I pretty much intuited this idea once I saw the title thumbnail but it isn't something I had put attention on before, but I am glad you brought it up cause I will be buying my first sets soon. So thank you.
I picked this video up on reddit and decided to subscribe. Looks like a good channel. I would have said something there, but I usually get yelled at because I guess I don't know what I'm doing on Reddit.
Interesting use of FEA Seth! Could you try that again but use a shallower taper? It would be interesting to see the difference. It seemed like there was a drastic difference in the taper angle between your model and the actual cutting tool shown on the website. Just curious. I don't have much experience with doing that kind of analysis but I might give it a whirl. Thank you for sharing!
I pulled some 3d models of bits from Mcmaster-Carr and re-ran with those, they have a radius to the stepdown, the results aren't as obvious, but the stepdown one still has a strain point with a greater level of strain focused right at the base of that taper... I'll be re-doing this with Tapered Ball bits vs straight edged ball bits as well in an upcoming video.
In my own shop, I tend to go with the cheapest bits, I do have a few Amana bits, mainly because that specific style bit wasn't available from other sources. But if it's a widely sold bit, I tend to go for the least expensive option, and usually that's SpeTools. Amana does some great marketing on social media, and I'm sure their materials used are superior to the cheapest other options, but I don't think they are 5x as good to warrant a price tag 5x that of the competition.
Two questions come to mind. In normal use case, how likely are we to have lateral forces get high enough for this to become an issue? Additionally, the tool makers eliminate that sharp corner if there was some kind of feathering to make it a bit of a curve instead of a sharp angle?
A lead-In to the taper would help to spread the load focal point. But there will still be a point where the load is much higher than that of a uniform shank and cutter. You're right, I purposely exaggerated the load for the colors to show better. I cannot show the load applied while the model rotates like a bit really does. It only takes a small amount of side load for the constant rotation of the bit to cause the focal point (actually a ring due to rotation) to break down and the bit to snap right at that point.
@@SethCNC I am just getting started, and fortunately have not broken in a bit yet. Did your experience with these vents were the cutter is smaller than the shank, they usually break at that point?
Some companies have a fillet (either a radius or other curved shape) instead of a chamfer transition from shank to flutes, such as Onsrud 40-101 and 40-102, KYOCERA 1625-0469L141, YG1 E5I02002, etc. Any way to stress test that idea vs the chamfer?
Yeah, I might have to pull some complete 3d models and run some more tests. However, it is still going to have a similar overall result. The stress focused at the base of the taper/chamfer versus spread out more. The focal region would be a little larger from a fillet. But it's still going to be more focused than the smaller shank option.
It looks like the chamfer you myself with is 45* but the but has a shallower taper although I wouldn't go against the consolation would it modify the results?
Overall there would still be a focus point of the stresses with a different angle chamfer. I'll have to check the actual numbers I used but I think it's more about 50⁰ I tried to match what I was seeing on the OPs post when the topic came up over on Facebook. And his chamfer looked a little more than 45⁰.
