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Ball End Mills - What's the secret?
- Thread starter Red96
- Start date
- Joined
- Apr 24, 2022
- Messages
- 185
I did some experimenting and ditched the A36 for this piece and ended up using 1018 instead. @Asm109 nailed it with his comment on A36. The 1018 cut pretty decently, but I found a couple of other key points that really helped make a decent finish.
Did the math to determine how deep I could pre-cut with a regular square end mill of a somewhat smaller diameter. The groove I need is 8mm dia., and the math dictated I could go 0.095" deep with a .250" end mill to remove the bulk of the material. With that square cut groove in place, as I cut with the 8mm ball end mill, the ball was only engaging on the two shoulders of the .250" cut. As the cut progressed down into that slot, the ball mill engages more and more material area, so DOC needs to decrease as the engagement increases to avoid chatter. Started out with something like a .010 cut, then .005, and soon only .001-.002 DOC per pass. The final .010" or so was done at .0005" DOC and very fast feed rates (2.5" in about 2 sec) Full engagement of the ball mill only happened at the very bottom of the cut, when all of the initial roughing cut was removed, which really helped minimize chatter compared to cutting the material away entirely with the ball mill. All ball mill cuts were done at my machines' max spindle speed of 3000rpm. The fast passes at .0005" DOC were giving a decent finish, and each cut got 2-3 spring passes in between setting the next DOC. The key seemed to be fast speeds and very, very shallow DOC for finish passes. Hope this helps somebody else.
Did the math to determine how deep I could pre-cut with a regular square end mill of a somewhat smaller diameter. The groove I need is 8mm dia., and the math dictated I could go 0.095" deep with a .250" end mill to remove the bulk of the material. With that square cut groove in place, as I cut with the 8mm ball end mill, the ball was only engaging on the two shoulders of the .250" cut. As the cut progressed down into that slot, the ball mill engages more and more material area, so DOC needs to decrease as the engagement increases to avoid chatter. Started out with something like a .010 cut, then .005, and soon only .001-.002 DOC per pass. The final .010" or so was done at .0005" DOC and very fast feed rates (2.5" in about 2 sec) Full engagement of the ball mill only happened at the very bottom of the cut, when all of the initial roughing cut was removed, which really helped minimize chatter compared to cutting the material away entirely with the ball mill. All ball mill cuts were done at my machines' max spindle speed of 3000rpm. The fast passes at .0005" DOC were giving a decent finish, and each cut got 2-3 spring passes in between setting the next DOC. The key seemed to be fast speeds and very, very shallow DOC for finish passes. Hope this helps somebody else.
Last edited:
- Joined
- May 4, 2019
- Messages
- 822
The CNC videos show the ball nose end mill inclined to the work. That way the center is never in the cut. Not very practical on manual machines. They need the head tilted, then later re-trammed.