Always breaking parting tools

[taiwanluthiers]

I think I might have found out why the parting tool keeps breaking...

Turns out the cross slide and compound gibs are loose.

Cross slide gib was so loose that I can physically rock the entire tool post back and forth. The compound is loose too but not to the same extent.

I corrected both of these problems.

I hope this will finally fix it.

 

[compact8]

.... Cross slide gib was so loose that I can physically rock the entire tool post back and forth. ....

I think that's backslash. If it is it should not cause tool breakage.

I broke mine for the first time yesterday. The reason is the insert being mounted improperly. Some tiny chips made their way to the contact area between the insert and the holder causing the insert not perpendicular to the axis of the spindle. As the insert went deeper into the workpiece, one side of the insert started rubbing the workpiece instead of cutting and that created abonormally big load on the insert which finally broke. The tip of the holder was also damaged slightly. From now on I will double check the cleanliness of the holder and the insert before mounting.

 

[taiwanluthiers]

I think that's backslash. If it is it should not cause tool breakage.

I broke mine for the first time yesterday. The reason is the insert being mounted improperly. Some tiny chips made their way to the contact area between the insert and the holder causing the insert not perpendicular to the axis of the spindle. As the insert went deeper into the workpiece, one side of the insert started rubbing the workpiece instead of cutting and that created abonormally big load on the insert which finally broke. The tip of the holder was also damaged slightly. From now on I will double check the cleanliness of the holder and the insert before mounting.

No it's the gibs... and it was very loose. To the point that even a large amount of shims are needed to correct it. Otherwise the entire toolpost can rock back and forth and up and down from the cutting force, not good for inserts.

 

[compact8]

No it's the gibs... and it was very loose. To the point that even a large amount of shims are needed to correct it. Otherwise the entire toolpost can rock back and forth and up and down from the cutting force, not good for inserts.

One way to tell whether the gibs are the causes is checking whether the finish of facing cut is bad. If it's good, I would doubt.

 

[davidpbest]

No it's the gibs... and it was very loose. To the point that even a large amount of shims are needed to correct it. Otherwise the entire toolpost can rock back and forth and up and down from the cutting force, not good for inserts.

Loose compound gibs will certainly cause insert cracking during parting operations. So will hanging the compound out in a cantilevered fashion. I only use indexable parting tools for a variety of reasons, and it took me a long time to perfect the practice and eliminate insert breakage and damaged indexable parting tools. What I have learned is encapsulated in the attached document. I hope you find it helpful.