I think I am doing something wrong with the end mills. (Detent thread #3)

S

Squashfan

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Jun 6, 2012
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If you have seen my previous threads, you will know I am on a quest to drill detents in some of my blades. Well, I got the Dremel mounted to the Dremel press and ordered a couple of Kyocera end mills. I tried the setup out this morning. I tinkered with different speeds, always with water as the coolant. But in just doesn't seem to be working. I am not using very much pressure, just enough to make contact with the work piece. After the bit makes contact, I let it run in the very, very shallow divot a couple of seconds. Then I back the bit off and apply more water to the blade. Should it take 30 minutes of work to drill this detent? Because that is looking like the amount of time it is going to take.

Maybe I am just too impatient but I feel like an end mill should do the job quickly, if it is the right tool.

Thanks,
Charles

EDIT: I should clarify something. There was a small, shallow divot form a trial with another bit. Even after about 5 minutes of drilling, in the aformentioned method, with the end mill, I still can't see that much of a difference in the diviot. That is my gauge.
 
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I switched over to a diamond bit and am getting better results. Same problem with the diamond though. Very very little swarf generation which tells me that it is not cutting very quickly. This is just sandvik steel. It is not like I am drilling D2.
 
I've used dremel diamond bits in my mill to drill detents in two different sandvik blades (one 14c28n not sure on the other) and I got good results by turning the head 90* and cutting with the side of the bit instead of the tip, the different direction of rotation seemed to really help cutting. It also threw the metal out of the hole instead of just rotating on top of it, I think that helped me too.

With your dremel press that may require doing it by hand, on my mill I set the bit just above the blade positioned where I needed it (again head at 90*) then raised the table up into it.
 
When drilling steel, especially higher carbon steel, what you generally want is slow speed and high pressure. Slow as in way slower than a dremel will go. If you don't have proper cutting oil, wd40 works better than nothing.

The reason the diamond burr doesn't cut very well when you plunge vertically is that the grains at the very tip aren't moving very fast if at all. They're just rotating, which doesn't grind very well. I've successfully drilled holes in hard steel with the round diamonds, but it takes some pressure and time. Grinding the divot with the side of the burr is an option, maybe you can set the blade in a jig and slide it up against the dremel while it's clamped in the stand, if you know what I mean? The diamond burrs can be run very fast too, which helps.
 
Well, the big problem is this bit, an end mill, doesn't seem to be the right tool for DRILLING in steel. I have been trying on and off all day to DRILL with it. Out of curiosity , I grabbed my tanto Blur. There is a hole in the blade already but the detent is really, really weak. I put the dremel down in RPM as low as it would go and voila! That same end mill was throwing giants chunks of steel. I was done in about ten seconds. It didn't help the weak detent but that wasn't really the point. So now I know, end mills are not, most emphatically not, for drilling straight down. If the hole is already there, it can inlarge it super well but forget about drilling.
 
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