering Other Topics" forum. It really does not fit here...

Mike McCann
MMC Engineering

 

[Member0]

it does fit here because its all about bolts and screws (so it is fasteners). But its true that I have been waiting for some assist for a while now...

 

[TVP]

Member0,

What was the actual failure mode of the passing knife? Local wear? Edge chipping? Large-scale deformation? Regardless of the exact cause, using a different lubricant improved the situation because it did one or more of the following:

reduced friction at the interface
reduced surface temperature of the passing knife
stabilized the wear pattern on the passing knife

The new lubricant was probably better formulated for this type of service, meaning it had improved temperature stability, higher viscosity, and increased additive content (anti-wear, extreme-pressure, friction modifiers).