Exploded a GTN3 holder

[Aukai]

4" diameter 316 SS, 135 rpm, I set the auto feed for the least amount of chatter(still some fine vibration) as the part was going the cut became silent, going well. Very quickly there was a big vibration, and before I could shut things down, the GTN3 holder snapped. I had previously parted with the same insert, I'm wondering if the bit should have been changed before attempting another 4" SS cut. My setup for parting is to indicate the blade with a dial indicator </= .0005 at least in and out deflection of the tool post. I use the auto feed to try, and stay ahead of the work hardening, and plenty of cutting oil. I also move the blade out of the holder, and hand spin the chuck to get to fresh metal. The piece of the of the insert that was imbedded in the cut was hard to remove, and it took awhile to get it out too.

 

[mmcmdl]

CSS is your friend here .

 

[7milesup]

I am wondering if there is not enough of the insert holder (blade) in the tool holder thereby introducing chatter and/deflection. Or did that insert tool holder break and that is what is left of it?

 

[MrWhoopee]

That's a deep part-off in difficult material. I'm not sure I'd even try. Is your saw not working?

 

[markba633csi]

Obviously he's a masochist and loves pain

 

[Shootymacshootface]

I haven't had the balls to part with the auto feed yet.

 

[Christianstark]

That blade looks too short to attempt such a cut. I know some of the blade broke, but seeing where the insert removal hole is gives me a good idea that the blade itself was not seated far enough in the holder to feel good about parting tough material.

 

[mikey]

If the crash happened about 2/3 of the way in, I bet the SFM dropped too low at that point. Since you were on auto-feed, your feed exceeded the point at which the insert is able to cut so it crashed. Next time, take it out of auto-feed and feed manually as the cut approaches center OR increase your speed.

 

[Aukai]

The blade is flipped in the holder, I guess I got fooled by the lack of noise, vibration, and the curls coming off nicely. I think that the tool bit into the work like Mikey suggested, It was approaching the half way point. The saw is not working, I need to get the electrician here to figure that out. Thank you all...

 

[Parlo]

If the crash happened about 2/3 of the way in, I bet the SFM dropped too low at that point. Since you were on auto-feed, your feed exceeded the point at which the insert is able to cut so it crashed. Next time, take it out of auto-feed and feed manually as the cut approaches center OR increase your speed.

The metal removal rate and therefore the load on the tool decreases as the diameter reduces when using a constant rpm and constant feed per rev. If the feed was excessive it would show at the beginning of the cut where the forces are greatest. I suspect the blade was too weak for the operation and a deeper blade and possibly wider would have been more suitable.