Post By PaulT
Breaking taps on the retract
Wondering if someone can help me. I'm trying to tap a 7/16-14 on the side of a part on a Mori Seiki NL2500 using a G88 tapping cycle. Everything goes fine until the retract. it starts to retract a ways and then the tap breaks. It has done this twice know, and I can't come up with what could be wrong. Any ideas?
Usually its a chip problem, mostly if some come out good and then out of nowhere, snap.
Sounds like chip evacuation issues. What material,tap style and lubricant?
I've only tried these 2 parts and the tap broke during the retract on both. The material is C1045, the tap is a Vega spiral tap and I'm using Cim-cool coolant. We have run thousands of these parts using the same stuff on a Bridgeport horizantal but I am bar feeding them on the Mori now. I have the whole part complete except for being unable to tap this hole. What would be the cause/solution for a chip evacuation issue? Thanks so much for the help!!
More info will help
Whats the material?
Blind or through hole?
Type of tap?
Size of hole?
The material is C1045. It is a blind hole tapped to a depth of 1.190" (30.226 mm) The tap is a Vega 7/16-14 spiral tap in a .3701 (9.4mm) hole. Cim-cool coolant is being used.
Double check to make sure the tap isn't slipping in the holder, check the shank for any signs of that.
Also on some machines there are parameters that must be properly set to enable rigid tapping. Has rigid tapping worked correctly on this machine on other jobs?
Here's a way to make sure that rigid tapping cycles are working correctly.
Get a 7/16-14 nut and clamp it losely in your vise.
Write a little test program to "tap" the nut with the spindle centered right over the nut.
The first time it runs is will push the nut down slightly in the vise jaws until the threads align, but when it reverses and pulls out the nut shouldn't move at all.
After the first run you should be able to clamp the nut and it should run repeatedly with no problem.
Doing this test will verify that your rigid tapping cycles are working correctly on the machine.
If Paul T's test works out ok - how deep is the drilled hole compared to the thread?
Coolant concentartion - usually the richer the better when tapping.
As a possible last resort, stop the tap at <> 3/4 hole depth depth, restart and then retract - it's helped me in the past as it breaks the swarf up.
Why are you using G88 instead of G84? Have you tried peck tapping? Have you considered a thread mill?
I think Paul might be on to something here. If the tap slips at all it's going to break on the way out. How far out is the tap befor it snaps? It could be bumping the bottom of the hole pushing the tap in the collet and when it reverses it breaks. Like rob stated as well, why not use a G84?
Check your coolant concentration. Taps are usually the first tools to start failing if your concentration is getting low.