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I have a slow-speed drill press which seems quite solid, the play is minimal. Normally, it does not cause problems. This conical bit:

conical bit

when applied to this 8 mm hole:

enter image description here

is an exception: the bit jumps and squeaks loudly, the machine resonates. As seen in the image, it is impossible to make an even chamfer. I was thinking about filling the hole with a 3d-printed plastic cylinder with a small pilot hole, but I am not sure it it would help, given that the material is a hard stainless steel. It is fastened in a 4.5 kg vice which can move freely, so that the bit position can be adjusted. The vice seems to be stable, despite the vibration.

How to make an even chamfer? Its angle of 45 deg is important.

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  • $\begingroup$ Could you show an image of the vice, and the drilling bit with the drill. I would like to see how is it held. Is it hand held or do you use a fixture to drive in the drill bit $\endgroup$ – NMech Dec 25 '20 at 13:23
  • $\begingroup$ I used the vice Draper 64585 and a medium-size table drill press with a crank, on a steel column of a 5 cm diameter. It is a typical consumer-grade drill press with an asynchronous motor. $\endgroup$ – scriptfoo Dec 25 '20 at 14:40
  • $\begingroup$ There is only one solution to this for SS, use a step bit. $\endgroup$ – Phil Sweet Dec 25 '20 at 18:16
  • $\begingroup$ ekstromcarlson.com/wp-content/uploads/… $\endgroup$ – Phil Sweet Dec 25 '20 at 18:22
  • $\begingroup$ A step drill will not produce a clean countersunk profile. (But step drills are certainly very useful tools for drilling large diameter holes in thin material). $\endgroup$ – alephzero Dec 25 '20 at 18:56
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If it is not a wear problem of the drill, and you encounter the problem just with this particular material, it might be that you are operating at a frequency which favours resonance and oscillations.

Can you try increasing the rpms or lowering it and see if the vibrations are less?

If that is the case you can attach some more mass (with a vice ) on the plate (an inertia block if you like) to lower the natural frequency. That combined with an increase of rpm might solve your problem.

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  • $\begingroup$ I would need to change the position of the transmission belt. I will try it and tell if it worked. $\endgroup$ – scriptfoo Dec 25 '20 at 18:45
  • $\begingroup$ I agree the basic cause of the problem is that the drill bit is not cutting. It seems to be tearing at the material rather than cutting it. Whether that is caused by a blunt drill, or the wrong speed or down pressure, is a guess. $\endgroup$ – alephzero Dec 25 '20 at 18:59
  • $\begingroup$ I agree it's difficult to do a proper "debugging" without a lot of information. Hopefully. Doubling the rpm might show significant improvement in vibration. Otherwise, the material might be too hard for the drill bit. $\endgroup$ – NMech Dec 25 '20 at 19:25

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