Quit breaking parting tool inserts

[taiwanluthiers]

I finally found the trick to not break parting tool inserts. I just watched a video where a guy recommends putting a bar between the cross slide and the parting tool insert, to support it. However that bar must be exactly the distance between the bottom of the holder and the top of the cross slide. What I found is if I mount the holder as shown in the picture, I was able to part a piece of 4140 to completion. The way they want you to mount it is too much stick out, and I'm wondering why, is it because of the way CNC holds their tools (they are held backwards).

Last insert, last side. I break that one and I have no more insert. Need to get more, and possibly get something that doesn't have such an aggressive positive rake.

If using a QTCP you won't be able to stick the holder all the way into its slot.

 

[mmcmdl]

Not following you here .

 

[taiwanluthiers]

Basically to stop breaking inserts you have to make it so it doesn't flex, but the way they WANT you to mount it is not going to do that (there's a good inch of extra stickout that it does NOT need).

So by burying the head inside the tool post, I've eliminated the reason why it keeps breaking.

 

[wayback machine]

I get it - But you have to have a tall enough slot in the tool post to accommodate the raised front clamp.

 

[mmcmdl]

The correct insert would do you wonders here . CNC lathes hold parting or grooving tools either way , and have holders to do so . They have right and left hand holders which can be ran in M3 or M4 spindle rotation . JMO here , your shims don't go the length of the holder . They should for maximum rigidity . The tool shank itself is more than adequate to support the insert . The insert you are using looks like it would work for plastic or aluminum , maybe not steel .

 

[compact8]

The way you mount it is pretty normal I believe. I have the same type of parting tool bar and insert, only a bit smaller ( 12 x 12 mm bar , 1.5 mm wide insert ). The length sticking out is equal to that of the insert. Never had any problem.

 

[pdentrem]

If you are parting a 3” diameter part, the stick out has to be over 1.5” just saying

 

[taiwanluthiers]

That particular tool has a maximum depth. Why stick out beyond that?

 

[benmychree]

Breaking too many inserts? Use HSS!

 

[homebrewed]

Breaking too many inserts? Use HSS!

HSS parting blades are trivial to sharpen as well. A quick touch-up on your grinder or belt sander and you've got a tool that does the job quite nicely.